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


                                                    FY 1992 FINAL PRODUCT Task 61
                                                           St=wtr/Flood Prog. & Ord.












                                                                C@ -



                                CSTORMWATER STUDY
                                HAZEL RUN WATERSHED
                           SPOTSYLVANIA COUNTY, VIRGRZA

                                     VCRMP GRANT
                                   NO. NA27OZO312-01














                                      Prepared by:

                             J. K. Timmons & Associates, P. C.
                                  711 N. Courthouse Road
                              Richmond, Virginia 23236-4099










                                      FINAL DRAFT
                                    December 17, 1993











                                            Table of Contents


                        Executive Summary     .....................      1

                        Purpose   ..............................         3

                        Watershed Description   ......................   3
                        Database Analysis   .......................      7

                        Hydrologic Analysis   ......................     9
                            General    ..........................        9
                            Methodology    ......................       10

                        Alternative Analysis   ...................      14
                            Alternative 1   ......................      14
                            Alternative 1 Costs   .................     17
                            Alternative 2   .....................       20
                            Alternative 2 Costs  ................     - 22
                            Alternative 3   ......................      23


                        Recommendations     .....................       26
     Cn                 Appendix A - Main Channel Flows     .........   27
                        Appendix B - Subwatershed Descriptions     .... 29

                        Appendix C - Watershed Soils    ............    33



                                             List of Figures
     VD                 Figure 1 Major Tributary Subwatersheds .... 6
     TA-
                        Figure 2 Alternative 1 Improvements Locations 16
      NO
                        Figure 3 Alternative 2 Improvements Locations2l

                        Figure 4 Alternative 3 Improvements Location 25









                                                  Executive Summary

                     Review of Problem


                                    Spotsylvania County is looking to alleviate flooding problems in the
                             Hazel Run watershed. Currently, two to three major storms per year contribute
                             to major flooding in parts of the seven square mile watershed that includes
                             Spotsylvania Mall and the Route 3 corridor west of Interstate 95. Flooding in
                             low lying areas within the City of Fredericksburg has been identified through a
                             1989 study for the cit , where the major problems are thought to stem from
                                                   y
                             upstream development in the mall area with little or no runoff restrictions in the
                             past.

                                    Spotsylvania County also lacks a defined flood plain along Hazel Run.
                             A defined flood plain is useful to the county in placing development restrictions
                             on property that may suffer property damage in a flood event. This study
                             includes defining main stream flood plains for that purpose.

                     Analysis

                                    J.K. Timmons & Associates collected field information for the study
                             including aerial topography, stream surveys, and stream morphology. This
                             information was used to analyze the run generated by current development
                             levels. These flows were then.compared to the flows that would have occurred
                             in the Hazel Run Watershed prior to any development in the area- (called
                             predevelopment flows). All stormwater management structures considered
                             would be designed to reduce today's flows to predevelopment levels.

                                    The flow analyses revealed that today's level of stormwate  r flows has
                             increased over predevelopment flows by 10-15%. This relatively     small increase
                             is due in large part to two factors, the shape of the Hazel Run watershed and
                             existing basins that occur within the watershed. The elongated shape of the
                             watershed affects the travel time for the stormwater, while existing basins, such
                             as the one in Carriage Hills, currently retain runoff from storms that were once
                             allowed to flow unimpeded.


                     Alternatives


                                    Several alternatives were analyzed to reduce the rate of flow throughout
                             the watershed and at Hazel Run's entrance into the City of Fredericksburg. The
                             alternatives included main stream and non-perennial channel retention facilities.
                             The high cost associated with the alternatives however, together with the
                             relatively small reduction in runoff (10-15%) caused these alternatives to be


              J. K Timmons & Associatas, P.C.









                              considered not cost effective.


                                     The Altoona Subdivision located near the Spotsylvania     Mall outfall
                              channel has had a history of spot erosion, and has received complaints from
                              homeowners in the past. The analysis has shown that while there is little
                              significant increase in 2- and 10-year flood flows, the higher-frequency low-
                              volume storms have increased due to the Spotsylvania Mall area development.
                              Coupled with the natural erodibility of "fall line" streams, the channel outfall
                              from the mall watershed would be best served by strearnbank stabilization to
                              preserve the bank integrity of this channel into the City of Fredericksburg.

              Recommendations


                              A surnmary oftecommendations follows:

                              1)     With no significant flooding or erosion problems, development in the
                                     Hazel Run Watershed can best be controlled through a Stormwater
                                     Management Ordinance.

                              2)     The County should maintain the existing retention facilities to include
                                     ponds and lakes that currently exist in the watershed, while limiting
                                     future development to existing runoff conditions down-stream.

                              3)     The Spotsylvania Mall outfall should be stabilized to prevent further low
                                     volume storm erosion though a cooperative effort with the City of
                                     Fredericksburg.






















               J. X Timmons & Associatas, P.C.                  2












          PURPOSE


                 The purpose of this Study is to provide the County of Spotsylvania with a
          management program to control flooding and property damage, soil loss and point
          and nonpoint source pollution due to stormwater runoff in the Hazel Run
          watershed in Spotsylvania County, Virginia.


          WATERSHED DESCRIPTION

                       The Hazel Run watershed is located primarily in the Hazel Run and
                 Courtland districts of Spotsylvania County. The area of this study is bound
                 on the north by Route 3 (Germanna Highway), on the west by Routes 620
                 and 639 (Harrison and Leavell's Road, respectively), on the south by Route
                 208 (Courthouse Road), and on the east by U. S. Route 1 and the
                 Fredericksburg City Limits.

                       The Watershed is composed of three major branches or
                 subwatersheds, the upper tributary that collects runoff from the Route 3
                 corridor, Hazel Run, and Long Branch. Each of these subwatersheds will be
                 described in more detail in the following sections.

                       Of particular concern to both the County and the City of
                 Fredericksburg is the impact of Spotsylvania Mall development in the upper
                 tributary that feeds Hazel Run. This report refers to this tributary as the
                 Spotsylvania Mall Tributary. The development of the mall with no
                 impoundment structures, along with other commercial development along
                 the Route 3 corridor has raised the question as to its impacts on the erosion
                 of downstream channels.


                       The study area contains in its reaches some 5015 acres, most of
                 which fall in the limits of Spotsylvania County. This area contains a mix of
                 development ranging from varying density residential developments to
                 commercial and industrial corridors. The study area is comprised of the
                 three major tributary branches. For this study, these branches are called
                 the Spotsylvania Mall, Hazel Run, and Long Branch tributaries.

                       These three major branches of the Hazel Run watershed converge in
                 the City of Fredericksburg, at which point Hazel Run continues for nearly
                 three miles before feeding the Rappahannock River just south of downtown
                 Fredericksburg.



           J. K Timmons & Assodates, P.C.          3









                         Spotsylvania Mall Tributary

                              The Spotsylvania Mall tributary drains 960 acres and is the
                         northernmost tributary in the study. This east to west tributary is
                         bound most approximately to the north by Route 3 and it extends
                         west to Salem Elementary School. This tributary is fed by the
                         commercial corridor fronting Route 3 and enters a closed system
                         under the parking lot of Spotsylvania Mall. It returns to open
                         channel flow prior to crossing Interstate 95 just south of its ramps at
                         Route 3. The flow, now in the City of Fredericksburg, travels just
                         south of the Altoona subdivision upstream of its confluence with
                         Hazel Run.


                               The development makeup of the Mall tributary is
                         predominantly commercial along the Route 3 corridor, where
                         development is currently 80% built out. A portion of the Shannon
                         Green development, north of Route 3 and in Fredericksburg,
                         contributes to the runoff in this tributary. South of the corridor, the
                         development becomes primarily medium density single family
                         housing. The average imperviousness over the Mall tributary is
                         estimated to be 31%.


                               Three BMPs exist in the Mall tributary, both in the vicinity of
                         the Maple Grove subdivision. One is-2.8 acres and lies directly south
                         of Waverly Village Drive, just upstream from Village Square
                         Shopping Center. The second lies approximately 2700 feet upstream
                         in Maple Grove, and covers 1.4 acres.

                               The third is a BMP to serve the south portion of the mall.
                         Under construction at the time of the study, the hydraulic
                         computations included the BMP as an existing structure for purposes
                         of determining stormwater flows.                                   -


                         Hazel Run 7ributary

                               The central branch is called the Hazel Run tributary. At 1850
                         acres, this watershed contains 37% of the study area's coverage. It
                         runs from its headwaters near the Five Mile Fork intersection at
                         Route 3 flowing east roughly parallel to Harrison Road to its junction
                         with Long Branch west of Interstate 95.

                               With the exception of the uppermost reaches of this tributary


            J. K 71mmons & Associatm, PC             4








                        being COMInffcial land use, roughly 90% of Hazel Run falls in
                        residential planned areas. Of this area, approximately 27% has been
                        constructed at the time of this study. The relatively low impervious
                        percentage (10.7%) for Hazel Run reflects the modest development
                        over the majority of this watershed.

                               There are no retention facilities in existence in the main
                        stream of Hazel Run. In the upper reach, new development includes
                        retention facilities to regulate the runoff. These developments
                        include the kr-)ummerlake and Queens Mill sections. Retention
                        facilities are also in place in the new Kingswood development as well
                        as the established Beauclaire Plantation.



                        Long Branch Tributary

                               The Long Branch Tributary is the southernmost tributary of
                        the study area. It flows west to east between Leavell's Road and
                                   9r"
                        Interstate 'D then turns north to its junction with Hazel Run. Its
                        area is the largest of the study at 2200 acres.

                               To the west of Interstate 95 and south of Harrison Road, Long
                        Branch contains much of the single family development as does Hazel
                        Run. This development includes some multiple family as well as
                        detached home subdivisions.


                               The Long Branch tributary can be divided into its upper reach
                        and lower reach, the division line being Interstate 95. The upper
                        reach, as described above, contains mostly residential and
                        agricultural land. The lower reach, to the east of Interstate is
                        industrially developed, contains both the Four Mile and Spotsylvania
                        Industrial Parks at the intersection of U.S. Route 1 and Courthouse
                        Road. TheSE@ parks, though not fully developed, are a large
                        percentage of the impervious area that averages 22%. Figure 1,
                        shown on the following page depicts the study area divided into the
                        three major tributary subwatersheds that flow into the City of
                        Fredericksburg.










            J. K Timmons & Associates, PC           5







                                                   FIGURE 1







                                                                   Ae




                                                                              F      e       sb

















                                                          LOW













                                                                   J.K TIMMONS & ASSOCIATES, P.C.
              MAJOR TRIBUTARIES                                      ENGINEERS * ARCHITECTS * SURVEYORS
                               F THE                                711 N. COURTHOUSE RD.         RICHMOND, VA
                            0                                      880.5.5TAPLES MILL RD.       HENRICO CO., VA
                                                                    4411 CROSSINGS BLVD.      PRINCE GEORGE. VA.
         HAZEL RUN WATERSHED                                       DA TE, 7-14-9J            SCALE. 1-@-JOOO'
                                                                   DRAWN 8 Y- PM
        MAUM =\0RAV\l&Ul\mfmlm\-
       jFXV.MV-ll /"-                                             I CHECKED 8 Y.            CAL C. CHK.:
         PREWOUS JOB NO.                                            1/08 NO.: 15-321








          DATABASE ANALYSIS

                 To evaluate the appropriate comprehensive stormwater management
          program for Spotsylvania County, it is first necessary to collect vital information
          pertaining to the characteristics of the watershed itself. This report is the result
          of a detailed analysis of the Hazel Run Watershed and its stormwater runoff
          characteristics and data. The data used in this study is described in detail below.


                 Aerial Survey-     The topography of the Hazel Run Watershed was
                                    mapped digitally by Photogrammetric Data Services, Inc.
                                    of Sterling, Virginia. Mapping compilation was
                                    completed at 1"=400' scale with 5' contours.

                                    Stormwater features such as stream channels, lakes,
                                    ponds, and dams are included in this mapping. Digital
                                    mapping of improvements, including buildings, roads,
                                    parking lots, and the like are included to allow accurate
                                    estimates of both levels of current development and
                                    percentage of impervious ground coverage in the
                                    watershed.



                 Soil Mapping-      Soil mapping is critical to -the analysis of runoff
                                    characteristics. Highly permeable soils, which include
                                    sandy or gravelly silts, tend to allow high levels of
                                    rainfall to be absorbed into the ground, reducing the
                                    imnoff from the storm event. Highly impervious soils,
                                    like many of Virginia's clays and silty clays, absorb very
                                    little rainfall, forcing higher levels of runoff, affecting the
                                    amount of rainfall that enters the main channels.

                                    This study uses as its soil reference the Soil Surve_v of
                                    Spotsylvania Count_v Virginia, published by the Soil
                                    Conservation Service in cooperation with Virginia Tech.

                                    '.From this survey soils are categorized into four soil
                                    @Irroups, A through D. The soils of the A group (there
                                    'were none found in the study area), consist of the most
                                    highly permeable soils, while the D soils comprised of
                                    mostly impervious clays and silts.

                                    Soils that predominate this study area are the B, C and
                                    D type soils. The D soils dominate the flood plain


           J. X Timmons & Assodates, P. C.         7








                                 regions and along the creek channels, while the B soils
                                 are generally found in the upper topography of the study.

                                 @@opies of the Soil Survey can be obtained upon request.

          Hydrologic Mapping-    ro evaluate the runoff generated in Hazel Run, it is
                                 necessary to compile the development plan with the soil
                                 mapping to further develop runoff characteristics within
                                 each watershed. The resulting inforination allows for
                                 detailed analysis of the runoff trend in each watershed.









































           J. K 71=ons  Assodateq,.RC.          8








       HMROLOGIC ANALYSIS
       GENERAL To assess the conditions that exist in the Hazel Run Watershed and
           determine recommendations for remedies that may be needed, parameters
           are established and assumptions made in the analysis of the system. These
           parameters are used to create the model that will estimate what happens
           during rainfall events.

               For the purposes of this study, the modeling utilizes the HEC-1
           computer program, described later in this section.

               One of the main assumptions of this study is to determine today's
           rate of flow verses the rate of flow prior to any development occurring in the
           watershed, including the development of ponds and lakes that exist today.
           The assumption isbased on the premise that streams that serve the
           undeveloped land are adequate to handle the flows, and that those flows
           could be matched to current flows to determine the adequacy of today's
           channels. Based on the increase in flow the watershed can then be
           analyzed for flow attenuation alternatives.

               The HEC-1 program is run for the 2, 10 and 100 year frequency
           storm events. Points are analyzed throughout the watershed to determine
           areas of increased runoff and to determine where, if any, control structures
           should be incorporated.

               Because the primary concern of this study is that of downstream
           flooding in the City of Fredericksburg, four primary analysis points are
           chosen for study. The points represent the following stream tributaries:

               1)   Hazel Run Confluence (City of Fredericksburg)
                    This analysis point is the first junction point that carries the
                    entire runoff from the study watershed.

               2)   Hazel Run T@-ibutary
                    This analysis point is taken in the Hazel Run tributary just
                    west of its confluence with the Long Branch tributary.

               3)   Long Branch 7@-ibutary
                    This analysis point is taken in the Long Branch just west of
                    its confluence with the Hazel Run tributary.




       J. K Timmons & Associates, R C.9









                        4)    Altoona Subdivision (City of Fredericksburg)
                              An area previously determined to have potential erosion
                              problems, the Altoona Subdivision is adjacent to the
                              Spotsylvania Mall tributary. A single cul-de-sac is within 30
                              feet of the channel.


                        These points are analyzed for predevelopment discharges versus the
                  existing runoff conditions. .

           AffiTHODOLOGY


                        The hydrologic model used in this study is the HEC-1 Flood Analysis
                  Program developed by the U.S. Army Corps of Engineers, for determining
                  the peak runoff volumes and rates. The HEC-1 model is an accepted
                  standard of the practice, and is selected because of its ability to simulate
                  the study area as well as its ability to interact effectively with the HEC-2
                  Water Surface Profile program, which is used to determine the main
                  channel flood plain..

                        The primary objectives in using HEC-1 are:

                  1)    To accurately model conditions of the watershed, both existing -and
                        predevelopment.

                  2)    To deliver a model to the County that is in the public domain that
                        will likely rMain a standard of the practice, allowing future
                        modifications as the watershed develops.

                  3)    To model the watershed so that many points within the watershed
                        can be checked for flow rates and flow times.

                  4)    To deliver a model that can be used by engineers who develop sites
                        within the watershed, allowing them to submit development impact
                        analyses on the watershed.

                        This study employs the SCS option in HEC-1 for infiltration
                  determination and hydrograph creation. Additional information on this
                  program is available in the HEC-1 Flood Hydrograph Package User's
                  Manual, September 1990.

                  HEC-1 employs the use of information relevant to the stream morphology
            and makeup to calculate flows in the watershed. This data is described more fully
             below:


            J. K Timmons & Associates, PC          10








            Drainage Areas

                        Based on the aerial topography and field verification of flow
                  directions, the drainage areas that make up watersheds within the Hazel
                  Run watershed are divided for input in the HEC-1 model. Drainage breaks
                  are chosen in critical analysis points, major road crossings, and in locations
                  where a significant change in land use occurs. Each division, or
                  subwatershed is numbered and described in Appendix B.

            Hydrologic parameters

                        The HEC-1 Model uses the following hydrologic input information to
                  simulate flows in each subwatershed:


                  1)    Channel Slope
                  2)    Channel Hydraulic Length
                  3)    Impervious Fraction
                  4)    SCS Curve Number
                  5)    Mannings Roughness Coefficient "n"
                  6)    Basin Lag Time
                  7)    Loss Parameters

            Rainfall Information

                        This study uses the 2, 10, and 100 year frequency storms with 24
                  hour durations as the standard storms for analysis.

            Reservoir Routing

                        For both existing and proposed reservoirs, ponds, lakes and other
                  impoundments, the HEC-1 model simulates the outlet performance using
                  stage- storage-discharge relationships unique to each.

            Reach Routing

                        HEC-1 uses input that indicates.the time and distance that
                  subwatershed flows require to flow through the downstream section. This
                  distance is not the hydraulic length of the downstream section but rather
                  the distance of thE@ main channel from the reach outfall to the downstream
                  outfall.


            Land Use

                        The land use, which tells us about the ground cover makeup, is taken


            J. K Timmons & Assodates,.P.C.








                   from the aerial photography of the watershed. The land use is used to
                   determine the SCS curve number as well as the impervious fraction for the
                   subwatersheds.

                          The land -use is used in large part to properly subdivide
                   (hydrologically) the watershed into its critical subwatersheds for study
                   using HEC-1. Where possible, the watersheds are divided where the type of
                   land use (commercial, industrial, residential) changes significantly.

                          The impervious fraction is the percentage of impervious surface
                   (rooftops, parking lots, roads, etc.) taken over the entire subwatershed
                   boundary. Within E@ach drainage area, a ten acre square representative of
                   the entire site is broken down into its impervious and pervious parts to
                   determine accurate impervious fractions. This method helps to create a
                   model that is tailored to the watershed.


            Soils


                          Soil propertiES affect the runoff potential of a watershed.
                   Permeability, or the ability of soil to absorb rainfall, contributes to reducing
                   runoff as it increases. The soil slopes affect the amount of water that can
                   permeate the soil. Steep slopes allow little infiltration, while flat slopes
                   allow for higher rates of absorption. The ground cover can significantly
                   affect the ability of rainfall to enter the soil. Brush, grass, and heavy weeds
                   all help to hold the water to allow for infiltration, while barren ground does
                   little to assist effective ground interception.

                          The soils in this study are classified by the Soil Survey of
                   Spotsylvania Count_y, Virginia published by the U.S. Soil Conservation
                   Service. The soils are categorized into four hydrologic groups for purposes
                   of engineering analysis. The groups are:

                          Group A - Soils having high infiltration rates even when thoroughly
                          wetted and consisting chiefly of deep, well- to excessively-drained
                          sands and gravels. These soils can transmit water at high rates.
                          Highly permeable.

                          Group B - Soils having moderate infiltration rates when thoroughly
                          wetted and consisting chiefly of moderately deep to deep, moderately
                          well to well-drained soils with moderately fine to moderately coarse
                          textures. Moderately permeable.

                          Group C      Soils having slow infiltration rates when thoroughly
                          wetted and consisting chiefly of soils with a layer that impedes


            J K Timmons & Assodates, PC.               12








                        downward movement of water, or soils with moderately fine to fine
                        texture. These soils have a slow rate of water transmission. Slightly
                        permeable.

                        Group D - Soils having very slow infiltration rates when thoroughly
                        wetted and consisting chiefly of clay soils with a high swelling
                        potential, soils with a permanent high water table, soils with a
                        claypan or clay layer at or near the surface, and shallow soils over
                        nearly impervious material. These soils have a very slow water
                        transmission rate. Impervious.

                        The groups found in the study area are listed in Appendix C.





































            J. K Timmom & Associates, P.C.          13









           ALMINATNE ANALYSIS

                  After analysis of the data within the watershed is performed to determine
           the stormwater flow rates in the main stream channels, it is necessary to look at
           improvement alternatives to achieve desired reductions in those rates. We
           determined that the rate of reduction desired for this project is to that of
           predevelopment levels. This will allow the stream to carry flows with no further
           erosion.


                  The first of the three improvements analyses consists of choosing multiple
           upland (out of major streams and floodplain) BMPs to -attenuate the flows and
           reduce pollutant transport,. The second alternative calls for major in-stream
           devices constructed to ternporarily slow the main channel flow- prior to its reaching
           the City of Fredericksburg. The third alternative consists of county controlled
           maintenance of existing lakes and ponds, while making improvements to points
           along the system where erosion and sedimentation are occurring.



           ALTFRNATM 1


                        BMPs, either as dry or wet ponds, are first considered for use as flow
                  attenuation devices. The basins will reduce the amount of runoff from each
                  of the watersheds served by the BMPs thereby reducing the total flow
                  entering the City of Fredericksburg.

                        These basins are schematically located to maximize the value as a
                  flood control device while minimizing the potential construction and
                  maintenance costs. Issues such as accessibility, topography, and
                  development percentage, all play a role in the initial locating of the
                  potential stormwater basins.

                        The existing lakes and ponds that are performing stormwater
                  attenuation functions are included as part of the BMP system. Because of
                  this inclusion, and to ensure the continued performance of those facilities,
                  the County will have to take over ownership and maintenance responsibility
                  for these existing facilities. This cost of ownership is included in the cost
                  analysis for the alternative.

                        The key issue regarding basin placement is that of wetland impacts.
                  The basins will have to receive a permit from the U.S. Army Corps of
                  Engineers if any inundation, removal, or other type of destruction to the
                  wetland habitat will occur in the implementation of the flood control plan.
                  Every effort will need to be taken to avoid and minimize the destruction of
                  wetlands, and so the basins are placed out of the main channels just


           J. K Timmozw & Assodates, PC.           14








                     upstream of the major wetland areas of the watershed.

                            When analyzing the hydraulic character of the watershed, it is
                     important to note that a method to reduce the peak flows downstream is
                     through a combination of releasing water that is currently attenuated by
                     stormwater structures, while detaining water in other areas. This
                     combination will reduce the "delayed peak" phenomenon that occurs on
                     large watersheds using many control facilities. The delayed peak is a shift
                     of the downstream -peak flow conditions caused by detaining water and
                     holding it for a period of time. In many cases, the delayed peak can
                     actually be greater than the existing peak without detention, which in the
                     case of this study, will not solve the problem.

                            The best hydraulic results occur by using the configuration of basins
                     within the watershed shown on Figure 2 as Alternative 1 Improvements.
                     The alternative consists of the County overtaking the maintenance and
                     ownership responsibilities of eleven existing facilities throughout the three
                     tributaries and constructing twelve new facilities to impede the runoff
                     levels.


                            The runoff levels are reviewed downstream at the Hazel Run
                     Confluence. The mSUltS of Alternative 1 on the watershed system is as
                     follows:


                            Storm Chamiel Peak Flow Rates (units in c1s)

                                      2 Year               10 Year            100 Year


                     Undeveloped         1458                3534               6112
                     Existing Cond.      1887                4144               6763
                     With Alt. 1         18,90               4202               6831


                            Note that the peak flows using flood control features upstream
                     actually increased the peak flow at the confluence by approximately 1%.

                            In reviewing potential locations to release water currently detained, it
                     is determined that the best hydraulic choices are those basins located
                     closest to the tributary confluence, namely in the area of the Industrial
                     Parks of Long Braxich. While releasing these flows may have helped reduce
                     the peak flows somewhat, the more important function that the existing
                     basins provide, nonpoint pollution reduction, is lost. While solving one
                     problem, a gre  ater one is created.




              J. K Timmons & Assodates, JRC.               15







                                          FIGURE       2










                  46
                                                                       e     sb


                                   7






























                                                        J.K TIMMONS 11, ASSOCIATES, P.C.
      Location of Improvements ENGINEERS * ARCHITECTS * SURVEYORS
                           for                          711 N. COUR7HOUSERD.      RICHMOND, VA
                                                        880J STAPLES A41LL RD.  HENRICO CO., VA
                 Alternatkve 1                          4411 CROSSINGS BLVD.  PRINCE GEORGE, VA.
                                                        DA 7E. 7-14-9J       SCA L E. IA@-JOOO'
                                                        DRAWN 8 K PM

                                                        CHECKED 8 Y.        CALC.' CHK.:
       PREwous 73-B N 0.                                JOB NO.: 15J21









                  ALTERNATM 1 (30STS


                        The following list is an estimate of the cost to Spotsylvania County
                  for implementing Alternative 1. The list includes both new construction
                  and upgrading existing facilities to properly attenuate the storms.
                  Maintenance and estimated land acquisition costs are also included.



                  IMP. DESCRIPTION               LAND CONSTR. MAINT.
                  NO.

                  1     West of Cherry Rd.       $8000     $60,000     $3000
                        Construct dry pond

                  2     East Cherry Rd.          $9500      $100,000   $3000
                        Construct dry pond

                  3     Chancellor Village       $5000      $30,000    $3200
                        Improve ex. wet pond































            J. K nmmons & Associatm, P.C.           17









                      4     Sheraton Hills             $8500      $90,000      $4500
                            Construct pond

                      5     Sheraton Oaks West         $15,000 $140,000 $4500
                            Construct (Iry pond

                      6     SE Cherry Rd,/Rte.620      $9500      $90,000      $3000
                            Construct dry pond

                      7     Salisbury                  $12,000    $150,000     $5000
                            Construct dry pond

                      8     Sheraton Oaks              $950  0    $100,000     $4500
                            Construct pond

                      9     Salem Station              $8250      $70,000      $5000
                            Construct dry pond

                      10    Queen's Mill West          $5000      $50,000      $3500
                            Improve ex. dry pond

                      11    Carriage Hills             $5000      $50,000      $4500
                            Improve ex. wet pond

                      12    Leavell's Ci' -ossing      $5000      $10,000      $3000
                            Improve ex. dry pond

                      13    Four Mile Fork Ind. Pk.    $5000      $16,000      $4000
                            Improve pond (Qin=Qout)

                      14    Beauclaire Plantation      $5000      $10,000      $4000
                            Improve ex. wet pond

                      15    Spotswood Heights          $11,250    $90,000      $3000
                            Construct dry pond

                      16    VDOT Commuter Lot          $2000      $50,000      $4000
                            Improve ex. dry pond

                      17    Rte 3/West Salem Ch.       $8000      $70,000      $5500
                            Improve b,-Lsin




              J. Y- Tinmons & ASSOCiatW., P.C.           18









                  18    Salem Ch. Elementary $5000          $110,000 $4000
                        Construct dr7 pond

                  19    Old Salem Church         $10,000    $50,000    $3000
                        Improve ex. ivet pond

                  20    Maple GrovqfVil.Square   $12,500    $50,000    $4500
                        Improve ex. wet pond

                  2-1   Toys-R-Us (Fred'Burg)    -          $20,000    -
                        Improve pond structures

                  22    Lower Spots. Mall        $10,000-   $70,000    $4500
                        Improve ex. dry pond

                  23    Maple Grove              $5000      $40,000    $3000
                        Improve ex. -wet pond


                                     TOTAL      $174,000    $1,516,000

                                     TOTAL ANNUAL MAINTENANCE $86,200


                        Costs associated with the implementation of this alternative are
                  extremely high. It is estimated that approximately $1,500,000 will be
                  required for the construction of the basin facilities in this plan. Annual
                  maintenance costs are nearly $90,000. Neither of these two costs includes
                  the high price of land acquisition for the nearly eighty acres of land for
                  construction and access.



















                nmmons & Associates, P.C.           19









           MMRNATnT 2


                        The second alternative is to reduce flows in the main channels by
                  constructing flow constriction devices in the channels. The devices will
                  allow base stream flows to pass through uninhibited. As stormwater flows
                  entered the stream channel, the restrictive walls, or dam effect, will take
                  place, reducing the flows at the outflow while storing the attenuated water
                  temporarily in the flood plain area.

                        The delayed peak effect has to be checked using this alternative
                  because it is essentially the same analysis as Alternative 1, only on a larger
                  scale.


                        Alternative 2; Improvements include three flow restriction devices, one
                  on the Long Branch tributary and two on the Spotsylvania Mall tributary.
                  Figure 3 shows the locations. The Long Branch device is located just south
                  of Harrison Road (Route 620), and the two mall tributary devices are
                  located west of Salem Church Road and Interstate 95.


                        The runoff IE!vels are reviewed downstream at the Hazel Run
                  Confluence. The results of Alternative 2 on the watershed system is as
                  follows:



                  Storm Channel Peak Flow Rates (units in c.Ls.)

                                 2 Year            10 Year          100 Year


                  Undeveloped      14:58             3534             6112
                  Existing Cond. 1887                4144             6763
                  With Alt. 2      1855              4190             6741

                        Like AlternELtive 1, the results of this alternative show that with the
                  improvements in place up stream, the flow in Fredericksburg shows little
                  reduction, and in the case of the 10 year peak flows, shows an actual
                  increase.













            J. K Timmons & Associates,.P.C.        20







                                           FIGURE       3











                                                                  F    de      sb






























                                                          J.K TIMMONS & ASSOCIATES, P.C.
       Location of Im- rovements ENGINEERS * ARCHITECTS * SURVEYORS
                                  P
                            for                           711 N. COURTHOUSE RD.    RICHMOND. VA
                                                          880J STAPLES A41LL RD. HENRICO CO., VA
                  Alternative 2                           4411 CROSSINGS BLVD. PRINCE GEORGE, VA.
                                                                                      A@_  s
                                                          DA TE. 7-14-93       SCALE- -3000

                                                          DRAWN BY' PU

                                                          CHECKED 3 Y'        CAL C. CHK:
       PREWOUS J'OB NO.                               =JOB NO.: 15321









                  ALTERNATIVE 2 COSTS


            Imp.  DESCRIPTION                     LAND      CONSTR. MAINT.
            No.

            1     Hazel RurVSalem Elem. Sch.      $15.1000  $90YO00     $7000
                  Construct weir upstream of road

            2     Long Branch/Harrison Rd.        $30,000   $175,000    $8000
                  Construct weir upstream of road

            3     Spots. MaIVI-95 Crossing        $20,000   $190,000    $10,500


                                 TOTAL            $75,000   $455,000

                   TOTAL ANNUAL ACkUqTENANCE                       $25,500


                        Costs for Alternative 2, while less than Alternative 1, will approach
                  $500,000 in construction costs. Annual maintenance will add another
                  $25,500 required for the program.

                        Another complicating factor of using Alternative 2 is the
                  aforementioned wetlands issues. There is impacted wetlands at the site of
                  the device, and a mitigation program will likely be required. Also, there is
                  the fact that storrawater is stored, temporarily "flooding" a portion of land
                  (primarily wetlands). It is uncertain what the permitting position of the
                  Corps of Engineers might be, but they will likely consider the limits of
                  inundation to be ivetland impacts. This position will make in-stream
                  restrictive devices difficult and costly to permit and construct.

















             J K Timmons & Assodates, P.C.         22









            ALTERNATNE 3



                         In evaluating the options to achieve the goals of this study, we again
                   turn to the major, component of the problem. Erosion and sedimentation
                   problems are occurring in and near Altoona, a subdivision located in the
                   City of Fredericksburg.

                         Using results obtained by studying the first two alternatives, we next
                   look at AlternatiW 3 Improvements. This involves no new basin
                   construction, takirLg over major existing facilities, and stabilizing the
                   downstream reach of the Spotsylvania Mall Tributary to alleviate the
                   erosion problems.

                         The reason for no new basin construction is as noted in the first two
                   alternatives. Delayed peaks caused by the basins do not suit the stated
                   goals of the flood control plan. The basins are a costly, and more
                   importantly, ineffective solution to the Fredericksburg erosion problem.

                         The county will maintain the existing major facilities under
                   Alternative 3 Improvements. This will ensure the continued flow character
                   of the watershed at its current level. These levels will -remain at current
                   levels by restricting future development from adding to the downstream
                   peak flow.


             Stabilizinz Altoona Subdivision

                         Corrective measures to low level flood damage and erosion occurring
                   in the Spotsylvania Mall outfall include the stabilization of the naturally
                   erosive stream- banks. As a result the commercial development in the
                   watershed, the minor storms produce more runoff. It is these low volume
                   storms that, Occurring at higher frequencies, have caused some of the
                   erosion problems that exist in the stream. The highly erosive nature of this
                   fall line channel increases its susceptibility of degradation. To effectively
                   protect the channel, stabilization must be provided to handle these low flow
                   storm events.


                         The stabilization of the Spotsylvania Mall tributary is made
                   beginning upstream east of its crossing Interstate 95 down to its confluence
                   with Hazel Run. Most of the problem areas occur downstream of the
                   Altoona Subdivision. The measures consist of large diameter rip rap (18"
                   min. diameter) lining the main channel for a distance of approximately
                   4,000 feet. Figure 4 shows the location where the stream bank


             J. Y, Timmons & Associates, P.C.        23








                 improvements need to be made.

                        The costs, aside from land acquisition whe re needed, is approximately
                 $120,000 for stream stabilization in the mall tributary, and maintenance
                 costs for the stream improvements is estimated to be less than $5,000 per
                 year.






















































            J. Y, n=ons & Assodatw, P.C.            24






                               FIGURE 4



                                                       Improvements Area



                                                         N

                                                    S      N




                                                F de     sb






























                                          J.K. TIMMONS 11, ASSOCIATES, P.C.
     Location of Improvements ENGINEERS *ARCBITECT$,* SURVEYORS
                    f or                  711 N. COUR7HOUSE RD. RICHMOND, VA
                                          880J STAPLES MILL. RD. HENRICO CO., VA
             Alternative 3                4411 CROSSINGS BLVD. PRINCE GEORGE, VA.
                                          WE- 7-14-9J    SCALE. 1`-@-3000'

                                          DRAWN 8 Y- PM

                                          CHECKED 8 Y-  CAL C. CHK.:
      PREWOUS JOB NO.                     JOB NO.: 15J21










           RECOATMFNDATIONS

                       Alternatives 1 and 2 involve large amounts of land acquisition, high
                 construction and ongoing maintenance costs. In place, these improvements
                 only reduce peak flows at the Hazel Run confluence by 1-2%, in some cases
                 actually increasing the downstream peak rate. In all, these alternatives do
                 not serve the stated goals of the study.

                       Alternative 3 satisfies the goals of the study with one exception. It
                 reduces the erosive effect of the higher frequency lower-flow storms that are
                 causing some problems in the Altoona Subdivision area, while maintaining
                 the integrity of the watershed as it is. The type of erosion protection in the
                 mall watershed will also promote wetland growth. Sediment that is
                 deposited among the -stone will create a bedding for many plant species that
                 can filter pollutants as the stormwater flows through, creating a desirous
                 dual benefit for both the City of Fredericksburg and the County of
                 Spotsylvania.

                       What Alternative 3 does not do is decrease the current runoff levels,
                 one of the initial goals. However, since the overall increase in the high
                 volume storms from predevelopment conditions is between 1045%, and
                 because no major ero'sion problems have been experienced in the rest of the
                 watershed, protection for the future is best handled through stormwater
                 ordinance measures.


           Protecting Future Develo)ment Flood Concerns

                       Effective flood control in Hazel Run depends on an effective approach
                 to the future development techniques used and required by Spotsylvania
                 County. While a developer may install an onsite Best Management Practice
                 (BMP) to control the immediate downstream channel, he may actually
                 accentuate the flows at the point where the stream enters the City of
                 Fredericksburg. An effective development plan must therefore be sensitive
                 to both site and regional constraints.

                       This is best achieved through a stormwater management ordinance
                 that will require new development to investigate its impacts on not only its
                 next door neighbor, but in the City of Fredericksburg. This will cause the
                 County of Spotsylvania to keep a master version of this stormwater
                 management study available for use by engineering consultants in their
                 impact assessments. By implementing this ordinance, Spotsylvania County
                 will be able to protect its own streams, but will be acting in good faith to
                 prevent any problems to her downstream neighbor, the City of
                 Fredericksburg.


           J. K Timmozw & Assodates, F.C.         26




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           Main Channel Analysis - HEC-1 Model


               The table below shows a comparison of the discharges found in critical areas
               of the study area. Both predevelopment and current levels are shown.

           Analysis Location              Predevelope             Current      % Increase
           (all discharges are in c.f.s.)

           Hazel Run Confluence
           2 Year                              1458                  1887          29%
           10 Year                             3534                  4144          17%
           100 Year                            6112                  6763        10.-5%

           Hazel Run Trib.
           2 Year                              508                   573           13%
           10 Year                             1199                  1341          12%
           100 Year                            2082                  2352          13%


           Long Branch
           2 Year                              694                   907           30%
           10 Year                             1668                  1932          16%
           100 Year                            2819                  3049          8%


           Altoona Subdivision
           2 Year                              542                   817           50%
           10 Year                             1277                  1503          17%
           100 Year                            2132                  2372          11%
























           J. K Tiamons &Aswc&teqP.C.             28




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             SUBWATERSHED DES11DRIPTIONS


                 The following section describes the subwatersheds used in the HEC-1 model
             that make up the study area. The subwatersheds are grouped into three
             categories corresponding to where they flow. They are the Hazel Run, Long
             Branch, and Spotsylvania Mall tributaries.

             Hazel Run Tributary - 1001) Series

             Subwatershed      Location
             ID Number         Descrip lion

             1000              West of Cherry Road

             1001              East of Cherry Road

             1002              Chancellor Green


             1003              Chancellor Village/Five Mile Fork

             1004              Chancellor Green


             1005              Sheraton Hills


             1006              Sheraton Hills


             1001              Sheraton Oaks West


             1008              Southeast Cherry Road/Harrison Road

             1009              Salisbury

             1010              Chancellor Landfill


             1011              Sheraton Oaks


             1012              Hazel Run/West of Salem Church Road

             1013              Hazel Run/East of Salem Church Road

             1014              Hazel Run/East Twin Springs Estates

             1015              Maple Grove

             1016              Hazel Run/Maple Grove Outfall



             J. K Timmons & Assodates, P C.           30









            1017             Hazel Run/Maple Woods Outfall

            1018             Hazel RurV`West of Interstate

            1019             Waverly Village

            1020             WaverlY Village/Interstate

            1021             Hazel Ruri/East of Interstate

            1022             Hazel Run Outfall



            Long Branch, Tributary - 2000 Series

            Subwatershed     Location
            ID Number        Descrip'Jon


            2000             Summerlake


            2001             Salem Station


            2002          7  Queens Mill West

            2003             Queens Mill East/Carriage Hills West

            2004             Carriage Hills East

            2005             Long Brancb/West of Interstate

            2006             Leavell's Crossing

            2007             Rollingwood Drive

            2008             Four Mile Fork Industrial Park


            2009             Long Brancb/East of Interstate

            2010             Spotsylvania Industrial Park West

            2011             Long Branch/Spotsylvania Industrial Park

            2012             Long Branch

            2013             Beauclaire Plantation


            2014             Four Mile Fork Shopping Center


            J. K Timmons & Associates, PC.          31








            2015             Grainger Mobile Home Park

            2016             Spotswood Heights/South Route 620

            2017             Long Brancb/Kingswood

            2018             Long Branch

            2019             Long Branch Outfall


            Spotsylvania. Mall Tributw-y - 3000 Series

            Subwatershed     Location
            ID Number        Descrip @ion

            3000             Upper Sheraton I-Tills

            3001             VDOT Commuter Lot


            3002             Sheraton Oaks/Salem Elementary School

            3003             Salem Elementary School

            3004             Old Salem Church

            3005             Maple Grove United Methodist Church

            3006             Village Square,/Upper Spotsylvania Mall

            3007             Toys-R-Us/Shannon Green

            3008             Maple Grove/Lower Spotsylvania Mall

            3009             Lower Spotsylvania Mall Outfall

            3010             Interstate East (in City of Fredericksburg)

            3011             Gateway Shopping Center (in City of Fredericksburg)

            3012             Altoona Subdivision (in City of Fredericksburg)

            3013             Greenbrier Shopping Center (in City of Fredericksburg)

            3014             Altoona West Subdivision (in City of Fredericksburg)





            J. Y, Timmons & Associates, ]:@C.      32










                                     APPENDIX C
                                  WATERSHED SOILS








	J.K. Timmons & Associates, P.C.		33
 








              The following is a list of the soils found in the watershed study area as compiled by the
              SCS Soil Survey of Spotsylvania County, along with their soil numbe r and hydrologic
              group--



                                                 soil          soil         Hydrologic
                                              Number         Description       Group
                                                 1B           Abell              B
                                                 2B          Altavista           C
                                                 4C2         Appling             B
                                                 4D2         Appling             B
                                                 5           Aquults             D
                                                 12B          Cecil              B
                                                 14B          Colfax             C
                                                 17C       Dystrochrepts         D
                                                 17D       Dystrochrepts         D
                                                 17E       Dystrochrepts         D
                                                 18B         Emporia             C
                                                 18C         Emporia             C
                                                 21B         Faceville           B
                                                 21C2        Faceville           B
                                                 23          Fluvaquents         D
                                                 24          Goldsboro           B
                                                 25C         Kempsville          B
                                                 27          Louisburg           B
                                                 29C2        Masada              C
                                                 30B         Mattaponi           C
                                                 31C2        Mattaponi           C
                                                 34B         Partlow             D
                                                 36B         Savannah            C
                                                 37B         Spotsylvania        C
                                                 44          Udorthents          45
                                                 B           Udorthents          D
                                                 46          Interstate          D



              For more information regarding the soils in this study, refer to the Soil Survey of
              Spotsylvania County, Virwigia.











              J. K Timmons & Associates, PC.                  34







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