[From the U.S. Government Printing Office, www.gpo.gov]

                                                  FINAL PRODUCT W94 Task 72
                                                  Portsmouth AAeted Carbon BMP Demonstration








                     THE CARBON/SAND FILTER:


            AN ANALYSIS OF POLLUTANT REMOVAL EFFICACY



                     COASTAL RESOURCES MANAGEMENT PROGRAM
                          GRANT NO. NA470ZO287-01 TASK #72







                               The City of Portsmouth, Virginia
                        Department of Engineering & Technical Services
                          801 Crawford Street Portsmouth, VA 23704

                            Project Manager: James S. Kitterman, III
                                     December 4, 1996









                        This report was 100% funded ($49,932) by the Virginia Department of Environmental
         TD             Quality's Coastal Resources Management Program through Grant #NA470ZO287-01
         192            of the National Oceanic and Atmospheric Administration, Office of Ocean and Coastal
         D37            Resource Management, under the Coastal Zone Management Act of 1972, as amended.
         1996           The views expressed herein are those of the author and do not necessarily reflect the
                        views of NOAA or any of its subagencies.
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                                                                   "STRACT




                           Ultra-urban environments, typically highly developed, downtown areas, are a significant source
                      of pollution in stormwater runoff, wiih few pervious areas and a high concentration of vehicular
                      activity. Lack of space and high property values make conventional Best Management Practices
                      (BMPs), such as detention basins, unfeasible. This report investigates the pollutant removal
                      effectiveness of a Carbon/Sand Filter, which in a space-saving effort, filters runoff in an
                      underground concrete sand filter. The filter also includes activated carbon intended to help reduce
                      pollution stemming from motor vehicle activity.

                           The report discusses the history of the ultra-urban environment and the pollutants associated
                      with this environment and their potentially toxic effects on aquatic life. It details the design and
                      construction of the Carbon/Sand Filter, an underground concrete structure approximately 34' x 10' x
                      8' that serves a parking lot in the downtown section of Portsmouth.              It also discusses the
                      stormwater monitoring and chemical analyses performed by the Hampton Roads Sanitation District
                      (HRSD) for the project.

                           The report gives a detailed statistical analysis of the chemical analysis results and discusses the
                      pollutant removal efficacy for fourteen chemical parameters. It also compares the pollutant removal
                      of this BMP to the publishes efficiencies of BMPs in other regions. It concludes that the
                      Carbon/Sand Filter is somewhat more efficient in removing many contaminants than a conventional
                      sand filter, which was concurrently tested.













                                                        ACKNOWLEDGEMENTS




                          The author would like to express sincere appreciation to a number of individuals and
                     businesses who have donated time, money, and expertise toward this project. Without them the
                     Carbon/Sand Filter would never have been built in the City of Portsmouth and would likely still be
                     on the drawing board. These individuals and organizations are:

                     The National Oceanic and Atmospheric Administration (NOAA) for financial support that allowed
                     the construction and monitoring of the Carbon/Sand Filter;

                     Jeannie Lewis, Laura McKay, and Virginia Witmer of the Virginia Department of Environmental
                     Quality (DEQ) for administrative support;

                     George Kennedy, Danny Barker, T.J. Johnson, and staff of the Hampton Roads Sanitation District
                     (HRSD) for their donation of discounted monitoring services and technical expertise;

                     Lamont W. (Bud) Curtis, P.E., Mike Barbachem, P.E., Greg Anderson, and Paul Michiels, P.E. of
                     URS Consultants for donation of design services for the Carbon/Sand Filter and other technical
                     expertise;

                     Tarmac America, Inc. for the donation of reduced cost 5000-lb concrete and free sand;

                     Calgon Carbon Corporation for the donation of 3000 pounds of its Fitrasorb 300 activated carbon
                     product;

                     John Carlock of the Hampton Roads Planning District Commission (HRPDC) for his expertise in
                     grant-funded projects and report preparation;

                     Engineers and staff at the City of Portsmouth, for continuous technical and administrative support;

                     A. Osman Akan, Ph.D., P.E. of Old Dominion University for technical advice on report
                         preparation; and

                     my family, who afforded me the time to complete this study.













                                                                            TABLE OF CONTENTS



                           ABSTRACT          ...................................................................................................     i


                           ACKNOWLEDGEMENTS                    .................................................................................


                           TABLE OF CONTENTS                .....................................................................................


                           LIST OF FIGURES            ...........................................................................................    v


                           LIST OF TABLES           ............................................................................................     vi


                           LIST OF EQUATIONS              ......................................................................................     vii

                           1.0    INTRODUCTION            ......................................................................................     1-1
                                  1.1   An Overview of the Carbon/Sand Filter Analysis                 ...........................................   1-1
                                  1.2   The Development of the Ultra-Urban Environment                   .........................................   1-2
                                  1.3   Regulations Governing Water Quality              ........................................................    1-5
                                  1.4   Response to Water Quality Regulations              ......................................................    1-6
                                  1.5   Conventional Best Management Practices                ...................................................    1-6
                                        1.5.1 Non-Structural BMPs            ...................................................................     1-6
                                        1.5.2 Structural BMPs          .........................................................................     1-7


                           2.0    REMOVAL OF ULTRA-URBAN POLLUTANTS FROM STORMWATER RUNOFF                                                       ... 2-1
                                  2.1   Pollutants in Stormwater Runoff           ...............................................................    2-1
                                        2.1.1 Agricultural Land Use           ...................................................................    2-1
                                        2.1.2 Suburban Land Use            ......................................................................    2-2
                                        2.1.3 Ultra-Urban Land Use            ...................................................................    2-3
                                  2.2   Effects of Ultra-Urban Pollutants on the Aquatic Environment                    ...........................  2-4
                                        2.2.1 Heavy Metals         ..............................................................................    2-4
                                              2.2.1.1     Cadmium      ..........................................................................    2-5
                                              2.2.1.2     Chromium      .........................................................................    2-5
                                              2.2.1.3     Copper   .............................................................................     2-6
                                              2.2.1.4     Lead  ..................  .............................................................    2-6
                                              2.2.1.5     Mercury    ............................................................................    2-6
                                              2.2.1.6     Silver  ..............................................................................     2-6
                                              2.2.1.7     Zinc  .................................................................................    2-6
                                        2.2.2 Hydrocarbons         .............................................................................     2-6
                                        2.2.3 Animal Wastes and Other Organic Material                   ..........................................  2-7
                                        2.2.4 Suspended Solids          .........................................................................    2-7
                                        2.2.5 Litter     .......................................................................................     2-8
                                  2.3   Mechanics for Ultra-Urban Pollutant Removal                 ..............................................   2-8
                                        2.3.1 Conventional BMPs             .....................................................................    2-8
                                        2.3.2 Ultra-Urban BMPs            .......................................................................    2-9
                                        2.3.3 The Carbon/Sand Filter            .................................................................    2-10
                                              2.3.3.1 Sedimentation          ....................................................................    2-11
                                              2.3.3.2 Filter Fabric       ......................................................................     2-11


                                                                                           iii










                                             2.3.3.3 Sand      ................................................................................  2-11
                                             2.3.3.4 Activated Carbon          ................................................................  2-12


                          3.0 SYNOPSIS OF THE CARBON/SAND FILTER PROJECT                                    .................................... 3-1
                                 3.1   Problem Identification         ........................................................................... 3-1
                                 3.2   BMP and Site Selection         .........................................................................  3-1
                                 3.3   Project Funding and Design Objectives             ....................................................... 3-4
                                 3.4   Carbon/Sand Filter Design         .....................................................................   3-5
                                 3.5   Request for Proposals          ............................................................................ 3-7
                                 3.6   Carbon/Sand Filter Construction           ............................................................... 3-8
                                 3.7   Stortnwater Sampling and Chemical Analysis                ............................................... 3-15


                          4.0    ANALYSIS OF POLLUTANT REMOVAL FOR THE CARBON/SAND FILTER                                               ........ 4-1
                                 4.1   Storm Event Sampling           ........................................................................... 4-1
                                 4.2   Chemical Parameters            ............................................................................ 4-2
                                 4.3   Chemical Analysis Results         .....................................................................   4-3
                                 4.4   Statistical Methods Used for Data Analysis             .................................................. 4-5
                                       4.4.1 Sample Means             ............................................................................ 4-5
                                       4.4.2 Paired T-test for Significance of Results            .............................................  4-5
                                       4.4.3 Correlation of Monitoring Data             ........................................................ 4-7
                                 4.5   Pollutant Data Analysis        .........................................................................  4-7
                                       4.5.1 Total Suspended Solids (TSS)              ......................................................... 4-7
                                       4.5.2 Nutrients       ................................................................................... 4-11
                                             4.5.2.1 Total Phosphorus (TP)            .......................................................... 4-12
                                             4.5.2.2 Total Kjeldahl Nitrogen (TKN)               ............................................... 4-14
                                             4.5.2.3 Ammonia (NH3)             ................................................................  4-16
                                       4.5.3 Oxygen Demand            .........................................................................  4-18
                                             4.5.3.1 Biochemical Oxygen Demand (BODO                      ...................................... 4-18
                                             4*5.3.2 Total Organic Carbon (TOC)               .................................................. 4-20
                                       4.5.4 Heavy Metals             ............................................................................. 4-22
                                             4.5.4.1 Total Recoverable Copper (T.R. Cu)               .......................................... 4-22
                                             4.5.4.2 Total Recoverable Zinc (T.R. Zn)             .............................................  4-24
                                             4.5.4.3 Hardness         ........................................................................... 4-26
                                       4.5.5 Hydrocarbons             ............................................................................. 4-28
                                 4.6 Discussion of Results            ............................................................................ 4-28


                          REFERENCES           ................................................................................................  REF- 1


                          APPENDICES:
                                 A- I        BMP Sizing Calculations
                                 A-2         Construction Plans
                                 A-3         Construction Bid Price Tabulations
                                 A-4         Climatological Data
                                 A-5         Statistical Analysis of Monitoring Data







                                                                                          iv












                                                                               LIST OF FIGURES



                            Figure 1 - 1. The Norfolk waterfront around 1875                .....................................................   1-2
                            Figure 1-2. Downtown Norfolk, looking east, in 1922                    ..............................................   1-3
                            Figure 1-3(a).      Downtown Norfolk, looking west, in 1925                   .......................................... 1-3
                            Figure 1-3(b).      Downtown Norfolk, looking west, in 1980                   .......................................... 1-3
                            Figure 14(a).       Downtown Norfolk, looking north, in 1995                  ......................................... 1-4
                            Figure 14(b).       Downtown Norfolk, looking south, in 1995                  ......................................... 1-4

                            Figure 2- 1 (a).    Stormwater wet pond at the Hampton Roads Regional Jail in Portsmouth                           ..... 2-9
                            Figure 2- 1 (b).    Stormwater wet pond at the Middletown Arch subdivision in Norfolk                          ......... 2-9
                            Figure 2-2.     Schematic of the Carbon/Sand Filter              ....................................................   2-10
                            Figure 2-3.     Internal structure of activated carbon           ....................................................   2-13

                            Figure 3-1.     Parking lot behind Portsmouth City Hall               ................................................  3-2
                            Figure 3-2.     Schematic of the Delaware Sand Filter             ..................................................    3-3
                            Figure 3-3.     Parking lot on High Street considered for the D.C. Sand Filter design                      ............. 3-3
                            Figure 3-4.     Schematic of the D.C. Sand Filter            .......................................................    3-4
                            Figure 3-5.     Site layout for the Carbon/Sand Filter            ...................................................   3-6
                            Figure 3-6(a).      Excavation of the filter structure location               ........................................... 3-8
                            Figure 3-6(b).      Excavated site of the filter structure        .................................................     3-9
                            Figure 3-7(a).      Construction of the diversion manhole              ...............................................  3-10
                            Figure 3-7(b).      Brick walls of the diversion manhole were erected                ................................   3-10
                            Figure 3-7(c).      The view from the diversion manhole toward the Carbon/Sand Filter                         .......... 3-11
                            Figure 3-8(a).      Excavation of the reentry manhole location                ......................................... 3-11
                            Figure 3-8(b).      A view from above of the ducts conflicting with the reentry manhole                       ......... 3-11
                            Figure 3-8(c).      A view down into the finished reentry manhole                 ....................................  3-12
                            Figure 3-9(a).      Construction of the Carbon/Sand Filter floor              .......................................   3-12
                            Figure 3-9(b).      Construction of the Carbon/Sand Filter floor              .......................................   3-13
                            Figure 3-9(c).      Construction of the Carbon/Sand Filter floor              .......................................   3-13
                            Figure 3-9(d). Construction of the Carbon/Sand Filter walls                   .......................................   3-13
                            Figure 3-9(e). Construction of the Carbon/Sand Filter walls                   .......................................   3-13
                            Figure 3-9(f). Construction of the Carbon/Sand Filter walls                   ........................................  3-13
                            Figure 3-9(g). Construction of the Carbon/Sand Filter walls                   .......................................   3-13
                            Figure 3-9(h). Construction of the Carbon/Sand Filter walls                   .......................................   3-13
                            Figure 3-9(i). Construction of the Carbon/Sand Filter top                     ........................................... 3-14
                            Figure 3-90). Construction of the Carbon/Sand Filter top                      .......................................... 3-14
                            Figure 3-9(k). Backfilling of the Carbon/Sand Filter                 ................................................   3-14
                            Figure 3-9(l). The finished Carbon/Sand Filter structure                      ............................................ 3-14
                            Figure 3-10(a). The underdrain system of the Carbon/Sand Filter                      ................................   3-14
                            Figure 3-10(b). The underdrain system of the Carbon/Sand Filter                      ................................   3-14
                            Figure 3-1 l(a). The underdrain pipe and cleanout in a stone bedding                       ............................ 3-15
                            Figure 3-1 l(b). Chamber 92 filled with sand and covered with filter fabric                       ..................... 3-15
                            Figure 3-1 1(c). The "pillowcase" being filled with activated carbon                     .............................  3-15





                                                                                             v












                                                                                  LIST OF TABLES



                             Table 4-1.     Storm event data        ..............................................................................      4-1
                             Table 4-2.     Specifications for chemical analyses performed for this project                      ...................... 4-3
                             Table 4-3.     Chemical analysis results of Carbon/Sand Filter testing                    ...............................  4-4
                             Table 4-4.     Sample mean data for total suspended solids (TSS)                    .....................................  4-8
                             Table 4-5.     Means and standard deviations for differences in TSS                     .................................  4-9
                             Table 4-6.     Summary of statistical analyses for TSS               .................................................     4-11
                             Table 4-7.     Sample mean data for total phosphorus (TP)                  .............................................   4-12
                             Table 4-8.     Summary of statistical analyses for T?               ...................................................    4-13
                             Table 4-9.     Sample mean data for total Kjeldahl nitrogen (TKN)                     .................................    4-15
                             Table 4-10.      Summary of statistical analyses for TKN                ...............................................    4-15
                             Table 4-11.      Sample mean data for ammonia (NH3)                  .................................................     4-17
                             Table 4-12.      Summary of statistical analyses for NH3               ................................................    4-17
                             Table 4-13.      Sample mean data for biochemical oxygen demand (BOD5)                            ........................ 4-19
                             Table 4-14.      Summary of statistical analyses for BOD5                 ..............................................   4-19
                             Table 4-15.      Sample mean data for total organic carbon (TOC)                    .....................................  4-20
                             Table 4-16.      Summary of statistical analyses for TOC                ...............................................    4-21
                             Table 4-17.      Sample mean data for total recoverable copper (Cu)                    ..................................  4-23
                             Table 4-18.      Summary of statistical analyses for Cu              ..................................................    4-23
                             Table 4-19.      Sample mean data for total recoverable zinc (Zn)                  .....................................   4-24
                             Table 4-20.      Summary of statistical analyses for Zn              .................................................     4-25
                             Table 4-21.      Sample mean data for hardness              ...........................................................    4-26
                             Table 4-22.      Summary of statistical analyses for hardness                ..........................................    4-27
                             Table 4-23.      Summary of pollutant removal efficiencies for the sand filter and the CSF                          ....... 4-29
                             Table 4-24.      Comparison of pollutant removal efficiencies for different BMPs                         ................. 4-30

























                                                                                                vi











                                                              LIST OF EQUATIONS



                      Equation 3-1. Calculation of the Water Quality Volume (WQV)          .................................. 3-5

                      Equation 4-1. Formula for the t-test test statistic  ..................................................... 4-6
                      Equation 4-2. Formula for the mean of sample differences       ......................................... 4-6
                      Equation 4-3. Formula for the standard deviation of sample differences      ......................... 4-6










































                                                                          vii













                                                            1.0 INTRODUCTION





                      1.1 An Overview of the Carbon/Sand Filter Analysis.

                          Water quality studies over the last several decades have repeatedly demonstrated the
                      deleterious effects of daily human activities on our nation's waterways. As recently as 1946, 30
                      million gallons per day of untreated domestic sewage were routinely routed directly to the lower
                      Chesapeake Bay and the James, Elizabeth, and Nansemond Rivers and other estuaries as a means of
                      disposal. These and other polluted discharges to receiving waters have significantly contributed to
                      reductions of and restrictions on fish catches and shellfish harvesting in the Hampton Roads
                      tributaries. Although many such practices have changed over the years, concern over the continuing
                      deterioration of these vital resources has compelled both government agencies and environmental
                      advocacy groups to further. identify and address the problems of water pollution.

                          The study of receiving water quality focuses on two different sources of pollution: point
                      sources and nonpoint sources. Point sources are those associated with industrial process wastewater
                      and municipal sewage, while nonpoint sources generally refer to stormwater runoff. Federal, state,
                      and local permitting programs have been designed to reduce pollutants in discharges from these
                      sources. These permits have allowed federal, state, and local governments to better regulate
                      commercial and industrial practices that adversely affect water quality and have encouraged
                      governments to implement measures to reduce pollution from publicly owned facilities.

                          Although the initial efforts of water quality programs were aimed at reducing point source
                      pollutant concentrations through effluent limits, more recent studies have indicated that contaminant
                      levels from nonpoint sources can be significantly higher than those from point sources.
                      Consequently, many industries and municipalities are required to address the quality of their
                      stormwater runoff. The response has been to implement Best Management Practices (BMPs) to
                      improve the quality of runoff before it reaches the Waters of the United States. These practices can
                      be non-structural BMPs, which reduce pollutant sources before rainfall or runoff is introduced to
                      them, structural BMPs, which remove pollutants already in a runoff stream, or a combination of the
                      two.


                          The engineering and planning communities are continually challenged with developing less
                      expensive and more effective BMPs. However, not all BMPs are applicable to every situation or
                      land use. Practices used in suburban areas are not always suitable for a highly urbanized area.
                      BMPs for agricultural land use are collectively very different than those for more urban areas. This
                      study analyzes the pollutant removal efficacy and shows the dollar costs of an innovative
                      stormwater structure, the Carbon/Sand Filter, designed for use in highly urbanized areas.

                          To better understand the purpose of analyzing this new BMP, a broader picture must be painted
                      of issues and technologies concerning "ultra-urban" runoff, or that from highly urbanized, often
                      "downtown," areas. The remainder of this section describes the development of the ultra-urban
                      environment and the resulting problems for the quality of stormwater runoff. It will also highlight
                      significant government regulations designed to address pollution in runoff and in receiving waters.



                                                                      1-1









                          Subsequent sections will detail the pollutants in the ultra-urban setting, their potential
                     environmental effects, and the processes through which they can be removed. This report will also
                     describe the Carbon/Sand Filter Project, its design, construction, and monitoring for certain
                     chemical parameters. It will conclude with a thorough analysis of the pollutant removal efficiency
                     of the filter and provide data that will allow comparisons to other BM[Ps.


                     1.2 The Development of the Ultra-Urban Environment.

                          The colonization of the Virginia coastal region began over 300 years ago. Though much
                     smaller in population, Portsmouth and Norfolk developed in much the same manner as cities such as
                     New York and Boston. The Tidewater region was one of the first areas permanently settled by the
                     British in the 17th century. Its comprehensive system of navigable waterways, including the James
                     River and the Chesapeake Bay, and its proximity to the Atlantic Ocean facilitated colonization and
                     allowed easy passage to Europe. Settlements were situated on the rivers and tidal estuaries
                     primarily for trade purposes, although some rivers provided a fresh water source and a removal
                     system for waste. Because the shipping trade and other associated industries thrived on the
                     waterways, the population was concentrated in these areas. Workers had to live at or near their
                     workplaces, as most had no means of transportation. Commercial businesses were, in turn,
                     supported by this population. Figure 1-1 offers   a glimpse of the Norfolk waterfront and shipping
                     industry in the nineteenth century.




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                     Figure 1-1.    The Norfolk waterfront around 1875. This is one of the oldest known photographs of
                     Norfolk (Walker, 1981).


                          As the population increased over time, the density of buildings, both residential and
                     commercial, also increased. Eventually piping systems were installed to improve drainage, and,
                     when indoor plumbing first became available, many raw sewage pipes were connected directly to
                     the storm drainage system. These small cities did not at that time have the technology to treat
                     sewage and, until the 1920's, did not appreciably understand the health problems associated with the
                     discharge of sewage to the waterways. For the most part, this discharge did not immediately exceed

                                                                     1-2








                      the waste assimilative capacity of the receiving waters because the populations were relatively small
                      and the waste discharge low. Figure 1-2 is a photograph of downtown Norfolk in 1922 that depicts
                      how densely developed the area had become.

























                                   Figure 1-2.    Downtown Norfolk, looking east, in 1922 (Walker, 198 1).



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                      Figure 1-3(a). Downtown Norfolk, looking               Figure 1-3(b). Downtown Norfolk from the
                      west, in 1925 (Walker, 1981).                          same perspective, in 1980 (Walker, 1981).


                          Today, the areas that once constituted the entire city are now called the central business
                      districts, or "downtown" areas. The expanding population radiated to the suburbs as the city's land
                      mass grew. In many ways, the shipping trade is not as active as it was in the past, but other
                      commercial industries and small businesses have filled the voids in the downtown areas. Now, in


                                                                      1-3








                      many cases, businesses are even more densely located, as high rise office buildings dot the
                      waterfront. Downtown residential areas are also still densely populated. Wetland areas have all
                      been destroyed in favor of urban land development. As sanitary sewage networks and treatment
                      plants were created to treat wastewater, efforts were made to disconnect the older sewage pipes
                      from the storm drainage system. Figures 1-3(a) and 1-3(b) illustrate these changes in the landscape.


                                                                                                    Figure 14(a). Down-
                                                                                                    town Norfolk, looking
                                                                                                    north, in 1995. The wa-
                                                                                                    ter body is the conflu-
                                                                                                    ence of the Elizabeth
                                                                                                    River's          southern
                                                                                                    branch, eastern branch,
                                                                                                    and main stem. The hi-
                                                                                                    rise at bottom left is in
                                                                                                    downtown Portsmouth
                                                                                                    (Marsala).




                      . ..........                             .... ..



                                                                                                    Figure 14(b). Down-
                                                                                                    town Norfolk, looking
                                                                                                    south, in 1995. The
                                                                            % dd-                   open parking area be-
                                                                                                    yond the church in the
                                                                                                    center is the MacArthur
                                                                                                    Center mall site. Ports
                                                                                                    mouth lies beyond the
                               Jio
                                                                                                    Elizabeth River (Mar
                                                                                                    sala).
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                           The character of the downtown area, or ultra-urban setting, is one of much human activity and
                      with a high concentration of the work force. Because many of these individuals drive automobiles,
                      parking lots are installed where space is not already consumed by office buildings or road and
                      sidewalk systems. As seen in Figures 14(a) and 14(b), impervious surface covers nearly all of the
                      downtown area, and there is very little unused space. These characteristics make the ultra-urban
                      environment a major concern for management of stormwater runoff quality. However, conventional
                      BMPs, both structural and non-structural, are very difficult to implement in such an area. Chapter 2
                      will further investigate the problems associated with the ultra-urban setting.




                                                                        1-4







                      1.3 Regulations Governing Water Quality.

                           Without regulations governing activities that affect water quality, there would likely be little
                      impetus to implement management programs. Discharge of municipal sewage and industrial wastes
                      clearly has a negative effect on water quality, and can promote the spread of waterborne diseases
                      that harm humans. Other discharges can degrade water quality such that it harms aquatic life.
                      Programs undertaken to improve water quality, however, are at a considerable expense to the public
                      and to commercial businesses and industries. For this reason there will always be some debate over
                      what degree of regulation is appropriate. The following discussion highlights the regulations that
                      have the most significant impact on water quality in the Hampton Roads region.

                           The defining federal legislation in water quality management is the Federal Water Pollution
                      Control Act (FWPCA) of 1956. This law established a program to provide funds for water pollution
                      research and for construction of wastewater treatment facilities, as wastewater had been identified at
                      that time as the primary source for waterbome diseases. The FWPCA has been amended a number
                      of times since its inception, with different names assigned to essentially the same, but evolving.
                      legislation. Amendments in 1972 led to the law's more common name, the Clean Water Act, and
                      created the National Pollutant Discharge Elimination System (NPDES), which established a system
                      of permits through which the government can control discharges from a wide variety of pollutant
                      sources.


                           The initial thrust of the NPDES program was to reduce pollutants from industrial process and
                      municipal sewage discharges. Litigation during the late 1970's resulted in the legal definition of
                      stormwater as a point source to be regulated under the NPDES program. The Water Quality Act of
                      1987 further amended the Clean Water Act to include schedules for reducing pollutants from
                      stormwater discharges associated with industrial activities and from municipal separate storm sewer
                      systems serving populations of 100,000 or more.

                           NP`DES stormwater discharge pen-nits require the implementation of a pollution prevention
                      plan in the case of industrial stormwater discharges and a stormwater management program for
                      municipal discharges. Each documents the proposed measures to be taken by the permittee to
                      control, at the source. pollutants that may be picked up by stormwater, as well as proposed methods
                      of removing pollutants that have already been picked up by the runoff. All municipal permits
                      contain an array of measures, called Best Management Practices (BMPs),.that are designed to
                      achieve both goals.

                           Other laws have been passed at the state and local levels that further address water quality
                      problems. In the Mid-Atlantic region, states have adopted legislation to reduce pollution in the
                      Chesapeake Bay. The Chesapeake Bay Preservation Act was passed by the Commonwealth of
                      Virginia in 1988. Localities, in tum, tailored the regulations to their communities to reduce the
                      water quality impacts due to property development. Development and redevelopment of areas
                      within Chesapeake Bay Preservation Areas must be accompanied by BMPs, both structural and non-
                      structural.


                           Stormwater Management Regulations have been adopted at the state level in Virginia as well as
                      in some local jurisdictions. Erosion and Sediment Control Regulations exist at both the state and
                      local levels. These and other various laws have specific requirements that reduce the deleterious
                      environmental effects of property development.



                                                                       1-5









                       1.4 Response to Water Quality Regulations.

                            Water quality management methods have been implemented and are regulated on a number of
                       levels. NPDES permits are approved and enforced at the federal level by the Environmental
                       Protection Agency (EPA) or its designee, which in Virginia is the Virginia Department of
                       Environmental Quality (DEQ). Stormwater discharge permits for both industrial facilities and
                       municipal storm sewer systems are issued by DEQ based on the management methods proposed in
                       each permit application, as well as any further measures required by DEQ.

                            In the case of permits for discharges related to industrial activities, a pollution prevention plan
                       is required for the facility and is implemented at the cost of the business. Required for municipal
                       permits is a stormwater management program detailing methods of reducing pollution in runoff.
                       Many costs of the program, such as publicly owned detention basins, street sweeping, public
                       education, and illicit discharge screening, are borne by the locality, but other elements entail further
                       requirements on individual property developers, such as erosion and sediment control measures and
                       privately owned detention basins.

                            Most environmental legislation applies to new construction and is seen as a cost of
                       development to the developer or property owner. Under most circumstances, existing properties are
                       "grandfathered" into such regulations as the Chesapeake Bay Preservation Act and the Virginia
                       Stormwater Management Regulations. However, when a property undergoes new construction,
                       even for a building addition, the newer regulations may apply to the whole facility. Depending on
                       the criteria used in a certain locality, a developer could be required to install a sizable BMP, such as
                       a detention basin for an addition to an existing parking lot.

                            These methods are generally designed to negate any additional impacts property development
                       might have on a receiving water. More difficult is the effort to apply structural controls to all
                       existing area where no new construction is planned. Such areas may still significantly contribute to
                       pollution in runoff, but, without retroactive regulations to require controls on private property, the
                       local government might be the only party to install such a control. With limited funding, the
                       number of BMPs that can be retrofitted to many existing areas by the locality is insufficient. To
                       successfully combat this problem, creativity in design must be used to devise more effective and
                       cost-effective means of installing structural BMPs.



                       1.5 Conventional Best Management Practices.


                       1. 5.1 Non-Structural BMPs.


                            Non-structural Best Management Practices have long been seen as the least expensive way to
                       reduce pollution in stormwater runoff. Usually these practices entail changing the behavior of
                       people who contribute, often unknowingly, to the problem. Elements that can be described as
                       pollution prevention are generally the least expensive BMPs. The more a practice performs some
                       mechanical function to eliminate pollutant sources, the more expensive the method becomes. The
                       following discussion describes non-structural controls, beginning with more preventative measures.

                            Public education efforts are directed at controlling three major sources of pollution: inotor
                       vehicle maintenance, spills of toxic substances, and lawn care maintenance. It is estimated that 4.4


                                                                         1-6








                        million gallons of used motor oil are improperly disposed of each year in Virginia (Hampton Roads
                        Planning District Commission, 1993). Evidence abounds of disposal of grass clippings to the storm
                        drain which end up in receiving waters. Fish kills in local lakes and ponds are most often
                        attributable to the decay of organic matter, including algae blooms and other aquatic vegetation,
                        which in turn depletes the water body of dissolved oxygen. In urban areas it is believed that these
                        blooms are largely created by the runoff of excess fertilizer from horneowners' lawns.

                             Education efforts concentrate on encouraging the disposal of used motor oil, antifreeze, and
                        other fluids at recycling centers rather than pouring them into storm drains.                Routine car
                        maintenance reduces fluid dripping while the vehicles are parked or in operation. Spill prevention is
                        encouraged among homeowners and. businesses so that toxic chemicals are not stored improperly
                        where they may be accidentally knocked over or otherwise deposite          -d to the ground and then the
                        storm drain. Lawn care education teaches to bag or compost lawn clippings or to leave them on the
                        newly cut grass. It also encourages soil testing to determine the proper application, if any, of
                        fertilizer, so that no excess fertilizer remains to run off. It is hoped that these efforts are directed at
                        citizens who do not realize that their behavior contributes to pollution in runoff and who will change
                        their behavior accordingly.

                             Other effective non-structural BMPs include street sweeping, storm drain cleaning, illicit
                        discharge inspection, and vegetative buffering. Street sweeping primarily removes trash and
                        particulate contaminants from roadways that would eventually make their way into the storm drains.
                        Storm drain cleaning removes trash, sediments, and organic materials, such as leaves and grass
                        clippings, before they can be carried by runoff to receiving waters. Inspection for illicit discharges
                        reveals any direct connections to the storm drain of wastewater that should be directed to the
                        sanitary sewer. It also identifies areas where leaking sanitary sewers are seeping into the storm
                        drain. Vegetative buffers are non-structural in the sense that they embody the effort to reduce the
                        amount of impervious cover on a newly designed site and allow infiltration of rainfall into the
                        ground, thus reducing the runoff stream that can carry pollutants.

                             While it is widely believed that non-structural methods are a very effective means of pollutant
                        reduction, there is very little data to substantiate the claim. Effectiveness of street sweeping and
                        storm drain cleaning can be measured in terms of tons of debris removed. However. public
                        education offers no reliable means of tracking the amount of pollutants that will not be directed to
                        receiving waters due to education efforts.



                        1.5.2 StructuraIBMPs.


                             The most common -and more effective structural BMPs in this region include detention basins.
                        infiltration facilities, and grass and biofiltration swales. The goal of these structures is to treat the
                        water by removing some of the pollutants through plant uptake or through natural processes that
                        take place in the underlying soil. Not all contaminants can be assimilated, though, and the result is a
                        muck layer that must be removed and property disposed of. Removal rates for these structures are
                        most often measured in percent phosphorus removal, although other contaminants, such as nitrogen
                        or suspended solids, are generally removed to a similar degree.

                             Detention basins are designed to accumulate runoff in a basin so that suspended pollutants have
                        time to fall to the basin floor in a relatively quiescent environment. Dry detention basins remain dry
                        when there is no rainfall and release stormwater more slowly than is accumulated during rainfall.


                                                                           1-7








                       Wet detention basins, also called wet ponds, have a permanent pool of water and an overflow weir
                       or riser that will release the excess stormwater when it reaches a certain level in the pond. During
                       dry weather the permanent pool is reduced only by evaporation. Pollutant removal rates for these
                       structures range from 10 percent to 60 percent depending on detention time (Center for Watershed
                       Protection, 1996). Detention basins are more productive if they contain constructed wetlands,
                       which, in turn, must be maintained and not over-burdened with pollutants. Short circuiting, in
                       which the runoff travels directly from one end of the basin to the outflow structure, reduces the
                       effectiveness of the BMP because the water does not have the benefit of a long detention time that
                       allows the natural filtering process to take place.

                            Infiltration trenches and basins are built underground and allow stormwater runoff to infiltrate
                       into the soil. They usually consist of layers of gravel and sand separated by filter cloth that provide
                       void space for the runoff to fill as it seeps into the ground. Trenches are longer and narrower than
                       basins and are usually used adjacent to parking lots. Removal efficiencies for infiltration devices
                       range from 50 percent to 70 percent depending primarily on the amount and rate of infiltration into
                       the ground (Center for Watershed Protection, 1996). Infiltration BNVs are often not the best
                       alternative in the Hampton Roads region because high groundwater levels, and in some cases clayey
                       soils, prevent proper infiltration of the runoff into the ground. They are also difficult to maintain
                       because all of the material providing void space must be periodically removed and replaced to
                       prevent clogging.

                            Biofiltration and bioretention facilities perform the same function as detention basins but are
                       usually used for sheet flow runoff from a parking area. They cannot treat the same capacity of
                       water as can a detention basin, but, because they are not inundated for long periods of time, they can
                       be more attractively landscaped with trees and shrubs. Removal efficiencies are on the order of 50
                       percent (Center for Watershed Protection, 1996).

                            Porous pavement is a relatively new structural management device which allows stormwater to
                       infiltrate into the pavement and ground below before it can create runoff. Therefore, this pavement
                       is only effective with flat slopes. Porous pavement also has a removal efficiency range of 50
                       percent to 70 percent (Center for Watershed Protection, 1996). Porous pavement tends to clog in a
                       relatively short time, requiring expensive vacuuming for maintenance.

                            It is virtually impossible to make numeric comparisons of non-structural and structural BUTs.
                       The degree of efficacy for a structural control is measured by chemical sampling of flow streams
                       into and out of a structure. Conversely, it is not practically feasible to measure the amount of
                       pollutants that will not be introduced to stormwater because of proper lawn care techniques or
                       proper maintenance of an automobile. Comprehensive stormwater management programs include
                       combinations of structural and non-structural BMPs.


                            Each structural BMP has its own related deficiencies. The primary problem associated with the
                       ultra-urban environment, however, is lack of space.         Detention, infiltration, and grass swale
                       structures all require -a substantial amount of space to significantly reduce pollutants in runoff.
                       Because of the density of buildings and population and degree of human activity in downtown areas,
                       there is rarely enough space to implement a successful structural BMP. Chapter 2 will further
                       investigate the problems unique to the ultra-urban environment.





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                       2.0 REMOVAL OF ULTRA-URBAN POLLUTANTS FROM STORMWATER RUNOFF.





                      2.1 Pollutants in Stormwater Runoff.


                          Types of pollutants found in stormwater runoff depend heavily on the land use of the drainage
                      area. The two major categories of land use considered for management of runoff are agriculture and
                      urban areas. The character of runoff from these environments.differs significantly because of the
                      substances found on the ground surface that are exposed to rainfall. However, the urban
                      environment can be further divided into industrial, commercial, residential and open/recreational
                      land uses. To illustrate the challenges in managing pollution from urban areas, this study will
                      compare the contaminants from suburban and ultra-urban land uses.


                      ZIJ      Agricultural Land Use.

                          Agriculture is responsible for much of the pollution in the Chesapeake Bay. Nutrients,
                      sediment, animal wastes, and pesticides are the primary nonpoint source pollutants from agricultural
                      lands. Nutrients are considered to be the most damaging to the Chesapeake Bay. The forms of
                      nutrient transport to receiving waters is diverse.

                          Commercial fertilizer and manure contain the nutrients, nitrogen, phosphorus, afid potassium,
                      to promote crop growth. However, not all nutrients in fertilizer are used for plant growth. Often
                      there are more nutrients than are needed for a crop in a season, and some forms of the nutrients will
                      not even be available for plant uptake. Nutrients not used by plants either remain in the soil or are
                      carried away by runoff.

                          In receiving waters, these nutrients have the same effect on aquatic plant life, spurring growth
                      of algae in the water column as well as growth of other aquatic vegetation. When this organic
                      material dies and is decomposed by bacteria, oxygen is consumed, reducing the dissolved oxygen
                      available for higher order organisms. Increased turbidity in the water caused by excess algae can
                      reduce sunlight penetration, thereby affecting submerged aquatic vegetation (SAV). Destruction of
                      the SAV eliminates the food source and habitat for small and juvenile fish and can disrupt the food
                      chain.


                          Nitrogen and phosphorus are available in soluble or particulate and organic or inorganic forms.
                      Whether carried by stormwater in a soluble form or attached to sediment, both nitrogen and
                      phosphorus can undergo chemical transformations in transport. Therefore, it is very difficult to
                      correlate the nutrient chemical form at the source to what appears in the receiving water. Inorganic
                      nitrogen and phosphorus are more readily available for uptake by algae. Although the growth-
                      death-decay process presents the biggest problem for the aquatic environment, some forms of
                      nitrogen can be toxic to both aquatic animals and humans. Ammonia is toxic to fish even in low
                      concentrations, and nitrate, when converted to nitrite after ingestion by humans, can cause
                      methemoglobinemia, a potentially fatal condition for infants.




                                                                     2 - I








                            Generally speaking, nitrogen is the limiting nutrient in marine environments, while phosphorus
                       is the limiting nutrient for freshwater systems. In the absence of the limiting nutrient, plant growth
                       is supported only by normal background levels of the nutrient in the water column. Introduction of
                       the limiting nutrient to the receiving water by runoff can lead to an explosion in plant growth.

                            Sediment can have a number of effects on the aquatic environment. As it settles ill the
                       receiving water, it covers up SAV and fish spawning areas. In suspension it, like algae, reduces
                       penetration of sunlight to the plant life at the bottom. It also can clog fish gills and filters of
                       shellfish. As a particulate substance, other pollutants can adsorb onto sediment particles to be
                       transported from the source to the receiving water.

                            Pesticides are designed to prevent damage to crops by insects and by other undesirable plants.
                       These chemicals kill, repel, or alter reproductive cycles of unwanted pests. They also can be toxic
                       to animals, including aquatic life. Small quantities may have serious effects on lower order
                       organisms. However, through bioaccumulation, in which a chemical accumulates in the tissue of
                       higher order organisms feeding on contaminated lower order organisms, chemical effects can be
                       transferred up the food chain.



                       Z1.2      Suburban Land Use.


                            The primary pollutants associated with the suburban environment are nutrients, organics,
                       suspended solids, hydrocarbons, and heavy metals. Nutrients, organic material, and suspended
                       solids are primarily the result of property development and maintenance for many small individual
                       properties, as opposed to the large properties in agricultural use. Hydrocarbons and heavy metals
                       are related to automotive traffic as people travel within urban areas. Because there are many
                       individually owned properties in urban areas, most stormwater management methods are very
                       different than those for agricultural land use.

                            Much of the nutrients in suburban storrilwater runoff come from fertilizers applied to
                       homeowner lawns. It is fair to say that most homeowners who maintain their lawns are not trained
                       in proper methods of fertilizer application. As a result, excess fertilizer is available for transport to
                       receiving waters by stormwater runoff. Atmospheric deposition of nutrients onto impervious
                       surfaces has also been identified as a source for nitrogen and phosphorus.

                            Organic material comes from the accumulation of leaves, grass clippings, animal waste, and
                       other yard debris. If this material is not properly disposed of, it will often find its way to the storm
                       drain system. After it is carried in runoff through the storm sewer, it decomposes in the receiving
                       water, consuming dissolved oxygen in the water needed by other aquatic life.

                            Suspended solids are associated with erosion stemming from construction activities. Most
                       undeveloped land on which new construction will occur lies in suburban areas. Although erosion
                       and sediment controls are required for construction sites by government regulations, improperly
                       maintained controls still lead to suspended solids carried in stormwater runoff. Smaller construction
                       or maintenance activities conducted by homeowners are infrequently inspected by local officials and
                       can result in delivery of suspended solids to receiving waters.

                            Hydrocarbons are found in all urban environments and represent the most significant difference
                       between agricultural and urban runoff. These contaminants are found in high concentrations where


                                                                         2 - 2








                       there is a large volume of traffic. Major thoroughfares, parking lots for shopping areas, and
                       automotive service and gas stations have the highest incidence of hydrocarbons in suburban areas
                       (Schueler, 1994). Secondary roads in residential neighborhoods typically do not accurnulate many
                       hydrocarbons because they are not used as frequently by motorists and generally support traffic only
                       from the nearby homes.

                            Heavy metals are also an indicator of automotive use, but these appear more where there is a
                       good deal of stop-and-go traffic. While present in the suburban environment, heavy metals are
                       more problematic in the ultra-urban environment and will be discussed in the following section.



                       2.1.3     Ultra-Urban Land Use.


                            The primary pollutants associated with the ultra-urban environment are hydrocarbons, heavy
                       metals, suspended solids, animal wastes, and litter. Hydrocarbons and heavy metals appear as a
                       result of vehicular activity, but in greater concentrations than in suburban areas because of a higher
                       concentration of traffic. Suspended solids, animal wastes, and litter are not necessarily more
                       prevalent than in suburban land uses.      However, because there is a much greater degree of
                       impervious area in densely developed downtown districts, these pollutants are carried in runoff,
                       with fewer greenspaces available to filter the runoff stream.

                            Hydrocarbons and heavy metals are both deposited to a greater degree in areas where there is
                       much stop-and-go traffic and where cars are parked. Because downtown areas are more congested
                       than other areas and have a higher concentration of traffic signals, vehicles at lower average speeds
                       spend more time on each linear section of road surface than on roads where they can move more
                       freely. This extra time allows for additional deposition of pollutants. In downtown parking lots or
                       on-street parking areas that serve retail businesses, vehicles have frequent turnover.        In such
                       conditions more oil and other fluid drippings are deposited to the ground while vehicles are warm.

                            Heavy metals are also more prevalent on road and parking lot surfaces in the ultra-urban
                       environment. Automotive traffic has been identified as responsible for over fifty percent of copper,
                       cadmium, and zinc in urban runoff streams (Schueler, 1994). Copper, which can be acutely toxic to
                       aquatic organisms, originates from brake pad wear. Atmospheric deposition, of which autornobile
                       emissions are a source, is also a contributor to copper loadings in urban runoff. Cadmium and zinc
                       appear as the result of tire wear.

                            Lead, chromium, silver, and mercury in runoff are also attributable to vehicular activity.
                       Unlike copper, cadmium. and zinc, which are deposited directly and immediately to the pavement
                       surface, these other metals appear as a result of atmospheric deposition originating in large part
                       from diesel automobile emissions (Schueler, 1994). Many of these pollutants can also appear as the
                       result of industrial activity, if there is such activity occurring in a particular downtown area.
                       Although not the focus of this study, industrial areas can sometimes constitute an ultra-urban
                       environment themselves.


                            Animal wastes are   the result of both pet and bird droppings. Litter occurs not only as an
                       intentional discarding of waste but also from overflowing trash receptacles. Suspended solids can
                       come from a myriad of sources in the ultra-urban setting. All three of these pollutants, however,
                       reach the receiving waters because the ultra-urban environment provides few filtering mechanisms.
                       In other land uses suspended solids and animal wastes in small quantities can be trapped by grass or



                                                                       2 - 3







                         other vegetation. Litter is generally heavy enough to resist very light stormwater flows. but man-
                         made drainage patterns create shallow concentrated flows capable of transporting litter.


                         2.2 Effects of Ultra-Urban Pollutants on the Aquatic Environment.

                              Studies on the effects of pollution from stormwater runoff on the aquatic environment are
                         limited. This is primarily due to the difficulty in simulating the episodic nature of storm events
                         rather than a lack of biotoxicity research.         Laboratory studies that investigate the effect of a
                         contaminant on a particular species perform either chronic or acute toxicity tests. Chronic toxicity
                         tests introduce the contaminant in a low concentration and record the long-terrn biological and
                         behavioral effects on the species. Acute toxicity tests examine the short-term effects of a stronger
                         concentration of the toxicant.


                              Delivery of stormwater runoff, however, will result in a pollutant spike in the receivine water
                         that is quickly diluted by the comparatively large volume of the receiving water. The spike is a
                         result of first flush runoff, in which the majority of the pollutants on the ground surface are        "'.ashed
                         away in the beginning stages of a storm event. Although the degree of dilution depends on a
                         number of variables, it is usually significant and rapid enough to limit the duration of exposure to an
                         organism such as to rule out acute toxicity exposure. For certain specific habitats, such as a
                         permanently inundated wetland for a juvenile fish species, the physical extent of the habitat may be
                         limited, and the organism might not be able to avoid a toxic runoff stream. Storm events and
                         pollutant delivery are too sporadic to be considered chronically toxic.

                              Despite the lack of data on the specific effects of stormwater runoff pollution, it is generally
                         accepted in the scientific field that these pollutants do have some biological and behavioral effects
                         on aquatic organisms. Assuming this to be the case, it is important to identify the potential fate of a
                         contaminant during its delivery from source to receiving water. One must also consider those
                         chemical forms of the contaminant that are bioavailable to aquatic species. Because many forms of
                         an individual pollutant might not be toxic in the aquatic environment, it is more appropriate to
                         concentrate on only those that can have a detrimental effect on a species.


                         2.2.1     Heavy Metals.

                              Heavy metals are found in the aquatic environment in a variety of chemical forms. Not all of
                         these forrns are bioavailable, and therefore toxic, to aquatic organisms. Additionally, the three
                         major taxonomic groups, fish, invertebrates, and aquatic plants, and even species within these
                         groups, exhibit varying responses to different contaminants. To detail the effects of the many
                         chemical forms of metals on the many aquatic species is beyond the scope of this study. Rather, it
                         will point out those chemical forms that are most consistently toxic to a number of species.

                              According to Welch (1980), the toxicity of heavy metals to aquatic life depends in a general
                         sense on the solubility of the compound in which it is bound. Insoluble or low-soluble compounds
                         are not readily available for uptake by aquatic organisms and therefore are not a direct threat to
                         biota. Soluble compounds are readily available for uptake, but the ionized form of the metal does
                         not move easily across membrane surfaces and is therefore not a direct threat to the organism.
                         Compounds of intermediate water solubility appear to be the most toxic to aquatic organisms.
                         Metal complexes with organic material are easily taken up and cause high body concentrations even



                                                                             2 -4







                       when the concentration of the metal Is low in the water. It is also important to note that niany inetal
                       forms that are toxic to aquatic life do not appear that way in stormwater runoff, but rather are the
                       result of biological ly-mediated reactions or other chemical reactions in the receiving water or tile
                       bottom sediments.


                            Herricks et at (1994) identified a wide range of toxic effects that heavy metals may have oil
                       Integrative ecosystem responses, including lethal, sublethal, and bioaccumulation effects. Extreme
                       sensitivity to particular metals can result in the elimination of a species, which Would not only
                       reduce the biodiversity of an ecosystem but could also create an imbalance in tile food web
                       structure. Metals are toxic at several levels in the biological hierarchy, which includes enzymes,
                       cells, organs, organ-systems, and organisms. In many species enzymes are created that bind metal
                       cations so as to inhibit any toxic effects. Once the metal concentrations overtake the enzyme
                       production, however, the metals become toxic to individual cells and can have severe detrimental
                       effects on organs and organ-systems.

                            The sublethal effects of metals can be felt within the ecological hierarchy, from organism to
                       species/population to community to ecosystem. Basic physiological functions, such as heart rate,
                       respiration and ventilation rate, muscular movement, and metabolically derived bioluminescence,
                       can be altered as can the growth of an organism. Subtle changes in organism behavior can also
                       effect its survival. Changes in swimming pattems and predator avoidance in individual organisms
                       and dispersal and migration of communities have been noted due to toxic levels of heavy metals.
                       Genetic diversity can also be altered by metal toxicity.

                            Kadlec and Knight (1996) and URS Consultants, Inc (1995) have detailed in their respective
                       studies the chemical forms of heavy metals found in receiving waters and their potential effects on
                       aquatic life.   Some heavy metals serve as micronutrients for aquatic biota in very low
                       concentrations. Copper and zinc assist in the growth of aquatic animals and plants and chromium
                       assists in the growth of animals. However, at slightly higher concentrations, copper and zinc
                       become toxic to many aquatic species. Cadmium, lead, mercury, and silver are also toxic to aquatic
                       life at low concentrations.


                       2.2.1.1   Cadmium.


                            Cadmium is most often found in its divalent state, Cd(II), in surface waters and IS Most Soluble
                       at low pH levels. In its ionic state it is bioavailable. It is also found as a complexed, soluble
                       compound that can be easily adsorbed onto organic particulates and become biologically
                       unavailable.   There is conflictinc, information as to whether cadmium has the potential to
                       bioconcentrate in aquatic organisms. The toxic effects of cadmium are acute mortality, reduced
                       growth, and inhibited reproduction.


                       2.2.1.2 Chromium.


                            Chromium can be found in its trivalent, Cr(Ill), and hexavalent, Cr(VI), states in surface
                       waters, although Cr(VI), which is the more toxic form, is chemically unstable and converts to
                       Cr(111) where organic material is present. Because Cr(111) hydroxides and chlorides are relatively
                       insoluble, they are not bioavailable to aquatic life. There is a wide range of sensitivity to chromium
                       but little evidence of biornagnification among animals. Mortality and decreased growth have be-In
                       attributed to exposure to chromium. These effects are more commonly found in plants than fish.




                                                                       2 - 5








                       2.2.1.3 Copper.

                            Copper occurs in surface waters as chelated compounds of Cu(I) and Cu(II). When complexed
                       with hydroxides, phosphates, sulfides, or carbonates, copper is insoluble and easily transported to
                       sediments, but it is relatively soluble when chelated with certain organic compounds. At very low
                       levels copper is a micronutrient necessary for protein synthesis. It is often used as an algicide
                       because it is toxic at low levels to some forms of algae, but not to most macroinvertebrates or fish.
                       However. changes in growth and smoltification, the physiological changes in fish in preparation for
                       the transition from freshwater to saltwater, have been noted in some fish species.


                       2.2.1.4 Lead.


                            Lead is found in surface waters in its divalent state, Pb(II). It is not bioavailable, except under
                       reducing conditions, because it readily forms insoluble salts and its ionic form is adsorbed onto
                       particulates suspended in the water column. While plants seem to be relatively insensitive to lead,
                       other organisms, especially gastropods, are sensitive to it. When biologically available, though, it
                       can biomagnify in aquatic organisms.


                       2.2.1.5   Mercury.

                            Mercury is found in three primary oxidation states. Elemental Hg(O), found in reduced
                       sediments, is volatile and easily transported throughout the environment.           Hg(I) is relatively
                       insoluble, whereas Hg(II) is soluble. Mercury is most toxic when methylated by bacteria in an
                       anaerobic environment, but this form is not abundant.


                       2.2.1.6 Silver.


                            Silver is the most toxic heavy metal and is toxic to all organisms, although plants seem to be
                                                                                         C@              Z@
                       less sensitive than animals. The monovalent form, Ag(I), is found in surface waters. As an
                       insoluble sulfide or when adsorbed onto organic matter, silver is not bioavallable.


                       2.2.1. 7 Zinc.


                            Zinc is a micronutrient essential for respiratory function in animals and for plant
                       photosynthesis and DNA synthesis. At more concentrated levels zinc becomes toxic, but aquatic
                       organisms show a wide range of sensitivities to it. It is most commonly found in surface waters in
                       its divalent state, Zn(11), where it forms ionic hydrates, carbonates, and complexes with organics,
                       and highly insoluble sulfides. Zinc does not biomagnify in aquatic organisms.


                       2.2.2     I-Iydrocarbons.

                            Petroleum hydrocarbons derive from oil products. In the ultra-urban environment, the primary
                       source of hydrocarbons is from drippings from automotive vehicles. Oil and grease contain many
                       different hydrocarbon compounds. A hydrocarbon is a compound of hydrogen and carbon. The
                       most commonly studied hydrocarbons in environmental engineering are polynuclear aromatic
                       hydrocarbons (PAHs), which possesses several fused benzene rings and are composed onk: of
                       carbon and hydrogen. PAHs are the result of incomplete combustion of organic compounds with
                       insufficient oxygen (URS Consultants, 1995).



                                                                        2 - 6







                            Hydrocarbons have a low water solubility, particularly those of higher molecular weight. Foi-
                       this reason, hydrocarbons are difficult to detect in water, and results of water quality studies often
                       show PAHs below detection limits (URS Consultants, 1995). Hydrocarbons tend to adsorb to
                       particulate material and settle to the sediment layer.      In this layer hydrocarbons can persist
                       indefinitely and have a continuing effect on benthic organisms. Some m 1croorIgan isms have the
                       ability to decompose hydrocarbons, but there is usually insufficient oxygen in tile sediment layer to
                       sustain such activity.

                            Many PAH compounds are known carcinogens and are very toxic to aquatic animals. While
                       finfish appear to have the ability to assimilate hydrocarbons in tissues to some degree, shellfish do
                       not have this capacity to the same extent. Because of the potential for accumulation in shellfish,
                       consumption poses a health risk for humans. There are a number of symptoms of exposure to
                       PAHs, including diminution of immune system activity, tumors and lesions, and organ tissue
                       erosion.



                       2.2.3    Animal Wastes and Other Organic Material.

                            Organic material originating from the ultra-urban environment has the same effect on the
                       receiving water as from any other land use, but to varying degrees. As organic material is
                       decomposed by microorganisms, dissolved oxygen is used. The risk for the aquatic environment is
                       that excessive decomposition of the material could result in oxygen deprivation of other organisms.

                            There are fewer animals and less vegetation in downtown areas, but where animal waste and
                       dead leaves are deposited to the ground in this environment, there are fewer spaces with vegetative
                       cover on which the material can collect and decompose. With no other place to go, this material is
                       washed into the storm drain and into the receiving water.

                            Pathogens present in animal wastes pose an additional danger to the aquatic environment.
                       Bacterial contamination has led to restrictions on shellfish harvesting in a number of areas in the
                       United States. High bacterial levels can also limit recreational use of waterways by humans.


                       2.Z4      Suspended Solids.

                            Suspended solids carried in stormwater runoff usually originate from construction sites. In an
                       extensively developed downtown area, there are fewer opportunities for new development, so the
                       sources for suspended solids are more limited. As is the case for animal waste and organic material,
                       however, there are few opportunities for trapping these solids before they are carried to the
                       receiving water. Therefore the amount of material that reaches the receivincy water can be as much
                       as that in suburban areas where more construction activity occurs.

                            Erosion and sediment controls are required for construction sites in downtown areas, just as for
                       suburban construction. Proper controls will greatly reduce solids carried in stormwater runoff.
                       Also, downtown areas are more often targeted for street sweeping measures in order to keep the
                       central business district clean. Many of the sediments that accumulate on the streets and in the
                       gutters are removed by street sweeping and prevented from entering the storm drains.





                                                                       2 - 7








                            Suspended solids cause the same problems found in water bodies draining agricultural land
                       uses. In the water column it can clog fish gills and shellfish filters and reduce penetration of sunlight
                       to the plant life at the bottom. As it settles to the bottom, it covers SAV and fish spawning areas.
                       Suspended solids also serve as a vehicle for transport of other pollutants that adsorb to the
                       individual particles.



                       2.2.5     Litter.


                            Litter is more of an eyesore than a significant threat to the aquatic environment. It can liann
                       aquatic animals through ingestion and can disturb the habitats of certain plants and animals as it
                       accumulates on the bottom or on the shoreline. Ironically, despite the relative insignificance of
                       litter as an environmental threat, it is the high visibility to humans that raises the consciousness of
                       pollution problems in receiving water bodies.



                       2.3 Mechanics for Ultra-Urban Pollutant Removal.


                            It is physically possible to remove nearly every pollutant in ultra-urban stormwater runoff to
                       satisfy current water quality standards. However, it is not economically feasible to construct the
                       equivalent of a small wastewater treatment facility at every outfall, which is what would be required
                       to remove all of these pollutants. The function of ultra-urban BMPs is to remove, in an economical
                       fashion, those pollutants of the highest concem for water quality. Conventional BMPs rely on
                       natural chemical and biological processes to remove pollutants as they settle out in a quiescent
                       environment. Ultra-urban BMPs must use a different technology to remove a somewhat different
                       set of contaminants, while at the same time conserving space.



                       2.3.1     Conventional BMPs.


                            The three basic mechanisms used to treat stormwater runoff are detention, infiltration, and
                       filtration. Most conventional BMPs rely on detention and infiltration, although some use filtration.
                       All ultra-urban BMPs use filtration as its primary mechanism for pollutant removal.

                            Detention facilities impound stormwater runoff to reduce flow velocities. When the velocity of
                       a flow is relatively low, there is not enough energy to keep particles in suspension.               These
                       suspended solids, and any pollutants adsorbed onto these particles, will settle to the bottom of the
                       basin, where they accumulate over time. Nutrients in the runoff flow will nourish the vegetation
                       that grows on the bottom and the banks of the basin. Other pollutants can be assimilated by both
                       aquatic plants and animals.


                            Most detention basins have two or more outlet structures. One is a smaller orifice or weir that
                       detains a certain volume of runoff and releases it at a controlled rate. It is possible to have more
                       than one of these control devices. The other primary outlet structure is a larger spillway that serves
                       as an overflow device to prevent flooding of the surr      ounding area. Detention facilities can be
                       designed to have a permanent pool or to remain dry during dry weather. Those that have a
                       permanent pool are generally called wet ponds and have a volume of water whose surface level is at
                       the bottom of the lowest outlet structure. Figures 2- ](a) and 2-1 (b) show two detention basins with
                       permanent pools. These facilities are commonly called wet ponds.


                                                                         2 - 8














                                                                                         77     7



                                                                                        7


                                                                                                     "92;
                                                                                                '7





                      Figure 2-1(a).    Stormwater wet pond at the              Figure 2-1(b).   Stormwater wet pond at the
                      Hampton Roads Regional Jail in Portsmouth.                Middletown Arch subdivision in Norfolk.


                           Infiltration facilities divert stormwater   runoff to percolate into the ground, where natural
                      filtration and biological processes can occur.   Infiltration is a viable alternative only when soils are
                      permeable and when the groundwater table        is far enough below the structure to allow a natural
                      filtration process. If the water table is too high, there is a risk of contamination of the groundwater
                      from the stormwater runoff.


                           Filtration in conventional BMPs is usually an attempt to approximate, or even enhance, a
                      naturally occurring infiltration process. The most common conventional filtration BMP is the filter
                      strip, or biofilter. This type of filter includes a vegetative layer of grass and other plants on the
                      surface, with an underlying layer of sand to promote filtration. Perforated collector pipes are often
                      included beneath the sand layer to collect the filtered runoff and reroute it to the storm drain. Other
                      designs simply allow the water to percolate into the ground.



                      2.3.2      Ultra- Urban BMPs.


                           Ultra-urban BMPs are designed to filter runoff in a confined area. Sand is usually the medium
                      of choice, although some BMPs use peat or compost, or a combination of media. To save space the
                      filter is located underground, most often in a self-contained concrete vault. The structure can then
                      be designed to accommodate any type of activity above it on the ground surface. Most commonly,
                      the area above the filter structure is used for parking, but the BMP can also be incorporated into a
                      building design.

                           If the filter is contained completely underground, there can be no comprehensive use of
                      vegetation as a natural pollutant filter because there is insufficient sunlight for the plants. Filters
                      using peat or compost must have a vegetative surface, usually grass, and in order to have exposure
                      to sunlight, must be located above ground. Storage of the Water Quality Volume (WQV), the first
                      flush of stormwater runoff that is most heavily laden with pollutants, can occur underground,
                      however, as it awaits transport to the filtering portion of the structure.

                           Most ultra-urban BMP designs also include a sedimentation chamber at the front end of the
                                                                                        - @ W4@
















                      structure to allow heavier suspended solids to settle out of the runoff stream before reaching the
                      filter section. Suspended solids, if not removed before filtration, can cause premature clogging of


                                                                         2- 9








                               the filter media. Some designs also provide a water seal, accomplished through use of a concrete
                               baffle, to trap hydrocarbons on the surface of the sedimentation chamber. This oil and grease must
                               be periodically removed from the water surface or it will remain indefinitely.



                               Z3.3          The CarbonlSand Filter.


                                      The Carbon/Sand Filter uses three mechanical processes by which to remove pollutants from
                               the runoff stream: sedimentation, mechanical straining, and adsorption. Figure 2-2 shows a
                               schematic drawing of the Carbon/Sand Filter that illustrates the different process chambers through
                               which the stormwater must flow. This BMP, like most ultra-urban BMPs, is designed as an off-line
                               facility, so that the WQV will pass through the structure but much of the stormwater flow will be
                               diverted to the primary storm drainage system. Chapter 3 will discuss more comprehensively the
                               design features of the Carbon/Sand Filter.







                                                                                                                                                       ACCESS MANHOLE





                                                                              ACCESS GRATE COVERS                                                      11" PVC DEWATERING
                                                                                                                                                       DRAIN WITH GATE VAL
                                                                  STRUCTURAL CONCRETE
                                                                         VAULT

                                                                                                                                                               0
                                                                                                                                                                 TFLOW TO
                                                                                                                                                                U
                                                                                                                                                               STORM SEWE


                                               ACCESS MANHO
                                                                                                                                                         CLEARWELL
                                                                                                                                                         CHAMBER
                                                                                                                    . .. . . .. .. .
                                                                                                                                                   0" PERFORATED PVC
                                                                                                                                                   COLLECTOR PIPE IN
                                                                                                                                                   8" GRAVEL BED

                                                                                                                                        10"-24" SAND FILTER BETWEEN
                                                                                                                                        GEOTECUNICAL FILTER CLOTH LAYERS

                                                                                                                           SELF-CONTAINED "PILLOW" OF
                                                                                                                           ACTIVATED CARBON, DESIGNED
                                                                                                                           FOR EASE OF MAINTENANCE

                                    FIRST 1/2- OF RUNOFF (WQV)                                                     DIVIDER WALL TO CREATE
                                    FROM FLOW SEPARATOR                                                            TWO TEST CHAMBERS

                                                                                                    INSPECTION WELL/CLEANOUT
                                                                                                    PIPE WITH WATERPROOF CAP

                                                                                 SEDIMENT CHAMBER WITH
                                                                                 WATER SEAL TO
                                                                                 TRAP HYDROCARBONS




                               Figure 2-2. Schematic of the Carbon/Sand Filter.


                                      Sedimentation occurs in the sedimentation chamber that holds most of the WQV as it awaits
                               treatment by the filter media. The water volume must pass through a layer of filter fabric, designed
                               to remove larger particles and trash that were not trapped in the sedimentation chamber, that lays on
                               top of the filter bed. The filter bed consists of six inches of activated carbon, to which soluble
                               metals and organic material can adsorb, and twelve inches of sand, which mechanically strains
                               particulate material from the stormwater flow.




                                                                                                  2- 10









                       2.3.3.1 Sedimentation.


                            Sedimentation is the, process used to remove particulate material from a liquid solution. Any
                       suspended particles that are heavier than the solution, in this case water, settle downward by
                       gravitational forces. The smallest size particle that will settle depends largely on the amount of
                       energy of the flow stream. The energy created by stormwater flow into the filter structure will cause
                       the resuspension of most of the particles that have settled on the chamber floor in previous storms.
                       As seen in Figure 2-1, there is a significant elevation difference between the permanent pool in the
                       sedimentation chamber and the invert of the pipe that channels stormwater flow into the structure.

                            There is a concrete baffle, a wall with a rectangular opening at the bottom, that serves as an
                       energy dissipater in the sedimentation chamber. While particles are continually resuspended by the
                       turbulence in the front portion of the chamber, the back side of the chamber remains relatively
                       quiescent. The chamber as a whole prevents larger particles from flowing over the spillway into the
                       filtration chamber.


                            The sedimentation chamber must be periodically cleaned to prevent excessive buildup of
                       sediments. If too much sediment remains in this chamber, it is more likely that it will pass through
                       to the filtration chamber.


                       2.3.3.2 Filter Fabric.


                            The filter media in the filtration chamber is covered with a layer of filter fabric (not shown in
                       Figure 2-2), which allows the passage of water flow and most particulates but traps larger objects on
                       the surface. Most street litter and leaves that will make their way into the storm drain and then the
                       BMP are light material, the litter usually a paper product, and are easily carried by the runoff
                       stream. In the turbulent environment of the sedimentation chamber, they can pass under the baffle
                       and float to the surface on the back portion of the chamber. They then pass over the spillway and
                       onto the filter surface.


                            Excessive amounts of this debris can cause premature clogging of the filter. The filter fabric
                       represents a planned-failure plane, where the potential for this type of clogging is recognized, and
                       the design accounts for maintenance needs. In the Carbon/Sand Filter maintenance crews can
                       simply lift out the filter fabric with the debris on its surface and replace it with another piece of
                       fabric. This type of periodic maintenance is much simpler than removing debris from the filter
                       media itself, having to scrape away layers of sand or activated carbon and then replacing them.


                       2.3.3.3 Sand.


                            In the Carbon/Sand Filter the top portion of the filter, with which the stormwater will come into
                       first contact, is the activated carbon, and the lower medium is the sand. This order was chosen for
                       ease of maintenance, so that the activated carbon could be easily maintained and manipulated for
                       testing purposes. It would be more appropriate to have the sand layer on the top to perform
                       mechanical straining of particulate matter, and the activated carbon layer below it to remove soluble
                       contaminants through adsorption. For illustrative purposes, it is easier to explain the pollutant
                       removal processes by discussing the sand filter medium first.

                            Sand filtration has been used in water and wastewater treatment for over one hundred years. In
                       a sense, the Carbon/Sand Filter is treating a wastewater stream, and this BMP is serving as a small,



                                                                      2- 1 1








                       crude wastewater treatment facility. The primary mechanism for pollutant removal by sand is the
                       use of meniscus forces to trap larger particles in tile pore spaces between sand grains (Knutson,
                       1994). The void space available to hold this particulate matter is limited. As the upper region of the
                       sand layer fills with particulates, the burden to remove additional particles from the storniwater
                       stream falls to lower regions of the sand layer that still have free void space. Eventually, all void
                       space will be used up. and breakthrough, when no further filtration is possible. will occur.

                           An ancillary treatment process that occurs during sand filtration is biological treatment.
                       Bacteria present in the sand layer are capable of removing organic material from tile stormx%ater
                       stream. The stormwater actually serves as the substrate, or food, for these microorganisms. As long
                       as there is a sufficient food source and sufficient oxygen, the bacteria will thrive until they die
                       naturally. Because of the intermittent nature of storm events, however, there is not a steady stream
                       of substrate on which the bacteria can feed.


                           Conversely. there have been some reports of sand filters containing a permanently inundated
                       sand layer that offered a proper aerobic environment with a substrate abundance but that
                       subsequently became anaerobic as the dissolved oxygen was used up by the microorganisms (Bell,
                       1994). This process of nitrification and denitrification is important in wastewater treatment in the
                       conversion of ammonia to nitrogen gas. However, it is unrealistic to assume that biological
                       treatment is sustained for long periods in ultra-urban BNTs unless such treatment is planned and
                       accounted for in the structure design to provide a continuously proper living environment for the
                       microorganisms.


                       2.3.3.4 Activated Carbon.


                           Activated carbon, like sand, is also used in water and wastewater treatment. The primary
                       purpose in both treatment processes is to remove soluble organic matter from tile water. In water
                       treatment, filtration systems can only remove organic material to a degree. The remaining material,
                       however, even at low concentrations, can cause taste and odor problems in drinking water, and in
                       some cases can lead to.toxic disinfectant byproducts, such as trihalomethanes. In wastewater
                       treatment, activated carbon is used as a polishing agent to further remove soluble organic rnateriai
                       before the treated wastewater is discharged back to the environment.

                           Activated carbon can remove this dissolved material because of its superior adsorptive
                       capacity. Adsorption using activated carbon occurs at the liquid-solid interface and is the process of
                       collecting a soluble substance, in solution, on a solid surface. The best adsorptive products are
                       those that provide the most surface area. In the case of activated carbon, carbonaceous material,
                       such as nut shells, wood, and coal, is heated to a red heat with insufficient oxygen to sustain
                       combustion. The material is then activated by introducing an oxidizing gas, which creates a very
                       porous structure inside the char. The activated carbon, therefore, has a very high internal surface
                       area for a relatively small amount of material. Activated carbon can have a surface area of up to
                       1400 square meters per gram (Nyer, 1992).

                           Adsorption is a mass transfer process that occurs in three steps (see Figure 2-3). The first step
                       is the advection and diffusion of the molecule through the liquid phase to tile solid phase, or tile
                       carbon surface. The second step is the diffusion of the molecule through the macropore system of
                       the carbon to the adsorption site within the micropores. The final step is the adsorption of the
                       molecule, the adsorbate, onto the carbon surface, the adsorbent.




                                                                     2 - 1 2








                          According to Nyer (1992), the adsorption step can occur as a physical or chemical process. In
                     physical adsorption a molecule is held at the solid surface by the surface tension of the solid.
                     Chemical adsorption involves the actual chemical bonding of a molecule at the solid surface.
                     Adsorption to activated carbon is a physical process.










                                                                             Macropore
                                                           0
                                                             0                  T
                                                              0              t6cropore


                                                             0 0           A     Area available to both
                                                                0 0 k'      ""Nk adsorbates and solvent
                                                             0      0         -i                Area available only to
                                                                                                solvent and smaller
                                                                                                adsorbate




                                                                   0             0
                                                                0 C
                                                                    0                               Area available
                                                                                              T@>- Gray no solvent

                                                             0-









                     Figure 2-3.   Internal structure of activated carbon (Adapted from Nyer, 1992).


                          Molecules can adsorb to the macropore surfaces of the carbon particle as well as to the
                     micropores, but the degree of adsorption at these sites is relatively small compared to that in the
                     micropores. As shown in Figure 2-3, larger molecules cannot penetrate the micropore structure as
                     can smaller molecules. Kinetics of the adsorption process are dependent on certain characteristics
                     of the molecules. Large molecules move more slowly through the micropores, and the adsorption
                     process is slower. Less soluble molecules will adsorb more quickly to the carbon surface.

                          Activated carbon products come in two forms, granular activated carbon and powdered
                     activated carbon. Granular activated carbon is approximately the same consistency as sand. The
                     product used in this study was Filtrasorb 300, a granular activated carbon product provided by
                     Calgon Carbon Corporation, Inc. Calgon Carbon reports that this product is effective in removing
                     benzene and toluene, two organic components associated with automotive fluids, as well as other
                     many other dissolved toxic organic chemicals (Calgon Carbon Corporation, Inc., 1988).




                                                                  2- 13











                                        3.0 SYNOPSIS OF THE CARBON/SAND FILTER PROJECT





                       3.1 Problem Identification.


                            The original plan to develop the Carbon/Sand Filter was conceived out of the need to
                       encourage the use of stormwater management BMPs in the downtown Portsmouth area. The City of
                       Portsmouth applied for a VPDES Municipal Stormwater Discharge Permit in May, 1993 and in it
                       proposed a Stormwater Management Program through which to comply with the federal regulations
                       of the Clean Water Act. The City began to implement many elements of the Program upon
                       submittal of the Permit application. To fund the Program, a Stormwater Management Utility was
                       created, whereby each property ox%.mer would pay for his property's contribution to stormwater
                       runoff.


                            With the creation of the Stormwater Management Utility came increased expectations from
                       both private citizens and business owners for practices to control pollution in stormwater runoff.
                       Conventional BMPs, structural and non-structural, are relatively easy to plan in suburban areas.
                       New requirements have been made of developers to implement BNTs at new construction sites.
                       Where there is ample space, large borrow pits and lakes are being retrofitted as regional BMPs for
                       existing developments to provide pollution control. Erosion and sediment controls, street sweeping,
                       and other programs are also used to reduce the contaminants that can be transported by a runoff
                       stream.


                            The central business district, however, poses a unique problem in planning for conventional
                       BUTs. In the City of Portsmouth, as in many core urban areas, the central business district is
                       almost completely developed with no space left for detention, infiltration, or other similar facilities.
                       The argument can also be made that such facilities do not fit aesthetically into this ultra-urban
                       landscape. High property values further preclude the use of conventional structural BUTs in the
                       downtown area. It is simply not economically prudent to allocate such expensive land toward a
                       detention basin when the 'land could be used to expand the footprint of a multi-story building.
                       Under certain circumstances such a difference in land use might determine the long-term
                       profitability of the development.

                            The Carbon/Sand Filter was the result of a brainstorm by the City of Portsmouth Public Works
                       Department to devise and fund an unconventional means of removing pollutants in runoff that
                       would also serve as a model BMP for future business development in the downtown area. With
                       incalculable support and technical assistance from local, state, and federal government agencies and
                       from a number of private companies, the City of Portsmouth showed that implementing a BMP in
                       the ultra-urban sector of a Hampton Roads community was a feasible alternative to conventional
                       BMPs.



                       3.2 BMIP and Site Selection.


                            Preliminary research revealed that a number of municipalities have been attempting to address
                       the same problems that Portsmouth is experiencing. Principal among these other localities were
                       Alexandria, VA, Washington, D.C., Austin, TX, and the state of Delaware. The City of Alexandria
                       inl993 prepared a document, "The Alexandria Supplement to the Northern Virginia BMP
                                                                         3-1







                      Handbook," compiling all known information for constructing unconventional ultra-urban BNTs.
                      This manual served as the starting point in the search for a demonstration BMP.

                           The City of Portsmouth considered for use in its downtown area all options included in the
                      Alexandria document. Two significant factors of Portsmouth's ultra-urban environment affecting
                      the decision were the relative flatness of the land and tidal intrusion in the storm drainage system.
                      Also, because there were no City-administered construction projects planned at the time for the
                      downtown section, the ultra-urban BMP had to be installed as a retrofit for an existing, City-owned,
                      developed property. It was assumed that the most appropriate site from which to remove a range of
                      ultra-urban pollutants would be a parking lot.

                           Ten different parking lots were considered for use for this project. Of these ten lots, four were
                      eliminated from consideration because they have no internal drainage structures, but rather sheet
                      flow to the adjacent City street. To install a new drainage system in one of these lots would have
                      made the project cost prohibitive. Three of the remaining lots are parking garages, for which it was
                      assumed that construction costs for a BMP structure would increase dramatically. One lot was
                      removed from consideration because of known flooding problems due to tidal influence.

                           The two remaining lots both appeared to be good candidates for a retrofit BNIP. One lot is
                      behind the City Hall building and contains 23 spaces, mostly for use by City vehicles (see Figure 3-
                      1). These spaces are for use by employees who need only temporary access to City Hall, and they
                      do not serve as permanent parking for these vehicles. The parking area has only a moderate degree
                      of turnover and is empty during the evenings and weekends. Stormwater runoff drains at a
                      significant slope to a curb line on one side of the lot, then to a catch basin in the curb, and to an
                      outfall to the Elizabeth River located approximately ten feet behind the curb line. The most
                      appropriate BMP for this site is the Delaware Sand Filter which is designed to be incorporated into
                      the curb and gutter drainage scheme. Figure 3-2 is a schematic drawing of the Delaware Sand Filter
                      design.









                                                                                                    Figure 3-1. Parking lot
                                                                                                    behind Portsmouth City
                                                                                                    Hall considered for the
                                                                                                    Delaware Sand Filter
                                                                                                    design. The catch basin
                                                                                                    that serves this lot is
                                                                                                    located    beside      the
                                                                                                    second vehicle on the
                                                                                                    right side.   The filter
                                                                                                    would be located in the
                                                                                                    grass area adjacent to
                                                                                                    the Elizabeth River.






                                                                       3-2







                                                                                                        Figure 3-2. Schematic
                                                                                                        of the Delaware Sand
                                                                                       STE4 GRATt
                                                                                                        Filter (City of Alexan-
                                                                                                        dria, 1993).




                                                                                ftWWCVV FAVEMEN'r'



                             lk@        ........
                                   @x "j@L'


                                       @"7
                                                                    . ...... ...


                                                             M'6

                             . ....... ..





                            The other site considered was an 83-space lot on High Street rented to private citizens working
                       in the downtown area (see Figure 3-3). The lot is nearly full during the week, but mostly empty in
                       the evenings and on weekends. Half of this lot, including 44 spaces, is paved with a significant
                       slope to a drop inlet in the middle of the lot. The other half of the lot, with 39 spaces, is gravel and
                       has little apparent slope in any direction. A ridge line separating the two halves seems to prohibit
                       flow from the gravel portion to the paved portion.


                                                          M                                             Figure 3-3. Parking lot
                                                                                                        on High Street consid-
                                                                                                        ered for the D.C. Sand
                                                                                                        Filter design. The left
                                                                      I'41                              half of the parking lot is
                                                               73
                                                                                                        asphalt with a drop inlet
                                                                                                        that can be seen just
                                                                                                        a
                                                                                                           ove the center of the
                                                                                                         b
                                                                             T
                                                                                                        photograph. The right
                                                                                                        half of the lot is gravel
                                                                                                        w
                                                                                                          ith no internal drain-
                                                                                                        age structures.








                       For this drainage scheme, a D.C. Sand Filter was considered to be most appropriate. Figure 3-4 is a
                       schematic representation of the original D.C. Sand Filter design, from which the Carbon/Sand Filter
                       structure was derived.






                                                                          3-3









                                                                                                      Figure 3-4. Schematic
                                                                                                      of the D.C. Sand Filter
                                                                                                      (City of Alexandria,
                                                                                                       1993).
                            Because of the volume of permanently parked cars at the High Street lot, it was deemed a better
                       site on which to construct the BMP. A field inspection revealed that there were considerably more
                       oil and grease spots on the High Street lot than on the City Hall lot, perhaps indicating that the
                       automobiles using the lot had not been serviced as regularly as are City vehicles. This was seen as
                       an opportunity to further clean up a hotspot for ultra-urban pollution. Finally, unlike the City Hall
                       lot, which is accessible to few people, the High Street lot is visible to those who either walk or drive
                       along this commercial corridor. As a demonstration project, a primary goal is to publicize the use of
                       a new technology to the maximum extent possible.

                            The High Street parking lot, although run by the City of Portsmouth Parking Authority, is
                       actually owned by the Portsmouth Redevelopment and Housing Authority (PRHA). The Board of
                       Commissioners for PRHA approved in the Spring of 1994 the use of this property for a stormwater
                       BMP.



                       3.3 Project Funding and Design Objectives.

                            At the time that the need for a demonstration BMP for an ultra-urban atmosphere was realized,
                       there were no additional funds available from the Stormwater Management Utility to finance the
                       project. City staff searched for another funding source and found the Virginia Coastal Resources
                       Management Program, administered by the Virginia Department of Environmental Quality (DEQ),
                       the most likely to give grant support to the project. A grant application was prepared in June, 1994.

                            Further research into the mechanics of a D.C. Sand Filter resulted in several modifications to
                       the original design to enhance its effectiveness for use in the City of Portsmouth. Staff from the
                       City of Alexandria conducted a tour of a number of BMPs within its jurisdiction and provided
                       insight for design alternatives based on some of their experiences with the BMPs. Discussions with
                       URS Consultants, Inc. led to the inclusion of activated carbon in the filter bed of the proposed BMP
                       to further remove a number of ultra-urban pollutants.



                                                                         3-4
 






                            URS Consultants, Inc. agreed to provide engineering services for the structural design of the
                       Carbon/Sand Filter as well as technical assistance in interpreting water quality monitoring results.
                       Tarmac America, Inc. offered to supply the project with 64 cubic yards of 5000 psi concrete for the
                       filter structure at a fifty percent reduced cost. It also donated 15 cubic yards of concrete sand to be
                       used as filter material in the BMP. Calgon Carbon Corporation agreed to supply 3000 pounds of
                       Filtrasorb 300 Granular Activated Carbon at no cost. The Hampton Roads Sanitation District
                       (HRSD) also donated staff time in collecting samples for analysis at its laboratory. The member
                       localities of the Hampton Roads Planning District Commission (HRPDC), through the Regional
                       Stormwater Management Committee, drafted a letter of support for the project, declaring their
                       interest in the results of the study.

                            The grant application, with evidence of corporate and public support, was submitted to DEQ
                       for funding from the 1994 Virginia Coastal Resources Management Program. Grant funding was
                       approved in the amount of $49,932 for the project to begin October 1, 1994 and to last for one year.

                            The objectives of the project as stated in the grant application were to: (1) increase the removal
                       of heavy metals, hydrocarbons, and other pollutants associated with ultra-urban runoff; (2) maintain
                       recognized efficiency for removal of suspended solids and nutrients that contribute to degradation of
                       the Chesapeake Bay; (3) reduce maintenance time and costs through planned-failure design; and
                       (4) provide a model BMP that can be used in urban areas both regionally and nationally.


                       3.4 Carbon/Sand Filter Design.

                            Once the site was selected for construction of the Carbon/Sand Filter, the site was surveyed by
                       the City to record the topographic features of the lot. Figure 3-5 is a planimetric drawing from the
                       City's Geographic Information System (GIS) that shows the configuration of the BMP within the
                       parking lot and the drainage system layout for the surrounding area. The survey information was
                       used in conjunction with the planimetric drawing to calculate the runoff volume to be treated by the
                       BMP. It was assumed that only the paved portion of the entire lot would drain to the BMP.

                            Also determined, using criteria defined by the City of Alexandria, was the appropriate size and
                       shape of the filter structure to fit within the profile of the existing storm drainage system. The
                       Carbon/Sand Filter was designed as an off-line facility that would treat the Water Quality Volume
                       (WQV), defined as the first half-inch of runoff from the impervious area of a drainage basin, and
                       allow for the flow of any additional volume to the primary storm drain. The paved lot is 65 feet
                       wide and 226 feet long. Equation 3-1 shows the calculation of the WQV.


                       WQV            ('/-.-in runoff) x (65 ft width) x (226 ft length) x (I ft/12 inch)        (Eqn 3-1)
                                      612 cubic ft



                            Appendix A-I shows the calculations for sizing the filter structure, using the worksheets
                       provided in the Alexandria Supplement to the Northern Virginia BMP Handbook (City of
                       Alexandria, 1993). The dimensions used in the calculations were subsequently changed slightly to
                       accommodate field conditions.






                                                                        3-5












                                                                 OUE  N       STREET






                                                ASPHALT                 MW- @RQ
                                                P@RKINC
                                                 11A
                                    V All
                                   IS" RH T
                                                                                            PAR@ NG AREA


                                                                                                                       ;zj


                                                              A, Z IC.
                           cc                                  rz-
                            ' /    '3'0    '; ......................
                          A R: N E

                                                   ..........





                                                          CAR=:%/SAND                           CENTRAL '1DEU-,1
                                                                                                BANK BUILDINC



                        --ECS
                         REST@




                                                                                                                 15,
                                              ........ .......                                                  t@
                                                                                                                Z;




                                                                         STREET





                      Figure 3-5.   Site layout for the Carbon/Sand Filter.


                           It was calculated from survey data that the diversion manhole, a manhole with an internal weir
                      to divert the WQV to the Carbon/Sand Filter, would have an invert elevation of 8.15 ft (City of
                      Portsmouth Datum, Mean Sea Level = 0 ft). The top of the weir in the diversion manhole was set at
                      an elevation of 9.61 ft. Calculations showed the invert elevation in the reentry manhole, where the
                      effluent from the Carbon/Sand Filter is returned to the primary drainage system, to be 5.50 ft.
                      Therefore, the maximum water surface elevation is slightly over four feet above the floor of the
                      structure. This shallow depth requires the structure to be longer and wider than is normally
                      designed in more hilly regions.

                           Appendix A-2 includes the actual design drawings, showing topographic features and
                      elevations, pipe invert elevations, structure dimensions and layout, BMP structural design, and
                      construction notes and details. These drawings have been formatted to fit into this text and are not
                      to scale.


                           As seen in Figure 3-5, the Carbon/Sand Filter is positioned close to the right of way for High
                      Street. This gives some degree of flexibility for future development of the property. A developer
                      can use this BMP with a multitude of design layouts, or the BMP can be removed and placed
                      elsewhere on the lot. The BMP is also situated so as to minimize the number of parking spaces
                                                                      sting of th
                      temporarily displaced during construction and te          e BMP.




                                                                      3-6








                            The structural design was provided by URS Consultants, Inc. Their time and materials were
                       donated to the project cause, allowing project funding to be used for construction and testing. The
                       filter structure was designed to support a heavy traffic loading (AASHTO H15-44 Truck Load) in
                       case a future entrance were to be located over the BMP. The structure would support loading from a
                       large truck, such as an 18-wheel rig or a garbage truck.

                            Steel grates were specified for maintenance access to the filter chamber, so that a City work
                       crew can remove the grates to change filter materials. Two manhole openings were included for
                       pumpout access to the sedimentation chamber, and a single manhole opening was positioned over
                       the clearwell chamber, which can be used for other maintenance needs.

                            The filter chamber was designed to have two parallel filter beds, separated by a concrete wall.
                       This design element is unique to this demonstration project to allow simultaneous testing of two
                       filter media with the same influent. When the stormwater flow passes through the sedimentation
                       chamber and over the wall leading to the filtration chamber, it will filter through either the filter of
                       sand or the filter of activated carbon and sand. The purpose of this feature is to be able to compare
                       pollutant removal results of each chamber, rather than to compare the results of the Carbori/Sand
                       Filter to those of another BW in another locality or region.

                            Filter chamber #1, the chamber to the north, was filled with twelve inches of sand underneath
                       six inches of activated carbon, separated by a layer of filter fabric. The activated carbon is
                       contained in "pillowcases" of filter fabric, sewn inexpensively by a local upholsterer, in order to
                       easily remove and replace the carbon medium. This feature allows a faster and simpler maintenance
                       visit, accomplishing one of the goals of the Carbon/Sand Filter project. Filter chamber #2, to the
                       south, was filled with eighteen inches of sand only. Both chambers have an underdrain system of
                       eight-inch perforated PVC pipe, supported by coarse aggregate stone. The underdrain angles up and
                       out of the filter bed to provide a cleanout for clogging.


                       3.5 Request for Proposals.

                            A request for proposals was advertised in The Virginian-Pilot on April 9, 1995 at a cost to the
                       project of $189.24. A public bid opening was conducted on April 20,1995. Three bid proposals
                       were received, and the lowest was offered by CPG, Inc in the amount of $39,630. It was originally
                       estimated during planning stages that construction of the filter structure would cost about $29,000.
                       After the design was completed, the City cost estimate for construction was $37,000. The lowest
                       bid was seven percent above this estimate, and the other t%vo bids were fourteen percent and
                       eighteen percent higher than the City estimate. Appendix A-3 shows unit and total bid price
                       tabulations for all three bidders.


                            Because the grant funding was only for $49,932, even the lowest construction price would only
                       leave approximately $10,000 to perform the necessary stormwater sampling and chemical analysis.
                       The City had estimated that these tasks would cost approximately $17,000. To reduce the need for
                       additional funding from another source, the City approached the Contractor, CPG, Inc, to discuss
                       ways in which to alter the design to reduce costs.

                            A number of design alternatives were considered to reduce construction costs. One of the
                       primary changes proposed was to use concrete block for internal walls rather than formed,
                       reinforced concrete. The Contractor countered that there would be no worthwhile savings if he had


                                                                        3-7








                      to hire a mason to perform this work. The Contractor suggested that some steel and concrete be cut
                      back, but the structural engineer reiterated that the amount of steel and concrete was appropriate for
                      the design loading.

                           It was agreed, however, to change the design for the internal wall separating the two filter
                      chambers. The original design called for a reinforced concrete beam to support the interior of the
                      filter structure and to have a small gap between the bottom of this beam and the wall separating the
                      filter media of each chamber. The new design removed this beam and brought the internal wall up
                      to the structure top. Even with this new design and with other minor suggestions, the Contractor
                      was unwilling to discount more than $600 worth of changes. The City decided to proceed with the
                      Contract to construct the Carbon/Sand Filter at the proposed cost and to identify  additional funding
                      for stormwater sampling and chemical analysis.



                      3.6 Carbon/Sand Filter Construction.


                           Construction began on May 30, 1995, with excavation of the site. Immediately, the Contractor
                      encountered problems, uncovering old foundations of buildings that had long since been
                      demolished. 'Most of the foundations were brick ranging from 18 inches to 48 inches in thickness,
                      but could be removed easily by a backhoe. Some of the foundations, however, were concrete and
                      required a jackhammer and an impactor for demolition. Figures 3-6(a) and 3-6(b) show the
                      excavation for the filter structure and several exposed brick and concrete foundations.            The
                      Contractor also uncovered several utility lines of undetermined origin. After consulting City
                      records and personnel from Virginia Power and Commonwealth Gas Services, constituting a delay
                      in the Contractor's work, it was determined that these clay pipes were abandoned in place and could
                      be removed.











                                                                                                   Figure 3-6(a). Exca-
                                                                                                   vation of the filter
                                                                                                   structure location. Note
                                                                                                   the exposed brick foun-
                                                                                                   dation on the left and
                                                                               nnM
                                                                                                   the concrete foundation
                                                                                              NA   just right of center. The
                              U, if
                                E
                                                                                             @i    wooden barriers in the
                                                                                           W,
                                                                                                   background protect the
                               ANW
                                                                                                   reentry manhole.
                                                                   1@, -@k













                                                                       3-8








                                                                                                           Figure 3-6(b). Exca-
                                                                                                           vated site of the filter


                                                                                                           brick foundations ex-
                                                                                                           structure.    There are


                                                                                                           posed along this wall.
                                                                                                           The pipe to the left runs
                                                               "W- @n '@"        11
                                                                       4N
                                                                                                           from the diversion man-
                                                                                                           hole to the Carbon/Sand
                                     A
                                                                                                           Filter.






                                                            ON





                             The Contractor requested a Contract change order to be reimbursed for additional labor and
                       equipment and for down time associated with foundation removal. The value for the additional
                       work was calculated by the Contractor to be $3,073.26. The Contract, however, specified that the
                       Contractor would bear the cost for any delays associated with utility conflicts. City of Portsmouth
                       contracts also designate excavation as unclassified, meaning that the City makes no assurances as to
                       the type of material that the Contractor must remove. Strictly interpreted, the Contractor must
                       remove any and all materials in the prescribed area at no additional cost to the City. City staff,
                       however, agreed that the concrete foundations did significantly and unexpectedly add to the required
                       time for excavation and subsequently agreed to pay the Contractor for this extra work. The City did
                       not pay additional money for removal of brick foundations because they were removed with relative
                       ease by the backhoe.

                             Concurrent with excavation was the construction of the diversion and reentry manholes and
                       laying of the pipe connecting these structures to the filter box. Figures 3-7(a), 3-7(b), and 3-7(c)
                       show the sequence of construction of the diversion manhole. Excavation of this area also uncovered
                       old foundations, as seen in Figure 3-7(a). A concrete footing was poured under the existing storm
                       drain pipe and the brick walls built to form the manhole. The reinforced concrete diversion weir
                       was constructed inside the manhole and the manhole rim and cover grouted in place at the final
                       stages of the project.















                                                                            3-9









                                                                                                    Figure 3-7(a).       Con-
                                                             A
                                                                                                    struction of the diver-
                                                                                                    sion manhole. The foot-
                                                                                                    ing was poured under
                                                                   P-                               the original storm drain
                                                                                                    pipe carrying drainage
                                                                                                    from the asphalt park-
                                                                                                    ing lot.      Note the
                                                                                                    e
                                                                                                     xposed brick foun-
                                                                                                    dations.
                                                                                        411


                                                                         i M,
                                                                                        71@

                                                                 M
                                                                  Mlmg
                                                                 'n





                                                                                    J



                                                                                                    Figure 3-7(b).      Brick
                                                                                                    walls of the diversion
                                                                                                    manhole were erected.
                                                                                                    The existing pipe was
                                                                                                    cut   open     and     the
                                                                                                    diversion            weir
                                                                                                    constructed at the latter
                                                                                                    stages of the project.
                                                                                                    The     pipe      opening
                                                                                                    shown leads to the
                                                                                                    Carbon/Sand Filter.










                           Another unforeseen problem arose in constructing the reentry manhole. Although shown on
                      the construction plan, a Virginia Power conduit running parallel to the primary storm drain system
                      under the High Street sidewalk was deeper and larger than expected. The conduit was eighteen
                      inches wide by four feet deep and encased in concrete. Also uncovered was a terra cotta Bell
                      Atlantic duct not shown on the plan, but located between the Virginia Power duct and the proposed
                      location for the reentry manhole. It was never determined whether the Bell Atlantic line was active,
                      so it was left in place. The bottom of the reentry manhole had to be lowered by eighteen inches to
                      an elevation of 4.02 ft so that the PVC pipe from the Carbon/Sand Filter to the manhole would fit
                      under the ducts. The manhole was then built with the ducts actually incorporated into the walls of
                      the structure. Figures 3-8(a), 3-8(b), and 3-8(c) show excavation of the reentry manhole location,
                      P,.

















































                      and the fully constructed manhole.




                                                                      3-1 0























                                                        @R"' x-q4@ï¿½"'WOI-





                                                                     @iW                                               Wa




                                                          4                                            OIL






                      Figure 3-7(c). The view from       the diversion      Figure 3-8(a).     Excavation    of the reentry
                      manhole toward the Carbon/Sand Filter, not yet        manhole location.   The concrete Virginia Pow-
                      constructed.                                          er duct can be seen in the center. The Bell
                                                                            Atlantic duct is behind the Virginia Power duct
                                                                            and cannot be seen from this angle.


                                                                                                    Figure 3-8(b). A view
                                                                                                    from above of the ducts
                                                                                                    conflicting with the
                                                                                                    reentry manhole. The
                                                                                                    terra cotta Bell Atlantic
                                                                                                    duct is in the center,
                                                                                                    beneath the steel sup-
                                                                                                    port.     The concrete
                                                                                                    Virginia Power duct is
                                                                                                    to the right. The exist-
                                                                                                    ing storm drain, not yet
                                                                                                    uncovered in this photo-
                                                                                                    graph, is below and to
                                                                                                    the left of the Bell
                                                                                       Ml@
                                                                                                    Atlantic duct.
                                                                                              IN






                                                                      3-1 1








                                                                            Figure 3-8(c). A view down into the finished
                                                                            reentry manhole. The existing storm drain pipe
                                                                            is to the left and has not yet been cut open in this
                                                                            photograph. The Bell Atlantic duct on the right
                                                                            can just b
                                                                                      e distinguished.








                                                    qW







                                                          '@s









                            After the manholes were complete and all pipe section laid, construction of the filter box
                       began. Steel rebar was positioned and tied within wooden form        s to provide reinforcement for the
                       concrete floor of the structure. Once the concrete floor was poured and smooth finished, forms were
                       constructed, steel tied, and concrete poured for the structure walls. Next, the forms and steel were
                       set for the concrete top, as were the manhole cover frames and steel grate frames. After the concrete
                       top was poured and cured, the outside of the structure was backfilled and graded to its previous
                       elevation. The sections of the asphalt lot and the brick sidewalk that had been removed for
                       construction of manholes and laying of pipe were returned to their original condition. Figures 3-
                       9(a) through 3-9(l) illustrate the construction process.


                                    V-W                                         Figure 3-9.     Construction process for the
                                                                                Carbon/Sand Filter. Figs. 3-9(a)-(c) show
                                                                                construction of the floor, figs. 3-9(d)-(h)
                                                                                show construction of the walls, and figs. 3-
                                                                                9(i)-(I) show the construction of the top,
                                                                                backfilling, and the finished structure.






                       (a)




                                                                        3-1 2


























                     (b)                             (C)                            (d)








                                                                                     4IR  6,
                                                                               m t Iml='  WIN   41L






                                          4




















                                                                (9)

                                                          Figure 3-9 (continued).


                                                                 3-13




















                                                                                        W@QV






























                                                                       (k)

                      Figure 3-9 (continued)

                           After construction of the filter box was complete, the Contractor secured the perforated PVC
                      underdrains on the floor of each filter chamber. Coarse aggregate stone was then placed around the
                      collector pipes and covered with a layer of filter fabric, provided by Contech Construction Products,
                      Inc, to contain the filter media above. A work crew from the City Public Works Department placed
                      sand, donated by Tarmac America, Inc, to the specified depths for each chamber. Activated carbon,
                      provided by Calgon Carbon Corporation, Inc in 55-pound bags, was poured by the crew into four
                      "pillowcases" of filter fabric, each thirty inches wide and seven feet long, and positioned on top of the
                      sand in filter chamber #1. Figure 3-10 shows the underdrain positioning, and Figures 3-10 shows the
                      inside of a filter chamber at several stages of the media installation process.


                      Figure 3-10. These two photographs show how the underdrain pipes
                      are situated and secured in the bottom of the filtration chambers.






                                                                                                                          iRt,








                                                             g',

                                                                 E37
                                                                      (a)                                                    (b)

                                                                       3-1 4








                                                P"77"",
                                                                       M111
                            P





                                              'N
                                                                                     UN

                                                                                  M,
                                                                                 N'N
                                                                                    gr,

                                          ":"5
                     iii"O
                                                                                                                    a




                                                     (a)                               (b)

                     Figure 3-11. Fig. 3-11(a) shows the underdrain and      cleanout  in a stone bedding. Fig. 3-11(b) is
                     charnber #2 filled with sand and covered with filter fabric. Fig. 3-1 l(c) shows the "pillowcase" being
                     filled with activated carbon in chamber # 1.



                     3.7 Stormwater Sampling and Chemical Analysis.

                          Stormwater sampling for the project was to be performed by URS Consultants, Inc (URS), with
                     the chemical analysis contracted to the Hampton Roads Sanitation District (HRSD). Staff from URS
                     visited the site to measure the internal dimensions of the structure and the pipes. The measurements
                     were used to install the flowmeters and sampling devices inside the Carbon/Sand Filter. Three
                     DataGator flow meters were used for the sampling, one inside the influent pipe entering the
                     sedimentation chamber and one inside each of the two collector pipes leading to the clearwell chamber.
                     The sampling devices, Sigma rotary samplers, were affixed to the walls of the structure. The samplers
                     were connected to the flowmeters so as to collect flow-weighted samples during storm events.

                          URS personnel was present for the first storm event. The crew reported that the clearwell chamber
                     was flooded with backflow coming from the direction of the reentry manhole. As a result, the sampling
                     equipment was tossed about the chamber, and the samples were contaminated by the backflow.
                     Because of the turbulent environment and the potential for irreparable damage to its valuable
                     equipment, URS elected to discontinue sampling services.

                          The City of Portsmouth subsequently contracted HRSD to perform stormwater sampling in
                     addition to the chemical analysis. HRSD installed a Marsh-McBirney flowmeter inside the influent
                     pipe and inside one of the effluent pipes. The flowmeters were connected to ISCO 3710 Samplers that
                     were stationed in steel drums on top of the filter structure. These samplers were programmed to siphon
                     through a plastic tube a sample from inside the prescribed pipe at intervals determined by the volume
                     of flow passing through the pipe. The samples were collected into one container to create a flow-
                     weighted sample. Only one flowmeter was used to trigger a sample from each effluent pipe because it
                     was assumed that the flow rates would be nearly identical for each effluent pipe.

                          To prevent further backflow into the Carbon/Sand Filter, a City Public Works crew cleaned the
                     primary storm drain downstream of the reentry manhole to remove any material clogging the system.
                     It was recognized at the time that tidal influence could be causing the backflow problem. In order to


                                                                      3-1 5







                      sample the filtered effluent, the backflow had to be completely eliminated. Otherwise, unfiltered
                      stormwater from the primary system or possibly a mixture including water from the Elizabeth River
                      would be collected.


                           At the first storm event sampled by HRSD, the sampling team witnessed further backflow into the
                      clearwell chamber. HRSD proposed to install a spring-loaded flap gate as a backflow preventer, which
                      was fabricated and installed prior to further sampling. Another problem was encountered in flow
                      measurement. The Marsh-McBirney flowmeters use an electromagnetic field to sense stormwater flow
                      velocity and a pressure transducer to measure flow depth inside the pipe. From these measurements are
                      calculated the volumetric flow rates. At certain points during the storm event, when there was no
                      backflow, the flow out of the effluent pipes was shallower in the pipe than could be measured by the
                      flowmeter.


                           Subsequent storms revealed yet another problem with the flowmeters. Flow data downloaded
                      from the meters yielded unusual flow patterns, including negative flow at times, for both flowmeters.
                      It was expected that some unusual patterns would exist in the clearwell chamber because of the
                      backflow.preventer. However, the influent readings could not be explained. HRSD staff recalibrated
                      the first meter, installed a replacement meter, and, when no further explanation could be offered,
                      presented the case to a panel of experts at a Marsh-McBirney conference. The only conclusion that
                      could be reached was that the Virginia Power duct paralleling the structure was interfering with the
                      electromagnetic field used by the flowmeter.

                           HRSD tried two other flowmeters that used other measurement techniques. An ISCO Doppler
                      Flowmeter, which uses an ultrasonic signal to measure flow velocity and a pressure transducer to
                      measure depth, was inserted into the influent pipe. Unusual readings were obtained from this
                      flowmeter as well and were considered to be unreliable. The final flowmeter used was an ISCO 3230
                      Bubbler Flowmeter, which uses a pressure transducer to measure the force needed to elicit a bubble
                      from the device. This meter also measures flow velocity and depth, but was used at the weir structure
                      leading from the sedimentation chamber to the filtration chamber. Data downloaded from this meter
                      were also considered to be unreliable.


                           After months of delays and invalid data, it was decided to collect the samples manually. For each
                      storm a crew from HRSD would determine whether there was enough flow to fill the sedimentation
                      chamber and spill over into the filtration chamber. If a sample was to be taken, it was performed by
                      turning on the ISCO Sampler to siphon samples from the influent and effluent pipes. This sampling
                      procedure was considered to be less than ideal, but unavoidable, given the field conditions.

                           HRSD staff also recognized that a significant flow from the gravel parking area was flowing into
                      the Carbon/Sand Filter through the grates above the filter chamber. The result was that stormwater
                      flow carrying high levels of suspended solids was flowing into the filter but not being measured in the
                      influent. This situation would create the appearance that there was a higher level of contaminants
                      leaving the BMP than was entering. To solve this problem, City crews barricaded the area of the access
                      grates with parking curb blocks and sandbags, which diverted the flow around the grates. This was
                      performed prior to the second sampling event.

                           The sampling problems occurred from September to December of 1995. Valid samples were
                      collected in the period from December, 1995 to July, 1996.





                                                                       3-1 6












                                    4.0 ANALYSIS OF POLLUTANT REMOVAL FOR THE CARBON/SAND FELTER.




                          4.1 Storm Event Sampling.

                                    Samples were collected for chemical analysis according to the schedule in Table 4-1. Efforts were
                          made to collect samples only for storm events preceded by three days of dry weather. Any storm that did
                          not produce enough volume to fill the sedimentation chamber and pass over into the filtration chamber
                          was not sampled. Without a flow through the filter, there is no effluent to collect from the underdrain
                          system.

                                    Table 4-1 also shows the high and low temperatures recorded for each day an event was sampled.
                          Because the testing period lasted from December to July, there is a wide range of temperatures for the
                          days on which storm events were sampled. A more comprehensive testing program could have evaluated
                          the effects of temperature on runoff pollutant concentration and on filtering efficiency for both the sand
                          and the activated carbon. To test a statistically significant number of storms for each season, however,
                          would likely require more than a year to achieve representative results. Budgetary and time constraint;;
                          preclude the study of temperature effects for this project.

                                    Rainfall data is included in Table 4-1 as recorded by the Portsmouth Weather Records Service,
                          located in the West Cradock section of Portsmouth, 2.8 miles south-southeast of the Carbon/Sand Filter
                          site. Appendix A-4 includes complete climatological data from December 1, 1995 to July 31, 1996. An
                          electronic rain gauge had been set up on the roof of the Children's Museum of Virginia building across
                          High Street from the Carbon/Sand Filter site. Miscommunication between City of Portsmouth staff and
                          URS Consultants, owner and operator of the rain gauge, resulted in a failure to record rainfall data for the
                          duration of the stormwater monitoring.



                                                                                        High                  Low                 Daysof
                               Event                                               Temperature           Temperature            Antecedent            Rainfall
                             Number            Date                Time                 (OF)                  (OF)             Dry Weather             (inches)
                                    I       Dec 9, '95            9:00 AM                49                    38                      12                0.62
                                    2       Feb 21, '96           12:00 ANV              68                    46                      32                0.68
                                    3       Mar 6, '96            11:47 PM               66                    58                      3                 0.36
                                    4       Mar 19, '96           1:45 PM                71                    46                      1                 0.19
                                    5       Mar 28, '96           10:40 AN4              48                    40                      5                 1.19
                                    6       Apr 24, '96           12:15 AM'              86                    64                      2                 0.204
                                    7       May 16, '96           6:15 AM                69                    56                      01                0.61
                                    8       Jun 24, '96           10:00 PM               94                    69                      3                 1.804
                                    9       Jul 3, '96            6:45 PM                87                    64                      2                 0.761
                                    10      Jul 15, '96           5:00 PM                88                    74                      0                 0.694
                                    11      Jul 18, '96           7:00 PM                93                    71                      2                 2.531
                                    12      Jul 25, '96           7:00 PM                93                    69                      5                 0.614
                          1 = Previous day's data reported because of time of sampling.                4 = Thunderstorm(s).
                          2 = Previous precipitation was a snowfidl event.                             5 = Heavy thunderstorm(s).
                          3 = Storm event began the previous evening.


                          Table 4-1. Storm event data.




                                                                                            4 - I









                    4.2 Chemical Parameters.


                         In developing the idea to construct and fund the Carbon/Sand Filter as a demonstration BMP, it was
                    seen as necessary to be able to compare the testing results of this BW to similar ones on other regions.
                    The City of Alexandria, Virginia, at the time the idea of the Carbon/Sand Filter was conceived, was
                    testing two of its new Delaware Sand Filters. It was decided to test for the same chemical parameters in
                    the Carbon/Sand Filter as were tested in the BMPs in Alexandria.


                         According to the original project proposal, twelve parameters were to be monitored: total copper,
                    total lead, total zinc, total petroleum hydrocarbons, total suspended solids, total phosphorus, nitrite +
                    nitrate, total Kjeldahl nitrogen, ammonia, biochemical oxygen demand, total organic carbon, hardness,
                    and pH. These were the parameters used for testing the Delaware Sand Filters in Alexandria. Budget
                    constraints required that the set of parameters be scaled down to one that would still represent the
                    pollutant removal capacity of the BMP.

                         It was postulated that, of the heavy metals being tested, lead would register the lowest reading from
                    the parking lot site that drains to the Carbon/Sand Filter. Most automobiles now use unleaded gasoline,
                    and a field survey revealed that few 'of those regularly parked in the lot had diesel fuel engines. Large
                    trucks, which commonly use diesel fuel, rarely enter this parking area. Copper and zinc, however, are
                    deposited by a broad spectrum of automobile types and could be expected to more prevalent at this site
                    than lead. Lead was therefore removed as a pollutant parameter for testing of the BUT.

                         Total petroleum hydrocarbons (TPH) is a test that measures the concentration of hydrocarbons in a
                    solution without attempting to further identify the concentrations of individual constituents. TPH is also
                    not a test that is used at the HRSD laboratory and would have to be subcontracted to another laboratory
                    at a significant cost. HRSD staff claimed that a more precise measurement of hydrocarbons in a solution
                    could be attained by measuring the individual constituents. The most common tests are for benzene,
                    toluene, ethylbenzene, and xylene, which together comprise a test commonly known as BTEX This test
                    and one for naphthaline were used to measure hydrocarbons for this project instead of the TPH test.

                         Nitrite + nitrate was also removed from the list of test parameters. Nitrite + nitrate, total Kjeldahl
                    nitrogen (TYN), and ammonia (NH3) all measure the amount of nitrogen in a solution, as present in
                    different chemical forms. Ammonia is an important parameter to measure for this project because that
                    contaminant can be very lethal to aquatic animals. TKN measures ammonia plus organic nitrogen and is
                    important as an indicator of fresh pollution by delivery of organic matter by stormwater (Krenkel and
                    Novotny, 1980). Nitrite + nitrate measures nitrogen that is undergoing or has undergone a biologically
                    mediated transformation. It is more a measure of "older" pollution and is not as great a threat as the
                    nitrogen forms measured by TKN (Krenkel and Novotny, 1980).

                         The removal of pH as a testing parameter was not by design but rather a result of'
                    miscommunication. In the original project proposal, City staff was to perform the sample collection and
                    submit the samples to the HRSD laboratory. pH was to be measured in the field by the sampling crew
                    and not at the laboratory. When the sampling services were later contracted to HRSD, it was never
                    specified for the HRSD sampling crew to test for this parameter. Nearly all twelve storm events had
                    been sampled when it was recognized that pH had not been routinely measured.

                         pH, a measure of the hydrogen ion concentration in a solution, is an important factor in many
                    chemical reactions.   pH affects the toxicity of a number of substances, including ammonia, which, in its
                    free form, increases in toxicity as the pH increases (Krenkel and Novotny, 1980). Because most
                    receiving waters are typically well-buffered, pH does not fluctuate greatly. Water quality sampling


                                                                       4-2







                         results published by the EPA recorded the pH of the Elizabeth River, in the vicinity of downtowli
                         Portsmouth, at 7.56 (City of Portsmouth, 1992). Results from stormwater testing performed for the City
                         of Portsmouth's VPDES Permit indicate that the pH for stormwater runoff from a broad set of land uses,
                         including the commercial use into which category this BMP site falls, ranges only from 5.22 to 7.07,
                         with an average pH of 6.19 (CH2M Hill with Woolpert Consultants, Inc., 1993). pH can theoretically
                         range from 0 to 14, with 7 being a neutral solution. A study of pollutant pathways and transformations
                         from source to and in receiving water would necessitate the measurement of pH, but this study can make
                         broader conclusions without its measurement.



                         4-3 Chemical Analysis Results.

                               Table 4-2 provides technical information for the chemical analyses of each pollutant parameter used
                         for testing of the Carbon/Sand Filter. It includes the units of measurement, the chemical analysis
                         method, and the method detection limits (MDL). For certain parameters the practical quantitation limits
                         (PQL) are used in place of the MDL. Also, the VPDES quantitation limits (VPDES QL), used for
                         judging the confidence of a result for use in reporting for VPDES permit requirements, are given for total
                         recoverable copper and total recoverable zinc.

                               Any figure below the MDL or the PQL should be considered suspect as to its exact value. For
                         statistical analysis, the reported values will be used for this study, but HRSD staff indicated that in such
                         situations it often uses a zero value for averaging purposes. A value below the VPDES QL is considered
                         negligible for reporting analysis results in accordance with municipal VPDES permits.



                                           Parameter                         Units        Method            MI)L         PQL       VPDES QL
                          Total Suspended Solids JSS)                        mg/L       S.M. 2540 E            I
                          Total Phosphorus (TP)                              mg/L       EPA 365.4             0.05
                          Total Kjeldahl Nitrogen (TKN)                      mg/L       EPA 351.2             0.05
                          Ainmonia (NH3)                                     mg/L       EPA 353.1             0.05
                          Biochemical Oxygen Demand (BOD)                    mg/L       S.M. 5210 B            I
                          Total Organic Carbon (TOC)'                        mgAL       EPA 415.1             0.5
                          Total Recoverable Copper (Cu)                      AWL        EPA 200.7              6                        10.0
                          Total Recoverable Zinc (Zn)                        Pg/L       EPA 200.7              2                       20.0
                          Hardness                                           mg/L       EPA 200.7              1
                          Benzene                                            @Lg/l,     EPA 624                           5.0
                          Toluene                                            Pg/L       EPA 624                           5.0
                          Ethylbenzene                                       Pg/L       EPA 624                           5.0
                          Xylene                                             @Ig/L      EPA 624                           5.0
                          Naphthaline                                        Pg/L       EPA 624                           5.0
                         1 = Analysis performed by Applied Marine Research Laboratory (AMRL) of Old Dominion University (ODU).

                         Table 4-2.        Specifications for chemical analyses performed for this project. Blank values indicate that
                         the category is not applicable.


                               Table 4-3 gives a complete listing of chemical analysis results, as provided by HRSD. The
                         following sections describe the methods of data analysis and then group the pollutant parameters into
                         five categories to analyze the results. These sections describe each parameter in more detail, note any
                         unusual results obtained from the laboratory analysis, and statistically analyze the interpretive
                         significance of the data. More general conclusions about the analysis results will be given in Section 4.6.




                                                                                     4 - 3













                                                                              TSS        TP            TKN             NH3           BOD            TOC         T.R. Cu         T.R.Zn        Hardness       Benzene         Toluene Ethylbenze            Xylene       Naphthaline
                                    Site             Date               (mg/L)           (mg/L)        (-R/L)          (-g/L)      (mg/L)           (mg/L)        (ug/L)         (UW'L)        (mgL)           (UgIL)          (USU          (ug/L)         (ug/L)          (ug/L)
                                 Influent         Dee 9,95                    10         0.11          0.12            <0.05             <1         1.98            13             41            2.00           NQ             NQ              NQ             NQ             NQ
                                                  Feb 21, f96                 37         0.08          0.40            0.05              3          1.64            20             32            1.49           NQ             NQ              NQ             NQ             NQ
                                                  Mar 6, '96                  15         0.11          0.75            0.36              5          7.80            25             35            2.25           NQ             NQ              NQ             NQ             NQ
                                                  Mar 19,96                   138        0.19          1.04            0.11              5          5.09            68             96            6.99           NQ             NQ              NQ             NQ             NQ
                                                  Mar 28,96                   14         0.06          0.37            0.12              3          7.09            18             41            2.11           NQ             NQ              NQ             NQ             NQ
                                                  Apr 24, '96                 8          0.26          0.90            0.13              7          5.06            39             69            2.70           NQ             NQ              NQ             NQ             NQ
                                                  May 16,96                   7          0.06          0.26            <0.05             3          4.05            8.0*           59            1.71           NQ             NQ              NQ             NQ             NQ
                                                  Jun 24,96                   7          OA 1          1.00            0.44              4          30.08           36             90            4.62           NQ             8.300           NQ             NQ             NQ
                                                  Jul 3,96                    19         0.13          0.76            0.17              11         10.26           32             65            7.36           NQ             NQ              NQ             NQ             NQ
                                                  Jul 15, '96                 13         0.1           0.39            <0.05             4          6.58            23             77            4.58           NQ             NQ              NQ             NQ             NQ
                                                  Jul 18,96                   9          0.09          0.52            0.12              5          6.91            18             73            5.68           NQ             NQ              NQ             NQ             NQ
                                                  Jul 25,96                   8          0.09          0.60            <0.05             6          10.22           28             115           4.14           NQ             NQ              NQ             NQ             NQ

                                 Sand             Dee 9,95                    93         0.13          1.13            <0.05        <2***           1.26            29             78            29.0           NQ             NQ              NQ             NQ             NQ
                                 Filter           Feb 2 1, '96                6          <0.05         0.27            0.13              3          2.72            21             59            1.87           NQ             NQ              NQ             NQ             NQ
                                 Chamber          Mar 6,96                    28         0.09          0.45            0.11              2          4.70            22             79            14.5           NQ             NQ              NQ             NQ             NQ
                                 Effluent         Mar 19,96                   100        0.11          0.54            0.1               2          3.26            21             158           11.3           NQ             NQ              NQ             NQ             NQ
                                                  Mar 28, '96                 4          0.11          0.64            0.19              7          5.36            30             193           11.5           NQ             NQ              NQ             NQ             NQ
                                                  Apr 24, '96                 6          0.18          0.80            0.08              4          7.89            36             32            32.8           NQ             NQ              NQ             NQ             NQ
                                                  May 16,96                   4          0.13          0.56            0.05              4          5.99            15             84            34.8           NQ             NQ              NQ             NQ             NQ
                                                  Jun 24,196                  42         0.24          1.96            0.44              34         40.98           37             272           17.4           NQ             16.0*0          NQ             NQ             NQ
                                                  Jul 3,96                    7          0.07          0.63            0.15              7          16.08           58             366           22.4           NQ             NQ              NQ             NQ             NQ
                                                  Jul 15,96                   4          0.07          0.12            <0.05             2          3.20            7              110           9.14           NQ             NQ              NQ             NQ             NQ
                                                  Jul 18,96                   3          0.06          0.36            <0.05             3          4.21            13             129           11.1           NQ             NQ              NQ             NQ             NQ
                                                  Jul 25,96                   2          0.06          0.61            0.06              3          6.68            16             179           17.6           NQ             NQ              NQ             NQ             NQ

                                 Carbon/Sand      Dec 9,95                    64         0.19          2.34            1.56              4          2.74            13             112           14.0           NQ             NQ              NQ             NQ             NQ
                                 Filter           Feb 2 1, '96                12         <0.05         0.30            0.14              2          1.90            21             64            6.01           NQ             NQ              NQ             NQ             NQ
                                 Chamber          Mar 6, '96                  61         0.09          0.48            0.29              2          4.50            25             63            8.59           NQ             NQ              NQ             NQ             NQ
                                 Effluent         Mar 19,96                   20         0.05          0.39            <0.05             2          1.60            16             116           17.8           NQ             NQ              NQ             NQ             NQ
                                                  Mar 28, '96                 3          <0.05         0.41            0.09              3          2.95            11             132           19.2           NQ             NQ              NQ             NQ             NQ
                                                  Apr 24, '96                 6          0.17          0.85            0.11              6          2.38            46             45            26.5           NQ             NQ              NQ             NQ             NQ
                                                  May 16,96                   5          0.09          0.25            <0.05             3          6.11            11             86            35.9           NQ             NQ              NQ             NQ             NQ
                                                  Jun 24,96                   36         0.22          1.85            0.31              29         41.71           30             220           21.3           NQ             11.100          NQ             NQ             NQ
                                                  Jul 3, '96                  8          0.08          0.67            0.14              6          7.18            54             362           20.5           NQ             NQ              NQ             NQ             NQ
                                                  Jul 15,96                   5          <0.05         0.13            <0.05             <1         7.05            <6.0           112           10.0           NQ             NQ              NQ             NQ             NQ
                                                  Jul 18, '96                 4          <0.05         0.27            <0.05             2          10.07           11             122           14.4           NQ             NQ              NQ             NQ             NQ
                                                  Jul 25, '96                 3          0.05          0.45            0.05              3          8.48            9              147           23.7           NQ             NQ              NQ             NQ             NQ

                                 NQ = Sample concentration below quantitation.                                                                                    QC Data obtained indicative of contamination (Blank Value              4.13 ug/L)
                                   Values below quantitation should not be used for compliance decisions concerning                                                          Analysis contracted to Reeds & Associates Lab.
                                                  Water Quality Standards because of a high degree of uncertainty.                                                  Due to saWle volume limitation, value reported is higher than MDL level.



                               Table 4-2. Chemical analysis results of Carbon/Sand Filter testing.







                      4.4 Statistical Methods Used for Data Analysis.

                           The results of each pollutant parameter are statistically examined in three ways. The first is art
                      examination of the sample means for each monitoring station: the influent, the sand filter effluent, and
                      the carbon sand filter, abbreviated CSF for this analysis, effluent. The means are compared iteratively as
                      data from certain storm events are scrutinized and screened for irregularities. The second method tests
                      the groups of data for each monitoring station to determine if there is a statistically significant difference
                      in the readings between the influent and sand filter effluent, the influent and the CSF effluent, and the
                      sand filter effluent and the CSF effluent. 'Me final method examines the correlation between the data
                      groups. A correlation between two groups assigns a numerical value to the propensity of the sample data
                      of one group to increase as that of another group increases. The results can indicate a tendency toward a
                      positive relationship, a negative relationship, or no apparent relationship.


                      4.4.1     SanWle  Means.

                           There are several steps in the evaluation of the sample means. First, the mean is calculated over all
                      storm events for the sample pollutant concentrations. The influent and each filter chamber effluent each
                      have a mean value. Next, any data that was the result of a known flaw in the filtering or sampling
                      process is removed from the data set. The data points are then examined for extreme outliers that
                      indicate an unusual and unrepresentative occurrence in the normal filtering or sampling process. As
                      these points are considered for removal from the data set, care is taken to remove only those data points
                      indicative of a process flaw and not points that are merely unexpected. Finally, the calculated means are
                      tabulated and compared to analyze the effectis of removing the data of selected storm events. The means
                      are used to point out indications of pollutant removal by either or both of the filter chambers and
                      pollutant removal advantages of one filter chamber over the other.


                      4.4.2     Paired T-testfor Significance of Results.

                           Although the sample means might indicate a difference in pollutant concentration between
                      monitoring groups, the difference may be due to variability in the sample data and not a true indication
                      of pollutant removal. The data, exclusive of storms that were removed as flawed data, are tested for
                      statistical significance in pollutant removal, using a paired t-test. The paired t-test method compares two
                      monitoring groups at a time, for instance the influent data to the sand filter effluent data, subtracting the
                      effluent data point from the influent data point for each storm. These differences are tabulated and
                      analyzed to see if there is a significant disparity that would indicate true pollutant removal. As explained
                      by Devore (1987), the t-test tests the hypothesis that the mean difference in pollutant concentration is
                      zero versus the alternative hypothesis that the mean difference in pollutant concentration is positive,
                      indicating true pollutant removal. This is represented statistically by

                                HO : @tl) = 01
                                H. : I'D > 01

                      where 9D = the mean of the differences in pollutant concentration.

                           This test assumes that the differences being examined are normally distributed for the entire
                      population, meaning all storm events in which stormwater passes through the filter, as well as for the




                                                                          4- 5







                     sample data. Because the alternative hypothesis is Ha : 9D > 0, and not Ha : PLD       0, the t-test is a one.-
                     tailed test. All tests are performed at a 90 percent confidence level.

                          The test statistic used is


                                                    tpaired      011 / Fn              (Eqn 4-1)

                     where     d = sample mean value of difference in concentration, and
                               SD = sample standard deviation for difference in concentration.


                          To determine d, the data points for each data set, grouped by monitoring station, are paired by storni
                     event. The data points from the set hypothesized to have lower values are subtracted from the other data
                     points. More specifically, the hypothesis of this study is that each filtration chamber effluent should
                     have lower pollutant concentrations than the influent and that the Carbon/Sand Filter effluent should
                     have lower pollutant concentrations than the sand filter effluent. Therefore, for the case of the influent to
                     sand filter comparison, the sand effluent concentration data point, the lower expected value, is subtracted
                     from the influent concentration, the higher expected value. That is,

                               Storm event #I:      d, = (influent concentration) - (sand effluent concentration)
                               Storm event #2:      d2 = (influent concentration) - (sand effluent concentration)
                               Storm event #i:      di  (influent concentration) - (sand effluent concentration) ...


                               Storm event #n:      dn  (influent concentration) - (sand effluent concentration)


                     where     -,I   F-di /n , and                                     (Eqn 4-2)
                               S.     @%2       =   V(Ed   2 - (idi)2 /n)/n- 1.        (Eqn 4-3)

                     lf tpaired @"' ta, n- I , where a = (100 - 90)% = 10% = 0. 10, then H. is rejected at a 90 percent confidence
                     level, meaning the evidence that there is an advantage in pollutant removal is statistically significant.
                     Otherwise, the random variation on the data cannot be ruled out as causing the difference between
                     sample means.

                          This test procedure is used for each comparison of monitoring groups, meaning that the influent data
                     is compared to the sand effluent data, the influent data is compared to the Carbon/Sand Filter effluent
                     data, and the sand filter effluent data is compared to the Carbon/Sand Filter data. The same procedure is
                     followed for each pollutant parameter. Section 4.5.1 Total Suspended Solids JSS) gives detailed
                     calculations for this methodology to illustrate the process. Subsequent sections that analyze the results
                     of other pollutant parameters only discuss the results of the statistical analysis. Actual calculations
                     performed in an Excel spreadsheet format can be referenced in Appendix A-5.

                          All formulae and methodology used in this section are common in statistical practice but, as
                     represented here, are adapted from Devore (1987).



                                                                         4 - 6







                       4.4.3 Correlation of Monitoring Data.

                            The third statistical method used to analyze the sample data is the calculation of the sainple
                       correlation coefficient. This coefficient measures the relationship between two sets of data. It gives;
                       statistical relevance to the tendency of one data set to increase or decrease as the other data set increases
                       or decreases. It will reflect a lack of any such behavior as well.

                            The sample correlation coefficient, r, is given by the following formula:
                                            r              nY-xiyi - (Exi)(Y-yi)                      (Eqn 4-4)
                                                 4nY-;72- -(y
                                                                X,) 2 @ny yi 2 - (yy,) 2

                       where xi and yj are data points, each related to a particular storm event, within the monitoring groups that
                       are being compared, such as the influent to the sand filter effluent.

                            The value of r ranges from -1, which indicates a strong negative relationship, to 1, which indicates a
                       strong positive relationship. For instance, a sample correlation coefficient of I in the example above
                       would indicate a strong propensity for the pollutant concentration in the sand filter effluent to increase as
                       the concentration in the influent increases and for it to decrease as the influent concentration decreases.
                       An r value of 0 indicates no relationship between the data sets.

                            Devore (1987), on whose work this discussion is based, reports that for 0 :5 Irl :!@ 0.5, the correlation
                       is weak. For 0. 8 :5; Irl :5 1, the correlation is considered to be strong. As for the test for significance in the
                       sample mean differences, Section 4.5.1 Total Suspended Solids (TSS) thoroughly illustrates the
                       calculation procedure, whereas subsequent sections relate only the results of the calculations for each
                       parameter. Appendix A-5 can be referenced for detailed calculations in an Excel spreadsheet format.


                       4.5 Pollutant Data Analysis.

                       4.5.1     Total Suspended Solids (TSS).

                            Total suspended solids (TSS) are measured by filtering the solution through a filter of 2.01im pore
                       size and drying the filtered material in an oven (Eaton et al, 1995). Any material in solution that, passes
                       through the filter is considered to be dissolved solids and not suspended solids. This analysis measures
                       any material of the minimum size and may include particulate forms of other parameters that are being
                       tested, such as metals or organic material. It is used to give a general indication of contaminant content
                       in water.


                            Table 4-4 provides the influent and effluent chemical analysis results for TSS. The first column
                       gives the influent concentration data for each storm event. The second and third columns provide data
                       for the sand filtration chamber and the CSF chamber, respectively. At the bottom are sample means for
                       the entire data set and selected subsets of the complete data.

                            Previous mention has been made of the problems associated with the first storm event on December
                       9, in which flow passed from the gravel lot directly into the filter chambers, bypassing the influent
                       sampling station. As seen in the data, the result was a significant increase in the TSS levels for the
                       effluents from the two filtration chambers. The data for this storm event is removed for this analysis to
                       prevent misleading results.


                                                                             4- 7







                           Total Suspended Solids
                           (TSS, mgtL)       ,

                               Date                                Influent       Sand Effluent      CSF EMuent


                             Dec 9, '95                                10                   93              64
                             Feb 21, '96                               37                   6               12
                             Mar 6, '96                                15                   28              61
                             Mar 19,'96                                138                  100             20
                             Mar 28, '96                               14                   4               3
                             Apr 24, '96                               8                    6               6
                             May 16, '96                               7                    4               5
                             Jun 24, '96                               7                    42              36
                             Jul 3, '96                                19                   7               8
                             Jul 15, '96                               13                   4               5
                             Jul 18, '96                               9                    3               4
                             Jul 25, '96                               8                    2               3


                          .......................................................................................... . ................................................. . . . .............-


                           Mean # 1                                    23.8                 24.9            18.9
                           Mean #2 (w/out 12/9)                        25.0                 18.7            14.8
                           Mean #3 (Wout 12/9, 3/19)                   13.7                 10.6            14.3



                          Table 44. Sample mean data for total suspended solids (TSS).


                                The storm event of March 19 also yields unusual readings. The influent concentration of TSS is
                          extremely high, as is that for the effluent from the sand filter. The mean TSS concentration for the
                          influent and for the sand filter effluent nearly doubles when the figures from this storm event are'
                          included (Table 4-4, mean #2 versus mean #3). The reading for the CSF effluent is slightly elevated but
                          still relatively consistent with results from other storm events for that chamber.

                                Were the results of the influent alone elevated, it could be theorized that some sand or dirt material
                          had been deposited in a large quantity on the lot. This condition could have occurred as a result of the
                          recorded snow event of March 7, less than two weeks earlier, if sand or dirt were used to melt the snow
                          and provide traction for vehicles and pedestrians. If the particles were large enough, such as heavier
                          granules of sand, it is possible that they settled out to a significant degree in the sedimentation chamber
                          and never reached the filtration chamber. Another possibility is that this type of material was trapped on
                          top of the filter by the layer of filter fabric or by the filter itself. This would not, however, account for
                          the elevated reading for the sand filter chamber effluent.

                                The prospect that sand or some other material could be deposited on the parking lot and that a finer
                          material that could pass through the sand filter was deposited into the sand filter chamber through the
                          access grates seems rather remote. Because the sand filter chamber is closer to the public sidewalk,
                          however, it is possible that fine sand and salt spread on the sidewalk as a countermeasure to snow could
                          have been swept into the access grates for the sand filter chamber but not into those of the carbon/sand
                          filter chamber. This possibility, although seemingly unlikely, is the only reasonable explanation for the
                          unusual chemical analysis results.

                                Eight of the remaining ten storm events yield results that would be expected of a filtration device.
                          In these cases both effluent concentrations are consistently lower the influent concentration but not
                          unexpectedly lower. The events of March 6 and June 24, however, show an increase in TSS



                                                                                            4 - 8








                             concentration for both effluents over the influent. This result could be an indication of either of two
                             possible conditions. First, there could have been some deposition of a material that entered the filter
                             chambers through the access grates, while bypassing the influent monitoring station. This was the case
                             for the December 9, 1995 storm in which stormwater flowed from the gravel lot into the filter chambers,
                             but that problem was subsequently fixed. The chemical analysis data for the June 24 storm seem to
                             indicate such a possibility because many of the parameters see an increase in concentration after
                             filtration. The second possibility is that a residue from previously filtered stormwater remained in the
                             filter and was flushed out by a more intense rain event that followed.

                                    The sample mean data seem to indicate that there is a slight pollutant removal by the sand filter but
                             that the effluent concentrations for the CSF are approximately the same as for the influent. After
                             removing the December 9 and March 19 storm event data, the sand filter sees a 23 percent decrease in
                             TSS whfle the CSF sees a four percent increase in TSS.

                                    The next step in the data analysis is to test for significance the apparent decrease in TSS
                             concentration for the sand filter and the apparent increase in TSS concentration for the CSF. Table 4-5
                             shows the mathematical differences between each monitoring group for each storm event. The sample
                             mean difference,'@F, is calculated using Equation 4-2 and the standard deviation of the sample differences
                             is calculated using Equation 4-3. The results are shown at the bottom of Table 4-5. Also shown are the
                             mean and standard deviation for sample differences when the March 6 and June 24 storm events are
                             removed from the data set. There is no known or apparent flaw in either the filtering process or the
                             sampling process for these storms, but because the readings are suspect, conclusions will be drawn with
                             and without the data from these storms. The June 24 data for all chemical parameters is particularly
                             indicative of some unusual circumstance.



                               Total Suspended Solids
                               (TSS, mg1L)                                               Sand          CSF            Influent -           Influent -         Sand Effluent -
                                                                      Influent       Effluent        Effluent      Sand Effluent         CSF Effluent          CSF Effluent
                                   Date                                   (1)            (2)             (3)        (4) = (1) - (2)       (5)    (1) - (3)      (6)       (2) - (3)


                                 Doe 9,195                                4-0            94              64                ---                   ---                      ---
                                 Feb 21, @96                              37             6               12                31                    25                       -6
                                 Mar 6, @96                               15             28              61                -13                   -46                      -33
                                 MaF 19. @96                              4-39           400             24                --                    ---                      ---
                                 Mar 28, @96                              14             4               3                 10                    11                       1
                                 Apr 24, '96                              8              6               6                 2                     2                        0
                                 May 16.'96                               7              4               5                 3                     2                        - I
                                 Jun 24..96                               7              42              36                -35                   -29                      6
                                 Jul 3, '%                                19             7               8                 12                    11                       - I
                                 Jul 15, 496                              13             4               5                 9                     8                        - I
                                 Jul 18, @96                              9              3               4                 6                     5                        -1
                                 Jul 25,'96                               8              2               3                 6                     5                        -1


                             .................. . ............................................................................................... . .................................................................................... ......... . ......................
                               Mean difference, 7                                                                          3.1                   -0.6                     -3.7
                               Standard deviation, s.                                                                      17.2                  20.9                     10.7

                               Exclusive of 3/6, 6/24 events
                               Mean difference, T                                                                          9.9                   8.6                      -1.3
                               Standard deviation,                                                                         9.2                   7.5                      2.1



                             Table 4-5. Means and standard deviations for sample differences in total suspended solids (TSS) data.


                                                                                                    4-9






                            The test statistic, tpa@d , is calculated, using Equation 4- 1, to test the null hypothesis that there is no
                       significant difference in pollutant concentration between monitoring groups. The calculated values for
                       t*,,d for the ten valid storm event data sets are shown below with the tabular value for t at cc = 0. 10 (a 90
                       percent confidence level) and n- I = 9:

                            Influent to Sand Filter Effluent:         tpi,d = 0.563             to.10,9 = 1.383
                            Influent to CSF Effluent:                 tp@d = -0.091             to.10,9 = -1.383
                            Sand Filter Effluent to CSF Effluent:     tpai.d = -1.086           to.10,9 = -1.383

                       The negative values indicate that the t-test is being evaluated at the lower end of the t distribution curve.
                       In these cases the sample mean difference reflects the opposite of what would be the expected result of
                       the filtration process, for instance that the pollutant concentration in the CSF effluent is actually higher
                       than that of the influent. The t-test examines whether this result is due to variability in the individual
                       data points. The absolute value of these figures is used to test the null hypothesis.

                            The statistical analysis of these results concludes that no rejection of the null hypothesis,

                                  HO : 9D = 0, is warranted in favor of
                                  H.: gD>O.

                       That is, statistically, there can be no rejection of the possibility that the difference in sample means is due
                       to variability of the data. This result does not mean that there is no difference between the monitoring
                       groups, only that this cannot be concluded with statistical certainty.

                            For comparative purposes, Table 4-5 also includes figures to test the significance in sample data
                       differences when the March 6 and June 24 storms are removed from the data set. This study will draw
                       conclusions about TSS removal both with and without the data for these two storms. Although the data
                       indicate a possible flow of polluted runoff through the filter that had bypassed the influent monitoring
                       station, particularly for the June 24 storm, there is no overwhelming evidence that there was a flaw in
                       either the filtering process or the sampling process for these storms. Because the values were somewhat
                       unexpected, however, the t-test is used to show how the filters truly performed if indeed these data points
                       were flawed.


                            The calculated values for tpred for the data of the eight remaining storm events are shown below
                       with the tabular value for t at cc = 0. 10 (a 90 percent confidence level) and n- I = 7:

                            Influent to Sand Filter Effluent:         tpai.d = 2.597            tO.10,7 = 1.415
                            Influent to CSF Effluent:                 tpaired = 2.743           tO.10,7 = 1.415
                            Sand Filter Effluent to CSF Effluent:     @ai,d = -1.604            tO.10,7 = -1.415

                       The statistical analysis of these results concludes that the null hypothesis,

                                  HO : @LD = 0, should be rejected in favor of
                                  Ha: @LD>O-

                       At a 90 percent confidence level it can be concluded that the difference in sample means is not due to
                       variability of the data but is indicative of a true difference in TSS concentration. It can be stated, in this



                                                                           4 - 1 0







                             case, that the sand filter and the CSF both remove TSS in the stormwater runoff and that the sand filteir
                             gives more TSS removal than the CSF. Table 4-6 summarizes the statistical analysis results.



                               Total Suspended Solids (TSS)

                                                                                        Influent:                Influent:              Sand Effluent:
                                   Statistic                                        Sand Effluent             CSF Effluent               CSF Effluent


                              Exclusive of 12/9, 3/19 events
                                 Change in pollutant concentration                          23%                     T 4%                     T 35%
                                 Test statistic, tpaired                                 0.569                      -0.091                   -1.094
                                 Tabular t-value, @0. 10' 9)                             1.383                      -1.383                   -1.383
                                 Test conclusion                                  Do not reject HO.         Do not reject HO.         Do not reject HO.
                                 Interpretation                                  Difference could be       Difference could be       Difference could be
                                                                                  variation in data.        variation in data.         variation in data.


                                 Correlation coefficient, r                              -0.14                      0.03                      0.84


                               Exclusive of 12/9, 3/19, 3/6, 6/24 events
                                 Change in pollutant concentration                          69%                     1 60%                    T 28%
                                 Test statistic, tpaired                                 3.040                      3.252                    -1.722
                                 Tabular t-value, t(O. 10, 7)                            1.415                      1.415                    -1.415
                                 Test conclusion                                      Reject Ho.                Reject H,                 Reject Ho.
                                 Interpretation                                  True concentration        True concentration         True concentration
                                                                                      difference.               difference.                difference.


                                 Correlation coefficient, r                              0.55                       0.88                      0.76



                             Table 4-6. Summary of statistical analyses for total suspended solids (TSS).


                                    Table 4-6 also shows the sample correlation coefficient, r, for each monitoring group comparison,
                             calculated using Equation 4-4. The coefficient shows no apparent behavioral relationship between the
                             influent data and either of the effluent data but does show a strong tendency for the TSS concentration to
                             increase or decrease in the CSF effluent as the concentration respectively increases or decreases in the
                             sand filter effluent. When the March 6 and June 24 storm data are removed from the sets, there appears.
                             to be a weak positive relationship between the influent TSS concentrations and the sand filter effluent
                             concentrations, a strong positive relationship between the influent concentrations and the CSF
                             concentrations, and a relatively strong relationship between the sand filter and CSF effluents. The
                             calculations illustrate the effect that the unexpected data results from these two storms have on the
                             statistical analysis.



                             4.5.2         Nutrients.


                                    Total phosphorus, total Kjeldahl nitrogen (TKN), and ammonia (NH3) all measure types of nutrients
                             in a solution. The effects of phosphorus and nitrogen have already been discussed. There are numerous
                             chemical tests that measure different forms of nitrogen. Two forms that are important to this study are
                             measured by total Kjeldahl nitrogen (TKN) and ammonia (NH3), which are further discussed below.


                                                                                                 4- 11







                           4.5.2. 1 Total Phosphorus (TP).

                                 Phosphorus is one of the primary pollutants through which different BN1Ps are compared. In the
                           Chesapeake Bay watershed, phosphorus is considered the "keystone" pollutant. In Virginia compliance.
                           with the Chesapeake Bay Preservation Act is predicated on meeting phosphorus removal requirements
                           for a particular development site. If the Carbon/Sand Filter or any other innovative BMP design is to
                           gain widespread use, it is imperative that its pollutant removal capabilities be documented, phosphorus
                           foremost among them.

                                 Total phosphorus (TP) is measured in a two-step process: first through digestion and then through
                           colorimetry (Eaton et a], 1995). Digestion involves the oxidation destruction of any organic matter
                           present in order to release phosphorus in the solution as orthophosphate. In colorimetry, a reagent is
                           added to the sample that will react with the orthophosphate to form a colored acid. The intensity of the
                           color change reflects the concentration of phosphorus in the sample.

                                 Table 4-7 provides the influent and effluent chemical analysis results for TP. The first column gives
                           the influent concentration data for each storm event. The second and third columns provide data for the
                           sand filtration chamber and the CSF chamber, respectively. At the bottom are sample means for the
                           entire data set and selected subsets of the complete data.

                                 Because of flow from the gravel parking lot directly into the filter chambers through the access
                           grates, the December 9 storm is removed from the data set. The June 24 storm data exhibits behavior
                           reflective of conditions similar to those of the December 9 event. Statistical analysis is performed on the
                           data, inclusive and exclusive of the June 24 storm.



                             Total Phosphorus
                             (TP, mg[L)

                                 Date                                 Influent      Sand Effluent      CSF Effluent


                               Dec 9, '95                              0.11               0.13               0.19
                               Feb 21, '96                             0.08               0.04               0.04
                               Mar 6, '96                              0.11               0.09               0.09
                               Mar 19, '96                             0.19               0.11               0.05
                               Mar 28, '96                             0.06               0.11               0.04
                               Apr 24, '96                             0.26               0.18               0.17
                               May 16, '96                             0.06               0.13               0.09
                               Jun 24, '96                             0.11               0.24               0.22
                               Jul 3, '96                              0.13               0.07               0.08
                               Jul 15, '96                             0.10               0.07               0.04
                               Jul 18, '96                             0.09               0.06               0.04
                               Jul 25, '96                             0.09               0.06               0.05

                           .............. .................................................... ................................................................................................


                             Mean # 1                                 0.1158            0.1075              0.0917
                             Mean #2 (w/out 12/9)                     0.1164             0.1055             0.0827
                             Mean #3 (Wout 12/9, 6/24)                0.1170             0.0920             0.0690



                           Table 4-7. Sample mean data for total phosphorus (TP).





                                                                                           4- 12







                                    The mean values for the influent TP concentration remain nearly the same for the data inclusive of
                             all storms, exclusive of the December 9 storm, and exclusive of the December 9 and June 24 storms.
                             The mean values for the data of both effluents, however, decrease as these storms are excluded from the
                             data sets. Mean #2 and mean #3 in Table 4-7 are the more meaningful results. When the December 9
                             storm only is excluded, the sand filter recognizes a nine percent decrease in TP, while the CSF
                             recognizes a 29 percent decrease. When both the December 9 and the June 24 storm events are excluded,
                             the sand filter yields a 21 percent decrease in TP, while the CSF gives a 41 percent decrease.

                                    As summarized in Table 4-8, the paired t-test, applied at a 90 percent confidence level, indicates
                             that for the data exclusive of the December 9 storm only, the difference in TP concentrations between
                             the influent and the sand filter effluent could be the result of variability in the data. It cannot be
                             conclusively said that there is a true T? removal for the sand filter. The test does indicate, however, that
                             there is a significant difference in TP concentration between the influent and the CSF effluent and
                             between the sand filter effluent and the CSF effluent. It can be concluded that the CSF does provide a
                             significant TP removal and that the CSF provides significantly more T? removal than the sand filter.

                                    When the June 24 storm event is also removed from the data set, there is, at a 90 percent confidence
                             level, a significant difference in the T? concentration between the influent data and the effluent data.
                             The conclusion is that the sand filter provides a true TP removal. Using this set of storm events, the CSF
                             still provides a true TP removal and provides significantly more T? removal than does the sand filter.


                               Total Phosphorus UP)

                                                                                       Influent:                  Influent:              Sand Effluent:
                                    Statistic                                       Sand Effluent              CSF Effluent               CSF Effluent


                               Exclusive of 12/9 event
                                 Change in pollutant concentration                        1 9%                       1 29%                     1 22%
                                 Test statistic, tped                                     0.545                      1.745                     2.975
                                 Tabular t-value. t(O. 10, 10)                            1.372                      1.372                     1.372
                                 Test conclusion                                  Do not reject HO'               Reject HO*                Reject Ho*
                                 Interpretation                                  Difference could be         True concentration        True concentration
                                                                                   variation in data.             difference.               difference.


                                 Correlation coefficient, r                               0.38                       0.43                      0.91


                               Exclusive of 12/9. 6/24 events
                                 Change in pollutant concentration                          21%                       41%                        25%
                                 Test statistic, tpaired                                  1.590                      3.379                     2.725
                                 Tabular t-value. t(O. 10, 9)                             1.383                      1.383                     1.383
                                 Test conclusion                                      Reject HO'                  Reject H,                 Reject Hol
                                 Interpretation                                   True concentration         True concentration        True concentration
                                                                                      difference.                 difference.               difference.


                                 Correlation coefficient r                                0.61                       0.70                      0.79



                             Table 4-8. Summary of statistical analyses for total phosphorus (TP).





                                                                                                 4 - 1 3







                           The normal expectation for correlation between the data sets would a positive one. It is expected
                      that, although both filters should provide some pollutant removal, if the pollutant concentration in the
                      influent for one particular storm event is higher than the concentrations for the other storm events, it give
                      a higher reading in the effluent for that event than the readings for other events. A similar correlation
                      between the sand filter effluent data and the CSF effluent data is expected. This test is used primarily to
                      flag instances of zero or negative correlation between data sets.      Either of these conditions does not
                      necessarily connote unreliable results, but rather that the results should be thoroughly examined for
                      unusual circumstances regarding the filtering or sampling process.

                           The sample correlation coefficients for each data set comparison are given in Table 4-8 for the
                      different sets of storm events. Considering the data sets when the December 9 storm only is removed,
                      the correlation between the influent and the sand filter effluent data and that between the influent and
                      CST effluent data each has a weak positive relationship. The relationship between the two effluent data
                      sets is strongly positive, indicating that both have very similar filtering behavior with respect to TP.
                      When the June 24 storm is also removed from the data sets, the positive relationship between the influent
                      data and the data for each effluent is stronger, and the relationship between the sand filter effluent and
                      the CSF effluent is slightly weaker, but still a strong one.

                           The results of these statistical analyses, considered together, lead to the conclusion that both the
                      sand filter and the CSF appear to effectively filter phosphorus from stormwater runoff. Additionally, the
                      CSF is somewhat more effective than the sand filter in removing phosphorus.


                      4.5.2.2 Total Kjeldahl Nitrogen (TK?V).

                           TKN measures the total organic nitrogen and the total ammonia nitrogen in a solution. These
                      unoxidized forms of nitrogen are important because they give an indication of the oxygen demand that
                      will be created as oxidation occurs. Oxygen consumed in these chemical processes is then unavailable
                      for higher order aquatic organisms. As mentioned in Section 4.2, TKN is a measure of "fresh" pollution
                      that will exert a higher oxygen demand rather than nitrogen forms that are more stabilized in the
                      receiving water (Krenkel and Novotny, 1980).

                           To measure TKN, the sample is digested with acid to convert all organic nitrogen to ammonia
                      nitrogen (Eaton et al, 1995). Colorimetry is then used to measure the ammonia content of the solution.
                      Table 4-9 provides the influent and effluent chemical analysis results and sample mean concentrations
                      for TKN.


                           For the reasons given in the discussions of total suspended solids and total phosphorus, the
                      December 9 storm event is removed from the data set. Statistical analysis of the data is given both with
                      and without the June 24 storm events in the data sets. It remains unclear as to whether a flaw in the
                      filtering process or the sampling process occurred during the June 24 event.

                           The mean influent concentrations are very close, regardless of whether the December 9 storm or the
                      December 9 and the June 24 storms are excluded from the calculation. Both effluent concentrations,
                      however, are lower when excluding the December 9 storm and are ftirther reduced when both storms are
                      removed from the data sets. When the December 9 storm is not considered, the sand filter gives a one
                      percent removal rate while the CSF gives a 13 percent removal rate. The mean CSF effluent
                      concentration of TKN is 13 percent lower than that of the sand filter. With both the December 9 and
                      June 24 storms excluded, the apparent TKN removal rate is 17 percent for the sand filter and 30 percent
                      for the CSF. The mean concentration for the CSF effluent is 16 percent lower than for the sand filter.


                                                                        4- 14







                              Total Kjeldahl Nitrogen
                              (TKN, mg/L)

                                  Date                                   Influent       Sand Effluent        CSF Effluent


                                Dec 9, '95                                 0.12                1.13               2.34
                                Feb 21, '96                                0.40                0.27               0.30
                                Mar 6, '96                                 0.75                0.45               0.48
                                Mar 19, '96                                1.04                0.54               0.39
                                Mar 28, '96                                0.37                0.64               0.41
                                Apr 24, '96                                0.90                0.80               0.85
                                May 16, '96                                0.26                0.56               0.25
                                Jun 24, '96                                1.00                1.96               1.85
                                Jul 3, '96                                 0.76                0.63               0.67
                                Jul 15, '96                                0.39                0.12               0.13
                                Jul 18, '96                                0.52                0.36               0.27
                                Jul 25, '96                                0.60                0.61               0.45


                            ......................................... . .......................................................................................... . ..................


                              Mean # 1                                    0.5925               0.6725             0.6992
                              Mean #2 (w/out 12/9)                        0.6355               0.6309             0.5500
                              Mean #3 (w/out 12/9,6/24)                   0.5990               0.4980             0.4200



                            Table 4-9. Sample mean &ta for total KjeldAl nitrogen (TW.




                              Total Kjeldahl Nittrogen
                              (TICN)                                                  Influent:                tnfluent:             Sand Effluent:
                                   Statistic                                      Sand Effluent             CSF Effluent              CSF Effluent

                              Exclusive of 12/9 event
                                Change in pollutant concentration                          1%                        13%                      13%
                                Test statistic, @aired                                  0.038                     0.782                     2.182
                                Tabular t-value, t(O. 10, 10)                           1.372                     1.372                     1.372
                                Test conclusion                                   Do not reject Ho*       Do not reject Ho*             Reject H..
                                Interpretation                                    Difference could be    Difference could be       True concentration
                                                                                  variation in data.       variation in data.           difference.


                                Correlation coefficient, r                               0.57                     0.65                      0.97


                              Exclusive of 12/9, 6/24 events
                                Change in pollutant concentration                      1 17%                        30%                     1 16%
                                Test statistic, tpired                                   1.300                    2.871                     1.908
                                Tabular t-value, t(O.10, 9)                              1.383                    1.383                     1.383
                                Test conclusion                                   Do not reject Ho*            Reject HO'               Reject Ho.
                                Interpretation                                    Difference could be     True concentration       True concentration
                                                                                  variation in data.           difference.              difference.


                                Correlation coefficient, r                               0.44                     0.66                      0.80



                             Table 4-10. Summary of statistical analyses for total Kjeldahl nitrogen (TKN).


                                                                                               4 - 1 5







                           The paired Mest for the data exclusive of the December 9 event concludes that the difference in
                      mean TKN concentrations between the influent and either effluent could be a result of variation in the
                      sample data. The CSF effluent concentration, though, is significantly lower than the sand filter effluent
                      concentration at a 90 percent confidence level, meaning that, based on this data set, there is an advantage
                      in organic plus ammonia nitrogen removal for the CSF over the sand filter.

                           When the June 24 storm event is also removed from consideration, the decrease in TKN from the
                      influent to the CSF effluent becomes significant. It is concluded in this case that the CSF provides true
                      pollutant removal, and that there is still a TKN removal advantage for the CSF over the sand filter. The
                      decrease in TKN between the influent and the sand filter effluent may still be due to variation in the
                      sample data.

                           For exclusion of the December 9 storm or both storms, the sample correlation coefficients are very
                      similar. As expected, there is a moderate positive relationship between the influent data and each
                      effluent data set, and there is a strong positive relationship between the two effluent data sets. The
                      statistical analysis results are summarized in Table 4-10.

                           Taken together, the analysis indicates a probable, but not irrefutable, removal of TKN for the sand
                      filter and a stronger probability of TKN removal by the CSF. The CSF is conclusively more effective in
                      removing TKN than the sand filter.


                      4.5.2.3 Ammonia (NH3).

                           As microorganisms decompose organic matter, oxidizing carbon to obtain energy, the nitrogen
                      remains unoxidized and is released to the water as ammonia (Davis and Cornwell, 1991). Ammonia can
                      be processed to a certain degree by aquatic plants but is toxic to most other aquatic life. It is also used by
                      some microorganisms in the presence of organic carbon to build cell tissue. When ammonia is oxidized
                      to nitrate, an oxygen demand is exerted. The oxygen consumed in this process is no longer available for
                      higher order organisms. Thus, ammonia is a contaminant of concern in aquatic chemistry.

                           Ammonia (NH3), also written as ammonia nitrogen (N-H3-N), is analyzed in a similar but simpler
                      fashion than TKN. It uses colorimetry to measure the ammonia content, but the organic nitrogen is not
                      first converted to ammonia nitrogen as for the TKN measurement (Eaton et al, 1995). Colorimetry does
                      not give the organic nitrogen content of the solution. Table 4-11 provides the influent and effluent
                      chemical analysis results and sample mean concentrations for NH3.

                           The December 9 storm is the only event removed from the data set for analysis Of NH3 removal by
                      the BMT. None of the other readings appears to be unusually skewed as to warrant deletion from the
                      data set. The June 24 storm data, which exhibits unusual behavior for many other pollutant parameters,
                      does not give the significant increases in NH3 as seen in previous analysis.

                           Exclu sion of the December 9 storm changes the mean concentrations for all three monitoring
                      stations, increasing the means slightly for the influent and sand filter effluent concentrations and
                      decreasing the CSF effluent concentration dramatically. The N113 concentrations are 14 percent lower
                      for the sand filter and 20 percent lower for the CSF than the influent concentrations. The CSF effluent
                      concentration is seven percent less than that of the sand filter.






                                                                         4- 16









                               Ammonia
                               (NH3, Mg/L)
                                   Date                                   Influent        Sand Effluent       CSF Effluent

                                 Dec 9, '95                                 0.04                0.04                1.56
                                 Feb 2 1, '96                               0.05                0.13                0.14
                                 Mar 6, '96                                 0.36                0.11                0.29
                                 Mar 19, '96                                0.11                0.10                0.04
                                 Mar 28, '96                                0.12                0.19                0.09
                                 Apr 24, '96                                0.13                0.08                0.11
                                 May 16, '96                                0.04                0.05                0.04
                                 Jun 24, '96                                0.44                0.44                0.31
                                 Jul 3, '96                                 0.17                0.15                0.14
                                 Jul 15, '96                                0.04                0.04                0.04
                                 Jul 18, '96                                0.12                0.04                0.04
                                 Jul 25, '96                                0.04                0.06                0.05


                             


                               Mean # 1                                    0.1383               0.1192              0.2375
                               Mean #2 (W/out 12/9)                         0.1473               0.1264              0.1173



                             Table 4-11. Sample mean data for ammonia (NH3).


                                   As summarized in Table 4-12, the t-test results conclude that the apparent NH3 removal by the sand
                             filter may be due to variation in the sample data, but that there is a true NH3 removal provided by the
                             CSF. There is no conclusive difference between the sample mean differences of the sand filter and of the
                             CSF. The difference in means may also be the result of variation in the sample data. The sample
                             correlation coefficients show moderate positive relationships between the influent data and the sand filter
                             effluent data and between the sand filter and CSF effluent data. There is a very strong positive
                             relationship between the influent data and the CSF effluent data. Together, these statistics suggest that
                             the CSF provides definite NH3 removal from stormwater runoff and that there is a strong possibility that
                             the sand filter provides NH3 removal, although somewhat less than the CSF.

                               Ammonia (NH3)                                           Influent:                 Influent:             Sand Effluent:
                                    Statistic                                      Sand Effluent              CSF Effluent              CSF Effluent


                               Exclusive of 12/9 event
                                 Change in pollutant concentration                       14%                        20%                    7%
                                 Test statistic, tPaired                                  0.781                     1.717                     0.379
                                 Tabular t-value, t(0.10, 10)                            1.372                     1.372                     1.372
                                 Test conclusion                                   Do not reject HO'            Reject H,             Do not reject H.-
                                 Interpretation                                    Difference could be     True concentration        Difference could be
                                                                                   variation in data.           difference.            variation in data.


                                 Correlation coefficient, r                               0.75                      0.92                      0.73



                             Table 4-12. Summary of statistical analyses for ammonia (NH3)


                                                                                                4- 17
 






                      4.5.3     Oxygen Demand

                           There are a number of chemical reactions, many biologically mediated, that require oxygen to
                      occur. When this oxygen becomes chemically bound, it is no longer available to higher order organisms.
                      Most oxygen demand is related to biodegradation of organic material, or carbonaceous demand, in a
                      solution. Other sources of oxygen demand are the oxidation of inorganic material, such as sulfides or
                      ferrous iron, and the oxidation of reduced forms of nitrogen, or nitrogenous demand.

                           There are many chemical analyses designed to measure the oxygen demand of these different
                      reactions in a solution. The most common tests are for biochemical oxygen demand (BOD), chemical
                      oxygen demand (TOC), and total organic carbon (TOC). The BOD and TOC analyses were used in thiis
                      project. 'These two tests give a reasonably comprehensive indication of the oxygen demanding
                      substances in the stormwater runoff being filtered, and are widely used in stormwater quality analysis.
                      This allows the results from the Carbon/Sand Filter to be compared to those of other BWs. Budgetary
                      constraints prevented further chemical analysis of oxygen demand.


                      4.5.3.1 Biochemical Oxygen Demand (BOD).

                           Biochemical oxygen demand (BOD) measures carbonaceous demand and the demand created by the
                      oxidation of inorganic material. The analysis most commonly used, and the one used for this project, is
                      the 5-day BOD (BOD5), in which the oxygen levels are monitored over a five-day period. In this
                      discussion, BOD is meant to be BOD5.

                           The BOD test measures the dissolved oxygen (DO) in a diluted sample at the beginning and at the
                      end of the five-day period (Eaton et al, 1995). The sample is diluted in cases where the BOD might
                      exceed the oxygen content of the sample over the course of the five-day test period. If there are likely
                      too few microorganisms to oxidize the organic matter, the sample is seeded bacteria, and nutrients
                      required by bacteria to carry out their functions can be added. The solution is incubated at a constant
                      temperature.

                           Table 4-13 provides the influent and effluent chemical analysis results and sample mean
                      concentrations for BOD. The exclusion of both the December 9 and the June 24 storm events most likely
                      give the most accurate appraisal of how the filters remove oxygen demanding substances from
                      stormwater runoff. The problems of the December 9 storm event have been well documented. The June
                      24 monitoring data once again exhibits highly unusual behavior. The BOD concentrations for both
                      effluent streams are ten times higher for this single storm event than the average value of the remaining
                      storm data. Although impossible to confirm, it is more likely that a foreign substance such as leaves and
                      other organic material and debris were deposited directly onto the filter beds than there being a regulady
                      occurring condition in the filtering process that would create an increase in BOD in the effluent.
                      Because these data points are such extreme outliers, they are not considered for the analysis.

                           The removal of the data from these two storms causes a mild, ten percent increase in the mean
                      influent BOD concentration. The reduction of the mean BOD concentrations for both effluents is more
                      dramatic, decreasing 38 percent for the sand filter effluent and 43 percent for the CSF effluent. As
                      apparent pollutant removal rates for oxygen demanding substances, there is a 29 percent decrease in
                      BOD concentration between the influent and the sand filter effluent and a 43 percent decrease between
                      the influent and the CSF effluent. The CSF appears to be 20 percent more effective in removing these
                      contaminants than the sand filter.




                                                                         4 - 1 8







                              Biochemical Oxygen
                              Demand (BOD, rng1L)
                                  Date                              Influent         Sand Effluent        CSF Effluent

                                Dec 9, '95                                 0.5              0.5                   4
                                Feb 21, '96                                3                3                     2
                                Mar 6, '96                                 5                2                     2
                                Mar 19, '96                                5                2                     2
                                Mar 28, '96                                3                7                     3
                                Apr 24, '96                                7                4                     6
                                May 16,'96                                 3                4                     3
                                Jun 24, '96                                4                34                    29
                                Jul 3, '96                                 11               7                     6
                                Jul 15,'96                                 4                2                     0.5
                                Jul 18, '96                                5                3                     2
                                Jul 25, '96                                6                3                     3

                             .......................................................... . .. .........................................................................................


                              Mean # 1                                     4.71             5.96                  5.21
                              Mean #2 (w/out 12/9, 6/24)                   5.20             3.70                  2.95



                             Table 4-13. Sample mean data for biochemical oxygen demand (BOD).


                                   The t-tests for the three flow comparisons all conclude that there is a significant difference in BOD
                             concentration at a 90 percent confidence level. The sample correlation coefficients all show moderate to
                             strong positive relationships between the data sets. These analyses are summarized in Table 4-14. The
                             conclusion of the statistical analyses is that the sand filter and the CSF both provide true removal of
                             oxygen demanding substances and that the CSF is more effective than the sand filter.



                              Biochemical Oxygen Demand
                              (BOD)                                                  Influent:                Influent:             Sand Effluent:
                                   Statistic                                     Sand Effluent             CSF Effluent             CSF Effluent

                              Exclusive of 12/9, 6/24 events
                                Change in pollutant concentration                        29%                      1 43%                    200%
                                Test statistic, @aked                                  1.928                      4.301                   1.567
                                Tabular t-value, t(O. 10, 9)                           1.383                      1.383                   1.383
                                Test conclusion                                    Reject Ho'                Reject H.'               Reject Ho*
                                Interpretation                                 True concentration       True concentration        True concentration
                                                                                    difference.              difference.              difference.


                                Correlation coefficient, r                              0.38                      0.74                     0.66



                             Table 4-14. Summary of statistical analyses for biochemical oxygen demand (BOD).







                                                                                               4- 19







                           4.5.3.2 Total Organic Carbon (TOC).

                                 The total organic carbon (TOC) test measures, as the name implies, the amount of organically
                           bound carbon in a solution. Unlike BOD, TOC does not measure other organically bound elements, such
                           as nitrogen and hydrogen, and inorganic material that can contribute to oxygen demand (Eaton et at,
                           1995). TOC is analyzed by breaking down the organic molecules, using heat and oxygen, ultraviolet
                           irradiation, chemical oxidants, or combinations of these, and converting the carbon to C02, a form that
                           can be quantitatively measured. Table 4-15 provides the influent and effluent chemical analysis results
                           and sample mean concentrations for TOC.

                                 As is the case for BOD, the exclusion of both the December 9 and the June 24 storm events most
                           likely give the most accurate appraisal of how the filters remove organic carbon from stormwater runoff.
                           The problems of the December 9 storm event have been discussed previously. The TOC concentrations
                           for the June 24 storm are extremely high in all three stormwater samples, over five times higher for this
                           single storm event than the average values of the remaining storm data.                                         Whereas the BOD
                           concentrations were high only in the effluent streams, the TOC is also high for the influent sample,,
                           indicating the presence of organic material passing completely through the filter. It is unusual, however,
                           that there was no increase in the BOD influent concentration for this event. In a general sense, the BOD
                           is expected to increase if there is an increase in TOC, although the reverse is not necessarily true. The
                           high TOC level could be due to decaying leaves and other organic material that were present in the
                           parking area. Because the TOC concentrations for this storm are far removed from the other readings,
                           the analysis will be conducted both with and without the data for this event.



                             Total Organic Carbon
                             (TOC, mg/L)                           Influent        Sand Effluent        CSF Effluent
                                Date


                               Dec 9, '95                            1.98                1.26                2.74
                               Feb 21, '96                           1.64                2.72                1.90
                               Mar 6, '96                            7.80                4.70                4.50
                               Mar 19, '96                           5.09                3.26                1.60
                               Mar 28, '96                           7.09                5.36                2.95
                               Apr 24, '96                           5.06                7.89                2.38
                               May 16, '96                           4.05                5.99                6.11
                               Jun 24, '96                           30.08               40.98               41.71
                               Jul 3, '96                            10.26               16.08               7.18
                               Jul 15, '96                           6.58                3.20                7.05
                               Jul 18, '96                           6.91                4.21                10.07
                               Jul 25, '96                           10.22               6.68                8.48


                           .................. ..................................................................................... ....... . ............. . ...................................


                             Mean # 1                                8.0633              8.5275              8.0558
                             Mean #2 (w/out 12/9, 6/24)              6.4700              6.0090              5.2220



                           Table 4-15. Sample mean data for total organic carbon (TOC).


                                 The exclusion of the June 24 storm dramatically decreases the TOC concentrations for the influent
                           and both effluents. This illustrates how greatly this particular storm skews the mean concentrations. The
                           reduction in TOC is greater for the effluent concentrations than for the influent concentration. With all


                                                                                           4-20








                            data included, the sand filter effluent realizes a six percent increase in TOC over the influent, and the
                            TOC remains the same from the influent to the CSF effluent. The CSF effluent concentration are six.
                            percent lower than that of the sand filter. With the December 9 and June 24 storms excluded, the sand
                            filter effluent concentration is seven percent lower and the CSF effluent concentration 19 percent lower
                            than that of the influent. The TOC concentration for the CSF effluent is 13 percent lower than for the
                            sand filter effluent.


                                  Table 4-16 summarizes the statistical analyses of the TOC data.                                    The t-tests for all three
                            comparisons using the complete data set conclude that the differences in TOC readings between the
                            influent and both effluents and between the sand filter effluent and the CSF effluent may be the result of
                            variability in the sample data. This is partly a result of the June 24 storm data. A large number for one
                            data point can significantly increase the standard deviation for the sample data if the other data points are
                            small. This in turn increases the statistical likelihood that calculated differences between pollutant
                            concentrations at different monitoring stations are due to variability in the data. It is more difficult to
                            make a conclusion about the true filtering capacity of the BW.

                                  When the December 9 and June 24 storm data are removed, the West concludes that there is a true
                            TOC reduction from the influent to the CSF effluent. The differences in TOC between the influent and
                            sand filter effluent and between the sand filter and CSF effluent could still be due to sample data
                            variability. It appears that the unusually high TOC readings for the July 3 storm event increase the
                            standard deviation, thus decreasing the test statistic.



                             Total Organic Carbon (TOC)

                                                                                   Influent:                 Influent:             Sand Effluent:
                                 Statistic                                      Sand Effluent             CSF Effluent              CSF Effluent


                             All events included
                               Change in pollutant concentration                      T 6%                      0%                          6%
                               Test statistic, @aired                                 -0.367                    0.006                    0.414
                               Tabular t-value, t(O. 10, 11)                          -1-363                    1.363                    1.363
                               Test conclusion                                Do not reject Ho.         Do not reject H..        Do not reject Ho.
                               Interpretation                                 Difference could be      Difference could be       Difference could be
                                                                               variation in data.        variation in data.        variation in data.


                               Correlation coefficient, r                             0.96                      0.96                     0.93


                             Exclusive of 12/9, 6/24 events
                               Change in pollutant concentration                      1 7%                       1 go/.                    13%
                               Test statistic, tpaired                                0.456                     1.543                    0.581
                               Tabular t-value, t(O. 10, 9)                           1.383                     1.383                    1.383
                               Test conclusion                                 Do not reject Ho.            Reject Ho*           Do not reject H.'
                               Interpretation                                 Difference could be       True concentration       Difference could be
                                                                               variation in data.           difference.            variation in data.


                               Correlation coefficient, r                             0.58                      0.59                     0.25



                            Table 4-16. Summary of statistical analyses for total organic carbon (TOC).




                                                                                             4- 2 1







                           The sample correlation coefficients for each comparison are extremely high when the complete data
                      sets are used. This is because the TOC concentrations have a strong positive relationship, even as those
                      of certain storrns stray far from the other readings. Such strong positive relationships discourage the
                      discounting of certain data points because the filtering process is behaving in an expected manner. When
                      the questionable storm data is removed, the correlations remain positive but are not as strong.

                           The conclusion from these analyses is that both filters probably provide a mild degree of TOC
                      removal but that the CSF does not provide significantly more removal than the sand filter.


                      4.5.4     Heavy Metals.

                           The sources of heavy metals and their potential toxic effects have been covered in previous
                      discussion. Budgetary constraints limited the number of metal parameters that could be analyzed for this
                      project. Copper and zinc were chosen to represent the metal group because of their relative abundance in
                      the ultra-urban landscape. Hardness is a measure of lighter metals and would not normally be included
                      in a category of heavy metals, but there is a correlation between hardness concentration and the toxicity
                      of heavy metals in an aquatic environment. Hardness is also a common parameter in analysis of BMP
                      efficiencies, so its inclusion for this project allows the Carbon/Sand Filter to be compared to other BUTs.

                           Total recoverable copper (Cu), total recoverable zinc (Zn), and hardness are all measured using the
                      same analytical method, the Inductively Coupled Plasma (ICP) method. The samples are digested in acid
                      to reduce interference by organic matter and to convert the metal associated with partic   ulates to a form
                      that can be recognized in 1CP spectroscopy (Eaton et al, 1995). Total recoverable copper and total
                      recoverable zinc are digested in a more dilute acid than is used analysis for total copper and total zinc. A
                      controlled plasma is used to superheat the sample until the molecules are completely dissociated and an
                      atomic emission is achieved. The light of this emission consists of many wavelengths, each measurable
                      element having a different wavelength. The amount of energy present at each wavelength is proportional
                      to the concentration of the element being measured.


                      4.5.4. 1 Total Recoverable Copper (Cu).

                           Table 4-17 provides the influent and effluent chemical analysis results and sample mean
                      concentrations for Cu. The data are very inconsistent in terms of an increase or a decrease in Cu
                      concentration between the influent and either effluent. Considering this inconsistency, none of the data
                      points seems to be an outlier or otherwise unusual. The data is analyzed with and without the December
                      9 storm because of the known problems during that event. The mean concentration values change very
                      little for each of the three monitored flows.


                           The Cu concentration is seven percent lower for the sand filter effluent and 23 percent lower for the
                      CSF than the influent when all storms are considered. The effluent concentration is 17 percent lower for
                      the CSF than for the sand filter. When the December 9 storm is excluded, the Cu concentration is 12
                      percent lower for the sand filter effluent and 24 percent lower for the CSF than the influent. The effluent
                      concentration is 13 percent lower for the CSF than for the sand filter. The apparent removal rates do not
                      change much when excluding the December 9 event.

                           The t-tests reflect the steadiness in the mean Cu concentrations as the December - 9 storm is
                      excluded. The test indicates that the difference in Cu concentration between the influent and each of the
                      effluents might be the result of variation in the sample data, although the test statistic tpaired is almost


                                                                        4- 2 2









                               Total Recoverable
                               Copper (Cu, pg/L)
                                   Date                          Influent          Sand Effluent          CSF Effluent

                                 Dec 9, '95                          13                    29                    13
                                 Feb 21, '96                         20                    21                    21
                                 Mar 6, '96                          25                    22                    25
                                 Mar 19, '96                         68                    21                    16
                                 Mar 28, '96                         18                    30                    11
                                 Apr 24, '96                         39                    36                    46
                                 May 16, '96                         8                     15                    11
                                 Jun 24, '96                         36                    37                    30
                                 Jul 3, '96                          32                    58                    54
                                 Jul 15, '96                         23                    7                     5
                                 Jul 18, '96                         18                    13                    11
                                 Jul 25, '96                         28                    16                    9


                             ................................................... . ......... . ..................... . ............ ...............................................................


                               Mean # 1                            27.3                   25.4                   21.0
                               Mean #2 (w/out 12/9)                28.6                   25.1                   21.7



                             Table 4-17. Sample mean data for total recoverable copper (Cu).




                               Total Recoverable Copper
                               (CU)                                                  Influent:                Influent:             Sand Effluent:
                                    Statistic                                    Sand Effluent             CSF Effluent              CSF Effluent

                               All events included
                                 Change in pollutant concentration                      1 7%                       23%                      17%
                                 Test statistic, tpaired                                0.667                    1.326                    1.510
                                 Tabular t-value, t(O. 10, 11)                          1.363                    1.363                    1.363
                                 Test conclusion                                Do not reject Ho'         Do not reject HO'            Reject Ho*
                                 Interpretation                                Difference could be      Difference could be       True concentration
                                                                                variation in data.        variation in data-           difference.


                                 Correlation coefficient r                              0.22                     0.33                     0.87


                               Exclusive of 12/9 event
                                 Change in pollutant concentration                      1 7%                       19%                      13%
                                 Test statistic, tpaired                                0.456                    1.543                    0.581
                                 Tabular t-valuc, t(O. 10, 10)                          1.372                    1.372                    1.372
                                 Test conclusion                                Do not reject HO'         Do not reject Flo.           Reject Ho*
                                 Interpretation                                Difference could be      Difference could be       True concentration
                                                                                variation in data.        variation in data.           difference.


                                 Correlation coefficient r                              0.26                     0.30                     0.89



                             Table 4-18. Summary of statistical analyses for total recoverable copper (Cu).



                                                                                              4 - 2 3








                            large enough in the influent to CSF effluent comparison to reject the null hypothesis and conclude a true
                            Cu removal for the CSF. The concentrations for the CSF effluent, however, are significantly lower than
                            those for the sand filter. In both sets of storm data the sample correlation coefficients show a weak
                            positive relationship between the influent Cu concentration and each effluent Cu concentration. The
                            positive relationship is very strong between the sand filter effluent data and the CSF effluent data. The
                            statistical analysis results are summarized in Table 4-18.

                                  The statistical analyses together suggest that there is likely a true Cu removal benefit for both the
                            sand filter and the CSF and that the CSF gives a greater Cu removal benefit than the sand filter.



                            4.5.4.2 Total Recoverable Zinc (Zn).

                                  Table 4-19 provides the influent and effluent chemical analysis results and sample mean
                            concentrations for Zn. The data show an increase in Zn between the influent and each effluent for eleven
                            of the twelve storm events. The data also shows no indication of the process flaws known to have
                            occurred during the December 9 event. When the data for this storm are removed, the mean Zn
                            concentrations increase for all three monitored flows.




                              Total Recoverable
                              Zinc (Zn, AgIL)
                                 Date                          Influent           Sand Effluent         CSF Effluent

                                Dec 9, '95                         41                   78                     112
                                Feb 21, '96                        32                   59                     64
                                Mar 6, '96                         35                   79                     63
                                Mar 19, '96                        96                   158                    116
                                Mar 28, '96                        41                   193                    132
                                Apr 24, '96                        69                   32                     45
                                May 16,'96                         59                   84                     86
                                Jun 24, '96                        90                   272                    220
                                Jul 3, @96                         65                   366                    362
                                Jul 15, 496                        77                   110                    112
                                Jul 18, '96                        73                   128                    122
                                Jul 25, ;96                        115                  179                    147


                            ................................................... . ................................... .......................... . ................ . ..............................


                              Mean # 1                             66.1                 144.8                  131.8
                              Mean #2 (Wout 12/9)                  68.4                 150.9                  133.5



                            Table 4-19. Sample mean data for total recoverable zinc (Zn).


                                  A cursory review of the chemical analysis data clearly shows that there is zinc export from both
                            filters. Because only one of the filter chambers uses activated carbon as a filtering medium, the carbon is
                            not the sole source of the zinc in the effluent. Both filter chambers use sand as a filtering medium and
                            have coarse aggregate stone as a bedding to support the underdrain system. Either of these materials
                            could be a source of zinc. It would be expected that the zinc content would decrease over time as
                            stormwater flows flush out the zinc. The data for the eight-month monitoring period show an increase in




                                                                                            4-2 4








                              Zri concentrations in the effluents, however.                      Further monitoring would be needed to affirm the
                              assumption that the zinc comes from one or both of these materials in the filter chambers.

                                    As summarized in Table 4-20, there is a 119 percent increase in Zn concentration for the sand filter
                              effluent and a 99 percent increase for the CSF effluent over the influent. The concentration for the sand
                              filter effluent is nine percent higher than for the CSF effluent, but in a relative sense this difference is
                              meaningless.         When the December 9 storm is excluded, there is a 121 percent increase in Zn
                              concentration for the sand filter effluent and a 95 percent increase for the CSF effluent over the influent.
                              The conpentration for the sand filter effluent is 12 percent higher than for the CSF effluent.

                                    The t-tests for all comparisons and scenarios conclude, as expected from looking at the raw data,
                              that there is a true difference in Zn concentration. The effluent Zri concentrations are significantly higher
                              than the influent concentration, and the sand filter effluent concentration is significantly higher than that
                              of the CSF, a useless comparison given that both effluents are so dramatically higher in zinc than the
                              influent.



                               Total Recoverable Zinc (Zn)

                                                                                     Influent:                 Influent:            Sand Effluent:
                                   Statistic                                      Sand Effluent             CSF Effluent             CSF Effluent


                               All events included
                                  Change in pollutant concentration                        119%                    99%                       9%
                                  Test statistic, tpaired                              -3.153                   -2.737                     2.124
                                  Tabular t-value, t(O. 10, 11)                        -1.363                   -1.363                     1.363
                                  Test conclusion                                    Reject Ho.                Reject HO'              Reject Ho'
                                  Interpretation                                True concentration        True concentration       True concentration
                                                                                     difference.               difference.             difference.


                                  Correlation coefficient, r                             0.36                     0.28                     0.96


                               Exclusive of 12/9 event
                                  Change in pollutant concentration                        121%                    95%                       12%
                                  Test statistic, tpaired                              -2.909                   -2.499                     2.275
                                  Tabular t-value, t(O.10, 10)                         -1.372                   -1.372                     1.372
                                  Test conclusion                                    Reject Ho.                Reject HO'              Reject Ho,
                                  Interpretation                                True concentration        True concentration       True concentration
                                                                                     difference.               difference.             difference.


                                  Correlation coefficient, r                             0.31                     0.27                     0.97



                              Table 4-20. Summary of statistical analyses for total recoverable zinc (Zn).


                                     The sample correlation coefficients show weak positive relationships between the influent and
                              effluent data. If the source of the zinc were in fact the sand or the stone in the filter chambers, there
                              would not necessarily be a positive relationship between the influent data and the effluent data. There
                              would be zinc export regardless of the influent Zn concentration. If it can be assumed that the amount of
                              zinc export from the filter materials is reasonably constant over all of the storm events, the fluctuation in


                                                                                                4 -2 5








                             the influent Zn concentration might have a limited effect on the effluent concentration. This would
                             account for the weak positive relationship. The correlation between the sand filter effluent data and the
                             CSF effluent data is very strongly positive, indicating that their behavior is consistently similar for
                             export of zinc.



                             4.5.4.3 Hardness.


                                   Hardness is not a measure of heavy metals, but the hardness of a solution does affect the toxicity of
                             heavy metals that are present in the solution to the aquatic environment. Technically, it is the sum of all
                             polyvalent cations in a solution. Practically, it is a measure of the calcium and magnesium content of the
                             water. It is measured using the ICP method to determine the calcium and magnesium content and then
                             calculating the hardness as CaC03- Calcium and magnesium are considered to be lighter metals.

                                   Water can be described as soft, moderately hard, hard, or extremely hard. Water with less than 75
                             mg/liter of is considered to be soft (Davis and Cornwell, 1991). To achieve the desired hardness
                             concentration in drinking water of 75-120 mg/liter, a softening process, such as a lime-soda or an ion
                             exchange process, can be used.

                                   Hardness itself does not have a toxic effect on the aquatic environment, but it does affect the
                             toxicity of other contaminants. Hardness has an antagonistic effect on the toxicity of heavy metals. As
                             the concentration of CaC03 increases, aquatic species are less sensitive to the heavy metal in the water
                             (Krenkel and Novotny, 1980).



                              Hardness
                              (as CaC03, Ing/L)
                                   Date                         Influent          Sand Effluent          CSF Effluent

                                 Dec 9, '95                        2.00                  29.0                 14.0
                                 Feb 2 1, '96                      1.49                  1.87                 6.01
                                 Mar 6, '96                        2.25                  14.5                 8.59
                                 Mar 19, '96                       6.89                  11.3                 17.8
                                 Mar 28, 496                       2.11                  11.5                 19.2
                                 Apr 24, '96                       2.70                  32.8                 26.5
                                 May 16, ; 96                      1.71                  34.8                 35.9
                                 Jun 24, '96                       4.62                  17.4                 21.3
                                 Jul 3, '96                        7.36                  22.4                 20.5
                                 Jul 15,'96                        4.58                  9.14                 10.0
                                 Jul 18, '96                       5.68                  11.1                 14.4
                                 Jul 25, '96                       4.14                  17.6                 23.7



                              M  e an  1                           3 794                 17 784               18.  158
                              Mean #2 (w/out 12/9)                 3.957                 16.765               18.536



                             Table 4-21. Sample mean data for hardness (as CaCO3), with data
                             reported at three significant figures.






                                                                                              4 - 2 6







                                   Table 4-21 provides the influent and effluent chemical analysis results and sample meal]
                             concentrations for hardness. Similar to the results for Zn, there is a dramatic increase in hardness
                             between the influent and each effluent for every storm event. The data also shows no indication of the
                             process flaws known to have occurred during the December 9 event. When the data for this storm are
                             removed, the mean hardness concentrations increase slightly for the influent and the CSF effluent and
                             decrease slightly for the sand filter effluent.

                                   As is the case with Zn, the data clearly show that there is export of calcium and magnesium from
                             both filters. The source of export for these elements is probably either the sand or the coarse aggregate
                             stone. As discussed for zinc, it would be expected that the calcium and magnesium content would
                             decrease over time as stormwater flows flush them out. The data support this theory somewhat for
                             hardness, with the concentration peaking in the middle of the monitoring period and subsequently
                             decreasing.

                                   As summarized in Table 4-22, there is a 369 percent increase in hardness concentration for the sand
                             filter effluent and a 379 percent increase for the CSF effluent over the influent. The concentration for the
                             sand filter effluent is two percent lower than for the CSF effluent, but in a relative sense this difference is
                             meaningless as it was for Zn. When the December 9 storm is excluded, there is a 324 percent increase in
                             hardness concentration for the sand filter effluent and a 368 percent increase for the CSF effluent over
                             the influent. The concentration for the sand filter effluent is I I percent lower than for the CSF effluent.



                              Hardness (as CaC03)

                                                                                    Influent:                 Influent:            Sand Effluent:
                                   Statistic                                     Sand Effluent             CSF Effluent             CSF   Effluent


                              All events included
                                Change in pollutant concentration                        369%                 T 379%                        2%
                                Test statistic, tpaired                                -4.528                   -5.784                  -0.195
                                Tabular t-value, t(O. 10, 11)                          -1.363                   -1.363                   1.363
                                Test conclusion                                     Reject H,                 Reject H,           Do not reject Fl,
                                Interpretation                                 True concentration        True concentration      Difference could be
                                                                                    difference.               difference.          variation in data.


                                Correlation coefficient, r                             -0.19                      0.00                    0.76


                              Exclusive of 12/9 event
                                Change in pollutant concentration                        324%                      368%                     11%
                                Test statistic, @aird                                  -4.096                   -5.379                  -1.232
                                Tabular t-value, t(O. 10, 10)                          -1.372                   -1.372                  -1.372
                                Test conclusion                                     Reject Ho.                Reject Ho.          Do not reject Ho.
                                Interpretation                                 True concentration        True concentration      Difference could be
                                                                                    difference.               difference.          variation in data.


                                Correlation coefficient, r                             -0.10                     -0.04                    0.88



                             Table 4-22. Summary of statistical analyses for hardness (as CaC03).





                                                                                               4-2 7








                         The t-tests strongly conclude, as expected from looking at the raw data, that there is a true)
                    difference in hardness concentration between the influent and each effluent. The effluent hardness
                    concentrations are significantly higher than the influent concentration. The difference between the sand
                    filter effluent concentration and that of the CSF may be due to variation in the sample data. The test
                    results are the same regardless of whether the December 9 storm event is included in the data set.

                         The sample correlation coefficients show weak negative relationships or zero relationship between
                    the influent and effluent data. This is due to the high variation of the effluent data with respect to the
                    influent data, which have little relative variation because the concentration values are low compared to
                    the effluent. It can be concluded from these coefficients that because the export of hardness is so great,
                    the influent concentrations have no real effect on what leaves the filter chambers. The correlation
                    between the sand filter effluent data and the CSF effluent data is strongly positive, indicating that their
                    behavior is consistently similar for export of calcium and magnesium.



                    4.5.5     Hydrocarbons.

                         Hydrocarbons and their toxic effects to the aquatic environment were discussed in Section 2.2-2
                    Hydrocarbons. The chemical analysis commonly used to measure hydrocarbons is the total petroleum
                    hydrocarbons (TPH) test. Because the HRSD laboratory does not perform this test, measurements were
                    determined for individual organic constituents. The volatile organic compounds, benzene, toluene,
                    ethylbenzene, and xylene, usually measured together in a test known as BTEX, and the polynuclear
                    aromatic hydrocarbon, naphthalene were all' measured using the purge and trap gas
                    chromotographic/mass spectrometric (GC/MS) method.

                         In the GC/MS method, the sample is purged by bubbling an inert gas through the sample to vaporize
                    the organic constituents, and the organics are collected on a sorbent trap (Eaton et al, 1995). The
                    compounds are then desorbed, using the same inert gas, onto the gas chromotograph, which separates the
                    compounds into stationary and mobile phases. The mass spectrometer ionizes the molecules into
                    charged species to detect the compounds. BTEX and naphthaline concentrations are determined all in
                    one test.


                         The concentrations for BTEX and naphthaline were below detection limits in nearly all samples. A
                    toluene reading was registered for the June 24 storm event, but HRSD staff noted that the quality control
                    blank was also measurable for this contaminant. It is concluded that an error occurred in the chemical
                    analysis.

                         That the concentrations for these organic constituents were consistently below detection limits is
                    surprising. It seems to refute the theory that the ultra-urban environment is a hotspot for hydrocarbons.
                    Of course, the analyses are of stormwater runoff from but one parking lot in the downtown area.
                    Although it is expected that the parking lot would be a source for hydrocarbons, it is possible that the lot
                    is an unusually clean one. Perhaps the concentration of organic compounds would be higher in runoff
                    from the adjacent roadway.



                    4.6 Discussion of Results.


                         Both the sand filter and the Carbon/Sand Filter provided pollutant removal for seven of the nine
                    chemical parameters that had detectable concentrations in the samples. Of these seven parameters, the



                                                                      4- 2 8








                       CSF provided a higher pollutant removal than the sand filter for six, with varying degrees of confidence.
                       Table 4-23 summarizes the results of the pollutant removal analysis.




                                                   Sand Filter                            Carbon/Sand Filter
                                                                                                                             Higher
                                          Low           High                         Low           High                     Pollutant
                       Pollutant      Analytical     Analytical                  Analytical    Analytical                   Removal
                       Parameter          Value         Value     Confidence         Value         Value     Confidence    Efficiency     Confidencc
                           (1)            (2)           (3)           (4)            (5)           (6)            (7)          (8)           (9) --

                         TSS              23%           69%         Medium           -4%           60%         Medium      Sand Filter     Medium
                         TP               9%            21%         Medium           29%           41%          High           CSF           High
                         TKN              I %           17%           Low            13%           30%         Medium          CSF           High
                         NH3              ---           14%           Low            ---           20%          High           CSF           Low
                         BODS             ---           29%           High           ---           43%          High           CSF           High
                         TOC              -6%           7%            Low            0%            19%         Medium          CSF           Low
                         Cu               7%            7%            Low            19%           23%          Low            CSF           High
                         Zn               -121%         -119%         High           -99%          -95%         High         Neither           ---
                         Hardness         -369%         -324%         High           -379%         -368%        High         Neither           ---



                       Table 4-23.     Summary of pollutant removal efficiencies for the sand filter and the Carbon/Sand Filter.


                             For each filter type, Table 4-23 gives the high and low mean concentration difference (columns two
                       and three and columns five and six, corresponding to data sets with different storms included. The
                       confidence is given for each pair (low/high) of removal efficiencies (columns four and seven). A low
                       confidence indicates that the t-tests for both the low and the high values concluded that the difference in
                       sample means may be due to variation in the data. A medium confidence indicates that one of the t-tests
                       made this conclusion, and a high confidence reflects a true concentratioin difference for both the low and
                       high values. Column eight shows which filter had better pollutant removal results, and column nine
                       indicates the degree of confidence that one filter truly outperforms the other. That confidence relates to
                       the t-test results for the difference between the two effluent concentrations. Note that for zinc and
                       hardness, neither filter is considered superior because they both export these contaminants.

                             Table 4-24 compares the pollutant. removal efficiencies of the sand filter and the CSF to those of
                       other BMPs. The comparison is only for those pollutants that are commonly reported in BMP
                       effectiveness studies. The other BMPs listed are those that conceivably could be used in the ultra-urban
                       landscape. The information for these other BMPs is derived from the "Urban Watershed Management:
                       A Workshop for Innovative Urban Watershed Restoration and Protection" document, published by the
                       Center for Watershed Protection. This agency is a source for the most current information on many
                       kinds of BMPs, drawing information frequently from newly published studies.

                             The pollutant removal data for the Carbon/Sand Filter does not compare favorably to the reported
                       values for other BMPs. Curiously, though, the pollutant removal efficiency for the sand filter tested in
                       this study is much lower than the value reported for sand filters in the Center for Watershed Protection
                       document. Because the design of the sand filter studied here is the same one used in other regions,
                       perhaps there is a regional effect on how pollutants are transported and filtered. Because of the inherent
                       difficulty in comparing BMPs tested under different weather conditions, the more meaningful
                       comparison is that of the two filters tested for this project. The percentage difference in pollutant



                                                                                 4- 29








                         removal between this sand filter and the Carbon/Sand Filter can be applied to reported values for sand
                         filters in other areas to see how a Carbon/Sand Filter would perform there.



                          BW Pollutant Removals
                                                                            Total
                                                                         Suspended             Total              Total
                              BMP Type                                      Solids         Phosphorus          Nitrogen

                          Carbon/Sand Filter                               (-4)-60             29-41              13-30
                          Sand Filter                                       23-69              9-21                1-17
                          Dry Extended Detention Pond                         30                10                 10
                          Dry Well                                            90                60                 50
                          Conventional Infiltration Trench                    90                60                 50
                          Porous Pavement                                     90                60                 80
                          Sand Filter (others)                                85                50                 35
                          Peat Sand and Compost Filters                       90               40-70              20-50
                          Biofilters                                          80                45                 25



                         Table 4-24. Comparison of pollutant removal efficiencies for different BMPs.








































                                                                                      4 - 3 0












                                                             REFERENCES




                      Barbachem, Michael J. and Ma@orie Mayfield. 1996. "Watershed Management in the Elizabeth
                      River: Moving Toward Implementation of the Watershed Action Plan." from Watershed Planning &
                      Management: Current Approaches and New Directions. Proceedings of the Norfolk Branch, Virginia
                      Section, American Society of Civil Engineers Annual Technical Seminar.

                      Bell, Warren. 1993. "A Catalog 6f Stormwater Quality Best Management Practices For Ultra-Urban
                      Watersheds." Engineering Dept., City of Alexandria, Virginia. 20 pp.

                      Bell, Warren. 1994. Personal communication. City Engineer. City of Alexandria, Virginia.

                      Calgon Carbon Corporation, Inc. 1989. "Adsorption Filtration Design Guidelines for Filtrasorb
                      Activated Carbon Water Treatment Systems." Calgon Activated Carbon Application Bulletin #27-
                      96a.


                      Calgon Carbon Corporation, Inc. 1988. "Filtrasorb 300 and 400 for Wastewater Treatment."
                      Activated Carbon Product Bulletin #27-33c.


                      Calgon Carbon Corporation, Inc. 1991. "Filtrasorb 300 and 400 Granular Activated Carbon for
                      Potable Water Treatment." Activated Carbon Product Bulletin #20-68g.

                      Calgon Corporation, Inc. 1979. "Designing Adsorption Systems for Liquid Phase Processes."
                      Bulletin #23-74.


                      Carlock, John M. 1996. Personal communication. Director of Physical and Environmental Planning.
                      Hampton Roads Planning District Comnuission.

                      Center for Watershed Protection. 1996. "Urban Watershed Management: A Workshop for Innovative
                      Urban Watershed Restoration and Protection." Silver Spring, MD.

                      CH2M Hill with Woolpert Consultants, Inc. 1993. Part 2 of the VPDES Storm Water Permit
                      Applicati for City of Portsmouth, Virginia.

                      City of Alexandria. 1993. Alexandria Sppplement to the Northern Virginia BMP Handbook.
                      Department of Transportation and Environmental Services, City of Alexandria, Virginia.

                      City of Portsmouth. 1995. Real Estate Database. Digital file.

                      City of Portsmouth. 1995. Property Report. Department of Economic Development.

                      City of Portsmouth. 1992. Application for NPDES Permit for the Cfty of Portsmouth Municipal
                      Sqparate Storm Sewer System, Part 1. Department of Public Works, City of Portsmouth, Virginia.

                      City of Portsmouth. 1991. Chesapeake B4y Preservation Area Overlay Ordinance. Chapter 9.1 of
                      the Code of the City of Portsmouth, Virginia.


                                                                  REF-I









                      Davis, Mackenzie L. and Cornwell, David A. 199 1. Introduction to Environmental En&eedpg. New
                      York: McGraw-Hill, Inc. 2d Edition. Ch. 5.

                      Devore, Jay L.    1987. ProbabilAy and Statistics for EggLneering and the Sciences. Belmont,
                      California: Wadsworth, Inc. 2nd Edition.

                      Eaton, Andrew D., Clesceri, Lenore S., and Greenberg, Arnold E., eds. 1995. Standard Methods for
                      the Examination of Water and Wastewater. Washington, D.C.: American Public Health Association.
                      I 91h Edition.

                      Environmental Protection Agency. 1990. National Pollutant Discharge Elimination System Permit
                      Application Regulations for Storm Water Discharges; Final Rule. 40 CFR Parts 122, 123, & 124.

                      Environmental Protection Agency. 1993. Guidance Spe@:j@g Management Measures for Sources of
                      NqMoint Pollution in Coastal Waters. Washington, D.C.: U.S. E. P.A. Office of Water.

                      Hampton Roads Planning District Commission. 1993. "Nonpoint Source Pollution: Be Part of the
                      Solution." Chesapeake.

                      Hampton Roads Planning District Commission. 1991. Best ManggMent Practices Design Guidance
                      Manual for HNnpton Roads. Chesapeake.

                      Hampton Roads Sanitation District. "Me Role We Play Cleaning the Waters of the Chesapeake
                      Bay." Public Information Pamphlet.

                      Herricks, Edwin E., Ian Milne, and Ian Johnson. 1994. Selecting Biological Test Systems to Assess
                      Time Scale Toxicily. Alexandria, VA: Water Environment Research Foundation. Project 92-BAR-1.

                      Jensen, Ric. 1993. "Urban Areas Curb Nonpoint Runoff." Environmental Protection. 4(8):38-40.

                      Kennedy, George. 1996. Personal Communication. Environmental Scientist. Hampton Roads
                      Sanitation District.


                      Kadlec, Robert H., and Robert L. Knight. 1996. Treatment Wetlands. Boca Raton: Lewis
                      Publishers. Pp. 490-531.

                      KrenkeL Peter A. and Novotrly, Vladimir. 1980. Water Quali1y Management. Orlando: Academic
                      Press, Inc. pp 207-239.

                      Knutson, John. 1994. "Can Sand Filters Really Remove Hydrocarbons from Urban Runoff.)" Wat.
                      Prot. Techniques. 1(3):93-4.

                      Lee, G. Fred and Anne Jones-Lee. 1994. "Are Real Water Quality Problems Being Addressed by
                      Current Structural Best Management Practices?" Public Works. ??:53-55,70-72.

                      Marsala, Mike. Date unknown. "Norfolk - Portsmouth." Postcard. N. Myrtle Beach, S.C.: Kruger,
                      Ltd.





                                                                   UF-2








                       Marsala, Mike. Date unknown. "Norfolk, Virginia." Postcard. N. Myrtle Beach, S.C.: Kruger, Ltd.

                       National Groundwater Association. 1993. "Treatment Technology for Contaminated Soils and
                       Groundwater." Short Course Materials. Pp.5-30 to 5-36.

                       Nyer, Evan K. 1992. Groundwater Treatment Technq!gW. New York: Van Nostrand Reinhold. 2nd
                       Edition. Pp. 90-111.

                       Pitt, Robert. 1994. "Me Risk of Groundwater Contamination from Infiltration of Stormwater
                       Runoff." Wat. Prot. Techniques. 1(3):126-8.

                       Pitt, Robert et al. 1993. Investigation of iMpropriate Pollutant Entries Into Storm Drainage
                       SygLems: A User's Guide. Cincinnati: Risk Reduction Engineering Laboratory, Office of Research and
                       Development, U.S. EPA. pp. 1,2,6.

                       Schueler, T.R. 1994. 'Tollutant Dynamics of Pond Muck." Wat. Prot. Techniques. 1(2):39-46.

                       Schueler, T.R. 1994. "Developments in Sand Filter Technology to Improve Stormwater Runoff
                       Quality." Wat. Prot. Techniques. 1(2):47-54.

                       Schueler, T.R. 1994. "First Flush of Stormwater Pollutants Investigated in Texas." Wat. Prot.
                       Techniques. 1(2):88-89.

                       Schueler, T.R. 1994. "Hydrocarbon Hotspots 'in the Urban Landscape: Can They Be Controlled?"
                       Wat. Prot. Techniques. l(l):3-5.

                       Schueler, T.R. 1994. "Innovative Leaf Compost System Used to Filter Runoff at Small Sites in
                       Northwest." Wat. Prot. Techniques. l(l): 13 -14.

                       Schueler, T.R.    1994.    "Failure Rates of Infiltration Trenches/Basis Assessed in Suburban
                       Maryland." Wat. Prot. Techniques. l(l):15-17.

                       Schueler, T.R. 1994. "Cars Are Leading Source of Metal Loads in California." Wat. Prot.
                       Techniques. l(l):28.

                       Schueler, T.R. 1994. "Sources of Urban Stormwater Pollutants Defined in Wisconsin." Wat. Prot.
                       Techniques. l(l):30-31.

                       Small,Dorothy. 1995. "What's in a Number? TPH." Virginia's Environment. 2(l):14-15.

                       Snoeyink, V.L. and D. Jenkins. 1980. WaterChgniga. New York: John Wiley& Sons.

                       Southeastern Virginia Planning District Commission with Hampton Roads Water Quality Agency.
                       1989. Rqdonal Stormwater Management Strategy for Southeastern Virginia.. Chesapeake.

                       Stilwell, Robert and Bob Bailey.        1993.     "Stormwater Sampling A Constant Mandate."
                       Environmental Protection. ?(?):54-56.





                                                                     REF-3








                     Tchobanoglous, George and Franklin L. Burton. 199 1. Wastewater ELigineering: Treatment,
                     Disposal, and Reuse. New York: McGraw-Hill, Inc. 3-Edition. pp.314-324.

                     URS Consultants, Inc. 1995. Technical Assessments in Support of the Elizabeth River Regional
                     Action Plan. for The Elizabeth River Project. Virginia Beach.

                     U.S. EPA. 1992. Environmental 1mRacts of Stormwater Discharges. EPA 841-R-92-001.

                     Center for Watershed Protection. 1996. Urban Watershed Management: A Workshop for Inno-v-ative
                     Urban Watershed Restoration and Protection. Silver Spring.

                     Virginia Department of Waste Management. 1990. "Toxicity Characteristic." Richmond. 4pp.

                     Walker, Carroll. 1981. Norfolk: A Tficentennial Pictorial Flistog. Norfolk: The Doming
                     Company/Publishers.

                     Welch, E.B. 1980. Ecological Effects of Wastewater. Cambridge: Cambridge University Press.
                     pp.286-293.









































                                                                 REF-4



I
I
I
I                   Appendix A-1
I
I             . BMP Sizing Calculations
I
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I
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I
I
I
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I



                                                                                                                             IV291 71f

                                                                                                                Page 1.of 3

                                                                ALEXANDRIA, VIRGINIA
                                                        ULTRA-URBAN BMP COMPUTATIONS



                       WORKSHEET Hl: COMPUTATIONS FOR D. C. SAND FILTER (ORIGINAL SINGLE
                                                                POOL CONFIGURATION)


                       Part 4: Considering data on
                       Worksheet E, select maximum                                                                                 Wf
                       ponding depth over filter:                                                                                  _L
                                         2h =                       ft;                           OPTIONAL             C    S
                                                                                                   BYPASS             DOOR
                                           h =        0. 71"___j f t             INFLrW            P PE                     7-          60"MINIMUM
                                From WORKSHEET E;                                PIPE                                                   HEADSPACE FOP
                                                                                                                                        MAINTENANCE
                                                                                                                            'dj
                                               0.337         acres                                                                      OUTFLOW
                                  a                                                         -L           6-@:OLLECTOR       I           PIPE
                                                                3                                ir-A        PIPE
                                WQV        1   612.1          ft                            ._LP         _Lf                L-e-.
                       Outflow by          gravity possible                                                    Ll

                       Effluent pump required

                       Part 5: Compute Minimum Area of Filter (Afm)-:
                                A fm       5451ad
                                           (df    + 9)
                                         (545 x           0.337       x      2.0                    2.0         +       0, 75@
                                             /_33, f.      f t2

                       Part 6: Considering Site                      Cgnstraints, Select Filter Width (Wf.L
                       and Compute Filter Length                       ( f I and Adiusted Filter Area (Af)-:

                                Wf   = 1      /0            ft;
                                Lf = Afm/ Wf

                                             133.6              /0
                                             13, Y           say    F- 14= f t
                                .Af      Wf x Lf                  /0      - x       /f
                                              140           ft2





                       BMP    SUPPLEMENT (REVISION 1) 8/1/93                                                                  Page 2-A4-10









                                                                   Worksheet HI
                                                                   Page 2 of 3

            Part 7:   Compute-the Storage Volume on Top of the     Filter(V Tf)
                  VTf   Af x 2h      NO      x   ISO
                                  ft3

            Part 8:   Compute Storage in Filter voids (Vv)-:
                      (Assume 40% voids in filter media)
                  VV = 0.4 x Af x (df + d  9)
                     = 0.4 x     IqO  x     2. 0  +    0-5,

                                   f t3


            Part 9: COMRute Flow Through Filter During Filling Period Wn):
                              (Assume 1-hour to fill per D.C. practice)

                  VQ   kAf(df + h)- ; use k    2 ft/day = 0.0833 ft/hr
                               df
                        0.3315
                       EG'"a-3 x    NO      )c    2.0    +   0. -t-5'     2.0
                         6q.2.  ] ft3


            Part 10:- Compute Net Volume to be Stored Awaiting Filtration
            -(Vst.L:
                  Vst   WQV - VTf    Vv - V Q
                                       210    -    14 0  -    6q. 2-
                                   ft3

            Part 11: Compute Minimum Length of Permanent Pool         pm)-:

                  L pm      Vst-        119                x    /0
                         (2h x Wf)

                                  ft








            BMP @UPPLEMENT (REVISION 1) 8/1/93                             Page 2-A4-11








                                                                    Worksh-eet H1
                                                                    Page 3 of 3

             Part 12: Compute Minimum Length of Sediment Chamber (Lsm)
                        (to contain at least 20% of WQV per Austin practice)

                   Lsm     0.2WOV -- "             /
                           (2h x Wf)

                                     ft

             Part 13: Set Final Length of Permanent Pool (L      P)
                   Lsm + 2ft               + 2      to. 7-  f t
                   If Lpm     Lsm + 2ft, Make L p    Lpm      13,     ft
                   If Lpm < Lsm + 2ft, make Lp      Lsm + 2ft               ft
             Part  14: Set Lenoth of Clearwell       cw) for Adequate Maintenance
                   Access (Minimum = 3 ft) and Compute Final Inside Length
                   (Ltil:
                   Lcw = I    @q  @ ft
                   Sum of -irntnet-i-er- partition thicknesses (tpi)     S,     ft
                   Lti   Lf + L P + Lcw + t pi
                                   +            +   3      +    'T

                                     ft


             Part 15: Design    Structural Shell to Accommodate Soil and Load
             Conditions at Site:

                   It may be economical to adjust final dimensions upward to
                   correspond with standard precast structures or to round
                   dimensions  upward to simplify layout during construction.

             Part  16: Design  Effluent Pump if Required:

                   Since pump  must be capable of handling flow when filter is
                   new, use k  = 20 feet/day    0.833 ft/hr

                   Q    XAf(df + h)
                           d f

                        (0.833 x            x            +          H/
                                   ft3/hr ; /3600              cfs;

                   x 448.8            gpm


             BMP SUPPLEMENT (REVISION 1) 8/1/93                              Page 2-A4-12



I
I
I
I                    Appendix A-2
I
I                 Construction Plans
I
I
I
I                               -
I
I
I
I
I
I
I
I
I






















                                                                                                                            CITY OF POP"I'SMOUTH
                                                                                         ENGINEERING AND TECHNICAL SERVICES DEPARTMENT
                                                                                                                            PORTSMOUTH,VIRGINIA                                                                                                                 MAP f,


                                                                                                                         PLAN AND PROFILE OF
                                                                                                             STORMWATER MANAGEMENT BMP

                                                                                                    PORTSMOUTH CARBON/SAND FILTER




                                                                                                                    -j.
                                                                                                                                      U EN






                                    MISTING   @@[email protected]
                                                                                                                                                          REET
                                                                                                                                                                           r-IF

                                                                                                                                                                                                                                       INDEX OF SHEETS


                                                                                                                                                                                                                                    I      PLAN SHEET
                                                                                                                                                                                                                                    S-1    STRUCTURAL
                                                                                                                                                                                                                                           PROFILE SHEET
                                                                                                                                                                                                                                    3      DETAIL SHEET


                                                                                 APPROVED
                                                                                                    I        C ORIQ@                 DATE                    RIC"IRD       HART@All. P.I.           DATE
                                                                                                         .. . .. .........                                         ....... ..     .....








                                                                                                                                                                                    QLJ EE N                           STREET                          (32')                                                                                                    RLI@ EEtC-T.Cl                          -OYED
                                                                                                                                                                                                                                                                                                             C)




                                                                                                                                                                           OR
                                                                       MiDDLE                          ASPHALT
                                                                       STREET
                                                                                                       PARKING
                                                                   MALL (60                                AREA                                                                                                                 PARKING AREA                                                                 CD
                                                                                                                                                                       \A                                                                                                                                                                                       I.RAELILoENCK AIGONCREF SI LIHILK 10 HE
                                                                                                                                                                                                                                                                                                                                                                TREPACED (SEE DETAIL) FOR STORM
                                                                                                                                                                                                                                                                                                                                                                DRAINAGE TRENCH AND MANHOLE 02.
                                                                                                                                                                                                                                                                                                                                                                2. ANY EXP05LD CONCRETE TO 8E RE MOAO SHALL
                                                                                                                                                                                                                                                                                                                                                                BE S CUT 'OR REMO-
                                                                                                                                               1.                                                                                                                                                                                                               3 CON RACTOR RLSFONSIELE FOR RE@L,IkCING ANY
                                                                                                                                                                                                                                                                                                             m                                                  DAMAGED CONCRETE 6"4 BRICK OUT IDE TRENCH.
                                                                                                                                                                                                                                                                                                             m                                                  4, S, ENALK TO BE SNEPT IN--- FINE SANG AFTER
                                                                                                                                                                                                                                                                                                                                                                1EPICE.1 7 OF eR,CK
                                               cD?                                                                                              GRAVE@                                                                                                                                                                                                          G NO I. DISTURB ViRGNA FCAER DUCT LINE.
                                             m ARINW                                                                IF                         PARK NG                                                                                                                                                                                                          6St LAILK TO BE SWE@T NITH FINE SAND AFTER
                                                                                                                                                  AREA                                                                                                                                                                                                          REPEACEME IOF BRICK
                                                                                                                                                                                                                                                                                                                                                                7, ALL FACKF@Ll SU ROUNDING CONCRETE STRUCTURE
                                                                                                                                                                                                                                                                                                                                                                AND F04"PE TRENG- IN 'HE GRA@L lXNlNC
                                                                                                                                                                                                                                                                                                                                                                S
                                                                                                                                                                                                                                                                                                                                                                      UP 10              11XIF
                                                                                                                                                                                                                                                                                                                                                                LOT SHALL BE EEC' 10 ED .11. 6- OF
                                                                                                                                                                                                                                                                                                                                                                C-SlItR RIN (111
                                                                                                                                                                                                                                                                                                                                                                NI I,
                                                                                                                                                                                                                                                                                                             c                                                    ALL -IINI; 1111 L'@llll
                                                                                                                                                                                                                                                                                                                                                                ,-INI 11,:-
                                                                                                                                                                                                                                                                                                             0                                                  .... ECI A L,NEES ON INCH STRIELI.
                                                                                                                                                                                                                                                                                                                                                                1C 5'D@W K. GUTTER. MANIHOLES. AND 5TGRM CRAN
                                                                                                                                                                                                                                                                                                                                                                1. B@ CLEARED OF ANY SILT. SAND. OR DEBRIS
                                                                                                                                                                                                                                                                                                                                                                UP
                                                                                                                                                                                                                                                                                                                                                                @G@ comFLlll N OF CONSTRUCTION
                                                                                                                                                                                                                                                                                                                                                                IPERFORATED @IJC I'lI`E TO BE PLICFD N FACI
                                                                           5;               IX                                                                                                                                                                                                                                                                  ITRATICLI CHMeE@ (SEE DEIAIL. SHEET 3),
                                                                                                                                                                                                                                           CENTRAL FIDELITY
                                                                                                                                                                                                                                            BANK BUILDING

                                                                                 SIT CIAI ;Illll@ICN       I
                                                                                 I'M    LAICH PILIT.LN'
                                                                                                                              PROP05LD ORA     CE
                                                                                     CUT     3.15 (ENOTTH)                    EAS MEN T (90- X 16)
                                                                                 ,0, OF  "EIR  -    20
                                                                                 Sump  =  7.94
                                                                                       VEM   I  PA91IZLI@                     R 3,          INA                  RLNNO,,T1.IPLXCF BRIG                                 IL
                                               REST.'S                                                     (D                                                                  "N'   BAFl
                                                                                                                                                     Q
                                                                                                                              EGG
                                     kGHT-O-A,7                                                                                                 5.9', 4


                                                                                     . .....                                                             FIT   MATCH CRADE
                                                                                                                                                             N                                 1-11 CH                   STREET- (100')-
                                                                                                                                                             IN       'Ul@l
                                                                                                                                                         IN, CUT F)     5.5oE
                                                                                                                                                         SEE PRO III 1 11 1.111                                                                                                                                   DRAWINGS NOT TO SCALE






                                                                                                                                                                                                                                                                                    YA PoTAN
                                                                                                                                                                                                                                                                                                                  11-5.94
                                                                                                                              it                                                                        OF CORD BOX


                                      OF GLANS G

                                                                                                                                                                                        of cuNc box                                                                                                          WT: "I's                                           .... ... ... t ot'll @IAII@Fkl A, RI I'll 0-H
                                                                                                                                                                                                                                                                                                             Q T14F VIRGINIA PO@tIi LLUCI- I'll EXACT LOCATION AND U-11 Of ItIf V1861- II,NIIR
                                    RIGHT-OF-WAY                                                                                                                                                                                              IW-S 5o*                                                       Q CT -1 HE DETERMINED BY THE CONTRILTOR IN, hE FIELD. GTRIS IN ON-ION %'Lt
                                                                                                                                                                                                               UF-WAY
                                                                                                                                                                                                       RIGHT-                          (TO BE DETERMINED IN FIELD)                                           DETERMINE THE DEPTH 01 THE MANHOLE AND THE NvERT AND RACE OF THE @.C @E
                                                                                                                                                                                                                                                                                            @D





















                                                                                          POSIMONING OF CONCRETE BOX & DIVERSION MANHOLE                                                                                                                                                      PROFILE        OF EFFLUEN 1 8" PVC PIPE
                                                                                                                          SCALE: I- . 5'                                                                                                                                                     SEE SECTION     2. SHEET $-I           scAIE: I- - 2*



                                                                                                                                                                                                                                                                                                                                                                                       C.B=

















                                                                                                                                                                                                                                                                                                                                                                                GENERAL STRUCTURAL NOTES:
                                                                                                                                                                                                                                                                                                                                                                                I@  THE C011RACTOR 1"'Ll 'f, I, "LE                                         or OTHER IT, y@
                                                                                                                                                                                                                                                                                                                                                                                    AS To rC,CS.                                       """ S.               -aS      01. 1. Of
                                                                                                                                                                                                                                                                                                                                                                                    ,LAC,G I SIT IN SHiLMRI, liC.,T
                                                                                                                                                                                       I-                                                                                                                                                                                           Dr,"     TLW LOAD ISID 11 THE 1E1- Or 1.1 1. -8 : XIS.To -- Rl- 'DID
                                                                                        - - - - - - - - - - -                                                                                                                                                                                                                                                                   3   PRIO     0 PLACING CONGREIE.                       LXG-FCN -11. BE M11111C Ul '@E
                                                                                                                                                                                                                                                                                                                                                                                    EXONE    R TO EXPLORE THE EXTENT GF ANY LOOSE SOFT OR OTHERAISE LIDEI-81f ATtRAL
                                                                                                                                                                                                                                                                                                                                                                                    SEE"'    BEDDiNC SHALL RE PLACED ITHERC SIECTFIO B1 THE TNG@IEEFE
                                                                                                                                                                                                                             -NICHOLS CO. 2                   BEARING CARS
                                                                                                                                                                                                                             19WI LOAD HANDED CARBON STEEL GA- D                                                                                     RE    ATED                 I.  STRUCT   RE IS DESIGNED IN AGI.IGINCE - ILE REPORTS AID SFECIFIC.1-5
                                                                                                                                                                                                                             ,_G,,FD Eou- 1-1)                                                                                                                                      OF TIE   'BUILDING GO I RID.IRE.EITI FOR REINFORG                       CD C           - 31-9)
                                                                                                                                                                                                                                                                                                                                                                                             N                                                              ,,@NCRETE' (AC
                                                                                                                                                                                                                                                                                                                                                                                    AND 'E IRCT.C.-                                    C--C'C -UC           F' (A. ' .R`o@
                                                                                                                                                                                                                                                                                                                                                                                                                                       Co,RjS51             STREIC", or
                                                                                                                                                                                                                                                                                                                                                                                5   XII CDNCRETE S.ALI G-,l A 28 DAY                                        A
                                                                                                                                                                                                                     - - - - - - - - - - - - - - - - - - - - - - -                         - - - - - - -                                                                            IODD 15, -D al P
                                                                                                            - - - - - - - - - - - -- -                          - - - - - -      T     - - - - - - - - - -
                                                                                                                                                                                                                                                                                                                                                                                fi  RON(ORG,NG 5T- S-11 1CNI.1U 10                     1SrU I-TH5 GR-DC 60 ("U"U `[10 T`CGG"PS1)
                                                                                                                                                                                                                                                                                                                                                                                1   .1, 1,- I-XI
                                                                                                                                                                                                                                                                                                                                                                                d.  ALL R-FoRGIND -RXID 1-INHUIS (G.X1 ) ON 1111 P-5 AND JIIAIII 11-L
                                                                                                                 TOP A,
                                                                                                                                                                                                                                                                                                                                                                                    El LAPPED 3E. BAR -.11CA A' SELIG. ..LESS WHER.ISE NOTED
                                                                                                                                                                                                                                                                                    I                                                                                           TV  GFELE AL DETA,LS Or FAek-l- AID PLACING OF RELN-CINC A.. ACHEKIC
                                                                                                                                                                                                                                                                                    I                                                                                               GOV A         HFIH-rll@                            HE IN ACCORDANCE -1 ACT jlft-hB No
                                                                                  __T                                                                                                                                               ffm                                                                                                                                                                                                IT I., 1",,          11... A, H11-:11. III
                                                                                                                                                                                                                                                                                                                                                                                                                                                            I AHI A". ill ," 1.        IT,

                                                                                                                                                                                                                                                              - - - - - -                                                                                                       To           R,                                        ,,,D .11 @,Cl GI,RING PCIIHNG 111-- -1
                                                                                                                                                                                                                                                                                                                                                                                             'Rl.Nl
                                                                                                                                                                                                                                                                                                                                                                                             A"
                                                                                                                                                                                                                                                                                                                                                                                                                                       ONI:
                                                                                                                                                                                                                                                                                                                                                                                    11, 1. OTT 1-NIF11 ""I
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       r A,
                                                                                                                                                                                                                                                                                                                                                                                                  -ALI .1 1 IIII-L. F11CR1 G11-11IND I'D GGIH GR- I@                                   AIT
                                                                                                                                                                                                                                                                                                                                                                                12  ALI STEEL
                                                                                                                                                                                                                                                                                                                                                                                    NEIA1111,                                          IIA ICAA@1,
                                                       CIA        IN RX,                                                                                                                                                                                                                                                                                                                                                                                    N. I
                                               AND TL .. CC



                                                                                                                      ,#5 Top Al BOTTOM
                                                                                                                              0 DING S )               1
                                                                                                                              - - - -- - - - - - -                                                                                                            - - - - - - - -
                                                                                                                                                                                                                                                                                                                                                                                                                                       DIX
                                                                                                                                                                                                                                                                                                                                                                                                                                       1. 1 E,              1.
                                                                                                              fNF NAH TYPE H-Ho7e)
                                                         CA11 L..                                               .-I                                                                                                                                 T F_ G- - PLIE IN
                                                         SrEp                                                       F- I GQ.R                                                                                                                       A..          CMI,                                    2,_6"
                                                                                                              OR --ED EQUAL
                                                                                                               G_R                                                                           PLAN
                                                                                                                                                                                      SCALE TIr - _,G_




                                                                                                                                                                                                                                                                                                                                                                                                                                                            NTEASECT;CN
                                                                                                                                                                                                                                                                                                                                                                                                                                       LOWING CON I INUO                   S
                                                                                                                                                                                                                                                                                                                                                                                                                                                            & iNTER9ECDONS
                                                                                                                                                                r-lo
                                                                                                                                                             F         T                                                                                                                                                                                                        _,EFJNFORQING A I                                      CORNERS
                                                                                                                                                                                                                                                                                    77!


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                                                                                                                                                                                            st-c I ION                                                                                                                                                                                                                                                                                 ?.*,G,@,. F lo
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        lN, E,
                                                                                                                                                                                             EcALE, 112'        V-O                                                                                                                                                                                                                    -Q

                                                    TOP OF SLAB                                        L 3.3.1/2 GALir                                                                                                                                                                         ALL                                                                                                                                     012- o@o             A"O
                                                                                                       loomr)                                                                                                                                                                                                                                                                                                                          1EI" PIPE
                                                                                                                                                                                                                                                                                                                                                                                                                                       HOT                  To. -- IT, 6,C2
                                                                                                                                                                              I "'ETTA, #4.                                                                                                          ADDITIONAL #A'X E F.
                                                                                                    5/.. 2.                                                                   (TYP.,                                                                                                                                                                   GRAPHIC SCALES                        _G                                        4ee.
                                                                                                                                                                                                                                                                    OPEN
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                                                                                                            '.'or      1.1
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                                                                                                                                                                                                                                                                                                                                                                                                                                       CIA














                                                                                                                                                                                                                                                                         2 c,

                                                                                                                                                                                                                                                                                            P ,C  PIPE









                                                                                                         Go
                                                                     @c
                                                                                                                                                                                                                        11 IXII I, A"                                                                                                                                                                                                  .9 F C
                                                                (.A. I SLID TEELNI@ No,                        C@Nc,                                                                             L
                                                                             DETAIL A                                                                                                                                                                                                                                                                      I  INCH      I FT.                                                          C/Ty OF POWSMOUTH
                                                               GRATE SUPPORT FRAME                                                                                                                                                        TYPICAL REINFORCING DETAIL                                                                           2*    1,     0 l' 2'                          4.                                        EA-16"I'VEFRING AND FECHNICAL
                                                                           S.AELL l- - l'-6'                                               DETAIL FOR 3'-(J"xi'-3"_VVALL 0PNG,                                                                  FOR '@VALL OPENINGS                                                                                                                                                                    SEROCES OEPARTYENr
                                                            rill                                                                                               ICALE 112@ - I -W                                                                                   NO SCALE                                                                                                     F TT                                                   FIL TE@R 50A
                                                                                                                                                                                                                                                                                                                                                          1/7 INCH - I                                                                 Min sMION-1;
                                                                                                                                                                                                                                                                                                                                              F. F711-                          Z".






















                                             GENERAL NOTES






                                                                                                                                                        A





                                                                P-





                                                                                                                       STANDAR0  MANHOLE 1                             -7 A---
                                                                                                                          STORM SEWER                         SPECIAL DIVERSION MANHOLE







                                                                                                                 A



                                  17
                                                                                                                                                                                                                                                                -7






                                                                                                                 STORM DRAIN  TRENCH  OLTAII. AND
                                                                                                               PAVEMENT REMOVAL AND  REPL,ACEMENT       TYPICAL BRICK SIDEWALK CROSS SECTION

                                                                                                                           -rage-                                    -IUA%f-





                                    P.1Z 1.





                                                                                                                                                                                                                                                  PAVEMENT PATCH TYrE A


                                                                                                       I OR OLWA ILRtNC



                                                                                                                      POSIHIONING OF PERFORATED PVC IN FILTRATION CHAMBER
                                                                                                                                              s-                                                                                   DRAWINGS NOT TO SCALE


                                                                                                                                                                                                                                                                                         C.-



I
I
I
I                    Appendix A-3
I
I          Construction Bid Price Tabulations
I
I
I
I
I
I
I
I
I
I
I
I
I





















                                                                                                                                CPG                                       TMC                                     VIRTEXCO


                     Item No.                       Item                          Quantity          Unit              Unit                Subtotal               Unit               Subtotal                Unit                 Subtotal
                                Furnish & Install Reinforced Concrete
                           1    Filter Box                                              I        lump sum           $29,976               $29,976              $31,680              $31,680               $31,000                $31,000
                           2    jFurnish & Install Diversion Manhole                    I           each            $1,200                $1,200               $1,800               $1,800                $2,875                 $2,875
                                IFumish & Install Standard Manhole -
                           3    Type I                                                  I           each            $1,200                $1,200               $1,950               S1,950                S2,975                 $2,875
                                IFumish & Install IS " Reinforced
                           4    Concrete Pipe, Class IV                                 45       linear feet        $40.00                $1,800               $49.00               $2,205                $28.75                 $1,294

                           5    Furnish & Install 8" PVC. Pipe                          19       linear feet        $40.00                 S760                $25.00                $475                 $28.75                 $546

                           6    Furnish & Install 8" Perforated PVC Pipe                30       linear feet        $20.00                 $600                $18.00                $540-                $28.75                 $863

                           7    Furnish & Install Select Bedding                        24          tons              $25                                        $25                 $600       -           $30                  $720

                           8    Furnish & Install Select Fill                           63       cubic yards          $18                 $1,134                 $19                $1,197                  $29                  $1,811
                                Furnish & Install Crushed Aggregate for                 19          tons              $20                  $380                  $28                 $532                   $30                  S570
                           9    Pavement Patch
                                Furnish & Install SM-2A Asphalt
                           10   Pavement for Patch                                      2           tolls             $250                 $500                  $275                $550                   $200                 $400
                                Remove & Replace 7" Concrete                                        square
                           I I  Sidewalk Band                                           I           yards             $400                 $400                  $125                $125                   $65                  $65
                                Remove & Replace 4" Concrete Base for                               square
                           12   jBrick Sidewalk                                         6                             S180                $1,080                 $70                 S420                   $83                  S498
                                ITOTAL                                                                                                 $39,630-00                                  $42,074 .00                               S43,516.75









                   Appendix A-3                                                                           Conmtruction bid price tabulation                                                                                      Page A-3-1



I
I
I
I                    Appendix A-4
I
I                 Climatological Data
I
I
I
I
I
I
I
I
I
I
I
I
I





         PWRS INSTRUMENTATION                                                                       Page I





                                PORTSMOUTH WEATHER RECORDS SERVICE


                                               Portsmouth, Virginia
                                      36 degrees 50 minutes 07 seconds North
                                       76 degrees 17 minutes 55 seconds West


         Instrumentation:


         Davis Weather Monitor IFWeatherLink Software: records time, temp, dew point, wind speed and
         direction; barometric pressure; rainfall; computes relative humidity, wind chill temp; records to
         memory high and low extremes of all readings aforementioned; graphs all aforementioned readings;
         real-time (PC visual) barometer trace; variable units (fahreiiheit/celsius: knots, mph, kph, M/S;
         inches, MM, NO)

         Standard cotton region shelter available for independent sensors

         Gemware - Electro-V Psychrometer, Hand-Electric

         R. M. Young Aerovane Precision Electronic Anemometer

         Maximum Gustmaster wind recorder (to 120 mph)

         Downeaster Wind Direction and Speed Indicator (to 100 mph)

         Airguide Aneroid Barometer (Compensated)
         Pr-onamic Tipping Bucket Electronic Rainguage (one spoon; measures to .01")


                  T.-

                         All-Weather Raingage (4 inch diameter, I I inch capacity; measures to .01 (NWS
                          specification)






         CompuTemp Plus electronic temperature sensor/display

         Additional Software:

         DOSFAX/WINFAX (fax transferrals/reception)
         Talking Weather Station 3.23 interface with Davis Weather Monitor 11
         WeatherGraphix 3.4 graphics/data analysis system
         WeatherBrief 3.2 text/visual data system
         WeatherView 2.5B data/graphics system
         Weathermation. WeatherModem 2.2 data/visual system






              PWRS INSTRUMENTATION                                                                                                               Page 2
              "Radar" (old Steve Root program for plotting SD's on the subgridded Limited Fine Mesh I grid)
              Hurrtrak 4.0 Professional Hurricane Tracking/Analysis System

              Visibility: estimated (straightline visual) from 20 foot level

              Database: (dating to July 1976)

              Weather Eye (data storage and analysis)
              Weather Eye Plus (data analysis and graphing)

                                                                      Internet addresses:


                                                               [email protected]
                                                                   [email protected]
                                                                      [email protected]




                                                                    PWRS Keyword Links:


                                    ACON / Articles/Database /Forecast/ Forecasts / Images/ Instrumentation/ Links/ Mall/ Marine/ NC/
                                    News/ Observations/ Radar/  Records / Severe / Sun & Moon / Surface / Synopses/ Tides/ Time/ Tropics





                                                                     Return to PWRS'Home Page
 






               Weather Data Denotations




               DENOTATIONS (Weather/sky conditions)                  Intensity Markings
               A   Hail        GF Ground fog   RW  Rainshower        Precipitation:
               AP  Small hail GL Glaze           S Snow              - Light
               B   Blowing     H Haze          SG  Snow granules     + Heavy
               C   Cloudy      IP Ice pellets  SP  Snow pellets      Sky Condition:
               CL  Clear       K Smoke         SU  Sunny             -Thin or Partial
               D   Dust        L Drizzle       TRW Thundershower     Departures from
               F   Fog        LTG Lightning      T Thunderstorm      Norms:
               FR  Frost       PC Partly Cloudy X  Obscured Sky     - below; + above
                               R Rain            Y Spray
                                               ZL  Freezing drizzle
                                               ZR  Freezing  rain


                                               -- -------- ----


               OTHER DENOTATIONS: NA, not available; NR, not recorded; TEMP, temperature;
                  MAX, maximum; MIN, minimum; T, trace of precipitation; INOP, inopera-
                  tive equipment; MPH, miles per hour; DN, departure from normal;
                  DEP, departure; YR, year; NORM, normal; DST LTG, distant lightning;
                  FROP or FROPA, frontal passage; AM morning; PM afternoon hours;
                  EVE evening hours; E estimated; VBL, variable wind directions


               -----------------------------------------------------------------------------



               COLUMN DENOTATIONS:
               D    Date                             PREC Precipitation
               HT   High Temperature                 WS  Maximum Wind Speed (Gust)
               LT   Low  Temperature                 WD  Direction of Maximum Wind Gust
               MT   Mean Temperature                 HB  High Barometer Reading (Inches)
               DN   Departure from Normal of High,   LB  Low Barometer Reading (Inches)
                    Low or Mean Temperature          SC  Dominant Daily Sky Cover
               HDD  Heating Degree Days              WXR TYPES Observed Weather Conditions
               CDD  Cooling Degree Days                           and Remarks
               -----------------------------------------------------------------------------


               NOTES: All temperatures are in degrees Fahrenheit. All precipitation
                       measurements are in inches. All wind speeds are in miles per hour.






                December, 1995


                - ----- ------- -- -------------- ---- - ----------- --------
                MONTHLY  SUMMARY  OF CLIMATOLOGICAL    DATA    PORTSMOUTH, VIRGINIA
                Portsmouth Weather Records Service
                Portsmouth, Virginia       23702-2017 (3 miles south / West Cradock Section)
                -----------------------------------------------------------------------------
                   Monthly summary of Local Climatological Data for Portsmouth, Virginia,
                  West Cradock Section, during the month of December, 1995. Time is EST.
                ---------------------------------------- ------------------------------------
                 D HT DN LT DN MT          DN HDD CDD PREC WD WS SC WXR TYPE/REMARKS

                ----------------   ------------------------------------------------------------
                 1  61   +3 33   -7 47.0   -2 18.0               SW 35   SU BREEZY
                 2  55   -4 43   +4 49.0    0 16.0               N 22    SU FROPA
                 3  70  +13 36   -2 53.0   +5 12.0               SSW28   PC MILD
                 4  57     038    0 47.5    0 17.5         0.01  NNE23   PC FROPA R-
                 5  58   +3 34   -3 46.0    0 19.0             T S 19    PC FROST (AM) F R--
                 6  54   -4 41   +4 47.5    0 17.5               NNE23   PC COOL
                 7  46   -9 29   -7 37.5   -8 27.5         0.34  NNE30   PC R IP S SG F FROPA
                                                                            0.30" ACCUMULATION
                 8  42  -13 26  -10 34.0  -11 31.0               NE 19   SU FR COLD
                 9  49   -7 38   +2 43.5   -2 21.5         0.62  NW 25    C R F FROPA
                10  40  -15 25  -10 32.5  -10 32.5               NW 27   SU FROPA BLUSTERY COLDER
                11  33  -17 22  -13 27.5  -15 37.5               WNW27   -PC COLD
                12  42   -9 26   -9 34.0   -9 31.0               SW 14   PC
                13  50   -4 29   -8 39.5   -6 25.5               SE 14    C
                14  65  +12 40   +5 52.5   +9 12.5               SW 25   PC
                15  70  +15 47  +11 58.5  +12   6.5              ESE17   PC GF F MILD
                16  57   +5 37   +1 47.0   +3 18.0         0.19  NW 33   PC F R RW FROPA F (EVE)
                17  42   -9 30   -4 36.0   -7 29.0               N 22    PC F(AM) BREEXY
                18  47   -4 29   -4 38.0   -4 27.0         0.05  ENE14    C F R- COLD
                19  44   -6 37   +4 40.5   -1 24.5         0.54  NNW20    C F R L FROPA
                20  37  -12 28   -6 32.5   -9 32.5         0.01  NNW37   PC RW-(AM) WINDY COLD
                21  41   -9 24  -10 32.5  -10 32.5               NNW26   PC BREEZY   COLD
                22  39  -10 25   -7 32.0   -9 33.0               NNW24   SU BREEZY   COLD
                23  39  -15 25  -10 32.0  -13 33.0               NNW21   SU BREEZY   COLD
                24  38  -17 25  -10 31.5  -13 33.5               NNW26   SU BREEZY   COLD
                25  38  -12 23   -9 30.5  -10 34.5               W   15  PC FROST-   (AM) COLD
                26  37   -9 26   -5 31.5   -7 33.5               NW  30  SU FROPA
                27  39   -6 24   -8 31.5   -7 33.5               NW  26  SU BREEZY   COLD
                28  39  -14 25  -10 32.0  -12 33.0               NW  23  SU BREEZY   COLD
                29  43   -7 28   -6 35.5   -7 29.5               N   22  SU NOT SO   COLD FR-(PM)
                30  53   +5 26   -6 39.5   -1 25.5               SW  18  PC FR (AM) NOT   SO COLD
                31  53   +2 43   +9 48.0   +6 17.0         0.02  SSE12    C R-   LF

                -- -- -- -- -- ---- -- ----                ---- -----
                SUMMARY OF DECEMBER 1995:


                TEMPERATURE:


                   Monthly mean:           High = 47.7 Low = 31.0 Mean = 39.4
                   Departure < Normal:     High = -5.0 Low = -4.1 Mean = -4.5

                    Degree Days:               Heating = 795.0     Cooling =     0.0
                    Number of Days Using:      Heating =       31  Cooling =      0

                    Days with maximum temperature >= 90: 0
                    Days with maximum temperature <= 32: 0
                    Days with minimum temperature <= 32: 19
                    Days with minimum temperature <= 0: 0








                PRECTPITATION:


                     Total month =        1.7811         Departure < Normal = -1.12"
                     Normal month =       2.9011                                or 61%
                     Average daily        0.0611   Normal daily = 0.09"
                     Number of days with measurable precipitation = 8

                     Year-to-date = 42.73"       Departure = -3.84" 92% of normal

                     Maximum for December = 5.73" in 1983               (Since
                     Minimum for December = 0.76" in 1988               1976)

                     Number of days   with   0.01" or more: 8                    Snowfall
                     Number of days   with   0.10" or more: 4          December total = 0.30"
                     Number of days   with   0.50" or more: 2       December maximum = 1.7011
                     Number of days   with   1.00" or more: 0                            in 1993

                 DAILY EXTREMES:      Low    temperature  =  22  on the llth
                                      High   temperature  =  70  on the 3rd & 15th
                         Maximum daily precipitation      = 0.62" on the 9th
                             Maximum 24-hour rainfall     = 0.62" on the 9th
                                     Maximum wind gust    = NW 37 mph on the 20th
                         Maximum barometric pressure      = 30.46" on the 29th
                         Minimum barometric pressure      = 29.42" on the 19th


                                                      NUMBER OF:


                Days Cloudy:                    4                  Days with thunderstorms: 0
                Days Partly Cloudy:             17                             Thunderstorms: 0
                Days Clear/Sunny:               10        Days with some type of snowfall: 1
                Days with Fog/Ground fog: 9
                ---------------------------------------------------------------------------
                YEARLY TOTALS:


                Temperatures                       Degree Days        Precipitation

                Mean maximum:      69.9 (+0.5) Heating: 3379.5        Aqueous:   42.73" (DEP -3.84")
                Mean minimum:      51.3 (+0.4) Cooling: 1782.5          Maximum monthly: 8.08"/OCT.
                Mean monthly:      60.6 (+0.4)                          Minimum  monthly: 1.33"/AUG.

                Highest:       101, July 24th                         Snowfall:               0.50"
                Lowest:          13, February 6th and 7th               Maximum  daily: 0.30"/DEC. 7
                Days with maximum temperature      >= 90: 48            Maximum monthly: 0.30"/DEC.
                Days with maximum temperature      <= 32: 02
                Days with minimum temperature      <= 32: 52            Days with some type of
                Days with temperature              <= 0: 00                snowfall:         6
                                                                        Days with measurable
                Number of:                                                precipitation: 107 or 29%
                Days   using  Heating:          194
                Days   using  Cooling:          166                   Days with thunderstorms: 20
                Days   Cloudy:                  47                    Number of thunderstorms: 22
                Days   Partly Cloudy:           244
                Days   Clear/Sunny:             74                    Greatest 24-hour period
                Days   with fog/ground fog:     96                      rainfall: 3.50"/Oct. 21st

                Wind   (Highest Recorded Wind Gust): West 52 miles per hour, NOV. 11
                Barometer: Highest 30.60" on March 10th; Lowest: 29.33" on February 4th
                ----------------------------------------------------------------------------






                January, 1996

                ------- ------- -- -------------- ---- - ----------- --------
                MONTHLY  SUMMARY  OF CLIMATOLOGICAL   DATA   PORTSMOUTH,   VIRGINIA
                Portsmouth Weather Records Service
                Portsmouth, Virginia      23702-2017 (3 miles south / West Cradock Section)
                -----------------------------------------------------------------------------
                   Monthly summary of Local Climatological Data for Portsmouth, Virginia,
                    West Cradock Section, during the month of January 1996. Time is EST.
                 - -- -- -- -- -- -- --- --- ---- -- -- -- --- ------------
                 D  HT   DN LT  DN   MT   DN   HDD  CDD   PREC   WD  WS SC WXR TYPE/REMARKS

                -----------------------------------------------------------------------------
                 1  45   -7 42  +5 43.5   -1 21.5         0.07   NE 15 C   F+ L R- DAMP
                 2  47   -2 42  +8  44.5  +3  20.5        0.25   NNW14 C   F+ L TRW (PM)
                 3  56   +8 32    0 44.0  +4  21.0        0.05   N 28  PC  F+ RW (AM) RW FROPA (PM)
                                                                           ACCUMULATION: TRACE
                 4  37  -10 28  -4  32.5  -7  32.5           T   NW 27 PC  SW(AM) COLD FR(PM)
                                                                           ACCUMULATION: TRACE
                 5  40   -5 29  -2  34.5  -4  30.5           T   NW 22 PC  SW--(AM) COLD
                                                                           ACCUMULATION: NONE
                 6  31  -18 26  -4  28.5 -11  36.5        0.45   NNE24 C   S COLD
                                                                           ACCUMULATION 4.511
                 7  41  -10 22 -12  32.0 -11  33.5        1.24   NNE31   C S IP ZR R F ZL-FROPA SW-
                                                                           ACCUMULATION: 1.0"
                 8  30  -15 22  -9  26.0 -12  39.0        0.10   NW 35 PC  ZL- S SW WINDY
                                                                           ACCUMULATION: 2.0"
                 9  39   -7 18 -10  28.5  -8  36.5               WSW24 PC
                10  40   -5 25  -4  32.5  -5  32.5               NNW26 PC  FROPA COLD
                11  29  -15 21  -7  25.0 -11  40.0               N 24  PC  COLD
                12  43   -4 28  -2  35.5  -3  29.5        1.13   WNW23 C   S IP R F FROPA S--
                                                                           ACCUMULATION: TRACE
                13  42   -5 26  -5  34.0  -5  31.0               WNW22 SU  FROST+(AM)
                14  52   +3 28  -2  40.0     025.0               WSW18 SU  FR+(AM) MILDER
                15  55   +8 37  +6  46.0  +7  19.0               NE 23 SU  FROPA
                16  44   -2 33  +5  38.5  +2  26.5         .01   NNE18 PC  RW-F-
                17  62  +13 39 +11  50.5 +12  14.5               S 17  PC  F+(AM)
                18  69  +19 44 +12  56.5 +15   8.5         .02   SE 40 PC  F(AM) RW- WINDY PM
                19  70  +25 31  +1  50.5 +13  14.5         .55   SSE64 PC  RW TRW FROPA
                20  31  -16 22  -6  26.5 -11  38.5               NNW24 PC  COLD
                21  36   -9 29    0 32.5  -5  32.5         .02   N 19 C    R-S-F FROPA
                22  38   -8 29    0 33.5  -4  31.5               NNE16 PC  F
                23  52   +3 29  -1  40.5  +1  24.5               SW 19 PC  F+(AM)
                24  67  +14 41  +9  54.0 +12  11.0         .52   SSW60 PC  WINDY RW+ FROPA
                25  41   -9 30  -2  35.5  -6  29.5               W 23  SU  BREEZY COLDER
                26  57   +8 25  -4  41.0  +2  24.0               ESE24 PC  FR(AM)
                27  64  +16 40 +10  52.0 +13  13.0         .77   ESE47 C   R F WINDY
                28  43   -4 31  +1  37.0  -2  28.0               SW 29 PC  FR- (PM)
                29  44   -4 32  +3  38.0  -1  27.0         .22   ENE18 C   FR- (AM) R-F
                30  49     037  +6  43.0  +3  22.0         .01   ESE15 PC  RW- F
                31  47   -2 30  -2  38.5  -2  26.5         .12   NE 28 C   R F FROPA

                -----------------------------------------------------------------------------
                SUMMARY OF JANUARY 1996:


                TEMPERATURE:


                   Monthly mean:          High = 46.5 Low = 30.6 Mean = 38.5
                   Departure < Normal: High = -1.3 Low = 0.1 Mean = -0.7

                    Degree Days:               Heating = 820.5     Cooling =    0.0
                    Number of Days Using:      Heating =     31    Cooling =     0

                    Days with maximum temperature >= 90: 0
                    Days with maximum temperature <= 32: 4
                    Days with minimum temperature <= 32: 22
                    Days with minimum temperature <= 0: 0









               PRECIPITATION:


                   Total month =       5.601,        Departure < Normal = +1.45"
                   Normal month =      4.15"                               or 135%
                   Average daily       0.18"    Normal daily = 0.1311
                   Number of days with measurable precipitation = 16

                   Year-to-date = 5.60"       Departure = +1.45" 135% of normal

                   Maximum for January      = 11.12" in 1987       (Since
                   Minimum for December = 1.07" in 1981            1977)

                   Number of days   with  0.01" or more: 16                 Snowfall
                   Number of days   with  0.10" or more: 10       January total = 7.50"
                   Number of days   with  0.50" or more:   5    January maximum = 8.90"
                   Number of days   with  1.00" or more:   2                       in 1980

                DAILY EXTREMES:     Low   temperature =  18  on the 9th
                                    High  temperature =  70  on the 19th
                        Maximum daily precipitation   = 1.24" on the 7th
                           Maximum 24-hour rainfall   = 1.69" on the 6th-7th
                                   Maximum wind gust  = SSE 64 mph on the 19th
                        Maximum barometric pressure   = 30.65" on the 26th
                        Minimum barometric pressure   = 29.38" on the 7th


                                                   NUMBER OF:


               Days Cloudy:                 10                 Days with thunderstorms: 2
               Days Partly Cloudy:          17                            Thunderstorms: 2
               Days Clear/Sunny:            4         Days with some type of snowfall: 8
               Days with Fog/Ground fog:    15
               -------------

               YEAR-TO-DATE:


               Temperatures                     Degree Days      Precipitation

               Mean maximum:    46.5 (-1.3) Heating:    820.5    Aqueous:    5.6011 (DEP +1.4511)
               Mean minimum:    30.6 (-0.1) Cooling:      0.0      Maximum monthly: 5.60"/JAN.
               Mean monthly:    38.5 (-0.7)                        Minimum monthly: 5.60"/JAN.

               Highest:       70, January 19th                   Snowfall:              7.50"
               Lowest:        18, January 9th                      Maximum  daily: 4.50"/JAN. 6
               Days with maximum temperature    >= 90: 0           Maximum monthly: 7.50"/JAN.
               Days with maximum temperature    <= 32: 22
               Days with minimum temperature    <= 32: 4           Days with some type of
               Days with temperature            <= 0: 0              snowfall:         8
                                                                   Days with measurable
               Number of:                                            precipitation: 16 or 50%
               Days  using  Heating:        31
               Days  using  Cooling:          0                  Days with thunderstorms: 2
               Days  Cloudy:                10                   Number of thunderstorms: 2
               Days  Partly Cloudy:         17
               Days  Clear/Sunny:             4                  Greatest 24-hour period
               Days  with fog/ground fog:   15                     rainfall: 1.69"/Jan. 6-7th

               Wind  (Highest Recorded Wind Gust): SSW 64 miles per hour, JAN. 19
               Barometer: Highest 30.65" on January 26th; Lowest: 29.38" on January 7th
               ---------------------------------------------------------------------------






                      February, 1996


                      -----------------------------------------------------------------------------
                      MONTHLY SUMMARY OF CLIMATOLOGICAL DATA - PORTSMOUTH, VIRGINIA
                      Portsmouth Weather Records Service
                      Portsmouth, Virginia                 23702-2017 (3 miles south / West Cradock Section)
                      -----------------------------------------------------------------------------
                          Monthly summary of Local Climatological Data for Portsmouth, Virginia,
                            West Cradock Section, during the month of February 1996. Time is EST.
                       - -- -- -- -- -- -- --- --- ---- -- -- -- --- ------------
                       D    HT    DN   LT    DN    MT      DN    HDD    CDD     PREC      WD   WS  SC  WIR   TYPE/REMARKS

                      -----------------------------------------------------------------------------
                       1    34 -16 27 -3 30.5 -10 34.5                                    NE 23 C COLD
                       2    35   -16 27      -6 31.0 -11 34.0                   0.60      INOP      C. F ZR GL TRW ZL
                                                                                                   ACCUMULATION: 0.5"
                       3    28   -23   22    -9   25.0   -16   40.0             0.10      INOP      C ZL IP+ S SW- FROPA
                                                                                                   ACCUMULATION: 1.0"
                       4    23   -27   12   -19   17.5   -23   47.5             0.25      INOP     PC S SW COLD
                                                                                                   ACCUMULATION: 2.5"
                       5    23   -21     8  -20   15.5   -21   49.5                       INOP     PC  COLD
                       6    31   -13   11   -17   21.0   -15   44.0                       INOP     PC  F-K-FR(AM)
                       7    39    -5   13   -15   26.0   -10   39.0                       S 19     PC  F-FR(AM) THAWING
                       8    54    +8   35    +6   44.5     +7  20.5             0.22      SW 26 C      T4
                       9    60   +11   35    +7   47.5     +9  17.5             0.01      WNW25    PC  RW F FROPA
                      10    61   +13   29    +1   45.0     +7  20.0                       SSW24    SU  FR (AM)
                      11    71   +20   44   +13   57.5   +17     7.5                      WNW37    PC  WINDY FROPA
                      12    44    -3   30    +1   37.0     -1  28.0                       WNW23    PC  FROPA VIRGA BREEZY
                      13    38    -8   22    -7   30.0     -7  35.0                       W 31     SU  WINDY COLD
                      14    51    -2   35    +2   43.0      0  22.0                       SW 30    PC  WARMFROPA BREEZY
                      15    51    -3   37    +3   44.0      0  21.0             0.04      ENE22    PC  RW-(AM)
                      16    38   -14   26    -8   32.0   -11   33.0             0.52      NNW36 C      R IP S S+ BS FROPA
                                                                                                   ACCUMULATION: 4.0"
                      17    35   -15   19   -13   27.0   -14   38.0                   T   NW 30    PC S-(AM) COLD
                                                                                                   ACCUMULATION: TRACE
                      18    40   -10   26    -7   33.0     -9  32.0                       NNW21    PC  FROPA BREEZY
                      19    56    +2   27    -8   41.5     -3  23.5                       SE 26    PC  FR(AM)
                      20    68   +13   46   +10   57.0   +11     8.0            0.68      SSE32    PC  F+(AM) RW F
                      21    64    +6   49   +13   56.5   -.10    8.5            0.10      SSE21    PC  R74 F+(AM)
                      22    68    +8   49   +11   58.5   -1-10   6.5            0.13      SE 16    PC  F+ (AM) RW
                      23    56    -3   50    +9   53.0     +3  12.0                       SE 17 C      RW (AM) F
                      24    68   +12   48   +10   58.0   -i-ll   7.0                      NW 36    PC  FROPA DRYING
                      25    70   +19   39    +5   54.5   -112  10.5                       WNW26    PC
                      26    73   +24   51   +17   62.0   -%20    3.0                      NNE17    PC  FROPA
                      27    72   +22   43   +11   57.5   +16     7.5                      S 18     PC  GF K (AM) WARM FROPA(PM)
                      28    74   +21   51   +17   62.5   -4-19   2.5                      W 29     PC  GF H (AM) K(AFT) FROPA
                      29    51    +2   30    +2   40.5     +2  24.5                       N 28     PC  PC

                      -----------------------------------------------------------------------------
                      SUNMARY OF FEBRUARY 1996:


                      TEMPERATURE:


                          Monthly mean:                    High = 50.9 Low =               32.4 Mean = 41.7
                           Departure < Normal:             High =        0.0 Low =           0.0 Mean =            0.0

                            Degree Days:                         Heating = 676.5             Cooling =         0.0
                            Number of Days Using:                Heating =            29     Cooling =           0

                            Days with maximum temperature >= 90: 0
                            Days with maximum temperature <= 32: 4
                            Days with minimum temperature <= 32: 15
                            Days with minimum temperature <= 0: 0








                PRECIPITATION:


                     Total month =        2.65"         Departure < Normal = -0.72"
                     Normal month =       3.37"                                or 79%
                     Average daily        0.091,   Normal daily = 0.12"
                     Number of days with measurable precipitation = 10

                     Year-to-date = 8.25"        Departure = +0.73" 110% of normal

                     Maxim-am for February = 6.32 in 1989              (Since
                     Minimum for February = 1.20" in 1991              1977)

                     Number of clays  with  0.01" or more: 10                   Snowfall
                     Number of days   with  0.10" or more:    8      February total = 8.00"
                     Number of days   with  0.50" or more:    3     February maximum = 21.0011
                     Number of days   with  1.00" or more:    0                         in 1989

                 DAILY EXTREMES:      Low   temperature =     8 on  the Sth
                                      High  temperature =    74 on  the 28th
                         Maximum daily precipitation =      0.68" on the 20th
                             Maximum 24-hour rainfall =     0.78" on the 20th-21st
                                     Maximum wind gust =    WNW 37 mph on the llth
                          (anemometers inoperative [glazed over] on the 2nd-7th (AM])
                         Maximum barometric pressure = 30.658" on the 5th
                         Minimum barometric pressure = 29.425" on the 11th


                                                      NUMBER OF:


                Days Cloudy:                   7                   Days with thunderstorms: 1
                Days Partly Cloudy:            21                             Thunderstorms: 1
                Days Clear/Sunny:              1         Days with some type of snowfall: 4
                Days with Fog/Ground fog: 12
                -------------

                YEAR-TO-DATE:


                Temperatures                       Degree Days       Precipitation

                Mean maximum:      48.6 (-0.7) Heating: 1495.0       Aqueous:     8.25" (DEP +0.73")
                Mean minimum:      31.5 (-0.0) Cooling:       0.0      Maximum monthly: 5.60"/JAN.
                Mean monthly:      40.1 (-0.3)                         Minimum monthly: 2.65"/.rEB.

                .Highest:       74, February   28th                  Snowfall:              15.50"
                Lowest:           8, February  5th                     Maximum  daily: 4.50"/JMI. 6
                Days with maximum temperature      >= 90:   0          Maximum monthly: 8.00"/FEB.
                Days with maximum temperature      <= 32:  26
                Days with minimum temperature      <= 32:  14          Days with some type of
                Days with temperature              <= 0:    0             snowfall:        13
                                                                       Days with measurable
                Number of:                                                precipitation: 26 or 43@,r
                Days   using  Heating:         60
                Days   using  Cooling:           0                   Days with thunderstorms: 3
                Days   Cloudy:                 17                    Number of thunderstorms: 3
                Days   Partly Cloudy:          38
                Days   Clear/Sunny:              5                   Greatest 24-hour period
                Days   with fog/ground fog:    27                      rainfall: 1.69"/Jan. 6-7th

                Wind   (Highest Recorded Wind Gust): SSW 64 miles per hour, JAN. 19
                Barometer: Highest 30.658" on February 5th; Lowest: 29.38" on January 7th
                ---------------------------------------------------------------------------






                March, 1996


                -----------------------------------------------------------------------------
                MONTHLY SUMMARY OF CLIMATOLOGICAL DATA - PORTSMOUTH, VIRGINIA
                Portsmouth Weather Records Service
                Portsmouth, Virginia       23702-2017 (3 miles south / West Cradock Section)
                -----------------------------------------------------------------------------
                   Monthly summary of Local Climatological Data for Portsmouth, Virginia,
                    West Cradock Section, during the month of March 1996.         Time is EST.
                -----------------------------------------------------------------------------
                 D HT DN LT DN MT           I-IN HDD CDD PREC WD WS SC WXR TYPE/REMARKS

                -----------------------------------------------------------------------------
                 1  46   -6 30   -3  38.0   -4 27.0       0.18   ESE19    CR-
                 2  46   -9 35   -1  40.5   -5 24.5       0.31   N 22   PC R-F(AM) GF
                 3  53   -1 27 -10   40.0   -5 25.0              WNW40  SU FROPA WINDY COLDER
                 4  48   -9 25 -12   36.5  -10 28.5              WSW20  SU COLD
                 5  72  +13 34   -6  53.0   +3 12.0              SSW42  PC WINDY WARM
                 6  66  +10 58 +19   62.0  +14  3.0       0.36   S 34 C    F R FROPA(LATE EVE)
                 7  66   +9 36   -1  51.0   +4 14.0       0.48   S 30 C    F R RW WARMFROP COLDFROP
                 8  36  -20 24 -13   30.0  -16 35.0       0.10   S   31 PC R-IP-S-SW
                                                                           ACCUMULATION: 0.40"
                 9  31  -24 18 -18   24.5  -21 40.5              W   25 SU RECORD COLD WINDY (AM)
                10  34  -23 23 -13   28.5  -18 36.5              WNW22  SU. BREEZY COLD
                11  40  -18 29   -7  34.5  -13 30.5              NE 28  PC BREEZY COLD
                12  50   -9 32   -7  41.0   -8 24.0              NNE32  PC BREEZY
                13  59   -3 27 -13   43.0   -8 22.0              NNW18  SU FR(AM)
                14  73  +13 36   -4  54.5   +5 10.5              W 22   PC MILD AFT
                15  79  +17 52 +12   65.5  +14       0.5  0.35   WSW32  PC T RW MILD
                16  62   +3 46   +7  54.0   +5 11.0              SE 20  PC
                17  50  -12 41   +2  45.5   -5 19.5       0.58   E 27 C    TRW F
                18  49  -10 45   +5  47.0   -3 18.0            T NE 15 C   F R-(PM)
                19  71  +12 46   +6  58.5   +9  6.5       0.19   SSW54    CR-F FROPA RW WINDY
                20  53   -7 40   +3  46.5   -2 18.5              SSW37  PC WINDY
                21  56   -5 36   -4  46.0   -4 19.0              WSW27  PC BREEZY
                22  51   -8 36   -2  43.5   -5 21.5       0.01   SSW27  PC RW-SW-F-
                                                                 NW 27
                23  55   -5 31   -7  43.0   -6 22.0              NW 33  SU
                24  62     029 -13   45.5   -6 19.5              SSE27  SU
                25  76  +15 41     0 58.5   -8  6.5              SSW36  PC MILDER
                26  72  +11 49   +8  60.5   -L9 4.5              SW 21  PC FROPA
                27  49  -15 40   -2  44.5   -8 20.5              N 29   PC WINDY COLDER
                28  48  -17 40   -5  44.0  -11 21.0       1.19   NE 25 C   R F L WINDY RAW
                29  43  -26 38   -7  40.5  -1-6 24.5      0.03   NNW24    CR- L- F
                30  56  -12 40   -8  48.0  -10 17.0              N 20   PC PLEASANT AFTERNOON
                31  61   -5 40   -6  50.5   -5 14.5       0.12   SE 15  PC R-F-

                -----------------------------------------------------------------------------

                SUMMARY OF MARCH 1996:


                TEMPERATURE:


                   Monthly mean:           High = 55.3     Low = 36.3 Mean = 45.8
                   Departure < Normal:     High = -4.5     Low = -3.2 Mean = -3.8

                    Degree Days:               Heating = 597.0     Cooling =      0.5
                    Number of Days Using:      Heating =       30  Cooling =      1

                    Days with maximum temperature >= 90: 0
                    Days with maximum temperature <= 32: 1
                    Days with minimum temperature <= 32: 11
                    Days with minimum temperature <= 0: 0








                  PRECIPITATION:


                      Total month =         3.90"           Departure < Normal       -0.53"
                      Normal month =        4.43"                                   or 88%
                      Average daily         0.13"     Normal daily = 0.14"
                      Number of days with measurable precipitation =            12

                      Year-to-date = 12.1511        Departure = +0.20" 102%     of normal

                      Maximum for March = 10.96" in 1994               (Since
                      Minimum for March = 0.89" in 1986                 1977)

                      Number of days     with  0.01" or more:    12                  Snowfall
                      Number of days     with  0.10" or more:    10           March total = 0.40"
                      Number of days     with  0.50" or more:      2        March maximum = 14.0001
                      Number of days     with  1.00" or more:      1                          in 1980

                   DAILY EXTREMES:       Low   temperature   =   18 on the 9th
                                         High  temperature   =   79 on the 15th
                           Maximum daily precipitation       =  1.19" on the 28th
                               Maximum 24-hour rainfall      =  1.19" on the 28th
                                       Maximum wind gust     =  SSW 54 mph on the 19th
                           Maximum barometric pressure       =  30.937" on the 10th
                           Minimum barometric pressure       =  29.196" on the 19th


                                                         NUMBER OF:


                  Days Cloudy:                    8                    Days with thunderstorms: 2
                  Days Partly Cloudy:             17                         # of Thunderstorms: 2
                  Days Clear/Sunny:               6          Days with some type of snowfall: 2
                  Days with Fog/Ground fog:       11


                  -------------     -------- - --- ----- -----
                  YEAR-TO-DATE:      (through  March  31st,  1996)

                  Temperatures                        Degree Days        Precipitation

                  Mean maximum:      50.9 (-2.0) Heating: 2094.0         Aqueous:    12.15" (DEP +0.20")
                  Mean minimum:      33.1 (-1.1) Cooling:          0.5      Maximum monthly: 5.60"/JAN.
                  Mean monthly:      42.0 (-1.6)                            Minimum monthly: 2.65"/FEB.

                  Highest:         79, March 15th                        Snowfall:               15.901,
                  Lowest:           8, February 5th                         Maximum daily: 4.50"/JAN. 6
                  Days with maximum temperature       >= 90:    0           Maximum monthly: 8.00"/FEB.
                  Days with maximum temperature       <= 32:   27
                  Days with minimum temperature       <= 32:   48           Days with some type of
                  Days with temperature               <= 0:     0             snowfall:         15
                                                                            Days with measurable
                  Number of:                                                  precipitation: 38 or 42@-
                  Days  using   Heating:          90
                  Days  using   Cooling-            1                    Days with thunderstorms: 5
                  Days  Cloudy:                   25                     Number of thunderstorms: 5
                  Days  Partly Cloudy:            55
                  Days  Clear/Sunny:              11                     Greatest 24-hour period
                  Days  with fog/ground fog:      38                        rainfall: 1.69"/Jan. 6-7th

                  Wind  (Highest Recorded Wind Gust): SSW 64 miles per hour, JAN. 19
                  Barometer: Highest 30.937" on March 10th; Lowest: 29.196" on March 19th
                  ---------------------------------------------------------------------------






                April, 1996


                ------- ------- -- -------------- ---- - ----------- --------
                MONTHLY  SUMMARY  OF  CLIMATOLOGICAL  DATA     PORTSMOUTH, VIRGINIA
                Portsmouth Weather Records Service
                Portsmouth, Virginia       23702-2017 (3 miles south / West Cradock Section)
                -----------------------------------------------------------------------------
                     Monthly summary of Local Climatological Data for Portsmouth, Virginia,
                   West Cradock Section, during the month of April 1996. Time is EST/EDT.
                -----------------------------------------------------------------------------
                 D HT DN LT DN MT           DN HDD CDD PREC WD WS SC WXR TY-@E/REMARKS

                -----------------------------------------------------------------------------
                 1   72  +5 50    +6  61.0  +5   4.0        0.61   NNW23  PC R F RW FROPA
                 2   56 -12 40    -4  48.0  -8  17.0        0.02   NNW32  PC RW (AM) WINDY
                 3   73  +6 37    -9  55.0  -1  10.0               WSW26  SU
                 4   83 +14 56    +8  69.5 +11        4.5          SW 27  SU
                 5   67    045    -2  56.0  -1   9.0               N 28   PC FROPA (AM)
                 6   48 -16 38    -7  43.0 -11  22.0        0.89   ENE21 C   R F FROPA COLD
                 7   52 -12 39    -4  45.5  -8  19.5               N' 22  PC
                 8   59  -7 35  -10   47.0  -9  18.0        0.03   SSW22  PC K-(AM) R-(EVENING)
                 9   46 -19 39    -7  42.5 -13  22.5        0.76   NNW35 C   R F FROPA BREEZY COLD
                10   5,3 -14 35 -10   44.0 -12  21.0               NNW29  PC VIRGA (AFT)
                11   70  +1 38    -7  54.0  -3  11.0               WNW25  SU
                12   15 +13 53    +7  69*0 +10        4*0          W 21   PC MILD
                13   86 +18 58    +9  72.0 +13        7.0          WSW25  PC MILD
                14   69  +1 53    +4  61.0  +3   4.0               SSW24  PC FROPA
                15   71  +2 49    +0  60.0  +1   5.0            T  SSE40  PC WINDY PM RW
                16   69    048    -1  58.5    0  6.5        1.52   WNW49  PC FROPA TRW(2) RW
                17   63  -7 44    -4  53.5  -6  11.5               NW` 28 PC BREEZY
                18   77  +7 40    -7  58.5    0  6.5               SE 21  SU
                19   79  +8 54    +5  66.5  +6        1.5    .06   SW 28  PC RW
                20   81 +10 60  +10   70.5 +10        5.5    .05   SSW31  PC RW(EVEI DST LTG (EVE)
                21   83 +11 61  +10   72.0 +10        7.0          W 24   PC
                22   88 +17 62  +13   75.0 +15        10.0         SW 29  PC BREEZY WARM
                23   86 +15 64  +14   75.0 +14        10.0   .20   SW 36  PC BREEZY TRW(PM)
                24   65  -9 47    -3  56.0  -6   9.0         .04   NNW33  PC RW(AM) FROPA COOLER
                2S   77  +3 48    -3  62.5    0  2.5               S 38   PC BREEZY
                26   81  +9 55    +4  68.0  +6        3.0    .09   SW 46  PC RW FRC?A
                27   64 -11 51    -1  57.5  -6   7.5               WSW20  PC PLEASANT
                28   76  +3 45    -'8 60.5  -2   4.5               SSE25  PC H-
                29   84 +10 58    +7  71.0  +9        6.0    .04   SSW32  PC RW(AM) TRW(AFT) H-
                30   77  +3 54    +2  65.5  +2        0.5    .89   SSW49  PC RW TRW WINDY F- FROPA

                -----------------------------------------------------------------------------
                SUMMARY OF APRIL 1996:


                TEMPERATURE:


                   Monthly mean:           High = 71.3      Low = 48.5 Mean = -39.9
                   Departure < Normal:     High = +1.6      Low = +0.3 Mean = +1.0

                     Degree Days:               Heating = 211.0     Cooling = 59.0
                     Number of Days Using:      Heating =      19   Cooling =    11

                     Days with maximum temperature >= 90: 0
                     Days with maximum temperature <= 32: 0
                     Days with minimum temperature <= 32: 0
                     Days with minimum temperature <= 0: 0








                PRECIPITATION:


                    Total month                5.20"          Departure < Normal = + 1.60"
                    Normal month (to date)     3.6011                               or 145%
                    Average daily              0.17"
                    Normal daily               0.12"
                    Number of days with measurable precipitation = 13

                    Year-to-date      17.35"    Departure = +1.80" 112% of normal

                    Maximum for April = 7.08" in 1991              (Since
                    Minimum for April = 1.21" in 1985              1977)

                    Number of days    with 0.01" or more:    13                 Snowfall
                    Number of days    with 0.10" or more:     6          April total = 0.0011
                    Number of days    with 0.50" or more:     5        April maximum = 1.1"
                    Number of days    with 1.00" or more:     1                         in 1983

                 DAILY EXTREMES:      Low  temperature   =   35 on the 8th and 10th
                                      High temperature   =   88 on the 22nd
                         Maximum daily precipitation     =  1.52" on the 16th
                            Maximum 24-hour rainfall     =  1.52" on the 16th
                                      Maximum wind gust  =  WNW 49 mph/SSW 49 mph on the 16th/30th
                         Maximum barometric pressure     =  30.341" on the 28th
                         Minimum barometric pressure     =  29.649" on the 16th


                                                      NUMBER OF:


                Days Cloudy:                   2                  Days with thunderstorms: 4
                Days Partly Cloudy:            24                       # of Thunderstorms: 5
                Days Clear/Sunny:              4         Days with some type of snowfall: 0
                Days with Fog/Ground fog: 4


                ----------------------------------------------------------------------------
                YEAR-TO-DATE: (through April 30th, 1996)

                Temperatures                      Degree Days        Precipitation

                Mean maximum:     56.0 (-1.1) Heating: 2305.0        Aqueous:   17.35" (DEP +1.8011)
                Mean minimum:     36.9 (-0.8) Cooling:       59.5      Maximum  monthly:     5.6011/JAN.
                Mean monthly:     46.4 (-1.0)                          Minimum  monthly:     2.65"/FEB.

                Highest:        88, April 22nd                       Snowfall:            15.90"
                Lowest:          8,   February 5th                     Maximum  daily:   4.50"/JAN. 6
                Days with maximum     temperature >= 90:    0          Maximum  monthly: 8.00"/FEB.
                Days with maximum     temperature <= 32:   27          Seasonal total:    16.20"
                Days with minimum     temperature <= 32:   48          Days with some type of
                Days with temperature             <= 0:     0            snowfall:        15
                                                                       Days with measurable
                Number of:                                               precipitation: 51 or 42%
                Days  using   Heating:         109
                Days  using   Cooling:         13                    Days with thunderstorms: 9
                Days  Cloudy:                  27                    Number of thunderstorms: 10
                Days  Partly Cloudy:           79
                Days  Clear/Sunny:             15                    Greatest 24-hour period
                Days  with fog/ground fog:     42                      rainfall: 1.69"/Jan. 6-7th

                Wind (Highest Recorded Wind Gust) : SSW 64 miles per hour, JAN. 19
                Barometer: Highest 30.937" on March 10th; Lowest: 29.196" on March 19th
                ---------------------------------------------------------------------------






                May, 1996


                -----------------------------------------------------------------------------
                MONTHLY SUMMARY OF CLIMATOLOGICAL DATA - PORTSMOUTH, VIRGINIA
                Portsmouth Weather Records Service
                Portsmouth, Virginia        23702-2017 (3 miles south / West Cradock Section)
                -----------------------------------------------------------------------------
                     Monthly summary of Local Climatological Data for Portsmouth, Virginia,
                      West Cradock Section, during the month of May 1996. Time is EST/EDT.
                                             -- --- --- ---- -- -- -- --- ------------
                 D   HT   DN LT  DN    MT    DN  HDD   CDD   PREC WD WS   SC WXR  TYPE/REMARKS

                -----------------------------------------------------------------------------
                 1   70   -5 47  -6    58.5  -6  6.5               E 25   SU COOLER
                 2   77   +3 52    0   64.5  +1  0.5               NE 21  PC H-K
                 3   83   +8 56  +3    69.5  +6        4.5         SSE25  SU K H-
                 4   87 +14  62  +8    74.5 +11        9.5         W 31   SU HUMID BREEZY
                 5   76   +4 58  +4    67.0  +4        2.0         ESE22  PC FROPA BREEZY
                 6   70   -5 57  +3    63.0  -1  2.0          .83  S 29   PC TRW+(AM) FROPA
                 7   57 -17  51  -3    54.0 -10 11.0          .84  E 24 C    R L F COOLER
                 8   67   -7 53  -1    60.0  -4  5.0          .02  SSE19  PC RW- F
                 9   79   +5 57  +4    68.0  +5        3.0      T  NNE21  PC F RW H
                10   88 +11  56  +2    72.0  +7        7.0         WSW25  PC F(AM) H-
                11   88 +10  68 +12    78.0 +11       13.0    .09  WSW55  PC HOT HUMID SQUALL LINE/
                                                                             TRW (EVE)
                12   68 -10  54  -3    61.0  -7  4.0          .03  NNW27  PC RW-(AM) FROPA COOLER
                13   64 -14  49  -8    56.5 -11  8.5               E 19   PC BREEZY COOLER
                14   63 -13  47 -11    55.0 -12 10.0          .04 N/SE18  PC RW-(AM)
                15   70   -7 44 -13    57.0 -10  8.0          .21  SSE21  PC R-(PM)
                16   69   - 856    0   62.5  -4  2.5          .61  SW 19 C   R-F RW
                17   80   +2 62  +4    71.0  +3        6.0      T  ESE16  PC F RW- H HUMID
                18   90 +10  64  +5    77.0  +8       12.0         WSW14  PC FH HOT HUMID
                19   97 +18  67  +8    82.0 +13       17.0         WSW14  SU FH(EARLY AM) HOT HUMID
                20   98 +22  70 +11    84.0 +16       19.0         WSW20  SU HOT
                21   93 +14  71 +11    82.0 +12       17.0         WSW23  PC H HOT BREEZY
                22   79   +1 63  +5    71.0  +3        6.0         NNE35  PC DST LTG FROPA COOLER
                23   85   +3 58  -2    71.5    0       6.5         SSE21  SU
                24   86   +5 65  +3    75.5  +4       10.5         SSE25  PC H DST LTG
                25   71   -9 61    0   66.0  -4        1.0    .10  NE 19   C FROPA TRW F
                26   72   -6 60  -1    66.0  -4        1.0    .02  SE 19   C RW F
                27   67 -10  58  -1    62.5  -5  2.5          .86  SE 30   C F RW TRW(2) L
                28   63 -15  58  -1    60.5  -8  4.5          .16  ESE16   C F RW(AM) COOL FROP
                29   65 -17  57  -5    61.0 -11  4.0            T  ENE19   C F L-
                30   67 -14  53  -9    60.0 -12  5.0          .09  NNE26   PC RW-(AM) F FROPA
                31   71 -13  47 -16    59.0 -15  6.0            00 SE  20  SU RECORD  LOW TEMP

                -- -- --- -- --- ---- --- ---                 --- -- -- -- ------ --- ----
                SUMMARY OF MAY 1996:


                TEMPERATURE:


                    Monthly mean:           High = 76.1      Low    57.5 Mean = 66.8
                    Departure < Normal:     High = -1.4      Low    +0.2 Mean = -0.6

                     Degree Days:               Heating = 79.5      Cooling = 135.0
                     Number of Days Using:      Heating =       is  Cooling =      16

                     Days with maximum temperature >= 90: 4
                     Days with maximum temperature <= 32: 0
                     Days with minimum temperature <= 32: 0
                     Days with minimum temperature <= 0: 0








               PRECIPITATION:


                    Total month               3.90"         Departure < Normal       0.20"
                    Normal month (to date)    4.10"                               or 95%
                    Average daily             0.13"
                    Normal daily              0.1311
                    Number of days with measurable precipitation = 13

                    Year-to-date =   21.25"   Departure = +1.60" 108% of normal

                    Maximum for May      = 8.06" in 1988         (Since
                    Minimum for May      = 1.02" in 1986         1977)

                    Number of days   with  0.01" or more:  13                Snowfall
                    Number of days   with  0.10" or more:   7           May  total = 0.00"
                    Number of days   with  0.50" or more:   4        May   maximum = 0.00"
                    Number of days   with  1.00" or more:   0

                DAILY EXTREMES:      Low   temperature =   44 on the 25th
                                     High  temperature =   98 on the 20th
                        Maximum daily precipitation    =   0.86" on the 27th
                            Maximum 24-hour rainfall   =   1.67" on the 6-7th
                                   Maximum wind gust   =   WSW 55 mph on the 11th
                        Maximum barometric pressure    =   30.417" on the 7th
                        Minimum barometric pressure    =   29.636" on the 21st


                                                    NUMBER OF:


                Days Cloudy:                  8                 Days with thunderstorms: 4
                Days Partly Cloudy:          16                       # of Thunderstorms: 5
                Days Clear/Sunny:             7        Days with some type of snowfall: 0
                Days with Fog/Ground fog: 13


                ----------------------------------------------------------------------------
                YEAR-TO-DATE: (through May 31st, 1996)

                Temperatures                     Degree Days      Precipitation

                Mean maximum:    60.1 (-1.1) Heating: 2384.5      Aqueous: 21.25" (DEP +1.61")
                Mean minimum:    41.1 (-0.6) Cooling:      194.5     Maximum monthly: 5.60"/JAN.
                Mean monthly:    50.6 (-0.9)                         Minimum monthly: 2.65"/FEB.

                Highest:       98, May 20th                       Snowfall:             15.90"
                Lowest:         8, February   5th                    Maximum daily: 4.50"/JAN. 6
                Days with maximum temperature    >= 90:    4         Maximum monthly: 8.00"/FEB.
                Days with maximum temperature    <= 32: 27           Seasonal total: 16.20"
                Days with minimum temperature    <= 32: 48           Days with some type of
                Days with temperature            <= 0:     0           snowfall:       15
                                                                     Days with measurable
                Number of:                                             precipitation: 64 or 42%
                Days  using  Heating:        124
                Days  using  Cooling:         28                  Days with thunderstorms: 9
                Days  Cloudy:                 35                  Number of thunderstorms: 10
                Days  Partly Cloudy:          95
                Days  Clear/Sunny:            22                  Greatest 24-hour period
                Days  with fog/ground fog:    55                     rainfall: 1.69"/Jan. 6-7th

                Wind  (Highest Recorded Wind Gust): SSW 64 miles per hour, JAN. 19
                Barometer: Highest 30.937" on March 10th; Lowest: 29.196" on March 19th
                ---------------------------------------------------------------------------






                June, 1996


                ------- ------- -- -------------- ---- - ----------- --------
                MONTHLY  SUMMARY  OF  CLIMATOLOGICAL   DATA     PORTSMOUTH, VIRGINIA
                Portsmouth Weather Records Service
                Portsmouth, Virginia        23702-2017 (3 miles south / West Cradock Section)
                -----------------------------      ------------------------------------------------
                     Monthly summary of Local Climatological Data for Portsmouth, Virginia,
                     West Cradock Section, during the month of June 1996. Time is EDT.
                -----------------------------------------------------------------------------
                 D HT DN LT DN MT            DN HDD CDD PREC WD WS SC WXR TYPE/REMARKS

                -----------------------------------------------------------------------------
                 1   78  -6  47  -17  62.5  -12  2.5              SSE21  SU RECORD AM LOW TEMP
                 2   80  -3  51  -12  65.5   -8        0.5        SE 21  SU
                 3   68  -14 57  -6   62.5  -10  2.5         0.25 NNE23  PC RW F
                 4   81    0 57  -7   69.0   -3        4.0        S 27   PC DST LTG F
                 5   81  -1  66  +3   73.5   +1        8.5       TWSW21  PC TRW- F FROPA H-
                 6   84  +1  65  +1   74.5   +1        9.5        ESE21  PC F+(AM)
                 7   90  +6  67  +1   78.5   +3       13.5       TS   24 PC F+L-(AM) H-
                 8   90  +3  70  +4   80.0   +3       15.0        S   28 SU BREEZY (AFT) HOT
                 9   86  +2  70  +4   78.0   +3       13.0   0.22 S   30 PC RW DST LTG BREEZY(AM)
                10   82  -2  72  +6   77.0   +2       12.0   0.04 S   26 PC F- RW HUMID
                11   82  -1  67  +4   74.5   +1        9.5   0.51 W   23 PC F- RW+ TRW DST LTG HUMID
                12   89  +4  67  +3   78.0   +4       13.0   0.38 S   27 PC TRW(2) F- H RW
                13   87  +4  66  +2   76.5   +3       11.5       TW   25 PC RW-(AM) F- H-
                14   90  +5  68  +4   79.0   +4       14.0        W   16 SU F-(AM) H
                15   90  +3  69  +3   79.5   +3       14.5       TSE  25 PC F-(AM) H TRW- DST LTG
                16   93  +7  70  +2   81.5   +5       16.5        S   22 PC F-(AM) H DST LTG
                17   90  +5  69  +2   79.5   +4       14.5        SSW24  PC
                18   94  +8  71  +4   82.5   +6       17.5        S/E19  PC HOT HUMID H
                19   91  +5  71  +3   81.0   +4       16.0        S 23   PC HOT HUMID
                20   92  +5  71  +2   81.5   +4       16.5   0.14 ESE21  PC H DST LTG TRW
                21   88  +2  70  +4   79.0   +3       14.0       TN 21   SU RW-(AM) H DST LTG
                22   94  +8  69  +2   81.5   +5       16.5        SW 20  SU H
                23   87  +1  75  +8   81.0   +4       16.0        21NNE  PC H
                24   94  +9  69  +3   81.5   +6       16.5   1.80 28 N   PC H HOT TRW(3)
                25   88  +4  69  +3   78.5   +3       13.5   0.15 18 SW  PC H F- TRW- FROPA
                26   79  -6  65  -2   72.0   -4        7.0        29NNE  SU PLEASANT
                27   82  -5  60  -8   71.0   -6        6.0        16NNE  SU
                28   86  -2  63  -4   74.5   -3        9.5        17NNW  SU H- WEAK FROPA
                29   81  -7  67  -1   74.0   -4        9.0        20ENE C   FROPA (AM)
                30   77  -10 59  -9   68.0  -10        3.0   0.36           RW (AM)

                -----------------------------------------------------------------------------

                SUMMARY OF JUNE 1996:


                TEMPERATURE:


                   Monthly mean:            High = 85.8      Low = 65.9 Mean = 75.9
                    Departure < Normal:     High = + 0.8     Low =    0.0 Mean = + 0.5

                     Degree Days:               Heating =      5.0  Cooling = 330.5
                     Number of Days Using:      Heating =        2  Cooling =     28

                     Days with maximum temperature >= 90: 11
                     Days with maximum temperature <= 32:        0
                     Days with minimum temperature <= 32:        0
                     Days with minimum temperature <= 0:         0








                  PRECIPITATION:


                       Total month                   3.8511          Departure < Normal         + 0.20"
                       Normal month (to date)        3.65"                                     or 105%
                       Average daily                 0.13"
                       Normal daily                  0.12"
                       Number of days with measurable precipitation = 9

                       Year-to-date =     25.10"      Departure =    +1.80" 108-@'- of normal

                       Maximum for June        = 7.56" in 1978              (Since
                       Minimum for June        = 0.94" in 1980               1977)


                       Number of days     with   0.01" or more:      9                    Snowfall
                       Number of days     with   0.10" or more:      8            June total = 0.0011
                       Number of days     with   0.50" or more:      2            June maximum = 0.0011
                       Number of days     with   1.00" or more:      1

                   DAILY EXTREMES:        Low    temperature    =   47  on the    lst
                                          High   temperature    =   94  on the    18th, 22nd, 24th
                            Maximum daily precipitation         =  1.80" on the 24th
                                Maximum 24-hour rainfall        =  1.95" on the 24th-25th
                                         Maximum wind gust      =  S    30 mph on the 9th
                            Maximum barometric pressure         =  30.344" on the Ist
                            Minimum barometric pressure         =  29.690" on     the 23rd


                                                            NUMBER OF:


                  Days Cloudy:                       2                     Days with thunderstorms: 7
                  Days Partly Cloudy:                19                           # of Thunderstorms: 10
                  Days Clear/Sunny:                  9          Days with some type of snowfall: 0
                  Days with Fog/Ground Fog: 13
                  Days   with  Dense    Fog:         2
                  ---- ---- ----- ----                       -------------------------------------------

                  YEAR-TO-DATE:


                  Temperatures                           Degree Days         Precipitation

                  Mean maximum:        64.3 (-0.8) Heating: 2389.5           Aqueous:     25.1011 (DEP +1.8011)
                  Mean minimum:        45.2 (-0.5) Cooling:        525.0        Maximum   monthly: 5.60"/JAN.
                  Mean monthly:        54.8 (-0.6)                              Minimum   monthly: 2.65"/FEB.

                  Highest:          98, May 20th                             Snowfall:               is.901,
                  Lowest:             8, February    5th                        Maximum   daily: 4.50"IJAN. 6
                  Days with maximum temperature          >= 90: 15              Maximum   monthly: 8.00"/FEB.
                  Days with maximum temperature          <= 32: 9               Seasonal total: 16.20"
                  Days with minimum temperature          <= 32: 45              Days with some type of
                  Days with temperature                  <= 0: 0                  snowfall:          15
                                                                                Days with measurable
                  Number of:                                                      precipitation: 73 or 40%
                  Days   using   Heating:            126
                  Days   using   Cooling:            56                      Days with thunderstorms: 16
                  Days   Cloudy:                     37                      Number of thunderstorms: 20
                  Days   Partly Cloudy:              114
                  Days   Clear/Sunny:                31                      Greatest 24-hour period
                  Days   with fog/ground fog:        55                         rainfall: 1.95"/June 24-25th

                  Wind   (Highest Recorded Wind Gust): SSW 64 miles per hour, JAN. 19
                  Barometer: Highest 30.937" on March 10th; Lowest: 29.196" on March 19th
                  ---------------------------------------------------------------------------






                July, 19 9 6


                -----------------------------------------------------------------------------
                MONTHLY SUMMARY OF CLIMATOLOGICAL DATA - PORTSMOUTH, VIRGINIA
                Portsmouth Weather Records Service
                Portsmouth, Virginia        23702-2017 (3 miles south / West Cradock Section)
                -----------------------------------------------------------------------------
                     Monthly summary of Local Climatclogical Data for Portsmouth, Virginia,
                       West Cradock Section, during the month of July 1996. Time is EDT.
                -----------------------------------------------------------------------------
                 D HT DN LT DN MT            DN HDD CDD PREC WD WS SC WXR TYPE/REMARKS

                -----------------------------------------------------------------------------
                 1   81  -5   70  +1  75.5   -2       10.5         NNE19  PC F H
                 2   92  +5   70  +1  81.0,  +3       16.0       T ESE16  PC F-H- DST LTG RW-
                                                                   W 16
                 3   87  -1   64  -5  75.5   -3       10.5   0.76  N 36   PC F-H-RW- TRW+ FROPA
                 4   78  -9   61  -9  69.5   -9        4.5         NW 27  PC COOLER
                 5   85  -3   58  -12 71.5   -7        6.5         WSW18  PC TIED RECORD LOW
                 6   89     0 69  -2  79.0   -1       14.0         S 18   PC H-
                 7   93  +3   68  -3  80.5    0       15.5         SSW18  PC H-
                 8   94  +4   73  +4  83.5   +4       18.5   0.53  NW 28  PC H- HOT HUMID TRW
                 9   92  +1   71   0  81.5    0       16.5   0.17  WSW18  PC F TRW-(AM) RW H
                10   82  -8   67  -5  74.5   -6        9.5         N 21   PC FROPA
                11   80  -9   65  -6  72.5   -8        7.5       T SE 19  PC RW- (LATE EVE)
                12   79  -11  70  -2  74.5   -7        9.5   2.78  ESE46 C   RW+TRW+F WINDY EVE
                13   88  -3   70  -4  79.0   -3       14.0   0.61  E 54 C    RW+TRW F HURRICANE BERTHA
                                                                             PASSES 25 MILES WEST OF
                                                                             STATION; MINIMUM BAROMETR
                                                                             PRESSURE 29.373"
                14   93  -2   74   0  83.5   +1       18.5   0.19  S 28   PC H TRW MUGGY
                15   88  -1   74  +1  81.0    0       16.0   0.69  SSW26  PC F-H MUGGY TRW (2)
                16   89     0 71  -1  80.0   -1       15.0         SSW19  PC F-H MUGGY
                17   93  +4   73  +1  83.0   +2       18.0         W 20   SU F-H HOT MUGGY
                18   93  +4   71  -1  82.0   +1       17.0   2.53  WSW32  PC F-H TRW+(3)
                19   88  -2   70  -1  79.0   -2       14.0   0.90  SW 24  PC F TRW+(AM) H-
                20   82  -9   67  -4  74.5   -6        9.5         N 22   SU FROPA DRIER
                21   85  -6   62  -11 73.5   -8        8.5         WNW16  SU PLEASANT
                22   90  +1   67  -6  78.5   -2       13.5       T S 20   PC GF-(AM) H RW-DST LTG
                23   84  -3   73  +1  78.5   -1       13.5         NNW18  PC F- H HUMID
                24   86  -3   72  +1  79.0   -1       14.0       T ESE15  PC F H RW-
                25   93  +4   69  -3  81.0   +1       16.0   0.61  SE 28  PC F H HUMID HOT TRW
                26   86  -3   71   0  78.5   -1       13.5   0.01  WNW18  PC FROPA RW-(AM)
                27   88  -1   65  -7  76.5   -4       11.5         ESE16  PC
                28   88     0 68  -3  78.5   -2       13.0         ESE21  PC H WARM HUMID
                29   81  -7   71  +1  76.0   -3       11.0   1.00  ESE16  PC F TRW+ RW
                30   88  +1   70   0  79.0    0       14.0       T SSW21 C   F RW-
                31   92  +3   68  -3  80.0    0       15.0   1.02  WSW47  PC H HUMID TRW(1)TRW+(2)

               -----------------------------------------------------------------------------

                SUMMARY OF JULY 1996:


                TEMPERATURE:


                    Monthly mean:           High = 87.3      Low = 68.8 Mean = 78.0
                    Departure < Normal:     High = -1.7      Low = -2.5 Mean = -2.2

                     Degree Days:                Heating =     0.0   Cooling = 404.5
                     Number of Days Using:       Heating =       0   Cooling =     31

                     Days with maximum temperature >= 90: 10
                     Days with maximum temperature <= 32:        0
                     Days with minimum temperature <= 32:        0
                     Days with minimum temperature <= 0:         0








                 PRECIPITATION:


                       Total month                 11.801,          Departure < Normal        + 6.7411
                       Normal month (to date) 5.06"                                          or 233%
                       Average daily                0.38"
                       Normal daily                 0.16"
                       Number of days with measurable precipitation = 13

                       Year-to-date =     36.9011    Departure = +8.54"       or 130% of normal

                       Maximum for July        = 11.80" in 1996          (Since
                       Minimum for July        = 1.3211 in 1978           1976)

                       Number of days     with  0.01" or more:     13                   Snowfall
                       Number of days     with  0.10" or more:     12           July total = 0.00"
                       Number of days     with  0.50" or more:     10          July maximum = 0.00"
                       Number of days     with  1.00" or more:       4

                   DAILY EXTREMES:        Low   temperature    =   58  on the  5th
                                          High  temperature    =   94  on the  8th
                            Maximum daily precipitation        =  2.78" on the 12th
                                Maximum 24-hour rainfall       =  3.43" on the 18th-19th
                                         Maximum wind gust     =  E 54 mph on the 13th
                            Maximum barometric pressure        =  30.295" on the llth
                            Minimum barometric pressure        =  29.373" on the 13th


                                                           NUMBER OF:


                  Days Cloudy:                      2                    Days with thunderstorms: 12
                  Days Partly Cloudy:              27                          # of Thunderstorms: 18
                  Days Clear/Sunny:                 2          Days with some type of snowfall: 0
                  Days with Fog/Ground Fog: 17
                  Days   with -Dense   Fog:         0
                  ---- ---- ----- ----

                  YEAR-TO-DATE:


                  Temperatures                          Degree Days         Precipitation

                  Mean maximum:       67.7 (-0.9),Heating: 2389.5           Aqueous:    36.90" (DEP +8.54")
                  Mean minimum:       48.6 (-0.8) Cooling:        929.5       Maximum   monthly: 11.80"/JUL.
                  Mean monthly:       58.1 (-0.9)                             Minimum   monthly:     2.65"/FEB.

                  Highest:          98, May 20th                            Snowfall:              15.90"
                  Lowest:            8, February    5th                       Maximum   daily:    4.50"/JAN. 6
                  Days with maximum temperature         >= 90: 25             Maximum   monthly: 8.00"/FEB.
                  Days with maximum temperature         <= 32:    9           Seasonal total:      16.20"
                  Days with minimum temperature         <= 32:   45           Days with some type of
                  Days with temperature                 <= 0:     0              snowfall:         15
                                                                              Days with measurable
                  Number of:                                                    precipitation: 86 or 40%
                  Days   using   Heating:          126
                  Days   using   Cooling:           87                      Days with thunderstorms: 28
                  Days   Cloudy:                    40                      Number of thunderstorms: 38
                  Days   Partly Cloudy:            139
                  Days   Clear/Sunny:               34                      Greatest 24-hour period
                  Days   with fog/ground fog:       72                        rainfall: 3.43"/July 18-19th

                  Wind   (Highest Recorded Wind Gust): SSW 64 miles per hour, JAN. 19
                  Barometer:     Highest 30.937" on March 10th; Lowest: 29.196" on March 19th
                  ---------------------------------------------------------------------------



I
I
I
I                     Appendix A-5
I
I         Statistical Analysis of Monitoring Data
I
I
I
I
I ,
I
I
I
I
I
I
I
I












                   TOTAL SUSPENDED SOLIDS (TSS), (mg1L)                                                                                                                       Storms Removed          none

                                                                                                                                                               Square                                        Square                                        Square
                     Date                                          Influent                   Sand                   CSF            Influent-Sand          Influent-Sand          Influent-CFS           Influent-CFS             Sand-CSF               Sand-CSF
                   Dec 9,95                                             10                    93                     64                     -83                    6889                       -54               2916                        29               841
                   _@e_b 2 1, '9 6                                      37                    6                      12                     31                     961                        25                625                         -6                36
                   Mar 6, '96                                           15                    28                     61                     -13                    169                        -46               2116                        -33              1089
                   Mar 19,96                                            138                   100                    20                     38                     1444                       118               13924                       80              6400
                   Mar 28, '96                                          14                    4                      3                      10                     100                        11                121                         1                  1
                   Apr 24, '96                                          8                     6                      6                      2                      4                          2                 4                           0                  0
                   May 16,96                                            7                     4                      5                      3                      9                          2                 4                           - I                I
                   Jun 24, '96                                          7                     42            __36                            -35                    1225                       -29               841                         6                 36
                   Jul 3,96                                             19                    7                      8                      12                     144                        11                121
                   Jul 15,96                                            13                    4                      5                      9                      81                         8                 64
                   Jul 18, '96                                          9                     3                                             6                      36                         5                 25
                   Jul 25,'96                                           8                     2                      3                      6                      36                         5--               25
                   MEANS                                                23.8                  24.9                   18.9
                   % Decrease in Concentration (neg. value              increase In conc)                                                   -4.9%                                             20.4%                                         24.1%
                   Sum of ditrerences                                                                                                       -14                                               58-                                           72
                   Mean Difference                                                                                                          6.3                                               10.2                                          3.9


                   TEST FOR SIGNIFICANCE IN DIFFERENCES
                   Sum of squared differences                                                                                                                      11098                                        20786                                       8408
                   Square of sum of differences                                                                                             196                                               3364                                          5184
                   n =                                                  12
                   Standard Deviation                                                                                                       31.74                                             43.18-               -                        26.93

                   t(paired), test statistic                                                                                                0.685                                             0.817                                         0.503
                   t(O.10,11), tubular value                                                                                                1.363                                             1.363                                         1.363

                   Conclusion                                                                                                      Do not reject Ho                             Do not reject Ho                              Do not reject Ho
                                                                                                                                   Difference could                             Difference could                              Difference could
                                                                                                                                    be variation in                              be variation in                               be variation in
                   Interpretation                                                                                                           data                                              duta                                          (tutu


                   CORRELATION
                   Sum of (Xi)*(Yi)'s                                                                                                       16026                                             5413                                          11406
                   Sum of (Xi) or (Yi)'s                                285                   299                    227
                   Sum of (Xi)^2        __                            21771                   21379                  9841                   --6.-62                                           0.00                                          0.65
                   Correlation betweei




                       Appendix A-5.                                                                            Statistical analysis of monitoring data.                                                                                           Page A-5-1














                   TOTAL SUSPENDED SOLIDS (TSS), (mgfL)                                                                                                                            Stonrns Removed          Dec9, Mar19

                                                                                                                                                                    Square                                         Square                                          Square
                      Date                                           Influent                   Sand                                    Influent-Sand           Influent-Sand           Influent-CFS            Influent-CFS             Sand-CSF                Sand-CSF
                   Feb 2 1, '96                                           37                     6                          12                  31                      961                     25                     625                          -6                   36
                   Mar 6, '96                                             15                     28                         61                  -13                     169                     -46                    2116                         -33              1089
                   Mar 28,96                                              14                     4                          3                   10                      100                     11                     121                          1                    1
                   Apr 24,96                                              8                      6                          6                   2                                                                      4                            0                    0
                   May 16,96                                              7                      4                          5                   3                       9                       2                      4                            -1                   1
                   Jun 24, '96                                            7                      42                         36                  -35                     1225                    -29                    841                          6                    36
                   Jul 3, '96                                             19                     7                          8                   12                      144                     11                     121                          -1                   1
                   Jul 15, '96                                            13                     4                          5                   9                       81                      8                      64__ _-I
                   Jul 18, '96                                            9                      3                          4                   6                       36                      5                      25                           -1
                   Jul 25, '96                                            8                      2                          3                   6                       36                      5                      25                           -1
                   MEANS                                                                                                    14.3
                   % Decrease in Concentration (neg. value                increase in conc)                                                     22.6%                                           4.4%                                                -34.9%
                   Sum of differences                                                                                                           31                                              -6                                                  -37
                   Mean Difference                                                                                                              3.1                                             -0.6                                                -3.7


                   TEST FOR SIGNIFICANCE IN DIFFERENCES
                   Sum of squared differences                                                                                                                           2765                                           3946                                          1167
                   Square of sum of di&rences                                                                                                   961                                             36                                                  1369
                   n=                                                     10
                   Standard Deviation                                                                                                           17.22                                           20.93                                               10.70


                   t(paired), test statistic                                                                                                    0.569                                           -0.091                                              -1.094
                   t(O.10,9), tabular value                                                                                                     1.383                                           -1.383                                              -1.383

                   Conclusion                                                                                                          Do not reject Ho                               Do not reject Ho                               Do not reject Ho
                                                                                                                                       Difference could                               Difference could                                Difference could
                                                                                                                                        be variation in                                be variation in                                 be variation in
                   Interpretation                                                                                                               data                                            data                                                data


                   CORRELATION
                   Sum of (Xi)*(Yi)'s                                                                                                           1296                                            2013                                                3454
                   Sum of (Xi) or (Yi)'s                                  137                    106                        143
                   Sum of (Xi)A2                                         2627                   2730                        5345
                   Correlation between groups, r                                                                                                -0.14                                           0.03                                                0.84





                        Appendix A-5.                                                                              Statistical analysis of monitoring data.                                                                                                Page A-5-2















                   TOTAL SUSPENDED SOLIDS (TSS), (mWL)                                                                                                                               Storrns Removed          Dec9, Mar19, Mar6, Jun24

                                                                                                                                                                      Square                                         Square                                          Square
                      Date                                            Influent                   Sand                     CSF             Influent-Sand          Influent-Sand            Influent-CFS            Influent-CFS             Sand-CSF                Sand-CSF
                   Feb 2 1, '96                                            37                     6                       12                      31                     961                     25                      625                       -6                      36
                   mar 28,96                                               14                     4                       3                       10                     100                     11                      121                       1                       1
                   Apr 24, '96                                             8                      6                       6                       2                      4                       2                       4                         0                       0
                   May 16,96                                               7                      4                       5                       3                      9                       2                       4                         -1                      1
                   Jul 3, '96                                              19                     7                       8                       12                     144                     11                      121                       - I                     I
                   Jul 15,96                                               13                     4                       5                       9                      81                      8                       64                        - I                     I
                   Jul 18, '96                                             9                      3                       4                       6                      36                      5                       25                        - I                     I
                   Jul 25,96                                               8                      2                       3                       6                      36                      5                       25                        - I                     I
                   MEANS                                                   14.4                   4.5                     5.8
                   % Decrease hi Concentration (neg. value                 increase in cone)                                                      68.7%                                          60.0%                                             -27.8%
                   Sum of differences                                                                                                             79                                             69                                                -10
                   Mean Difference                                                                                                                9.9                                            H.6                                               -1.3


                   TEST FOR SIGNIFICANCE IN DIFFERENCES
                   Sum of squared differences                                                                                                                            1371                                            989                                               42
                   Square of sum of differences                                                                                                   6241                                           4761                                              100
                   n =                                                     8
                   Standard Deviation                                                                                                             9.19                                           7.50                                              2.05


                   t(paired), test statistic                                                                                                      3.040                                          3.252                                             -1.722
                   t(O.10,7), tabular value                                                                                                       1.415                                          1.415                                             -1.415
                   Conclusion                                                                                                               Reject lio                                      Reject Ho                                       Reject Ho
                                                                                                                                                  True                                           True                                              True
                                                                                                                                          concentration                                  concentration                                   concentration
                   Interpretation                                                                                                           difference                                      difference                                      difference


                   CORRELATION
                   Sum of (Xi)*(Yi)'s                                                                                                             582                                            846                                               234
                   Sum of (Xi) or (Yi)'s                                   1  5-                  36
                   Sum of (Xi)^2                                           2353                   182                     328
                   Correlation betwee                                                                                                             0.55                                           0.88                                              0.76







                        Appendix A-5.                                                                               Statistical analysis of monitoring data.                                                                                                 Page A-5-3













                  TOTAL PHOSPHORUS (TP), (mgL)                                                                                                                                 Storms Removed          none


                                                                                                                                                                Square                                         Square                                        Square
                     Date                                           Influent                 Sand                   CSF              Influent-Sand          Influent-Sand          Influent-CFS            Muent-CFS               Sand-CSF                Sand-CSF
                  Dec 9, '95                                          0.11                   0.13                   0.19                   -0.02                0.0004                   -0.08                 0.0064                  -0.06                 -0.0036
                  Feb 21,96                                           0.08                   0.04                   0.04                   0.04                 0.0016                   0.04                  0.0016                  0.00                  0.0000
                  Mar 6,96                                            0.11                   0.09                   0.09                   0.02                 0.0004                   0.02                  0.0004                  0.00           -0.0000
                  Mar 19, '96                                         0.19                   0.11                   0.05                   0.08                 0.0064                   0.14                  0.0196                  0.06                  -0.0036
                  Mar 28, '96                                         0.06                   0.11                   0.04                   -0.05                0.0025                   0.02                  0.0004                  0.07                  0.0049
                  Apr 24, '96                                         0.26                   0.18                   0.17                   0.08                 0.0064                   0.09                  0.0081                  0.01                  0.000-1
                  May 16, '96                                         0.06                   0.13                   0.09                   -0.07                0.0049                   -0.03                 0.0009                  0.04         --0.0016
                  Jun 24, '96                                         0.11                   0.24                   0.22                   -0.13                0.0169                   -0.11                 0.0121                  0.02                  0.0004
                  Jul 3,96                                            0.13                   0.07                   0.08                   0.06                 0.0036                   0.05                  0.0025                  -0.01                 0.0001-
                  Jul 15,96                                           0.10                   0.07                   0.04                   0.03                 0.0009                   0.06                  0.0036                  0.03                  0.0009
                  Jul 18, '96                                         0.09                   0.06                   0.04                   0.03                 0.0009                   0.05                  0.0025                  0.02                  0.0004
                  Jul 25, '96                                         0.09                   0.06                   0.05                   0.03                 0.0009                   0.04                  0.0016                  0.01                  0.0001
                  MEANS                                             0.1158                  0.1075                 0.0917
                  % Decrease In Concentration (neg. value = increase in cone)                                                              7.2%                                          20.9%                                         14.7%
                  Sum of differences                                                                                                       0.10                                          0.29                                          0.19
                  Mean Difference                                                                                                          0.0083                                        0.0242                                        0.0158


                  TEST FOR SIGNIFICANCE IN DIFFERENCES
                  Sum of squared differences                                                                                                                    0.0458                                         0.0597                                        0.0157
                  Square of sum of differences                                                                                             0.0100                                        0.0841                                        0.0361
                  n =                                                   12
                  Standard Deviation                                                                                                       0.0639                                        0.0692                                        0.0340

                               test statistic                                                                                              0.45i                                         L'2_10
                                                                                                                                                                                                                                       1.615
                  t(O.10,11), tabular value                                                                                                1.363                                         1.363                                         1.363

                  Conclusion                                                                                                       Do not reject Ho                              Do not reject Ilo                                 Reject Ho
                                                                                                                                   Difference coiad-                             Difference could                                      True
                                                                                                                                    be variation in                               be variation in                                concentration
                  Interpretation                                                                                                           data                                          data                                      difference


                  CORRELATION
                  Sum of (Xi)*(Yi)'s                                                                                                       0.1628                                        0.1422                                        0.1532
                  Sum of (Xi) or (Yi)'s                               1.39                   1.29                   1.10
                  Sum of (Xi)'12         -                          0. IV6_7 --0.1747                       ----0.1474
                  Correlation between groups, r                                                                                            0.37                                          0.36                                          0.85



                       Appendix A-5.                                                                            Statistical analysis of Monitoring data.                                                                                            Page A-5-4















                   TOTAL PHOSPHORUS (TP), (m I'Y                                                                                                                                  Storms Removed - Dec9


                                                                                                                                                                   Square                                         Square                                         Square
                   -Date                                             Influent                  Sand                   CSF              Influent-Sand           Influent-Sand          Influent-CFS            Influent-CFS             Sand-CSF                Sand-CSF
                   Feb 2 1, '96                                         0.08                   0.04                   0.04                   0.04                  0.0016                   0.04                  0.0016                   0.00                  0.0000
                   Mar 6,96                                             0.11                   0.09                   0.09                   0.02                  0.0004                   0.02                  0.0004                   0.00                  0.0000
                   Mar 19,96                                            0.19                   0.11                   0.05                   0.08                  0.0064                   0.14                  0.0196                   0.06                  0.0036
                   Mar 28,96                                            0.06                   0.11                   0.04                   -0.05                 0.0025                   0.02                  0.0004                   0.07                  0.0049
                   Apr 24, '96                                          0.26                   0.18                   0.17                   0.08                  0.0064                   0.09                  0.0081                   0.01                  0.0001
                   May 16, '96                                          0.06                   0.13                   0.09                   -0.07                 0.0049                   -0.03-                0.0009                   0.04                  -0.0016
                   Jun 24, '96                                          0.11                   0.24                   0.22                   -0.13                 0.0169                   -0.11                 0.0121                   0.02                  0.0004
                   Jul 3, '96                                           0.13                   0.07                   0.08                   0.06                  0.0036                   0.05                  0.0025                   -0.01                 0.0001
                   Jul 15,96                                                                   0.07                   004                    0.03                  0.0009'                  0.06                  0.0036           -003                          0.0009
                   Jul 18, '96                                          0.09                   0.06                   0.04                   0.03                  0.0009                   0.05                  0.0025                   0.02                  0.0004
                   Jul 25,96                                  1         0.09                   0.06                   0.05                   0.03                  0.0009                   0.04                  0.0016                   0.01                  0.0001
                   MEANS                                      1       0.1164                  0.1055                 0.0827
                   % Decrease in Concentration (neg. value              increase in cone)                                                    9.4%                                         28.9%                                            21.6%
                   Sum of differences                                                                                                        0.12                                           0.37                                           0.25
                   Mean Difference                                                                                                           0.0109                                       (1.033                                           0.0227


                   TEST FOR SIGNIFICANCE IN DIFFERENCES
                   Sum of squared differences                                                                                                                      0.0454                                         0.0533                                         0.0121
                   Square of sum of differences                                                                                              0.0144                                       0.1369                                           0.0625
                   n
                   Standard Deviation                                                                                                        0.0664                                       0.0639                                           0.0253


                   t(palred), test statistic                                                                                                 0.545                                          1.745                                          2.975
                   t(O. 10,10), tabular value                                                                                                1.372                                          1.372-                                         1.372

                   Conclusion                                                                                                        Do not reject Ho                                   Reject Ilo                                      Reject Ho
                                                                                                                                      Difference could                                      True                                           True
                                                                                                                                       he variation in                                concentration                                  concentration
                   Interpretation                                                                                                            data                                       difference                                     difference


                   CORRELATION
                   Sum of (Xi)*(Yi)'s                                                                                                        0.1485                                       0.1213                                           0.1285
                   Sum of (Xi) or (Yi)'s                                1.28                   1.16                   0.91
                   Sum of (Xi)^2                                      0.1846                 0 1578                  0.1113
                   Correlation between groups, r                                                                                             0.38                                           0.43                                           0.91




                       Appendix A-5.                                                                              Statistical analysis of monitoring data.                                                                                              Page A-5-5















                   TOTAL PHOSPHORUS (TP), (m                                                                                                                                       Storms Removed           Dec9, Jun,24

                                                                                                                                                                    Square                                          Square                                         Square
                     Date                                            Influent                  Sand                    CSF              Influent-Sand          Influent-Sand            Influent-CFS           Influent-CFS              Sand-CSF                Sand-CSF
                   Feb 21, '96                                          0.08                   0.04                    0.04                   0.04                  0.0016                    0.04                  0.0016                   0.00                  0.0000
                   Mar 6, '96                                           0.11                   0.09                    0.09                   0.02                  0.0004                    0.02-                 0.0004                   0.00                  0,0000
                   Mar 19, '96                                          0.19                   0.11                    0.05                   0.08                  0.0064                    0.14                  0.0196                   0.06                  0.0036
                   Mar 28, '96                                          0.06                   0.11                    0.04                   -0.05                 0.0025                    0.02                  0.0004                   0.07                  0.0049
                   Apr 24, '96                                          0.26                   0.18                    0 17                   0.08                  0.0064                    0.09                  0.0081                   0.01                  0.0001
                   May 16, '96                                ---0.06------                       13                   0.()9----.---          -0:07                 0.0049                    -0.03                 0.0009                   0.04                  0.0016
                   Jul 3, '96                                           0.13                   0.07                    0.08                   0.06                  0.0036                    0.05                  0.0025                   -0.01                 0.0001
                   Jul 15,96                                            0.10                   0.07                    0.04                   0.03                  0.0009                    0.06                  0.0036                   0.03                  0.0009
                   Jul 18, '96                                          0.09                   0.06                    0.04                   0.03                  0.0009                    0.05                  0.0025                   0.02                  0.0004
                   Jul 25, '96                                          0@09                   0.06                    0.05                   0.03                  0.0009                    O@04                  0.0016                   0,01                  0,0001
                   MEANS                                              0.1170                   0.0920                0.0690
                   % Decrease in Concentration (neg. value = increase in cone)                                                                21.4%                                           41.0%                                          25.0%
                   Sum of differences                                                                                                         0.25                                            0.48                                           0.23
                   Mean Difference                                                                                                            0.0250                                          0.0480                                         0.0230


                   TEST FOR SIGNIFICANCE IN DIFFERENCES
                   Sum of squared differences                                                                                                                       0.0285                                          0.0412                                         0.0117
                   Square of sum of differences                                                                                               0.0625                                          0.2304                                         0.0529
                   n =                                                    10
                   Standard Deviation                                                                                                         0.0497                                          0.0449                                         0.0267


                   t(paired), test statistic                                                                                                  1.590                                           3.379                                          2.725
                   t(O.10,9), tabular value                                                                                                   1.383                                           1.383                                          1.383
                   Conclusion                                                                                                              Reject Ho                                      Reject Ito                                      Reject Ho
                                                                                                                                              True                                            True                                           True
                                                                                                                                        concentration                                   concentration                                  concentration
                   Interpretation                                                                                                          difference                                     difference                                     difference


                   CORRELATION
                   Sum of (Xi)*(Yi)'s                                                                                                         0.1221                                          0.0971                                         0.0757
                   Sum of (Xi) or (Yi)'s                                1.17                   0.92                    0.69
                   Sum of (Xi)^2                                      0.1725                   0.1002                0.0629
                   Correlation between groups, r                                                                                              0.61                                                                                           0.79






                       Appendix A-5.                                                                               Statistical analysis of monitoring data.                                                                                                Page A-5-6













                   TOTAL KJELDAHL NITROGEN (TKN), (mgfL)                                                                                                                             Storms Removed            none

                                                                                                                                                                      S(-k!!Ure                                                                                        Square
                      Date                                            Influent                  Sand                    CSF               Influent-Sund          Influent-Sana            Influent-'CFS           lulluent-CFS              Sand-CSF                Sand-CSF
                   Dee 9, '95                                             0.12                  1.13                    2.34                    -1.01                 1.0201                   -2.22                  4.9284                    -1.21                  1.4641
                   Feb 21, '96                                            0.40                  0.27                    0.30                    0.13                  0.0169                   0.10                   0.0100                    -0.03                  0.0009
                   Mar 6, '96                                             0.75                  0.45                    0.48                    0.30                  0.0900                   0.27                   0.0729                    -0.03                  0.0009
                   Mar 19, '96                                            1.04                  0.54                    0.39                    0.50                  0.2500                   0.65                   0.4225                    0.15                   0.0225
                   Mar 28, '96                                            0.37                  0.64                    0.41                    -0.27                 0.0729                   -0.04                  0.0016                    0.23                   0.0529
                   Apr 24, '96                                            0.90                  0.80                    0.85                    0.10                  0.0100                   0.05                   0.0025                    -0.05                  0.0025
                   May 16, '96                                            0.26                  0.56                    0.25                    -0.30                 0.0900                   0.01                   0.0001                    0.31                   0.0961
                   Jun 24, '96                                            1.00                  1.96                    1.85                    -0.96                 0.9216                   -0.85                  0.7225                    0.11                   0.0121
                   Jul 3,96                                               0.76                  0.63                    0.67                    0.13                  0.0169                   0.09                   0.0081                    -0.04              ----0.0016
                   Jul 15, '96                                            0.39                  0.12                    0.13                    0.27                  0.0729                   0.26                   0.0676                    -0.01                  0.0001
                   Jul 18,96                                              0.52                  0.36                    0.27                    0.16                  0.0256                   0.25                   0.0625                    0.09                   0.0081
                   Jul 25, '96                                 1          0.60                  0.61                    0.45                    -0.01                 0.0001                   0.15                   0.0225                    0.16                   0.0256
                   MEANS                                                                        0.6725                0.6992
                   % Decrease in Concentration (neg. value                increase in cone)                                                     -13.5%                                         -18.0%                                           4.0%
                   Sum of differences                                                                                                           -0.96                                          -1.28                                            -0.32
                   Mean Difference                                                                                                              -0.0800                                        -0.1067                                          -0.0267


                   TEST FOR SIGNIFICANCE IN DIFFERENCES
                   Sum ot'squared differences                                                                                                                         2.5870                                          6.3212                                           1.6874
                   Square of sum of difterences                                                                                                 0,9216                                         1.6384                                           0.1024
                   n                                                      12
                   Standard Deviation                                                                                                           0.4777                                         0.7498                                           0.3907


                   t(paired), test statistic                                                                                                    -0.580                                         -0.493                                           -0.236
                   t(O. 10, 11), tabular value                                                                                                  1.363                                          1.363                                            1.363

                   Conclusion                                                                                                           Do not reject Ito                               Do not reject Ho                                Do not reject Ho
                                                                                                                                        Difference could                                Difference could                                Difference could
                                                                                                                                         be variation in                                 be variation in                                 be variation in
                   Interpretation                                                                                                               data                                           data                                             data


                   CORRELATION
                   Sum of (Xi)*(Yi)'s                                                                                                           5.2839                                         4.9684                                           8.6696
                   Sum of (Xi) or (Yi)'s                                  7.11                  8.07                    8.39
                   Sum of(Xi)^2                                                                 7.4(_,17_______1T0_64_9
                   Correlation between groups, r                                                                                                0.32                                           0.00                                             0.83




                       Appendix A-5.                                                                                Statistical analysis of monitoring data.                                                                                                 Page A-5-7














                     TOTAL KJELDAHL NITROGEN (TKN), (mg/L)                                                                                                                                  StornLs Removed            Dec:9

                                                                                                                                                                             Square                                           Square                                            Square
                        Date                                             Influent                    Sand                    CSF               Influent-Sand            Influent-Sand            Influent-CFS             Influent-CFS              Sand-CSF                 Sand-CSF
                     Feb 21, '96                                             0.40                    0.27                    030                      0.13                   0.0169                    0.10                   0.0100                     -0.03                  0.0009
                     Mar 6, '96                                              0.75                    0.45                    0.48                     0.30                   0.0900                    0.27                   0.0729                     -0.03                  0.0009
                     Mar 19,96                                               1.04                    0.54                    039                      0.50                   0.2500                    0.65                   0.4225                     0.15                   0,0225
                     Mar 28,96                                               0.37                    0.64                    0A]                      -0.27                  0.0729                    -0.04                  0.0016                     0.23                   0.0529
                     Apr 24, '96                                             0.90                    0.80                    O@85                     0.10                   0.0100                    0.05                   0.0025                     -0.05                  0.0025
                     May 16,96                                               0.26                    0.56                    0.25                     -0.30                  0.0900                    0.01                   0.0001                     0.31                   0.0961
                     Jun 24, '96                                             1.00                    1.96                    1.85                     -0.96                  0.9216                    -0.85                  0.7225                     0.11                   0.0121
                     Jul V96                                                 0.7(,                   0.63                    O@(,7                    0.1.3                  0.0169                    0.09                   o.oo8l                                            0.0010
                     Jul 15, '96                                             0.39                    0.12                    0.13                     0.27                   0.0729                    0.26                   0.0676                     -0.01                  0.0001
                     Jul 18, '96                                             0.52                    0.36                    0.27                     0.16                   0.0256                    0.25                   0.0625                     0,09                   0.0081
                     Jul 25, '96                                  1          0.60                    0.61                    OA5                      -0.01                  0.0001                    0.15                   0,0225                     0.16                   0.0256
                     MEANS                                                                           0.6309
                     % Decrease in Concentration (neg. value                 increase in conc)                                                        0.7%                                             13.4%                                             12,8%
                     Sum of differences                                                                                                               0.05                                             0.94                                              0.89
                     Mean Difference                                                                                                                  0.0045                                           0.0855                                            0.0809


                     TEST FOR SIGNIFICANCE IN DIFFERENCES
                     Sum of squared differences                                                                                                                              1.5669                                           1.3928                                            0.2233
                     ï¿½quare of sum of differences                                                                                                     0.0025                                           0.8836                                            0.7921
                     n =                                                     I I                                    --
                     Standard Deviation                                                                                                               0.3958                                           0.3623                                            0.1230


                     t(paired), test statistic                                                                                                        0.038                                            0.782                                             2.182
                     t(O.10,10), tubular value                                                                                                        1.372                                            1.372                                             1.372


                                                                                                                                              Do flot I-4-ject III)                            Oto Illot reject fill                                           1140
                                                                                                                                              Differcrice could                                Difference could                                          True
                                                                                                                                               be variation in                                  be variation in                                   concentration
                     Interpretation                                                                                                                   data                                             dat                                           difference


                     CORRELATION
                     Sum of (Xi)*(Yi)'s                                                                                                               5.1483                                           4.6876                                            6.0254
                     Sum of (Xi) or (Yi)'s                                   6.99                    6.94                    6.05
                     Sum of (Xi)^2                                        5.1787                     6.6848                 5.5893
                     Correlation between groups, r                                                                                                    0.57                                             0.65                                              0.97          1
                                                                                                                                                                                                                      L                                                I



                         Appendix A-5.                                                                                   Statistical analysis of monitoring data.                                                                                                      Page A-5-8















                   TOTAL KJELDAHL NITROGEN (TKN), (mg/L)                                                                                                                          Storms Removed - Dec9, Jun24


                                                                                                                                                                     Ir!re                                        Square                                         Square
                      Date                                           Influent                 Sand                    CSF              Influent-Sand           Influent-Sand           Influent-CFS           Influent-CFS             Sand-USF                Snnd-'CSF
                   Feb 21, '96                                         0.40                   0.27                    0.30                   0.13                  0.0169                   0.10                  0.0100                   -0.03                 0.0009
                   Mar 6, '96                                          0.75                   0.45                    0.48                   0.30                  0.0900                   0.27                  0.0729                   -0.03                 0.0009
                   Mar 19,'96                                          1.04                   0.54                    0.39                   0.50                  0.2500                   0.65                  0.4225                   0.15                  0.0225
                   Mar 28, '96                                         0.37                   0.64                    0.41                   -0.27                 0.0729                   -0.04                 0.0016                   0.23                  0.0529
                   Apr 24, '96                                         0.90                   0.80                    0.85                   0.10                  0.0100                   0.05                  0.0025                   -0.05                 0.0025
                   May 16, '96                                         0.26                   0.56                    0.25                   -0.30                 0.0900                   0.01                  0.0001                   0.31                  0.0961
                   Jul 3, '96                                          0.76                   0.63                    0.67                   0.13                  0.0169                   0.09                  0.0081                   -0.04                 0.0016
                   Jul 15, '96                                         0.39                   0.12                    0.13                   027                   0.0729                   0.26                  0.0676                   -0.01                 0.0001
                   Jul 18, '96                                         0.52          1        0.36                    0.27                   0.16                  0.0256                   0.25                  0.0625                   0.09                  0.0081
                   Jul 25, '96                                         0.60                   0.61                    0.45                   -0.01                 0.0001                   0.15                  0.0225                   0.16                  0.0256
                   MEANS                                              0.5990                  0.4980                0.4200
                   % Decrease in Concentration (neg. value = increase in cone)                                                               16.9%                                          29.9%                                          15.7%
                   Sum of differences                                                                                                        1.01                                           1.79                                           0.78
                   Mean Difference                                                                                                           0.1010                                         0.1790                                         0.0780


                   TEST FOR SIGNIFICANCE IN DIFFERENCES
                   SLIM of squared di       ences                                                                                                                  0.6453                                         0.6703
                                                                                                                                                                                                                                                                 0.2112
                   Square of sum ot'ditki-ences                                                                                              1.0201                                         3.2041                                         0.6084
                   n =                                                   10
                   Standard Deviation                                                                                                        0.2457                                         0.1972                                         0.1293


                   t(paired), test statistic                                                                                                 1.300                                          2.871                                          1.908
                   t(O.10,9), tabular value                                                                                                  1.383                                          1.383                                          1.383


                   Conclusion                                                                                                        Do not reject Ho                                   Reject Ho                                      Reject Ho
                                                                                                                                      Difference could                                      True                                           True
                                                                                                                                       be variation in                                concentration                                  concentration
                   Interpretation                                                                                                            data                                       difference                                     difference


                   CORRELATION
                   Sum of (Xi)*(Yi)'s                                                                                                        3.1883                                         2.8376                                         2.3994
                   Sum of (Xi) or (Yi)'s                               5.99                   4.98                    4.20
                   Sum of (Xi)12                                      4.1787                  2.8432                2.1668
                   Correlation between groups, r                                                                                             0.44                                           0.66                                           0.80





                       Appendix A-5.                                                                              Statistical analysis of monitoring data.                                                                                              Page A-5-9













                  AMMONIA (NH3), (mg/L)                                                                                                                                           Storms Removed           none

                                                                                                                                                                   Square                                         Square                                         Square
                     Date                                            Influent                 Sand                    CSF              Influent-Sand          Influent-Sand           Influent-CFS            hifluent-CFS             Sand-CSF                Sand-CSF
                  Dee 9,95                                             0.04                   0.04                    1.56                   0.00                  0.0000                   -1.52                 2.3104                   -1.52                 2.3104
                  Feb 2 1, '96                                         0.05                   0.13                    0.14                   -0.08                 0.0064                   -0.09                 0.0081                   -0.01                 0.0001
                  Mar 6, '96                                           0.36                   0.11                    0.29                   0.25                  0.0625                   0.07                  0.0049                   -0.18                 0.0324
                  Mar 19, '96                                          0.11                   0.10                    0.04                   0.01                  0.0001                   0.07                  0.0049                   0.06                  0.0036
                  Mar 28,96                                            0.12                   0.19                    0.09                   -0.07                 0.0049                   0.03                  0.0009                   0.10                  0.0100
                  Apr 24, '96                                          0.13                   0.08                    0.11                   0.05                  0.0025                   0.02                  0.0004                   -0.03                 0.0009
                  May 16, '96                                          0,04                   0.05                    0.04                   -0.01                 0.0001                   0.00                  0.0000                   0.01                  0.0001
                  Jun 24, '96                                          0.44                   0.44                    0.31                   0.00                  0.0000                   0.13                  0.0169                   0.13                  0.0169
                  Jul 3, '96                                           0.17                   0.15                    0.14                   0.02                  0.0004                   0.03                  0.0009                   0.01                  0.0001
                  Jul 15,96                                            0.04                   0.04                    0.04                   0.00                  0.0000                   0.00                  0.0000                   6-0-0                 0.0000
                  Jul 18,96                                            0.12                   0.04                    0.04                   0.08                  0.0064                   0.08                  0.0064                   0.00                  0.0000
                  Jul 25, '96                                          0.04                   0.06                    0.05                   -0.02-                0.0004                   -0.01                 0.0001                   0.01                  0.0001
                  MEANS                                               0.1383         1        0.1192                 0.2375
                  % Decrease in Concentration (neg. value = increase in conc)                                                                13.9%                                          -71.7%                                         -99.3%
                  Sum of differences                                                                                                         0.23                                           -1.19                                          -1.42
                  Mean Difference                                                                                                            0.0192                                         -0.0992                                        -0.1183


                  TEST FOR SIGNIFICANCE IN DIFFERENCES
                  Sum of squared differences                                                                                                                       0.0837                                         2.3539                                         2.3746
                  Square of sum of differences                                                                                               0.0529                                         1.4161                                         2.0164
                  n                                                      12
                  Standard Deviation                                                                                                         0.0849                                         0.4508                                         0.4479


                  t(paired), test statistic                                                                                                  0.782                                          -0.762                                         -0.915
                  t(O.10,11), tabular value                                                                                                  1,363                                          -1.363                                         -1.363

                  Conclusion                                                                                                         Do not reject Ho                               Do not reject Ho                               Do not reject Ho
                                                                                                                                     Difference could                               Differritce could                              Difference could
                                                                                                                                      he variation in                                be variation in                                be variation in
                  Interpretation                                                                                                             data                                           data-                                          data

                  CORRELATION
                  Sum of (Xi)*(Yi)'s                                                                                                         0.3218                                         0.3735                                         0.3080
                  Sum of (Xi) or (Yi)'s                                1.66                   1.43                    2.85
                  Sum of (Xi)112                                     0.4188                   0.3085                 2.6821
                  Correlation between groups, r                                                                                              0.77                                           -0.03                                          -0.06




                       Appendix A-5.                                                                              Statistical analysis of monitoring data.                                                                                            Page A-5-1 0














                   AMMONIA (NH3), (mg(L)                                                                                                                                            Storms Removed= Dec9


                                                                                                                                                                     Square                                         Square                                          Square
                      Date                                            Influent                  Sand                   CSF               Influent-Sand          Influent-Sand           Influent-CFS            Influent-CFS              Sand-CSF               Sand-CSF
                   Feb 21, '96                                          0.05                    0.13                   0.14                    -0.08                 0.0064                   -0.09                 0.0081                    -0.01                 0.0001
                   Mar 6, '96                                           0.36                    0.11                   0.29                    0.25                  0.0625                   0.07                  0.0049                    -0.18                 0.0324
                   Mar 19,96                                            0.11                    0.10                   0.04                    0.01                  0.0001                   0.07                  0.0049                    0.06                  0.0036
                   Mar 28,96                                            0.12                    0.19                   0.09                    -0.07                 0.0049                   0.03                  0.0009                    0.10                  0.0100
                   Apr 24,96                                            0.13                    0.08                   0.11                    0.05                  0.0025                   0.02                  0.0004                    -0.03                 0.0009
                   May 16,96                                            0.04                    0.05                                           -0.0 L___ -           0.0001                   0.00                  0.0000                    0. 0-1                0.000-1-----
                   Jun 24, '96                                          0.44                    0.44                   0.31                    0.00                  0.0000                   0.13                  0.0169                    0.13                  0.0169
                   Jul 3, '96                                           0.17                    0.15                   0.14                    0.02                  0.0004                   0.03                  0.0009                    0.01                  0.0001
                   Jul 15,96                                            0.04                    0.04                   0.04                    0.00                  0.0000                   0.00                  0.0000                    0.00                  0.0000
                   Jul 18, '96                                          0.12                    0.04                   0.04                    0.08                  0.0064                   0.08                  0.0064                    0.00                  0.0000
                   Jul 25, '96                                          0.04                    0.06                   0.05                    -0.02                 0.0004                   -0.01                 0.0001                    0.01                  0.0001
                   MEANS                                               0.1473                   0.1264                 0.1173
                   % Decrease in Concentration (neg. value = increase in cone)                                                                 14.2%                                          20.4%                                           7.2%
                   Sum of differences                                                                                                          0.23                                           0.33                                            0.10
                   Mean Difference                                                                                                             0.0209                                         0.0300                                          0.0091


                   TEST FOR SIGNIFICANCE IN DIFFERENCES
                   Sum of squared ditlerences                                                                                                                        0.0837                                         0.0435                                          0.0642
                   SqTTC "r -Hum U    &(Iiftruri -com                                                                                          0.05  .21)                                     0.1099                                          0.0100
                   ri =                                      -           I I
                   Standard Deviation                                                                                                          0.0888                                         0.0580                                          0.0796


                   t(paired), test statistic                                                                                                   0.781                                          1.717                                           0.379
                   t(O.10,10), tabular value                                                                                                   1.372                                          1.372                                           1.372

                   Conclusion                                                                                                          Do not reject I lo                                 Reject 110                                  Do not   reject tio
                                                                                                                                       Difference could                                       True                                    Difference could
                                                                                                                                        be variation in                                 concentration                                  be variation in
                   Interpretation                                                                                                              data                                       difference                                          data


                   CORRELATION
                   Sum of (Xi)*(Yi)*s                                                                                                          0.3202                                         0.3111                                          0.2456
                   Sum of (Xi) or (Yi)'s                                1.62                    1.39                   1.29
                   Sum of (Xi)1,2                                      0.4172                   0.3069        1       0.2485
                   Correlation between groups, r                                                                                               0.75                                           0.92                                            0.73




                        Appendix A-5.                                                                              Statistical analysis of monitoring data.                                                                                              Page A-5-1 1














                  BIOCHEMICAL OXYGEN DEM ND (BOD5), (m                                                                                                                       Storms Removed           none


                                                                                                                                                               Square                                       Square                                         Square
                     Date                                          Influent                 Sand                   CSIF             Influent-Sand          Muent-Sand             Influent-CFS           Influent-CFS             Sand-CSF               Sand-CSF
                  Dec 9, '95                                             0.5                    0.5                    4                    0                        0                        -3.5                 12.25                    -3.5            12.25
                  Feb 2 1, '96                                           3                      3                      2                    0                        0                        1                    1                        1                   1
                  Mar 6, '96                                             5                      2                      2                    3                        9                        3                    9                        0                   0
                  Mar 19,96                                              5                      2                      2                    3                        9                        3                    9                        0                   0
                  Mar 28, '96                                            3                      7                      3                    -4                       16                       0                    0                        4                   16
                  Apr 24, '96                                            7                      4                      6                    3                        9                        1                    1                        -2                  4
                  May 16,96                                              3                      4                      3                    - I                      1                        0                    0                        1                   1
                  Jun 24, '96                                            4                      34                     29                   -30                   900                         -25                  625                      5                   25
                  Jul 3,'96                                              11                     7                      6                    4                        16                       5                    25                       1                   1
                  Jul IS, '96                                            4                      2                      0.5                  2                        4                        3.5                  12-25                    1.5              2.25
                  Jul 18,96                                              5                      3                      2                    2                        4                        3                    9                        1                   1
                  Jul 25, '96                                            6                      3                      3                    3                        9                        3                    9                        0
                  MEANS                                             4.7083                 5.9583                 5.2083
                  % Decrease in Concentration (neg. value = Increase in cone)                                                               -26.5%                                            -10.6%                                        12.6%
                  Sum of differences                                                                                                        -15                                               -6                                            9
                  Mean Difference                                                                                                           -1.25                                             -0.50                                         0.75


                  TEST FOR SIGNIFICANCE IN DIFFERENCES
                  Sum of squared ditlerences                                                                                                                      977                                              712.5                                     63.5
                  Square of surn of differences                                                                                             225                                               36                                            81
                  n =                                                    12
                  Standard Deviation                                                                                                        9.3335                                            8.0312                                        2.2714


                  t(paired), test statistic                                                                                                 -0.464                                            -0.216                                        1.1"
                  t(O.10,11), tabular value                                                                                                 -1.363                                            -1,363                                        1.363

                  Conclusion                                                                                                      Do not reject Ho                              Do not reject Ho                              Do not reject Ho
                                                                                                                                  Difference could                              Difference could                              Difference could
                                                                                                                                    be variation in                              be variation in                               be variation in
                  Interpretation                                                                                                            data                                              data                                          data


                  CORRELATION
                  Sum of (Xi)*(Yi)'s                                                                                                        344.25                                            300                                           1117
                  Sum of (Xi) or (Yi)'s                              56.50                 71.50                  62,50
                  Sum of (Xi),*,2                                   340.25                1325.25                 972.25
                  Correlation between groups, r                                                                                             0.03                                              0.03                                          0.98




                       Appendix A-5.                                                                           Statistical analysis of monitoring data.                                                                                          Page A-5-12















                  BIOCHEMICAL OXYGEN DEM ND (BODS), (mg//                                                                                                                  Storms Removed= Dec9, .1un24


                                                                                                                                                            Square                                       Square                                       Square
                     Date                                         Influent                Sand                   CSF              Influent-Sand         Influent-Sand          Influent-CFS           Influent-CFS            Sand-CSF               Sand-CSF
                  Feb 21, '96                                                                                                             0                       0                     1                      1
                  Mar 6, '96                                             5_                  2                     2                      3                       9                     :1                     9
                  Mar 19, '96                                            5                   2                     2                      3                       9                     3                      9                        0                   0
                  Mar 28, '96                                            3                   7                     3                      -4                      16                    0                      0                        4                   16
                  Apr 24, '96                                            7                   4                     6                      3                       9                     1                      1                        -2                  4
                  May 16,'96                                             3                   4                     3                      - I                     1                     0                      0                        1                   1
                  Jul 3,96                                               11                  7                     6                      4                       16                    5                      25                       1                   1
                  Ad 15,'96                                                         -------2                       0..5                   2                       4                  3.5                   12.25                        1.5             2.25
                  Jul 18,96                                              5                   3                     2                      2                       4                     3                      9                        1                   1
                  Jul 25,96                                              6                   3                     3                      3                       9                     3                      9                        0                   0
                  MEANS                                            5.2000                3.7000                 2.9500
                  % Decrease in Concentration (neg. value = increase In cone)                                                             28.8%                                      43.3%                                              20.3%
                  Sum of differences                                                                                                      15.0                                       22.5                                               7.5
                  Mean Difference                                                                                                         1.50                                       2.25                                               0.75


                  TEST FOR SIGNIFICANCE IN DIFFERENCE S
                  Sum of squared differences                                                                                                                      77                                       75.25                                        26.25
                  Square of sum of differences                                                                                            225                                        506.25                                             56.25
                  n =                                                    10
                  Standard Deviation                                                                                                      2.4608                                     1.6541                                             1.5138


                  t(paired), test statistic                                                                                               1.928                                      4.301                                              1.567
                  t(O.10,9), tabular value                                                                                                1.383                                      1.383                                              1.383
                  Conclusion                                                                                                        Reject Ho                                    Reject Ho                                    Reject Ho
                                                                                                                                          True                                       True                                               True
                                                                                                                                  concentration                                concentration                                concentration
                  Interpretation                                                                                                    difference                                   difference                                   difference


                  CORRELATION
                  Sum of (Xi)*(Yi)'s                                                                                                      208                                        182                                       129.0000
                  Sum of (Xi) or (Yi)'s                             52.00                 37.00                  29.50
                  Sum of (Xi)",2                                         324            169@0000                115.25
                  Correlation between groups, r                                                                                           0.38                                       0.74                                               0.66





                       Appendix A-5.                                                                          Statistical analysis of monitoring data.                                                                                       Page A-5-13










                    TOTAL ORGANIC CARBON -C),(-g/L)                                                                                                                               Storms Removed            none

                                                                                                                                                                   Square                                         Square                                          Square
                      Date                                            Influent                 Sand                   CSF              Influent-Sand          Influent-Sand           Influent-CFS            Influent-CFS             Sand-CSF                 Sand-CSF
                    Dec 9, '95                                         1.98                    1.26                   2.74                     0.72                0.5184                    -0.76                0.5776                    -1.48                 2.1904
                    Feb 21, '96                                        1.64                    2.72                   1.90                     -1.08               1.1664                    -0.26                0.0676                    0.82                  0.6724
                    Mar 6, '96                                         7.80                    4.70                   4.50                     3.10                9.6100                    3.30                 10.8900                   0.20                  0.0400
                    Mar 19, '96                                        5.09                    3.26                   1.60                     1.83                3.3489                    3.49                 12.1801                   1.66                  2.7556
                    Mar 28,96                                          7.09                    5.36                   2.95                     1.73                2.9929                    4.14                 17.1396                   2.41                  5.8081
                    Apr 24, '96                                        5.06                    7.89                   2.38                     -2.83               8.0089                    2.68                 7.1824                    5.51                  30.3601
                    May 16,96                                          4.05                    5.99                   6.11                     -1.94               3.7636                    -2.06                4.2436                    -0.12                 0.0144
                    Jun 24, '96                                        30.08                   40.98                  41.71                    -10.90              118.9100                  -11.63               135.2569                  -0.73                 0.5329
                    Jul 3, '96                                         10.26                   16.08                  7.19                     -5.82               33.8724                   3.08                 9.4864                    8.90                  79.2100
                    Jul 15, '96                                        6.58                    3.20                   7.05                     3.38                11.4244                   -0.47                0.2209                    -3.85                 14.8225
                    Jul 18,96                                          6.91                    4.21                   10.07                    2.70                7.2900                    -3.16                9.9856                    -5.86                 34.3396
                    Jul 25, '96                                        10.22                   6.68                   8.48                     3.54                12.5316                   1.74                 3.0276                    -1.80                 3.2400
                    MEANS                                              @8.0633                                        8.055H                   - -
                    % Decrease in Concentration (neg. value = increase in conc)                                                                -5.8%                                         0.1%                                           5.5%
                    Sum of differences                                                                                                         -5,57                                         0.09                                           5.66
                    Mean Difference                                                                                                            -0.4642                                       0.0075                                         0.4717


                    TEST FOR SIGNIFICANCE IN DIFFERENCES
                    Sum of squared differences                                                                                                                     213.3375                                       210.2583                                        173.9-860
                    Square of sum of differences                                                                                               31.0249                                       0.0091                                         32.0356
                    [I =                                                  12
                    Standard Deviation                                                                                                         4.3771                                        4.3720                                         3,9464

                    t(paired), test statistic                                                                                                  -0.367                                        0.006                                          0.414
                    t(0.10,1 1), tabular value                                                                                                 -1.363                                        1.363                                          1.363

                    Conclusion                                                                                                        Do not reject Ho                               Do not reject Ho                               Do not reject Ho
                                                                                                                                      Difference could                               Difference could                               Difference could
                                                                                                                                       be variation in                                be variation in                                be variation In
                    Interpretation                                                                                                             data                                          data                                           data


                    CORRELATION
                    Sum of (Xi)*(Yi)'s                                                                                                     1678.4702-                                    1640.4309                                      2052.5068
                    Sum of (Xi) or (Yi)'s                              96.76                   102.33                 96.67
                    Sum of (Xi)A2                                    1391.1992              2179.0787              2099.9209
                    Correlation between groups, r                                                                                              0.96                                          0.96                                           0.93



                        Appendix A-5.                                                                              Statistical analysis of monitoring data.                                                                                            Page A-5-14














                  TOTAL ORGANIC CARBON (T C), (_91L)                                                                                                                       Storms Removed          Dec9, Jun24

                                                                                                                                                             Square                                       Squa-re                                       Square
                     Date                                         Influent                 Sand                   CSF             Influent-Sand          Influent-Sand          Influent-CFS          Influent-CFS                 Sand-CSF           Sand-CSF
                  Feb 2 1, '96                                       1.64                  2.72                   1.90                  -1.08                1.1664                  -0.26                0.0676                   0.82                 0M6724
                  Mar 6, '96                                         7.80                  4.70                   4.50                  3.10                 9.6100                  3.30                 10.8900                  0.20                 0.0400
                  Mar 19,96                                          5.09                  3.26                   1.60                  1.83                 3.3489                  3.49                 12.1801                  1.66                 2.7556
                                                                     7.09                  5.30                   2.95                  1.73                 2.9929                  4.14                 17.1396                  2.4 1                5.8091
                  Apr 24, '96                                        5.06                  7.89                   2.38                  -2.83                8.0089                  2.68                 7.1824                   5.51                 30.3601
                  May 16,96                                          4.05                  5.99                   6.11                  -1.94                3.7636                  -2.06                4.2436                   -0.12                0.0144
                  Jul 3,96                                           10.26                 16.08                  7.18                  -5.82                33.8724                 3.08                 9.4864                   8.90                 79.2100
                  Jul 15, '96                                        6.58                  3.20                   7.05                  3.38                 11.4244                 -0.47                0.2209                   -3.85                14.8225
                  Jul 18, '96                                        6.91                  4.2-1                  10.07                 2.70                 7.2900                  -3.16                9.9856                   -5.86                34.3396
                  Jul 25, '96                                        10.22                 6.68                   8.48                  3.54                 12.5316                 1.74                 3.0276                   -1.80                3.2400
                  MEANS                                              6.4700                6.0090                 5.2220
                  % Decrease in Concentration (neg. value = increase in cone)                                                           7.1%                                         19.3%                                         13.1%
                  Swn of differences                                                                                                    4.61                                         12.48                                         7.87
                  Mean Difference                                                                                                       0.4610-----                                  1.2480                                        0.7870


                  TEST FOR SIGNIFICANCE IN DIFFERENCES
                  Sum of squared differences                                                                                                                 94.0091                                      74.4238                                       171.2627
                  Square of sum of differences                                                                                          21.2521                                     155.7504                                       61.9369
                  n =                                                 10
                  Standard Deviation                                                                                                    3.1952                                       2.5571                                        4.2826


                  t(paired), test statistic                                                                                             0.456                                        1.543                                         0.581
                  t(O.10,9), tabular value                                                                                              1.383                                        1.383                                         1.383


                  Conclusion                                                                                                     Do not reject 11o                                Reject Ho                                Do not reject Ilo
                                                                                                                                 Difference could                                    True                                  Difference could
                                                                                                                                  be variation in                               concentration                               be variation in
                  Interpretation                                                                                                        data                                       difference                                      data


                  CORRELATION
                  Sum of (Xi)*(Yiys                                                                                                     443.297                                    380.3689                                        339.7786
                  Sum of (Xi) or (Yi)'s                              64.70                 60.09                  52.22
                  Sum of (Xi)12                                   482.4724              498.1307               352.6892
                  Correlation between groups, r                                                                                                                                                                                    0.25





                       Appendix A-5.                                                                          Statistical analysis (if monitoring data.                                                                                       Page A-5-15














                    TOTAL RECOWIZABLE COPPER (T.R. Cu                            ug/l,                                                                                              Stomis Removed           none


                                                                                                                                                                     Square                                         Square                                          Square
                      Date                                            Influent                    Sand                   CSF             Influent-Sand           Influent-Sand           Influent-CFS           Influent-CFS              Sand-CSF                Sand-CSF
                    -5ec 9, '95                                           13                      29                     13                          -16                    256                 0                          0                    16                     256
                    Feb 21, '96                                           20                      21                     21                          -1                     1                   -1                         1                    0                      0
                    Mar 6, '96                                            25                      22                     25                          3                      9                   0                          -0                   -3                     9
                    Mar 19,96                                             68                      21                     16                          47                     2209                52                         2704                 5                      25
                    Mar 28, '96                                           18                      30                     11                          -12                    144                 7                          49                   19                     361
                    Apr 24, '96                                           39                      36                     46                          3                      9                   -7                         49                   -10                    100
                    May 16,96                                             8                       is                     11                          -7                     49                  -3                         9                    4                      16
                    Jun 24, '96                                           36                      37                     30                          -1                     1                   6                          36                   7                      49
                    Jul 3, '96                                            32                      58                     54                          -26                    676                 -22                        484                  4                      16
                    Jul 15, '96                                           23                      7                      5                           16                     256                 18                         324                  2                      4
                    Jul 18, '96                                           18                      13                     11                          5                      25                  7                          49                   2                      4
                    Jul 25, '96                                           28                      16                     9                           12                     144                 19                         361                  7                      49-
                    MEANS                                                 27.3         1--25.4                           21.0   ......
                    % I)ccresse In Concentration (neg. value              increase ill Colic)                                                        7.0%                                       23.2%                                           17.4%
                    Sum of differences                                                                                                               23                                         76                                              53                        -
                    Mean Difference                                                                                                                  3.5                                        6.9                                             3.4


                    TEST FOR SIGNIFICANCE IN DIFFERENCES
                    Sum of squared differences                                                                                                                              3779                                           4066                                        889
                    Square of sum of differences                                                                                                     529                                        5776                                            2809
                    n =                                                   12
                    Standard Deviation                                                                                                               18.43                                      18.05                                           7.72


                    t(paired), test statistic                                                                                                        0.667                                      1.326                                           1.510
                    t(O.10,11), tabular value                                                                                                        1.363                                      1.363                                           1.363

                    Conclusion                                                                                                         Do not reject Ho                                Do not reject Ho                                   Reject llo,
                                                                                                                                       Difference could                                Difference could                                         True
                                                                                                                                        he variation in                                 be variation In                                 concentration
                    Interpretation                                                                                                                   data                                       data                                      difference


                    CORRELATION
                    Sum of (Xi)*(Yi)'s                                                                                                               8870                                       7755                                            8419
                    Sum of (Xi) or (Yi)'s                                 328                     305                    252-
                    Sum of (Xi)"12                                        11684                   9835                   7892        1
                    Correlation between groups, r                                                                                                    0.22                                       0.33                                            0.87




                        Appendix A-5.                                                                               Statistical analysis of monitoring data.                                                                                             Page A-5-16














                    TOTAL RECOVERABLE COPPER (T.R. Cu), (ua/l,                                                                                                                             Storms Removed= Dec9


                                                                                                                                                                           Square                                           Square                                            Square
                       Date                                             Influent                   Sand                     CSF               Influent-Sand            Influent-Sand           Influent-CFS             Influent-CFS               Sand-CSF                Sand-CSF
                    Feb 21, '96                                              20                      21                       21                      -1                       1                       -1                       1                        0                        0
                    mar 6,96                                                 25                      22                       25                      3                        9                       0                        0                        -3                       9
                    Mar 19,96                                                68                      21                       16                      47                    2209                       52                     2704                       5                        25
                    Mar 28, '96                                              18                      30                       11                      -12                    144                       7                       49                        19                       361
                    Apr 24, '96                                              39                      36                       46                      3                        9                       -7                      49                        -10                      10.0
                    mily 10''96                                              8                                                11                                                                       _3
                    Jun 24,96                                                36                      37                       30                                                                       6                       36                        7                        49
                    Jul 3,96                                                 32                      58                       54                      -26                    676                       -22                    484                        4                        16
                    Jul 15,96                                                23                      7                        5                       16                     256                       18                     324                        2                        4
                    Jul 18, '96                                              18                      13                       11                      5                       25                       7                       49                        2                        4
                    Jul 25, '96                                              28                      16                       9                       12                     144                       19                     361                        7                        49
                    MEANS                                        1           28.6        1         25.1                     21.7
                    % Decrease in Concentration (neg. value                  increase in cone)                                                        12.4%                                          24.1%                                               13.4%
                    Sum of differences                                                                                                                39                                               76                                                37
                    Mean Difference                                                                                                                   3.5                                              6.9                                               3


                    TEST FOR SIGNIFICANCE IN DIFFERENCES
                    Sum of squared differences                                                                                                                              3523                                             4066                                                 633
                    Square of sum of differences                                                                                                      1521                                           5776                                                1369
                    n =                                                      I I
                    Standard Deviation                                                                                                                18.40                                          18.82                                               7.13


                    t(paired), test statistic                                                                                                         0.639                                          1.218                                               1.564
                    t(O.10,10), tabular value                                                                                                         1.372                                          1.372                                               1.372

                    Conclusion                                                                                                              Do not reject Ho                                 Do not reject 110                                     Reject Ho
                                                                                                                                            Difference could                                 Difference could                                            True
                                                                                                                                             be variation in                                  be variation in                                   concentration
                    Interpretation                                                                                                                    data                                           data                                         difference


                    CORRELATION
                    Sum of (Xi)*(Yi)'s                                                                                                                8493                                           7586                                                8042
                    Sum of (Xi) or (Yi)'s                                    315                   276                      239
                    Sum of (Xi)A2                                          11515                   8994                     7723
                    Correlation between groups, r                                                                                                     0.26                                           0.30                                                0.89




                        Appendix A-5.                                                                                  Statistical analysis of monitoring data.                                                                                                   Page A-5-17













                   TOTAL RECOVERABLE ZINC                       R. Zn), (UgfL)                                                                                                     Storms Removed            none

                                                                                                                                                                       Square                                         Square                                        Square
                      Date                                            Influent                   Sand                   CSF              Influent-Sand          Influent-Sand           Influent-CFS            Influent-CFS              Sand-CSF               Sand-CSF
                   Dec 9,95                                              41                      78                     112                     -37                    1369                    -71                    5041                     -34                   1156
                   Feb 21, '96                                           32                      59                     64                      -27                    729                     -32                    1024                     -5                      25
                   Mar 6,96                                              35                      79                     63                      -44                    1936                    -28                    784                      16                   -256
                   Mar 19,96                                             96                      158                    116                     -62                    3844                    -20                    400                      42                    1764
                   Mar 28,96                                             41                      193                    132                     -152                   23104                   -91                    8281                     61                    3721
                   Apr 24, '96                                           69                      32                     45                      37                     1369                    24                     576                      -13                   -169
                   May 16, '96                                           59                      84                     86                      -25                    625                     -27                    729                      -2                      4
                   Jun 24, '96                                           90                      272                    220                     -182                   33124                   -130                   16900                    52                    2704
                   Jul 3, '96                                            65                      366                    362                     -301                   90601                   -297                   88209                    4                       16
                   Jul 15, '96                                           77                      110                    112                     -33                    1089                    -35                    1225                     -2                      4
                   Jul 18, '96                                           73                      128                    122                     -55                    3025                    -49                    2401                     6                       36
                   Jul 25, '96                                           115          1          179                    147                     -64                    4096                    -32                    1024                     32                    1024
                   MEANS                                                 66.1                    144.8                  131.8
                   % Decrease in Concentration (neg. value               increase in conc)                                                  -119.2%                                            -99.4%                                          9.0%
                   Sum of difterences                                                                                                           -945                                           -788                                            157
                   Mean Difference                                                                                                              -82.5                                          -65.2                                           17.4


                   TEST FOR SIGNIFICANCE IN DIFFERENCFS
                   Sum of squared differences                                                                                                                          164911                                         126594                                         10879
                   Square of sum of differences                                                                                                 893025                                         620944                                          24649
                   n =                                                   12
                   Standard Deviation ___                                                                                                       90.70                                          82.49                                 -28.32

                   t(paired), test statistic                                                                                                    -3.153                                         -2.737                                          2.124
                   t(O.10,11), tabular value                                                                                                    -1.363                                         -1.363                                          1.363
                   Conclusion                                                                                                              Reject Ho                                      Reject Ho                                       Reject Ho
                                                                                                                                                True                                           True                                            True
                                                                                                                                         concentration                                  concentration                                  concentration
                   Interpretation                                                                                                          difference                                     difference                                      difference


                   CORRELATION
                   Sum of (Xi)*(Yi)'s                                                                                                           124765                                         111337                                       316538
                   sum or (Xi) or (Yi)"4                                 793                     1739                   158,
                   Sum of (Xi)^2                                         59877                354564                  289391
                   Correlation between groups, r                                                                                                0.36                                           0.28                                            0.96




                        Appendix A-5.                                                                              Statistical analysis of monitoring data.                                                                                              Page A-5-18



         mmmmmmmm MM MM MMMM @=M







                   TOTAL RECOVERABLE ZINC                       R. Zn), (ug/L)                                                                                                  Storms Removed           Dec9


                                                                                                                                                                    Square                                        Square                                       Square
                      Date                                          Influent                   Sand                   CSF             Influent-Sand          Influent-Sand           Influent-CFS           Influent-CFS             Sand-CSF                Sand-CSF
                   Feb 2 1, '96                                         32                     59                     64                     -27                    729                     -32                   1024                     -5                     25
                   Mar 6, '96                                           35                     79                     63                     -44                    1936                    -28                   784                      16                     256
                   Mar 19, '96                                          96                     158                    116                    -62                    3844                    -20                   400                      42                     1764
                   Mar 28,'96                                           41                     193                    132                    -152                   23104                   -91                   8281                     61                     3721
                   Apr 24, '96                                          69                     32                     45                     37                     1369                    24                    576                      -13                    169
                   May 16,'96                                           59                     84                     86                     -25                    625                     -27                   729                      -2-                    4
                   Jun 24, '96                                          -9-0               __ifi - -_ - - ____ -2-2-0                        -182                   33124                   -130                  16900                    52                     2704
                   Jul 3,96                                             65                     366                    362                    -301                   90601                   -297                  88209                    4                      16
                   Jul 15,96                                            77                       10                     12                   -33                    1089                    -35                   1225                     -2                     4
                   Jul 18,'96                                           73                     128                    122                    -55                    3025                    -49                   2401                     6                      36
                   Jul 25,96                                            115                    179                                           -64                    4096                    -32                   1024                     32                     1024
                   MEANS                                                68.4                   150.9                  133.5
                   % Decrease in Concentration (neg. value              increase In conc)                                                    -120.7%                                        -95.3%                                         11.5%
                   Sum of differences                                                                                                        -908                                           -717                                           191
                   Mean Difference                                                                                                           -82.5                                          -65.2                                          17.4


                   TEST FOR SIGNIFICANCE IN DIFFERENCES
                   Sum of squared differences                                                                                                                       163542                                        121553                                          9723
                   Square of sum of differences                                                                                              824464                                         514089                                         36481
                   n=
                   Standard Deviation                                                                                                        94.12                                          86.50                                          25.31


                   t(paired), test statistic                                                                                                 -2.909                                         -2.499                                         2.275
                   t(O.10,10), to.hu.1ar value                                                                                               -1.372                                         -1.372                                         1.372
                   Conclusion                                                                                                           Reject 110                                     Reject llo                                    Reject lit)
                                                                                                                                             True                                           True                                           True
                                                                                                                                      concentration                                 concentration                                  concentration
                   Interpretation                                                                                                       difference                                    difference                                     difference


                   CORRELATION
                   Sum of (Xi)*(Yi)'s                                                                                                        121567                                         106745                                         307802
                   Sum of (Xi) or (Yi)'s                                752                    1660                   1469
                   Sum of (Xi)/12                                      58196                 348480                 276847
                   Correlation between groups, r                                                                                             0.31                                           0.27                                           0.97





                       Appendix A-5.                                                                             Statistical analysis of monitoring data.                                                                                           Page A-5-19



        ,MMMM









                   HARDNESS
                                   (mg/L)                                                                                                                                     Storms Removed           none

                                                                                                                                                               Square                                        Square                                         Square
                     Date                                          Influent                  Sand                  CSF              Influent-Sand          Influent-Sand          Influent-CFS           Influent-CFS             Snnd-CSF               Sand-CSF
                   Dec 9, '95                                         2.00                   29.00                 14.00                  -27.00               729.0000                 -12.00               144.0000                 15.00                 225.0000
                   Feb 2 1, '96                                       1.49                   1.87                  6.01                   -0.38                0.1444                   -4.52                20.4304                  -4.14                 17.1396
                   Mar 6,96                                           2.25                   14.50                 8.59                   -12.25               150.0625                 -6.34                40.1956                  5.91                  34.9281
                   Mar 19,96                                          6.89                   11.30                 1780                   -4.41                19.4481                  -10.91               119.0281                 -6.50                 42.2500
                   Mar 28, '96                                        2.11                   11.50                 19.20                  -9.39                88.1721                  -17.09               292.0681                 -7.70                 59.2900
                   Apr 24, '96                                        2.70                   32,80                 26.50                  -30.10               906.0100                 -23.80               566.4400                 630                   39.6900
                   May 16,'96                                         1.71                   34.80                 35.90                  -33.09               1094.9481                -34.19               1168.9561                -1.10                 1.2100
                   Jun 24, '96                                        4.62                   17.40                 21.30                  -12.78               163.3284                 -16.68               278.2224                 -3.90                 15.2100
                   Jul 3, '96                                         7.36                   22.40                 20.50                  -15.04               226.2016_                -13.14               172.6596                 1.90                  3.6100
                   Jul 15,96                                          4.58                   9.14                  10.00                  -4.56                20.7936                  -5.42                29.3764                  -0.86                 0.7396
                   Jul 18,96                                          5.68                   11.10                 14.40                  -5.42                29.3764                  -8.72                76.0384                  -3.30                 10.8900
                   Jul 25,96                                          4.14                   1760                  23.70                  -13.46               181.1716                 -19.56               382.5936                 -6.10                 37.2100
                   MEANS                                            3.7942       --- 17-842                        18.1583
                   % Decrease in Concentration (neg. value = increase In cone)                                                            -368.7%                                     -378.6%                                         -2.1%
                   Sum of differences                                                                                                     -167.88                                       -172.37                                       -4.49
                   Mean Difference                                                                                                        -13.9900                                    -14.3642                                        -0.3742


                   TEST FOR SIGNIFICANCE IN DIFFERENCES
                   Sum of squared differences                                                                                                                  3608.6568                                     3290.0087                                      487.1673
                   Square of sum of differences                                                                                           28183.6944                                 29711.4169                                       20.1601
                   n=                                                   12
                   Standard Deviation                                                                                                     10.7027                                       8.602                                         6.6434


                   t(paired), test statistic                                                                                              4.528                                         -5.784                                        -0.195
                   t(O.10,11), tabular value                                                                                              -1.363                                        1.363                                         1.363

                   Conclusion                                                                                                             Reject Ilo                                Reject Ho                                  Do not reject Ho
                                                                                                                                          True                                          True                                   Difference could
                                                                                                                                     concentration                                concentration                                 be variation in
                   interpretation                                                                                                         difference                                 difference                                       data


                   CORRELATION
                   Sum of (Xi)*(Yi)'s                                                                                                     766.6265                                    827.3714                                    4580.4337
                   Sum of (Xi) or (Yi)'s                              45.53                  213.41                217.90
                   Sum ol'(Xi)^2                                   219.3133              4922.5965             -4-7251.43-82
                   Correlation between groups, r                                                                                          -0.19                                         0.00                                          0'  76




                       Appendix A-5.                                                                            Statistical analysis of monitoring data.                                                                                         Page A-5-20













                    HARDNESS, (mg/L)                                                                                                                                                        Storms Removed             Dec9

                                                                                                                                                                            Square                                           Square                                             Square
                       Date                                              Influent                   Sand                    CSF             -iiiii-luent-Sand            Muent-S,                Influent-CFS            Influent-CFS               Sand-CSF                    Sand-CSF
                    Feb 21, '96                                             1.49                    1.87                    6.01                     -0.33                  0.1444                    -4.52                  20.4304                    -4.14                   17.1396
                    Mar 6, '96                                              2.25                    14.50                   8.59                     -12.25                 150.0625                  -6.34                  40.1956                    5.91                    34.9281
                    Mar 19,96                                               6.89                    11.30                   17.80                    -4.41                  19.4481                   -10.91                 119.0281                   -6.50                   42.2500
                    Mar 28,96                                               2.11                    11.50                   19.20                    -9.39                  88.1721                   -17.09                 292.0681                   -7.70                   59.2900
                    Apr 24, '96                                             2.70                    32.80                   26.50                    -30.10                 906.0100                  -23.80                 566.4400                   6.30                    39.6900
                    May 16,96                                               1.71                    34.80                   35.90                    -33.09                 1094.9481                 -34.19                 1168.9561                  -1.10                   1.2100
                    Jun 24, '96                                             4.62                    17.40                   21.30                    -12.78                 163.3284                  -16.68                 278.2224                   -3.90                   15.2100
                    Jul 3, '96                                              7.36                    22.40                   20.50                    -15.04                 226.2016                  -13.14                 172.6596                   1.90                    3.6100
                    Jul 15, '96                                             4.58                    9.111                   10.00                    -4.5(,                 20.7936                   -5.42                  29.37o-l                   -0.8(,                  0.7396
                    Jul 18, '96                                             5.68                    11.10                   1440                     -5.42                  29.3764                   -8.72                  76.0384                    -3.30                   10.8900
                    Jul 25, '96                                             4.14                    17.60                   23.70                    -13.46                 181.1716                  -19.56                 382.5936                   -6.10                   37.2100
                    MEANS                                                   3.9573                  16.7645                 18.5364
                    % Decrease in Concentration (neg. value = increase in conc)                                                                      -323.6%                                          -368.4%                                           -10.6%
                    Sum of differences                                                                                                               -140.88                                          -160.37                                           -19.49
                    Mean Difference                                                                                                                  -12.8073                                         -14.5791                                          -1.7718


                    TEST FOR SIGNIFICANCE IN DIFFERENCES
                    Sum of squared differences                                                                                                                              2879.6568                      -                 3146.0087                                          262.1673
                    Square of sum of differences                                                                                                     19847.1744                                       25718.5369                                      379.8601
                    n =                                                      I I
                    Standard Deviation                                                                                                               10.3700                                          8.9887                                            4.7711


                    t(paircd), test statistic                                                                                                        -4.096                                           -5.379                                            -1.232
                    t(O.10,10), tabular value                                                                                                        -1.372                                           -1.372                                            -1.372


                    Conclusion                                                                                                                       Reject Ho                                        Reject Ho                                 Do not reject Ho
                                                                                                                                                     True                                             True                                      Difference could
                                                                                                                                               concentration                                    concentration                                    be variation in
                    Interpretation                                                                                                                   difference                                       difference                                        data


                    CORRELATION
                    Sum of (Xi)*(Yi)'s                                                                                                               708.6265                                         799.3714                                      4174.4337
                    Sum of (Xi) or (Yi)'s                                   43.53                   184.41                  203.90
                    Sum of (Xi)A2                                       21 . 133                4081.5965                4529.4382
                    Correlation between groups, r                                                                                                    -0.10                                            -0.04                                             0.88




                         Appendix A-5.                                                                                   Statistical analysis of monitoring data.                                                                                                   Page A-5-21



















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