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

























                        PHASE II STORM WATER MANAGEMENT PLAN
                                       FOR THE
                                 LAKE ERIE WATERSHED
                                    INTERIM REPORT
              FOR THE PERIOD OCTOBER 1, 1994 THROUGH SEPTEMBER 30, 1995







                        DER GRANT/CONTRACT NO. - CZ1:94.01PE
                             GRANT TASK NO.  CZ1:94.05PE
                                   ME NO.    94465




                                 Co-ashl

            PENNSYLVANI-4
               -- mmm@








               A REPORT OF THE PENNSYLVANIA DEPARTMENT OF ENVIRONMENTAL
          RESOURCES TO THE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION
                       PURSUANT TO NOAA AWARD NO. - NA470ZO248
            OA@wl, 94WINU6














                               TABLE OF CONTENTS




        Part 1:   Project Status Report

        Part 2:   Newsletters

        Part 3:   Draft copies of Sections 3 through 6 of the Final Report

                  - Section 3:  Watershed Characteristics
                  - Section 4:  Watershed Technical Analysis - Modeling
                  - Section 5:  Development   of  Watershed   Technical
                                Standards and Criteria
                  - Section 6:  Stormwater Management Techniques

























     QI




   I
   I
   I
   I
   I

                                                                         PART 1: PROJECT STATUS REPORT
   I
   I
   I
   I
   I
   I
   I

   --A




   'A










     A








     I





                                                                                 CHESTER
                                                                                 ENVIRONMENTAL



             Ref. No. 4026-02
             September 27, 1995                                                                            SEP 2 7 IM


             Mr. John, Mong
             Erie County Department of Planning
             Erie County Court House
             Erie, Pennsylvania 16501

             Dear Mr. Mong:

             Re: Lake Erie Area Watershed Stormwater Management Plan
                    30-Month Project Status Report

             I am pleased to provide the following report on the status of the Lake Erie Area Watershed
             Stormwater Management Plan at this the 30-month point in the project.

             GENERAL

             On March 1, 1993, Erie County authorized Chester Environmental to complete a Phase II
             Pennsylvania Act 167 Watershed Stormwater Management Plan for the Lake Erie Watershed.
             According to the requirements of the Commonwealth of Pennsylvania's agreement with Erie
             County and the County's agreement with Chester Environmental, the plan is to be completed
             by June 30, 1996. The total budget for the project is $323,818 (Chester Environmental,
             $230,082; Erie County, $93,736). Pennsylvania will reimburse the County 75 percent of the
             total project cost.

             The County's agreement with the Commonwealth specifies the following payment schedule:

                                                Payment for                Cumulative             Cumulative Payment
                        Period                     Period                  Payment                 (Percent of Total)

                 1/2/93 - 6/30/93               $ 8,550.00               $ 8,550.00                           3.5
                 7/1/93 - 6/30194                 80,000.00                  88,550.00                      36.5
                 7/1/94 - 6/30/95                 80,000.00                 168,550.00                     .69.4
                 7/1/95 - 6/30/96                 74,313.50                242,863.50                      100.0

             WORK PROGRESS AS OF SEPTEM[BER 1, 1994

             The following paragraphs describe our work progress and status of our charges to the project
             as of September 1, 1995.



                                                                                600 Clubhouse Orive
                                                                                Moon Township. Pennsylvania 15108
                                                                                412-269-5700, Fax 412-269-5749






           Mr. John Mong
           Page 2
           September 27, 1994


               Task I-Project Mitiation

               This task covers the administrative work required to initiate the agreements between the
               Pennsylvania Department of Environmental Protection (DEP), the County, and Chester
               Environmental.

               Task 1 was completed at the inception of the project. This included meetings and
               negotiations with DEP, preparation of the documents required to proceed to Phase 11,
               and execution of our contract with Erie County.

               No work remains to be completed under this task.

               Billings under this task total $3,536 or 99.75 percent of the budgeted total ($3,548).

               Task 2--Project Coordination/Public Participation

               This task consists of project coordination and reporting requirements as well as
               implementing a public participation program consisting of a project newsletter,
               meetings with the Watershed Plan Advisory Committee (WPAC), a training session,
               and public hearing.

               Task 2 will be ongoing throughout the project. Elements of this task completed to date
               include conducting three Phase II WPAC meetings and issuing twelve newsletters to the
               WPAC members and other interested parties.

               Work remaining to be completed under this task consists of the continued publication of
               the newsletter and conducting the remaining WPAC meetings, training session, and
               public hearing.

               Charges under this task total $23,324 or 79.7 percent of the budgeted total ($29,264).

               Task 3--Data Collection Review and Analysis

               Task 3 involves the efforts required to gather, review, and analyze the basic
               information required to complete the technical and institutional planning steps. The
               following work has been completed under this task:

                   Collection, review, and compilation of flood problem information from Flood
                   Information Studies completed throughout the watershed.

                   Analysis of Flood Information Studies and the extraction of data describing
                   stream flow and    velocity relationships at various locations throughout the
                   watershed.






            Mr. John Mong
            Page 3
            September 27, 1994


                     Collection of rainfall data from the region and the analysis of this information to
                     produce the determination of storm volume/duration/frequency relationships for
                     the region.

                     Compilation, review, and analysis of stream obstruction data contained in the
                     prior plan.

                     Identification, inspection, and measurement of additional obstructions as
                     required to supplement the available information.

                     Development of initial estimates of obstruction capacities.

                     Collection of topographic mapping covering the area and the compilation of the
                     hard copy topographic maps into a base map.

                     Purchase of digital elevation models spanning the area.

                     Preparation and distribution of municipal questionnaires.

                     Compilation of the stormwater problem information contained in the municipal
                     questionnaire responses.

                     Compilation of the existing and proposed flood protection facilities information
                     contained in the returned questionnaires.

                     Contacting DEP to obtain information relative to existing and proposed flood
                     protection facilities in the watershed.

                     Compilation of     the existing and proposed        stormwater control facility
                     information contained in the returned municipal questionnaires.

                     Obtaining and incorporating TIGER file data into the project GIS database.

                     Obtaining and incorporating the County street centerline data into the project
                     GIS database.

                     Obtaining and incorporating the Landsat Thematic Mapper Imagery into the
                     project GIS database.

                     Discussing municipal questionnaire responses at the WPAC meeting.

                     Requesting streamflow monitoring records from the City of Erie.

                     Collecting streamflow data from U.S.G.S records.






            Mr. John Mong
            Page 4
            September 27, 1994



                     Obtaining projected future land use information from Erie County.

                 Work under this task is essentially complete.

                 Charges under this task total $30,632-50 or 100 percent of the budgeted total
                 ($30,636).

                 Task 4--Institutional Data Preparation

                 This task involves the evalu  ation of the municipal ordinances in order to prepare a
                 municipal ordinance matrix. This matrix is intended to display the current stormwater
                 management provisions contained in the various municipal ordinances.                 Work
                 completed to date includes:

                     Receipt of stormwater management ordinances currently           in effect in the
                     watershed.

                     Preliminary review of the content of the ordinance.

                     Providing the County with a sample municipal ordinance matrix to be used in
                     compiling the matrix for the Lake Erie Area Watershed.

                     Consulting with members of the staff of the Erie County Planning Department
                     concerning procedures for the assembly of the municipal ordinance matrix.

                     Receipt and analysis of the completed municipal ordinance matrix.

                     Compilation of overall summary municipal stormwater management ordinance
                     matrix.


                 Work remaining under this task consists essentially of fuW editing of the ordinance
                 matrix and incorporation of the matrix into the plan report.

                 Charges under this task total $2,492 or 88.0 percent of the budgeted total ($2,832).

                 Task 5-Data Preparation for Technical Analysis

                 This task  involves the engineering work necessary to transform the raw information
                 collected in Task 3 into a form that can be@ directly used for the later technical tasks in
                 the overall planning program. Work completed under this task includes the following:

                     Initial classification of the satellite imagery to produce a preliminary land use
                     classification.






           Mr. John Mong
           Page 5
           September 27, 1994



                   Delineation of subwatersheds and subbasins.      A total of 1,603 individual
                   subareas have been delineated.

                   Digitization of the delineated subareas and incorporation of the subarea
                   boundaries into the project GIS.

                   Digital elevation models have been incorporated into the project GIS for the
                   purpose of calculating subarea slope area characteristics.

                   Digitization of the hydrologic soil group boundaries is ongoing.

                   Stream segment length information has been measured and assembled for each
                   of the 1,600 delineated subareas.

                   Locations of reported stormwater problem areas have been transferred to the
                   base maps for subsequent digitization.

                   Locations of existing and proposed flood control and stormwater management
                   facilities have been transferred to the base maps for subsequent digitization.

                   The existing land cover database and GIS coverage for use in the hydrologic
                   model have been completed.

                   Locations of reported stormwater problem areas have been digitized and
                   included in the GIS.

                   Locations of existing and proposed flood control and stormwater management
                   facilities have been digitized and included in the GIS.

                   Locations of significant obstructions have been digitized into the GIS.

                   Strearnflow velocity information for various streams and locations throughout
                   the watershed have been extracted from published flood information studies for
                   use in -developing travel time estimates for modeling purposes.

                   Dimensional statistics have been developed for each of the 1,600 subareas.

                   Digitization of the hydrologic soil group boundaries has been completed.

                   The geographic information system based analyses required to develop input
                   parameters for use in the Penn State Runoff Model have been completed.






           Mr. John Mong
           Page 6
           September 27, 1994


                   The County's land use projections have been incorporated into the project GIS
                   and estimated future conditions model input parameters have been developed.

                Work under this task is essentially complete with the exception of finalizing the
                documentation of the completed activities in the final report and appendices.

                Charges under this task total $49,522.50 or 92.1 percent of the budgeted total
                ($53,748).

                Task 6--Model Selection and Setup

                Model selection and setup involve the selection and preparation of a hydrologic model
                appropriate for the analysis of the existing and projected land characteristics of the
                watershed. Work completed to date under this task includes the following:

                   The Penn State Runoff Model has been selected for use on this project.

                   Input data files containing the required topology and layout information have
                   been prepared for all of the watersheds.

                   The dimensions of the runoff model have been expanded to accommodate the
                   size of the Elk Creek Watershed.

                   Data describing the physical dimensions of the subareas have been, incorporated
                   into the model files.


                   Testing of the model input files has been completed..
                   Work regarding the determination of         stream segment 'information and
                   characteristics of small lakes in the watershed is completed.

                   All input model files have been finalized.

                Work on this task is essentially complete.

                Charges to date under this task total $22,360 or 100 percent of the budgeted total
                ($22,368).

                Task 7


                Task 7 consists of the completion of the hydrologic modeling runs and the
                documentation of the results. Work completed under this task includes the following:






            Mr. John Mong;
            Page 7
            September 27, 1994


                    The hydrologic model has been successfully calibrated against measured stream
                    flows.

                    Hydrologic model runs have been completed for the 2-, 5-, 10-, 25-, 50-, and
                    100-year return frequency 3-, 6-, 12-, and 24-hour duration storms. This
                    modeling was completed for each of 25 separate watersheds. This entailed the
                    completion of 600 individual model runs.

                 Work remaining under this task includes completion of 25-year return frequency,
                 24-hour duration storm model runs under future conditions.

                 Charges under this task total $29,896.40 or 98.2 percent of the budgeted total
                 ($30,452).

                 Task 8


                 Task 8 consists of the analysis of the results of the modeling and data collection efforts
                 and the development of recommended standards and criteria for the watershed. Work
                 completed under this task includes the following:

                    Selection of the design storm duration.

                    Selection of the design storms return frequencies.

                    Selection of the design storm temporal distribution.

                    Calculation of peak discharge release rate percentages throughout the watershed.

                    Identification of permissible computational techniques.

                 Work remaining under this task consists of the finalization of the standards and criteria
                 based upon input received from the WPAC and the County and completion of the
                 necessary documentation in the plan report.          Charges to. date total $5,499 or
                 66.3 percent of the budgeted amount ($8,288).

                 Task 9


                 This task consists of the assembly of the model stormwater management ordinance. As
                 of September 1, 1995, no work had been completed on this task. However, an initial
                 draft of the model ordinance was completed in the middle of September.

                 As of September 1, 1995, no charges were made to the task budget of $5,616.






             Mr. John Mong
             Page 8
             September 27, 1994


                Task 10-Plan Report Preparation

                This task consists of the preparation of a report documenting the investigations,
                findings, and recommendations of the planning process. To date, the following work
                has been completed under this task:

                    Completion of draft Section 1 --Introduction.

                    Completion of draft Section 2--Legal Framework for Stormwater Management.

                    Completion of draft Section 3--Watershed Characteristics.

                    Completion of draft Section 4--Modeling.

                    Completion of draft Section 5--Development of Watershed Technical Standards
                    and Criteria.

                    Completion of draft Section 6--Stormwater Management Techniques.

                Work remaining und    er this task consists of the preparation of the report as work
                progresses.

                Charges to date under this task total $8,126 or 39.2 percent of the total ($21.620).

                Task 11-Plan Adoption

                Work under this task involves work to be performed in conjunction with securing plan
                adoption. This work will be completed at the close of the project.

                No charges have been made to this task which has a total budget of $2,210.

                Direct Costs


                This category represents cost items for the purchase of data and.materials, travel, mail,
                telephone, printing costs, and miscellaneous expenses.

                Charges to date total $12,165.76 or 62.4 percent of the budgeted amount ($19,500).

             STATUS OF BUDGET AND SCBEDULE


             The status of our budget and progress relative to the schedule contained in our contract with
             the County is summarized in Figure 1. This graph compares our progress and total charges     ' by
             work task to the schedule'. -As is indicated in Figure 1, we are essentially on schedule for all
             tasks through Task 8. We anticipate that we will be essentially complete with the remaining






            Mr. John Mong
            Page 9
            September 27, 1994


            tasks, including preparation of the draft report by December 31, 1995. This will be in general
            accordance with our schedule with Erie County and approximately six months ahead of the
            June 30, 1996, completion date in the County's agreement with the Commonwealth of
            Pennsylvania.

            We estimate that our work is approximately 85 percent complete versus a scheduled
            completion rate of 90 percent as of September 1, 1995.            Billings to that date total
            $188,009.16. This represents 82 percent of our total budget. The project continues to be
            essentially on budget relative to progress and cost.

            Please contact me at 269-5828 if you have any questions.

          -Yery -truly yours


          ,16ii@ 14. ^Masl     P. E.
            Technical Manager

            JMM/dJe/2

            Enclosures






                           Figure 1
            Status 'of Schedule and.Budget


             2
             3
             4
             5            OWN
             6
             7
             8
             9
             10



        Tota I

               0      .20      40      60     -80      100
                       Percent of Total Effort


            Scheduled 0 Completed El Billed.




 I
 I
 I
 I
 I
 I                             PART 2: NEWSLETTERS
 I
 I
 I
 I
 I
 I
 I
 I
 I
 I
 I
 I
 I





                       a             rie                                          an                                          ae**.*

             Volume 2 Issue 5                                                                                            October 1994
                                                 LakeErie Watershed
                        Eighteen Month Project Progress Report
             Project Has
             Reached 18 Month
             Point

             On N1.arch 1, 1993, Erie County
             authorized the initiation of an Act 167
             Watershed Stormwater Management
             .Plan for the Lake Erie Area Watershed.
             September 1, 1994 marked the 18
             month point in the project. According
             to the requirements of Erie County's
             agreement with the Commonwealth of
             Pennsylvania, the plan is to be
             completed by June 30, 1996.
             This issue of the newsletter presents a        Mustration ofstreamr comprising the LakeErie Area Watershed (stream locations and
             general overview of the progress that          municipal boundaries extractedfrom U.S. Census Bureau TIGER FUes.
             has been achieved on the Lake Erie
             Area        Watershed         Stormwater         Data Collection Review and Analysis
             Management Plan during the initial 18
             month period.                                                              Activities

                                                          Data collection review and    analysis activities involve efforts necessary to
             Public                                       gather, review, and analyze   the basic information required to prepare the
             Participation is                             watershed stormwater management plan. Work completed under this category
                                                          of tasks includes the following:
             Ongoing                                      1.  Collection, review and analysis of Flood Information Studies completed
             Elements of the public participation             throughout the watershed.
             program completed to date include
             conducting two Watershed Plan                2.  Collection and analysis of rainfall data and determination of storin
             Advisory Committee meetings and                  volume, duration, and frequency relationships for the region.
             issuing ten newsletters to members of
             the    Watershed      Plan     Advisory      3.  Compilation of stream obstruction information.
             Committee and other interested
             parties. Public participation elements       4.  Assembly of digital and hard copy base mapping.
             will continue throughout the project
             and will include additional Watershed        5.  Collection and compilation of municipal questionnaire information about
             Plan Advisory Committee meetings,                stormwater problems and facilities.
             continued     publication    of     this
                   L ke E S[ormwaler M agemenl                                                                        P   d














             newsletter, and a public hearing at the      6. Acquisition of satellite imagery of the area.
             close of the projecL





        *2                                                         Lake Erie Stormwate.r Management Update
             Data Preparation for Technical Analysis                                                      Summary
             Activities under this category involve the engineering work necessary to
             transform the raw data collected under the data collection phase into a form        The project is currently on schedule
             that can be directly used for technical analysis. Work completed under this         in terms of progress achieved. In the
             category of tasks includes the following:                                           coming months, work will focus on
                                                                                                 the hydrologic modeling activities
             1. A total of 1,600 individual watersheds and subwatersheds have been               and the use of the model to develop
                delineated and their boundaries digitized.                                       appropriate     stormwater      control
                                                                                                 standards.     The results of these
             2. Digital elevation models have been         incorporated into the project         efforts will be discussed in future
                geographic information system (GIS) to be used to estimate ground slopes         Watershed Plan Advisory Committee
                throughout the planning area.                                                    meetings.
                                                                                                  This newsletter is published semi-
             3. Classification of land cover classes for the purpose of estimating runoff         monthly as a means of informing
                characteristics has been completed.                                               interested parties of the progress
             4. Locations of storinwater problems and facilities have been digitized into         of the planning process and
                the project GIS.                                                                  encouraging their input into the
                                                                                                  planning process. We encourage
             5. Dimensional statistics for each of the delineated watersheds and                  you to direct any questions or
                subwatersheds have been calculated.                                               comments to:
             Data Preparation for Technical Analysis                                              Erie County Department of Plan-
                                                                                                  ning:
             Model selection and setup involve the selection and preparation of a hydrologic
             model to be used in developing the technical stormwater management                   Sharon L. Knoll
             standards. Work completed under this category of tasks includes the following:       Eric County Court House
                                                                                                  Erie, PA 16501
             1 .Ile Penn State Runoff Model has been selected for use on this project.            (814) 451-6336

             2. Input data files containing the required watershed and subwatcrshed               or
                topology and layout information have been prepared for all of the
                watersheds.                                                                       Chester Environmental


             3. Testing of the model input files has begun.                                       John M. Maslanik
                                                                                                  Chester Environmental
             4. Data describing the physical dimensions of the watersheds has been                P.O. Box 15851
                assembled into the model input files.


        Erie County Department Of P1         9
        Eric County Court House
        Eric, Pennsylvania 16501





                          a                rie                  mwa                           ana                                                          0*1+

              Volume 2 Issue 6                                                                                                          December 1994

                        Overview of Hydrologic Modeling Activities
                Purpose of                                        of runoff volumes and rates under a                mathematical mpresentations of the
                                                                  range of conditions.                               physical factors that affect runoff
                Hydrologic                                                                                           rates.      The hydrologic model
                                                                  The typical structure of hydrologic                typically contains a set of algorithms
                Modeling                                          computer models is illustrated in                  to convert rainfall on a subbasin to
                                                                  Figure 1. As is indicated in Figure                runoff and another set of algorithms
                  Hydrologic modeling plays two roles             1, the models generally consist of                 to route the runoff from the subarea
                  in stormwater management planning               three major components:                            downstream through the stream
                  under Act 167. First, it provides A                                                                channel. The algorithms are linked
                  means     to    describe       hydrologic                  1. input data                           . Output from one becomes input to
                  conditions in the watershed and                            2. the computer program                 another - so as to represent the
                  quantify the impact of existing and                        3. model output                         integrated behavior of the watershed
                  potential future land development                                                                  system.
                  activities on stormwater runoff and             Input data typically includes           land
                  stream flows.      Second, hydrologic           data, stream channel data,              and
                                                                                                                     'Me third part of the computer
                  modeling provides the technical                 meteorologic data.             Land     data       model is the output or results of the
                  basis for the selection of stormwater           typically includes tributary            area       analysis.      Typical output from
                  control standards and criteria that             measurements and layout,                 soil      hydrologic        models          includes
                  are appropriate for the watershed.              characteristics, land cover,            and        estimates of peak flow rates,
                  This is particularly true for the               ground slope. Channel data includes                discharge hydrographs, total runoff
                  development of specific stormwater              information describing factors that                volumes, and the contribution of
                  release rate percentages as discussed           affect the capacity and time of travel             flows from the each subbasins -to
                  in the February 1994 issue of this              of stormwater runoff through stream                peak flow rates experienced at
                  newsletter.                                     channels.          Meteorologic         data       downstream locations.          This last
                                                                  includes total precipitation and                   output is particularly important to
                  Definition of                                   variations in rates of rainfall over               the determination of release rate
                  Hydrologic                                      time.                                              percentages that are an important.
                                                                                                                     aspect      of , the           stormwater
                  Modeling                                        The computer program consists of                   management control standards.
                  The amount of stormwater runoff that
                  results from rainfall and the rate at                       Figure 1: Hydrologic                   Modeling Schematic
                  which the runoff moves through a                                Physical Data                                       Meteorological Data
                  watershed are affected by a number of                      Drainage areas                                         Rainfall volume
                  physical factors.        These factors                     Land cover                                             Storm duration
                                                                             Soil characteristics                                   Time 4istributioa
                  include the volume 'and rate of                            Ground slopeii                                         Area distribution
                                                                             Channel capacity
                  rainfall and the physical features and                     Channel flow velocities
                  characteristics of the ground upon
                  which it falls.


                  Hydrologic     modeling       refers      to                                         Hydrologic Model
                  computerized computational metho;ds
                      L ke E S[or                                               ler M                      gemenl Updale







                                                                                                      ,mr




                  that are used to mathematically
                  describe the effects of the various                        Runoff rates and volumes                                 Contributions to
                                                                               :,ts,soch tsubsro:t:ad ad                         downstream peak flow totes
                  factors that affect rainfall - runoff                      thr  hot the or robed                                    by each sablissia
                  relationships and produce estimates

                                                                                                                                                                  _J





              2                                                          Lake Erie Stormwater Management Update
         Model Selection                                  Assembly of the                                  files that describe the hydrologic
                                                                                                           conditions that waist in over 1,4W
         There are a number of hydrologic                 Penn State Runoff                                specific subareas that, together, form
         models available for use. Among the              Model                                            the Lake Eric Area watershed.
         models considered for use in this                                                                 Current activities consist of final
         watershed      were     the    US.      Soil       We are currently in the final stages           data input file assemble and testin&
         Conservation Services' IR-20 model,                of assembling and testing the Penn             Once this is completed, hydrologic
         the US. Army Corps of Engineers!                   State Runoff Model representations             modeling under a range of
         BEC-1 model, and the Penn State                    of the Lake Erie Area Watershed.               precipitation conditions will begin.
         Runoff Model.          Of the available            This includes the assembly of the
         models, the Penn State Runoff Model                following specific model input                  This newsletter is published semi-
         has been selected for use in the Lake              information:                                    monthly as a means of informing
         Eric Area watershed. The Penn State
         Runoff Model (PSRM) was selected for               A_   Subbasin physical Features                 interested parties of the progress of
         a number of reasons, including:                                                                    the planning process and encourag-
                                                                 1. tributary land area                     ing their input into the planning
          1.   PSRM offers the ability          to               2. land slopes                             process. We encourage you to di-
               analyze the timing of flow                        3. overland flow widths                    rect any questions or comments to:
               contributions originating from                                                               Erie County Department of Plan-
               various locations throughout                 B.   Subbasin Hydrologic Conditions             ning:
               the watershed. This capability
               is particularly important in the                  1. runoff curve numbers                    Sharon L. Knoll
               evaluation of the effects of                      2. 'percentage impervious area             Erie County Court House
               various stormwater control                                                                   Erie, PA 16501
               tech*niques;       and         the           C.   Drainage Channel Features                  (814) 451-6336
               development of release rate
               percentage control standards.                     1. strearn bankftdl capacity               or
                                                                 2. channel travel times
         2.    PSRM offers flexible data                         3. overbank flow adjustments               Chester Environmental
               input and output modes.                      D.   Meteorological Inputs                      John M. Maslanik
         3.    PSRM is widely accepted for                                                                  Chester Environmental
               use throughout Pennsylvania                       1. rainfall volumes                        P.O. Box 15851
               for   the     preparation        of               2. rainfall distributions                  Pittsburgh, PA 15244
               watershed wide stormwater                                                                    (412) 269-5828
               management plans under Act                   The information listed above has
               167.                                         been assembled into model input



         Erie County Department of Planning
         Erie County Court House
         Erie, Pennsylvania 16501







                o
                        a                                                                                                                   ,e*
                        a               rie

              Volume 3 Issue I                                                                                                   Februuy 1995

                    Model Stormwater Mann:Fement Ordinance

              Role of Stormwater                                       Form and Content of Stormwater
              Management                                                                     Ordinances
              Ordinance                 -                    In general, stormwater management ordinance provisions can be implemented by
              The ultimate purpose of stormwater             adopting them as a single purpose ordinance or by incorporating them as
              management is to control surface               amendments to to existing development ordinances (zoning and subdivision/land
              water runoff resulting from land               development ordinances). However, all stormwater management ordi                 'nances
              development activities so as to avoid          should include the following key provisions that are necessary in order to
              the occurrence of stormwater runoff            implement the performance standards and criteria of the watershed plan.
              related problems such as flooding,             APPLICABILITY
              stream erosion, and sedimentation.
              Under the provisions of Act 167, the           The activities to which the provisions of the stormwater management ordinance
              means through which this is to be              apply must be defined.
              accomplished is through the                    STORMWATER PLAN REQUIREMENTS
              enforcement of local municipal
              ordinances that contain specific
              stormwater management provisions               The local ordinance should precisely describe stormwater management plan
              which must be satisfied by land                submission requirements. This includes the requirement for preparation by
              developers.    The responsibility for          qualified experts and the specification of the content and the form of the
              the @ adoption        and     subsequent       information that must be included in the plan.
              enforcement of the ordinances lies             DESIGN STORM CHARACTERISTICS
              with    the     local     municipalities.
              Consequently, the local stormwater             The Stormwater Management Plan will recommend storm frequencies,
              rTianagement ordinance provisions              durations, distributions, and associated rainfall volumes that should be used in
              represent the mechanism through                the design of stormwater management measures (This topic was introduced in
              which the stormwater management
              goals are accomplished.                        the December 1993 issue of this Newsletter). These design storm criteria should
                                                             be established by the municipalities as a provision of their stormwater
              For this reason, one of the         major      management ordinances.
              elements of the Lake Erie Area                 STORMWATER MANAGEMENT CONTROL STANDARDS
              Watershed Stormwater Management
              Plan will consist of the development
              of model ordinance provisions.                 The Stormwater Management Plan will recommend specific stormwater control
              These model ordinance provisions               standards that should be met by land developers in order to adequately manage
              can    be     used      by   the     local     stormwater runoff from their activities (This topic was introduced in the
              municipalities as a          guide for         February 1994 issue of this Newsletter). The local stormwater management
              modifying or supplementing their               ordinances must   specify these stormwater control standards.
              existing ordinances so as to include           METHOD OF STORMWATER CALCULATIONS
              provisions that are critical to the
              effective      implementation           of     There are a wide number of methods for estimating stormwater runoff. In order
              stormwater management within their
                    L ke E S[ormwa[er Ma agemen[ L                                                                              P   da













              specific   municipalities     and      the     to ensure that the appropriate methods are used, maintain consistency throughout
              watershed as a whole.                          the watershed, and facilitaie plan review, the ordinance should specify the use of
                                                             a limited number of acceptable computational techniques.





        *2                                                                     Lake Erie Stormwater Management Update

                     Form and Content of Stormwater
                                                                                                                      This newsletter is published semi-monthly as
                                                                                                                      a means of mfomung interested parties of the
                                Ordinances (Continued)                                                                progress of the planning process and
                                                                                                                      encouraging their input into the planning
                                                                                                                      process. We encourage you to drect any
        CONTROL TECHNIQUES                                                                                            questions or comments to:

        Each developer must select the technique or combination of techniques that are Most                           Faie County Department of Planning:
        appropriate to the specific site. However, the stormwater management ordinance                                           Shmn L. Knoll
        should identify general control techniques that are proven and appropriate for (Ise in                                   Erie County Court House
        the watershed. The developers are to use his catalog of approved techniques to                                           Erie, PA 16501
        select their control methodologies. The ordinance should also encourage the use Of                                       (814) 451-6336
        stormwater volume reduction measures where feasible. It should also contain design                                                  or
        standards for the identified control techniques.                                                              Chester Envimninental
        PLAN REVIEW PROCEDURES                                                                                                   John M. Maslanik
                                                                                                                                 Chester Environmental
                                                                                                                                 600 Clubhouse Drive
        The ordinance should identify the specific procedures that will be followed during                                       Moon Township, PA 15108
        the review of developers' stormwater management plan submissions.                                                        (412) 269-5828

        CONTINUING MAINTENANCE PROVISIONS


        The o  'rdinance should require the submission of a maintenance plan for all proposed stormwater management facilities. The
        ordinance should also provide for the provision of construction or performance bonds and maintenance bonds consistent
        with the Municipal Planning Code. The ordinance may also establish a system of financing public maintenance costs.

        FEES


        The municipal ordinance may provide for a fee schedule to cover the cost of reviewing developers' plan submissions.

        INSPECTIONS


        The ordinance should include a schedule for periodic inspections of stormwater facilities during the course of construction.

        ENFORCEMENT REMEDIES AND PENALTIES


        In order to enforce the provisions of the stormwater management ordinance, municipalities should incorporate into their
        ordinance remedies and penalties similar to those prescribed in the Municipalities Planning Code.



        Erie County Department of Planning
        Erie County Court House
        Erie, Pennsylvania 16501





                                       rie                                              a

           Volume 3 Issue 2                                                                                                            April 1995
              Review of Existing Model Ordih ance Provisions
                                                                  Completed
             The February 1995 issue of this                  of the 25 municipalities:                     municipalities     in   the watershed
             newsletter contained a discussion of                                                           currently enforce one or more of these
             the vital role that the local municipal          I .Subdivision and Land                       ordinances      will    facilitate    plan
             ordinances will play in implementing                Development Ordinances and                 implementation.
             stormwater management throughout                    Regulations
             the watershed. The local ordinances              2. Zoning Ordinances                          A matrix of stormwater management
             will be the vehicle through which land           3. Flood Damage Prevention                    Provisions is provided on the reverse
             developers are required to include                  Ordinances                                 side of this newsletter.               The
             effective stormwater controls into their         4. Stormwater Management                      information contained in the matrix
             development projects. The Lake Erie                 Ordinances                                 indicates the extent to which the
             Area        Watershed          Stormwater                                                      required stormwater management
             Management         Plan     will    present      The ordinances were reviewed to               elements are contained            in the
             ordinance provisions     which must be           determine the manner in which the             ordinances currently in force in each
             contained     in     the    municipalities'      following    general     categories     of    municipality. As the matrix indicates,
             ordinance packages in order to                   provisions   related    to    stormwater      several of the municipalities (the 6
             accomplish      effective      stormwater        management are addressed.                     with existing stormwater management
             management.                                                                                    ordinances) currently have provisions
                                                              I .General land use planning                  in effect that directly relate to specific
             As an initial  step in the development              standards                                  requirements for the control of
             and ultimate   adoption of the required          2. Stormwater control requirements            stormwater and the design of
             ordinance provisions, the Erie County            3. Specified runoff calculation               stormwater management facilities.
             Department of Planning completed a                  methods                                    However, in most cases the municipal
             review of ordinances currently in                4. Design standards for stormwater            ordinances are essentially silent on
             effect in the 25 municipalities in the              controls                                   stormwater control issues.         In all
             Lake Erie Area Watershed.               The      5. Erosion and sedimentation control          cases, amendments to the current
             review determined what types of                     requirements                               ordinance packages will be required
             stormwater management provisions                 6. Formal plan review process                 to     implement       the     stormwater
             are    contained      in    the    existing      7. Established basis for permitting fees      management plan.
             ordinances and the general extent to             8. Specified facilities inspection
             which these provisions wiU have to be               schedule
             modified     in order to accommodate             9. Identified maintenance provisions            This newsletter is published semi-monthly
             implementation of the Lake Erie Area.                                                            as a means of informing interested parties
             Watershed Stormwater Management                  Of the 25 municipalities that are               of the progress; of the planning process and
             Plan. The findings of this review will           located in the watershed, 24 - have             encouraging their input into the planning
                                                                                                              process. We encourage you to direct any
             be presented in the Stormwater                   adopted individual subdivision/land             questions or comments to:
             Management Plan document to assist               development ordinances, 21 have                 Eric County Departmen.t of Planning:
             municipalities in evaluating their               adopted zoning ordinances, and 6 have                     David Skellic
             existing ordinances in light of the plan         adopted     stormwater       management                   Eric County Court House
             recommendations.                                 ordinances. 'ne existing stormwater                       Eric, PA 16501
                                                              management ordinances and current                         (814) 451-6336
             ne scope of the review of existing               subdivision and land development                                    or
                                                                                                              Chester Environmental
                   Lake E Slormwaler M nagemen[ [ pdale














             ordinances consisted of reviewing the            ordinances are the preferred locations                    John M. Maslanik
             following general types of ordinances            for instituting stormwater management                     Chester Env ironmental
             and regulations as they exist for each           requirements. The fact that most of the                   600 Clubhouse Drive
                                                                                                                        Moon Township, PA 15 109





           +2                                                                                               Lake Erie Stormwater Management Update


                                                                                        Lake Eric Area Watershed Matrix ofStarmwater Ordinance Provisions

                                                                                                                          Dtwa              rim             rim
                                                          1.11=7       calmildnes @.c'.-.:                                          a
                                                                                                 Z.                    Facility D"i a s.b. Wide              Review     kiniswomm          litepectiomi    Ferimakiiis
                 masicipality            tuidards         C im           mediod                               Lands       standards    Requirvinests      Procedures    I- pro'sSioas       Schedule          Fees
                 Consume                                                                                         I
                 Ttivesibip              0           1    0               0                 0                                0                               010- 0                                           0
                 lSlkCr"k
                 T'..ip                  0                0               0                                 0                0               (D              0          1    0               0                0
                 Bris City               0                0               0                 0          1    0                0               (D              0          1    0               0          i
                 Scroush                 0                0               0                 0               0                0               (D                              (D              0
                 Fauvism,
                 Tovaship                0                0               0                 0               0 1              0               (D              0               0               0                0
                 Fmkft
                 To'catbip               0                0               0                 0               0                0               Q               a               0               0
                 Girard
                 aciroagh                                                                                   0                Q               (D                              0               0
                 Girard
                 Tircuslkip                               0                                                                  0                                               0               0                0
                 Gress                                                                                      0                                                                                                 0
                 Tow:.hip                0                0               0           i     0                                0               (D              0          1    0           1   0
                 Grecefield
                 Township                C)               0               0                 0               0                C)                              0          !    CD          1   0                0          1
                 Harbotereek
                 Toessibip               0                0               0                 CD              0                0               0         i     0          1    0               0                0
                 LI-11C.."...            0                0               0                 0                                0               (D+S                       i    (D              (D               A
                 Lzarence raft                                                                                                                                                                                0
                 Tow.esi                                                  0                 0               0-+0                             (D              0          11
                 -                       0                0                                                 0                                                                CD              (D
                 McKs"
                 Borough                 0                0               0                 0               0                01              G)              0               0               0                0
                 To='-                                                                                                                                                       0           1                    0          1
                 MIJ)"
                           9             0           1    0               0                 0               0                                                                                (D
                 Tow ip                                                                                                      CD        I
                 ?dot* EMI
                 lko'odgb                                 0               0                 (D              Q                0               0                               0           1   0                0
                 Mardi F.S.
                 Ta.% kip
                                                          0               (D                (D              (D               (D                                                          1   0                0'
                                         0                0                                                                                  (D                              0
                                                                          0                                 0                0                                                           1   0                0
                 Spilas    am                                                                                                                                                                (D
                 T,.,r
                           .h"           0                0               0                 (D         1    0 J              0               0               0               0
                 Toussbip                                                 (D                                0                0
                                                                                                                                                                             0               0
                 VeTs.,:.g               0                0               0                 0               0                0               0               0                                                0
                 wathostos                                                                                                   0
                 To-kip                                   (D              0                 0               0                                                6               o           T   o                0
                 Waserford
                 Towswirp                0                0               0                 0               0                0               CD              0               Q           1   0                0
                                         0                0               0                 0               0                0               (1)             0               0               0                0

                 0         Topic iiat auctioned in ordinance - will r"u"a"incis                                                           Topic caucused to ordemeace but                           will be feq.xId

                                                                          [email protected]




           Erie County Department of Planning
           Erie County Court House
           Erie, Pennsylvania 16501





                                          rie                                                 an

                Volume 3'Issue 3                                                                                                                 June 1995
                    Overview of PENNVIEST Stormwater Project
                                                                  Loan Program
                Program                                           sanitary sewer systems.                           Program Funding
                Overview                                          (3) The Commonwealth's stormwater                 and Budget
                                                                  management program is enhanced by
                PAAU 11 of 1911 has been amended                  the availability of funding to resolve            Funds for the loans are provided by
                to    authorize     the       Pennsylvania        existing flood problems identified in             Act 16 of 1988.         These loans for
                Infrastructure Investment Authority               watershed     stormwater       management         StOrmwater      projects     have       been
                (PENNVEST) to provide low interest                plans.                                            available since November 10, 1993,
                loans to governmental units for the                                                                 when the PENNVEST board approved
                construction    or    rehabilitation       Of     (4) Municipalities       which     do ' not       the first two loan applications.
                stormwater      projects      and        best     regulate stormwater management for                Currently, there are a total of fifteen
                management practices to address Point             development activities in a manner                approved loans with a cumulative loan
                or nonpoint source pollution associated           consistent with the requirements of the           amount of $15 million. Nine of these
                with stormwater.           Examples of            Stormwater Management Act of 1978                 projects      are     currently       . under
                stormwater      projects    eligible      for     are brought into compliance prior to              construction.     In addition, there are
                funding are construction of (1) new or            loan approval.      These municipalities          eight pending PENNVEST stormwater
                updated storm sewer systems to                    must adopt implementing ordinances                project    loan      applications      which
                eliminate stormwater flooding' or to              consistent with the Act.                          -request total funding of $2.3 million.
                separate stormwater from sanitary                                                                   Several other municipalities have
                sewer systems, (2) detention basins to            Pennsylvania DER's                                expressed their intent to submit their
                control stormwater runoff, and (3)                                                                  loan applications for stormwater
                stormwater facilities to implement best           Role                                              projects in 1995.
                management practices that reduce non-             The    Pennsylvania Department of
                point source pollution.                           Environmental Resources' staff act as             Application Process
                Program                                           technical      consultants        to      the     and Deadlines
                                                                  PENNVEST administrative staff. The
                Importance                                        Departments engineers serve as project            The      Pennsylvania         Infrastructure
                                                                  managers for each stormwater project              Investment Authority has developed an
                This PENNVEST             loan program            which is funded by PENNVEST,                      established procedure for making
                provides low interest loans for                   beginning at the planning stage and               applications for PENWEST financial
                Pennsylvania's       municipalities        to     continuing through the completion of              assistance. This procedure is outlined
                develop and upgrade infrastructure for            construction. Ile Department project              on the reverse side of this newsletter.
                stormwater drainage. This program                 managers provide engmieermg services
                has the following benefits:                       which include conducting planning                 Pending cut-off dates for the submittal
                                                                  consultation          meetings           with     of applications are September 27,
                (1) It has made it possible for                   municipalities, reviewing project plans           1995, for action at the November 29,
                municipalities      to    resolve      storm      and       specifications,     rating      and     1995, PENNVEST Board meeting and
                drainage problems which are safety                recommending .           projects          for    January 24, 1996, for the March 20,
                ha7_q ds and to separate stormwater               PENNVEST           funding,       conducting      1996, Board meeting.               Questions
                drainage from combined sewer                      interim      and     final      construction      concerning           the        PENNVEST
                systems.                                          inspections,     participating      in    and     Stormwater Program in          Erie County
                                                                  representing the PENNVEST program                 can be addressed to:
                     Lake E Slormwaler M agemenl lJpdale














                (2) This program supplements other                at preconstruction conferences and                                Duria Lathia
                PENNVEST- programs which assist                   assisting PENNVEST in. conducting                                      DER
                communities to upgrade water and                  educational programs.                                           (717).772-5661





          *2                                                         Lake Erie Stormwater Management Update


               PENNSYLVANIA INFRASTRUCTURE INVESTMENT AUTHORITY
              FLOW CHART FOR APPLICATION FOR FINANCIAL ASSISTANCE
                                     STORMWATER PROJECTS

                          APPLICANT                                        JOINT ACTION
          Obtains    application   fo rm    PENNVEST;                                                 This newsletter is published semi-
          arranges Planning Consultation meeting with                   Planning Consultation         monthly as a means of informing
          DER Project Manager and submits stormwater                           Meeting                interested parties of the progress of
          ordinance, if existing.                                                                     the planning process and encourag-
                                                                                                      ing their input into the planning
                               T                                                                      process. We encourage you to di-
                  DER PROJECT MANAGER                                      JOINT ACTION               rect any questions or comments to:
          Prepares Planning Consultation Report; sends                                                Erie    County      Department       of
          to applicant; if available, applicant sends              III-      Predesign or             Planning:
          stormwater ordinance to DER for review, if                    preapplication meeting
          proposed.
                                                                                                      David Skellie
                                                                                                      Erie County Court House
                                                                                                      Erie, PA 16501
                         APPLICANT                                           APPLICANT                (814) 451-6336
          If required, adopts ordinance in compliance                     Designs project and         or
          with Act 167, and ensures compliance with                W
          Watershed Itormwater Management Plan, if                      prepares documentation.
          appropriate.                                                                                Chester Environmental


                                                                                                      John M. Maslanik
                               T                                                                      Chester Environmental
                         APPLICANT                                            PENNVEST                P.O. Box 15851
          Completes     Application    and    sends      to               PENNVEST Board              Pittsburgh, PA 15244
          PENNVEST for processing,                                              Action                (412) 269-5828
                                                                                   1

                                                                            -TP--PLICANT, DER,
                  APPLICANT AND PENNVEST                                      CONTRACTOR
                           Loan Closing                                 Preconstruct ion Meeting


                                                    APPLICANT

                                                 Start construction




          Erie County Department of Planning
          Erie County Court House
          Erie, Pennsylvania 16501





                                         rie                                                a

              Volume 3 Issue 4                                                                                                            August 1995
                       Preliminary Proposed Stormwater Control
                                                                          Criteria
              Introduction                                      The following storm characteristics              Storm Volumes
                                                                have been developed for use in the
              Previous issues of this newsletter have           Lake Erie Area Watershed:                        Storm volumes associated with the
              discussed the concept of stormwater                                                                24 hour duration mean annual, 10,
              control standards and criteria and their          Storm Duration                                   25, and 100 year return frequency
              application in the Lake Erie. Area                                                                 storms     were       determined       from
              Watershed. The hydrologic modeling                The recommended storm duration for               previous research to be as follows:
                                            z             M          in the watershed is the 24 hour
              work required to establish standards and          use
              criteria appropriate for this watershed           storm. This value was selected because           Mean annual storm = 2.62 inches
                                                                the hydrologic modeling indicated that,          10 year storm = 3.75 inches
              has been completed and recommended                                          0
                                                                for the great majority of the subbasins          25 vear storm = 4.61 inches
              stormwater management standards and               .       0
              criteria have been developed.            This     in the watershed, the 24 hour duration           100 year storm = 6.19 inches
                                                                storm created the largest peak discharge
              newsletter presents these recominended
              standards and criteria.      They will be         of the candidate durations tested. As a          Storm Distribution
              further discussed at a future Watershed           result, the use of the 24 hour storm
              Plan Advisory Committee meetin1g.                 represents     an      appropriate       and     The U.S. Soil Conservation Service
                                                                conservative criteria.                           Type 11 Synthetic Storm Distribution
              Storm                                                                                              has been selected for use in the Lake
                                                                Storm Return Frequencies                         Erie Area Watershed.          This storm
              Characteristics                                                                                    distribution is supported by extensive
                                                                It is recommended that           stormwater      research and is the distribution most
              Criteria                                          management facilities in the watershed           frequently      used     in   stormwater
              One element of the stormwater                     should be designed to control the mean           management calculations.
              management standards and criteria                 annual, 1,0 year, 25 year, and 100 year
              deals      with       describin-         the      return frequency storms. The mean                Runoff Control
                                                                annual storm was included because this
              characteristics of the rainfall events to         general.ly represents the threshold of           Standards
              be used to develop the required                   storms producing overbank flooding
              controls.   The critical rainfall event                                                            Runoff control standards refer to
              characteristics are as follows:                   The 100 year return frequency storm              limits placed upon the peak rate of
                                                                event was selected because a number       . of   discharge to be permitted following
                                                                identified obstructions have capacities                  1@
              1.   An identified duration of the                less than the flows from storms of this          completion      of land       development
                   particular rainfall event.                                                                    activities       (post        development
                                                                magnitude, and because control of the            conditions). The basic runoff control
              2.   An identified frequency of                   100 year storms will tend to preserve            standard recommended for use in the
                   occurrence of the storm event.               the    flood     plain    and      floodway      watershed is that the peak rate of
                                                                boundaries as defined in completed               dischar-e from a land development
                                                                flood insurance studies.
              3.   An identified volume or total                                                                 site should not exceed the rate that
                   amount of rainfall that can be               The intermediate 10 and 25      year return      occurred prior to development (pre-
                   expected from a particular storm.            frequency storms were selected in order          development). This minimum control
                                                                verify that the performance of runoff            standard may be waived if the
              4.   An identified distribution or                control systems will generally parallel          municipality       determines     that    the
                    Lake E Slormwaler M nagemen[ L                                                                                    P   date














                   pattern of precipitation falling                                                              discharge will be made to Lake Erie or
                   during the storm.                            predevelopment conditions between the            a     properly        designed      regional
                                                                upper and lower control boundary                 stormwater control facility through
                                                                conditions.





        *2                                                             Lake Erie Stormwater Management Update

        adeq uately     designed      and     sized    detention techniques in order to meet          The application of the indicated release
        stormwater conveyance facilities.              the basic runoff control standard.        In   rate percentages will serve to prevent
                                                       these areas, the post development peak         stormwater      control    efforts     from
        The hydrologic analysis identified             rate of discharge is limited to either         inadvertently creating worse problems
        areas in the watershed where adequate          70%, 80%. or 90% of the pre-                   further downstream. They will also
        protection      requires    that     further   development      peak    dischar ge    rate.   introduce a factor of safety into the
        limitations to the allowable peak rate         Areas of the watershed for which the           regional     slormwater       management
        of discharge are appropriate if the            use of these release rate percentages is       program.
        developer intends to use stormwater            recommended are illustrated below.
                                                     I                                              I

             Release Rate Percentage
                        70
                        80
                        90
                        100





                                                                                            -W






                                                   T
                                           Ah-







                                          Proposed Stormwater Runoff Control Sta                ndards Map


        Erie County Department of Planning
        Erie County Court House
        Erie, Pennsylvania 16501


























         PART 3: DRAFT COPIES OF SECTIONS 3 THROUGH 6 OF THE FINAL REPORT


              SECTION 3:   WATERSHED CHARACTERISTICS


              SECTION 4:   WATERSHED TECHNICAL ANALYSIS - MODELING


              SECTION 5:   DEVELOPMENT OF  WATERSHED TECHNICAL STANDARDS AND
                           CRITERIA


              SECTION 6:   STORMWATER MANAGEMENT TECHNIQUES











                                      LAKE ERIE AREA WATERSHED
                                  STORMWATER MANAGEMENT PLAN
                                                    SECTION III
                                     WATERSHED CHARACTERISTICS




              GENERAL DESCRIPTION

              The designated Lake Erie Area      watershed is   located  in Erie County    in northwestern
              Pennsylvania. The watershed spans the northern part of the county 39 miles east to west and
              extends between 2.5 and 12.7 miles in a north to south direction, encompassing a total area of
              approximately 360 square miles along the shore of Lake Erie. The watershed includes all of
              the land in Erie County that drains to Lake Erie, excluding the Conneaut Creek watershed
              that empties into Lake Erie at Conneaut, Ohio. Portions of the watershed lie outside of Erie
              County in the states of New York and Ohio. A general watershed map is presented as Plate


              P(LITICAL:FE: T:UMS.'"..-
                                                              ...........
                                                                ...... .........

              A total of 25   Pennsylvania municipalities are situated in whole or in     part within this
              watershed. These municipalities are listed in Table III-1.


                                                      Table III-1

                                               Watershed Municipalities



                                Conneaut Township             McKean Borough
                                Elk Creek Township            McKean Township
                                Erie City                     Milkreek Township
                                Fairview Borough              North East Borough
                                Fairview Township             North East Township
                                Franklin Township             Platea Borough
                                Girard Borough                Springfield Township
                                Girard Township               Summit Township
                                Greene Township               Venango Township
                                Greenfield Township           Washington Township
                                Harborcreek Township          Waterford Township
                                Lake City Borough             Wesleyville Borough
                                Lawrence Park Township










              Lake Erie SWMP
              4026-02

















































































              Lake Erie SWMP                                      111-2
              4026-02
















                                            .............
                                                    . .................
                                                  ..........M
                                                ..................
                                                                           .............
             .............                      .. .................


             TOPOGRAPHY


             The Lake Erie Area watershed lies within two physiographic provinces. The plain adjacent
             to Lake Erie is located in the Eastern Lake Section of the Central Lowland Province, while
             upland areas of the watershed are contained in the Glaciated Section of the Appalachian
             Plateaus Province. Each physiographic province and its respective section is separated from
             the other by an erosional scarp running from southwest to northeast through the County,
             approximately three to four miles inland from Lake Erie. The dominant topographic features
             of the watershed are the 47 miles of shoreline on Lake Erie and Presque Isle, which forms
             the bay and harbor for the City of Erie.



             Except for the relatively level western third of the watershed and the three to four mile wide
             lake plain, the remainder of the watershed is characterized by rolling hills. The watershed is
             split by numerous valleys formed by erosion and containing streams that empty into Lake
             Erie. Elevations range from the average Lake Erie elevation of 571 feet above mean sea
             level to 1,550 feet above mean sea level at the southern edge of the watershed in Greenfield
             Township.




             GEOLOGY




             The bedrock of the Lake Erie Area watershed was formed from sediments deposited on the
             floors of ancient seas. The sedimentary rock layers underlying the county are from 6,000 to
             7,500 feet thick. Shale of the Upper Devonian age underlies most of the soils, developing
             from layers of silt and clay alternating with thin strata of sandstone. Sandstone that was
             formed from 'sandy sediments caps some of the higher hills. With the exception of
             Pleistocene age sands at Presque Isle, rocks of the Pennsylvanian system are exposed in the
             Lake Erie Area watershed. The Cattarugus Formation of the Pennsylvanian system consists
             primarily of red, gray, and brown shale and sandstone. The Conneaut Group of the
             Cattarugus Formation includes alternating gray, brown, greenish, and purplish shales and
             siltstones.



             Erie County was covered by at least three different glaciers, the last glaciation occurring
             approximately 10,000 to 15,000 years ago. As the glaciers melted and receded, they left the





             Lake Erie SWMP                              111-3
             4026-02









              landscape covered, with debris or glacial till that was carried from the north by the ice. The
              glacial till consists of a mixture of former soils and some granite, limestone, quartzite, and
              sandstone. The till also contains various amounts of sandstone and acid shale bedrock that
              was ground into fine particles by the ice. This glacial material ranges in size from clay
              particles to boulders.


              SOILS


              Soils in the Lake Erie Area watershed can be divided into two broad groups based on
              as sociation with a specific parent material. These groups are soils formed in unconsolidated
              water sorted materials and soils formed in glacial till. The predominant soil associations in
              the Lake Erie Area Watershed include the following:



                              0 Conotton-Birdsall Association

                              * Wayland-Chenango-Braceville Association

                              0   Canadice-Caneadea Association

                              *   Erie-Langford Association

                              0   Sheffield-Platea Association

                              0   Venango-Cambridge Association


              In addition, soils can be further categorized by hydrologic groups which are determined by. a
              soil's infiltration rate.    Many factors influence infiltration rate,       including physical
              composition, chemical composition, dominant slope, and depth of soil profile. The Soil
              Conservation Service (S.C.S.) has defined groups of soils having similar hydrologic
              properties which directly influence the volume and rate of stormwater runoff.                These
              hydrologic soil groups are defined as follows.


                      Group A:    Soils having a high infiltration rate, even when thoroughly wetted,
                                  and consisting of deep, well to excessively drained sands or gravels.


                      Group B:    Soils having a moderate rate of infiltration when wetted and
                                  consisting chiefly of moderately deep to deep, moderately well to well
                                  drained soils with moderately fine to moderately coarse texture.







              Lake ae SWMP                                 111-4
              4026-02









                     Group C: Soils having a slow rate of infiltration when thoroughly wetted,
                                 consisting chiefly of soils with a layer that impedes movement of
                                 water or soils with moderately fine to fine texture.


                     Group D:    Soils having a very slow rate of infiltration rate when 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.


              As the soil descriptions imply, runoff potentials increase from a minimum for Group A soils
              o a maximum for Group D soils. Soils along the lake plain were formed in unconsolidated
              water sorted materials.    These soils have substrata of sands, silts, and gravel and are
              t


              characterized by slow and very slow infiltration rates. Therefore, they fall in between the C
              and D hydrologic classes. Soils in upland areas in the central and northeastern portions of
              the watershed were primarily formed in glacial till. These somewhat poorly drained soils are
              in the C hydrologic class.



              For the purposes of classifying soil types for stormwater management, this investigation
              identified two additional classifications: water bodies and urban land.           Water bodies
              represent areas covered by water, a condition which results in direct runoff of precipitation.
              Urban land consists of land which is so altered by earth moving or so obscured by buildings
              or other structures that the original soils cannot be identified. In some places, cuts have
              removed all or nearly all the natural soil horizons. In other places, fills have buried the
              original soils.   Urban soils are generally assigned Group C hydrologic characteristic
              reflecting the characteristics of the predominant natural soils i ni the area.



              A map illustrating the distribution of soil groups throughout the watershed is provided in
              Plate IH-2. The distribution of soil groups throughout the watershed was determined based
              upon soil series information mapped on the S.C.S. soil survey for Erie County. The
              aggregation of individual soil series into appropriate hydrologic soils groups was performed
              using soil classification information from S.C.S. Technical Release 55.




              CLIMATE


              Climatic data are available from the Weather Bureau station at Erie.. The average annual
              temperature is about 47 degrees Fahrenheit. The mean annual freeze-free period is about




              Lake Erie SWMP                              111-5
              4026-02






             195 days, being extended by about 45' days per year by the moderating effect that the lake
             waters exert on the temperature. The summer mean temperature is about 67 degrees
             Fahrenheit and the winter mean is about 27 degrees Fahrenheit.




             PRECIPITATION


             Long term precipitation data is available from the Erie airport weather station. Normal
             annual precipitation at this station totals 39.39 inches and is well distributed throughout the
             year. Maximum precipitation occurs during the month of September (3.89 inches) while the
             minimum month in terms of precipitation is February (2.12 inches). The annual snowfall in
             the winter months exceeds 54 inches, with heavy snow sometimes experienced in late April.
             Snow is produced as polar air masses travel south over unfrozen lake waters. The air masses
             absorb considerable amounts of moisture in these lower levels as they move over the Great
             Lakes. As the warm, moistened lower air parcels reach land and rise through the cold air
             above, heavy snow squalls are produced that are capable of depositing 12 to 24 inches of
             snow on the leeward side of the lake. Lake Erie is subject to this "lake effect" snowfall
             during November and December. As the         lake surface freezes over, snowfalls of this type
             become less frequent.




             HYDROLOGY


             The portion of the watershed covered by this plan consists of approximately -- square
             miles of Erie County that drains to Lake Erie, excluding the Conneaut Creek watershed that
             empties into Lake Erie at Conneaut, Ohio. The designated Lake Erie Area watershed is
             actually a number of individual watersheds that drain into Lake Erie. The watershed also
             includes areas which drain directly into the lake without well defined stream channels. The
             major named streams and tributaries included in the Lake Erie Area watershed are listed in
             Table EII-2.




                 U. S. Geological Survey Stream Gauging Stations

                 The United States Geological Survey (U.S.G.S.) publication Water Resources Data
                 for Pennsylvania indicates that two long term, currently operating stream gauging
                 stations are located in the Lake Erie Area watershed. The first station is located on
                 Raccoon Creek near West Springfield on the upstream side of a highway bridge on
                 Sanford Road. The second gauge is on Brandy Run near Girard, 100 feet upstream
                 from a highway bridge on Tannery Road. The Raccoon Creek station has been in



             Lake Erie SWMP                              111-6
             4026-02









                 operation since October 1968 while the period of record for the Brandy Creek gauge
                                                                                                   I
                 dates back to May 1986. The U.S.G.S. also operates a crest gauge partial record
                 station on Mill Creek at the 38th Street Bridge.





                                                       Table 111-2

                                                     Named Streams




                                  Cascade Creek                Mill Creek
                                  Crooked Creek                Raccoon Creek
                                  Eightmile Creek              Sevenmile Creek
                                     Scott Run                    Elliots Run
                                  Elk Creek                    Sixmile Creek
                                     Brandy Run                Sixteenmile Creek
                                     Falk Run .                   Baker Creek
                                     Goodman Run               Trout Run
                                     Halls Run                 Turkey Creek
                                     Lamson Run                Twelvemile Creek
                                     Little Elk Creek          Twentymile Creek
                                     Porter Run                Walnut Creek
                                  Fourmile Creek                  Bear Run
                                  Garrison Run                    Beaver Run
                                  Marshall Run                 Wilkins Run
                                  McDannel Run





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

              .... .. . .. ........ ...
                                                                                 ..... OEM

              Delineated Flood Prone Areas


              Stream reaches which are identified as prone to flooding under 100 year flood conditions in
              Flood Insurance Studies published by the U.S. Department of Housing and Urban
              Development are illustrated on Plate 111-3 (located in the map pocket appended to this
              report).


              Reported St6rmwater Problem Areas

              The delineated flood prone areas established by flood insurance studies relate    primarily to
              stream flooding during major storm events. As such they do not provide information
              concerning more minor flooding problems or stormwater problems separate from stream
              flooding such as street flooding, soil erosion or stormwater pollution instances.




              Lake Erie SWMP                             111-7
              4026-02











              Each of the municipalities in the watershed was contacted to solicit information relative to
              stormwater conditions which are perceived locally to be problems. In many cases, these
              problems may be somewhat localized, and related to local drainage limitations apart from
              stream flooding and may occur at a high frequency. Also, information relative to stormwater
              problems   in addition to flooding (i.e., accelerated erosion, sedimentation and water
              pollution) was requested.



              Data obtained through these efforts were supplemented by a review of Flood Insurance
              Studies conducted in the watershed to produce the listing of identified stormwater problem
              areas that is presented in Table 111-3 and illustrated on Plate 111-3 (located in the map pocket
              appended to this report). A total of 109 specific problem areas were reported in 15 of the
              municipalities in the watershed.



              The predominant type of stormwater related problem reported by the municipalities is
              flooding. Over 70% of the individual problems were reported as flooding problems and
              additional approximately 20% of the problems were described as a combination of flooding
              accompanied by stream bank erosion and sedimentation. The remaining approximately 10%
              of the reported problems were attributed specifically to soil erosion and sedimentation.



              Suggested solutions were offered for 70 of the reported problem areas. The suggested
              solutions include structural approaches such as constructing new or increasing the capacity of
              existing storm sewers, increasing the capacity of culverts, and constructing stormwater
              detention facilities. Also included are such remedial actions as stream dredging for the
              removal of accumulated silt, the clearing of debris from trash racks, culvert and bridge
              openings and the removal of obstructions from the stream bed. Improvements to the existing
              storm sewer systems are the predominant types of solutions identified (51% of the cases).
              Efforts to clea@ the stream channel are offered as a solution to existing problems is roughly
              29% of the cases. Providing erosion protection,       increasing stream channel capacity, and
              employing runoff detention basins are identified as potential solutions to a much lesser
              extent. All of the suggested solutions offered restore or increase hydraulic capacities. It is
              important to note that the ultimate success of any of these efforts will require that the
              incremental increases in hydraulic capacity not be offset by future increases in stormwater
              runoff. The nature of the problems c   urrently encountered in the watershed and the types of
              solutions increase the importance of effective stormwater management in the watershed.







              Lake Erie SWMP                              111-8
              4026-02


















                                                                                                                                                                    Table 111-3
                                                                                                                                           Summary of Reported Stormwater Problems




                                                                                                                                                                                                                           Number of             Types of
                                        Map                                                                                                                                                                                Properties            Properties
                                        Code                Municipality                        Description               Stream/Location                       Reported Causes                       Frequency             Affected              Affected                        Pioposed Solutions


                                     PA            Conneaut Township                  No response


                                     PH-1          Elk Creek Township                 Hooding                           Little Elk Creek            Sedimentation                                         n/a                   n/a                  A, R            Stream dredging


                                     PC- I         Eric City                          Flooding                          Mill Creek                  Volume                                            > I per year              2- 10                R, C            -.n/a
                                     PC-2          Erie City                          Flooding                          Cascade Creek               Volume, illegal sanitary connections              < I per year              > 10                 R               Remove illegal connections
                                                                                                                         sanitary sewers
                                     PC-3          Eric City                          Flooding                          Cascade Creek               Volume, illegal sanitary connections              < I per year              2- 10                R               Remove illegal connections,
                                                                                                                         sanitary sewers                                                                                                                             --clean-sewer-_
                                     PCA           Erie City                          Flooding                          Cascade Creek               Volume                                            < I per year              2- 10                R               Charge grade, increase pipe
                                                                                                                                                                                                                                                                     size, remove illegal connections
                                     PC_5          Eric City                          Flooding                          Mill Creek                  Volume                                            > I per year                  I                C               Separate sewers
                                                                                                                         combined sewers
                                     PC-6          Erie City                          Flooding                          Unnamed                     Volume, velocity                                  < I per year              n/a                  n/a
                                     PC-7          Eric City                          Flooding                          McDanncl Run                Volume                                            < I per year              2-10         .-----R                 Clean Mouth, upsize pipe


                                     PD- I         Fairview Borough                   Flooding, sedimentation           Trout Ran                   Volume, obstmetion                                > I per year         -2-10                     A, I            _n/a
                                     PD-2          Fairview Borough                   Erosion                           Trout Run                   n1a                                                    n/a                  >-10-                R, C
                                     PD-3          Fairview Borough                   Flooding, erosion, _              Trout Run                   Volume, velocity                                  > I per year              2- 10       _U, R                    _n/a
                                     PDA           Fairview Borough                   flooding, erosion,                Trout Run                   Volume, velocity, obstruction,                    > I per year              2-10                 U, C            n/a
                                                                                      sedimentation, landslide                                      direction
                                     PD-5          Fairview Borough                   Flooding                          Trout Run                   Volume                                            > I per year              > 10                 R, C            n/.
                                     PD-6          Fairview Borough                   Erosion, landslide                Trout Run                   Volume, velocity                                  > I per year                                   _U              n/a


                                     PE- I         Fairview Township                  Flooding                          Bear Run                    Obstruction                                       > I per year              2- 10             U. A. R            Remove debris and beaver dams
                                                                                                                                                                                                                                                                     and.realign channel-
                                     PE-2          Fairview Township                  Flooding                          Unnamed                     Volume, direction                                 > I per year              2- 10                R, I            Increase storm sewer sizes, use

                                                                                                                                                                                                                                                                         .vate lake as retention brasin
                                                   Fairview Township                  Erosion                           Trout Run                   Volume, veloci                                                              2-10                 U, R            Install Velocity dissipators
                                     PE-3                                                                               Trout Run                   Volume, directi                                   < I per year              2-10
                                                                                                                                                                                                      < I per year
                                     PEA           Fairview Township                  Flooding, erosion                                                                on                                                                            U, R            Install storm sewer---


















                                                                                                                                                                    Table 111-3
                                                                                                                                          Summary of Reported Stormwater Problems




                                                                                                                                                                                                                           Number of             Types of'
                                        Map                                                                                                                                                                                Properties           Properties
                                        Code                Municipality                      Description                 SLreani/Location                      Re tied Causes                        Frequency             Affected             Affected                         Proposed Solutions
                                     PE-5          Fairview Township                 Erosion                           Unnamed                       Velocity, direction                              > I per year               2- 10               R               Install storm sewer
                                     PE-6          Fairview Township                 Flooding                          Unnamed                       Obstruction                                      > I per year               2- 10               R               Increase storm sewer sizc---
                                     PE-7          Fairview Township                 Flooding                          Unnamed                       Volume                                           > I per year               2-10       _R__                     In-stall storm sewers & catch basins_
                                     PE-8          Fairview Township                 Flooding, erosion                 Walnut Creek                  Volume, obstruction                              > I per year               > 10                R               Increase storm Sewer SiLC & install
                                                                                                                                                                                                                                                                     catch basins
                                     PE-9- Fairview Township                         Flooding, erosion                 Walnut Creek                  Volume, velocity                                 > I Per Year               > 10                R               Install stinin sewers & catch basins
                                     PE-10         FairvicwTownship                  Flooding                          Walnut Creek                  Volume, direction, obstruction                   > I per year               2-10                U, R            Remove debris and realign channel
                                     PE-11         Fairview Township                 Erosion                           Porter Run                    Volume, direction                                > I per year               2-10                U               Install velocity dissipalor. lengthen
                                                                                                                                                                                                                                                                     culvert, realign channel
                                     PE-12         Fairview Township                 Erosion                           Elk Creek                     Volume, direction                                > I per year               2-10                U, A            Install velocity dissipator
                                     PE- 13        Fairview Township                 Erosion                           Brandy Run                    Volume, velocity, direction                      > I per year               R/U                 R               Install velocity dissipator, lengthen
                                                                                                                                                                                                                                                                     culvert
                                     PE-14 -       Fairview Township                 Flooding                          Trout Run                     Obstruction                                      > I per year               I-         -Road flooding           Remove debris, install debrisgratc
                                     PE-15         Fairview Township                _floodir% erosion                  Unnamed                       Direction                                        > I per year               2-10                R               Install culvert


                                     PF- I         Franklin Township                 Flooding                          Little Elk Creek              Volume, obstructions                             < I per year               n/a                 n/a-            n/a


                                     PG-.I----     Gi.rard Borough                   No response


                                     PH- I         Girard Township                   Flooding                          Unnamed                       Volume, velocity                                 > I per year               I                   R               Storm sewer construction (completed)


                                     PI            Greene Township                   None reported


                                     Pi-           Greenfield Township               No response


                                     PK- I         tlarborcreck Township             Flooding                          Fourritile Creek              Lack of maintenance of drainage way              > I per year               2-10                U, R            Improved maintenance
                                     PK-2          Harborcreck Township              Flooding                          Unnamed                       Volume                                           > I per year               > 10                R               n/a
                                     PK-3          Harborcreek Township              Flooding, erosion                 Unnamed                       Volume, obstruction                              < I per year               > 10                R               Improved maintenance
                                     PK_4          Harborcreck Township              Flooding                          sixmile Creek                 Obstruction                                      < I per year               2-10                R               Improved maintenance
                                     PK-5          Harborcreck Township           -  Hooding                           Unnamed                       Volume, ohs - cdon                               > I per year               > 10                R               n/a
                                     PK-6          Hai                               Flooding                          Sixmile Creek                 Obstruction                                      < I per year               2-10        _R                      n/a



                                                   M M410                                                                                                                                                            M                                         M M=                                                                            M                                        M








                                                                                                                                                                                       Table 111-3
                                                                                                                                                          Summary of Reported Stormwater Problems




                                                                                                                                                                                                                                                    Number of                Types of
                                              Map                                                                                                                                                                                                    Properties              Properties
                                          -Code-                   Muni'll'ality                         Description                     Stream/Location                           Reported Causes                           Frequency                Affected               Affected                             Proposed Solutions
                                          PK-7 -          _11arborcreek Township                Flooding                              Sixmile/Sevennaile              Volume                                                 > I Per year                   > 10                  R_                Impioved maintenance
                                          PK-8            Harborcreek Township                  Flooding                              Unnamed                         Lack of maintenance of drainage way                    > I per year                   > 10                  U. R              Improved maintenance
                                          PK-9            Harborcreck Township                  Flooding                              Sevenmile Creek                 Volume                                                 > I per year                   > 10                  U, R              Improved maintenance


                                          PLA             Lake City Borough                     Erosion                               Unnamed                         Direction                                                   n/a                       I                     n/a             -,n/a-
                                          PL-2            Lake City Borough                     Erosion, landslide                    Elk Creek                       Volume, direction                                           n/a                       I                     n/a               n1a
                                          _PL-3           -Lake City Borough                    Hooding                               Elk Creek                       Volume                                                      n/a                       >10                   n/a               n/a
                                          PL-4            Lake City Borough                     n1a                                  unnamed                          n/a                                                         n/a                       n/a                   n/a               n/a
                                          PL-5            Lake City Borough                     n/a                                   Unnamed                         n/a                                                         n/a                       n/a                   n/a             __n/a
                                          PL-6            LAke City Borough                     Wa                                    Unnamd.                         tu'a.                                                       n1a.                      Pja                   ul'a              Pja
                                          PL-7            Lake City Borough                     n/a                                   Unnamed                         n/a                                                         n/a                       n/a                   n/a             _n/a
                                          PL-8            Lake City Borough                     Flooding                              Unnamed                         Volume                                                      n/a                       2-10                  n/a               n/a
                                          PL-9__          -U, kc City-Bo-rough                  n/a                                   Unnamed                         n1a                                                n/a                                > 10-                                   n/a
                                          PIAO            Lake City Borough                     n/a                                   Elk Creek                       volume                                                      n/a                       I                     D/a               n/a
                                          PI.- I I        Lake City Borough                     Flooding                              Elk Creek                       Volume                                                      n/a                       > 10
                                          PL-12           Lake City Borough                     Flooding. pollution                   Elk Creek                       Volume                                                      n/a                       > 10                  n/a             _n/a


                                          Pm4             Lawrence Pui k Township               Flootling                             Four Mile Creek                 Obstruction                                            < I per year                   > 10                  R, C              Keep sucains clear oftleluis, eliminate
                                                                                                                                                                                                                                                                                                    multiple bridge piers
                                          PM-2            Lawrence Park Township                Flooding                              Four Mile Creek                 Obstruction                                            < I per year                   I                     C                 Keep streams clear of debris, eliminate
                                                                                                                                                                                                                                                                                                    multiple bridge piers


                                          PN              McKean Borough                        None reported


                                          PO_ I           McKean Township                       Flooding                              Elk Creek                       Volume, obstruction.                                   < I per year                   2- 10            U, R. C. I             n/a
                                          .PO-2           McKean Township                       Flooding, erosion                     Elk Creek                       Volume, velocity                                       < I per year                   2-10       R, C, I                      n/a
                                          PO-3            -McKean Township                      Flooding                              ElkCreek                        Volume                                                 < I per year                   2-10           U, A. R, C. I          _A/a
                                          POA             McKean Township                       Flooding                              Elk Creek                       Volume                                                 < I per year                   2-10                  A. R              n/a


                                          PP_ I           Millcreck Township                    Flooding                              Mill Creek                      Volume, velocity                                       < I per year                   I            _R,C                       n1a
                                          PP-2            Millcreck Township                    Flooding                              Mill Creek                   I  Volume                                                                     -1-2-10              1      Roadway                Enlargeculvert


















                                                                                                                                                                                   Table 111-3
                                                                                                                                                       Summary of Reported Stormwater Problems




                                                                                                                                                                                                                                               Numberof                Types of
                                            Map                                                                                                                                                                                                 Properties             Properties
                                            Code                 Municipality                          Description                    Stream/Location                          Reported Causes                           Frequency               Affected              Affected                            Proposed Solutions
                                         PP-3           Millcreck Township                    Flooding                             Mill Creek                     Volume                                                 < I per year              2- 10                  R,C                Revamp @totin sewer syst -tit
                                         PP-4           Millcreck Township                    Flooding                             Mill Creek                     Volume                                                 < I per year              2- 10                    R                Install levees
                                         PP-5           Millcreck Township                    Flooding                             Mill Creek                     Volume                                                 < I per year              2- 10                    R                Enlarge Storm Sewers
                                         PP-6           Millcreek Township                    Flooding                             Mill Creek                     Volume, obstruction                                    < I per year                  I                    R                Clear channel
                                         PP-7           Millcreck Township                    Flooding                             Walnut Creek                   Volume                                                 < I per year              2- 10                    R                Revamp storm sewersystem
                                         PP-8           Millcreek Township-                   Flooding                             Walnut Creek                   Volume, obstruction                                    > I per year              > 10                     It             Install detention facility
                                         PP-9           Millcreck Township                    Flooding                             Walnut Creek                   Volume. obstruction                                    < I per year              2-10                     R                Revamp storm sewer system
                                         PP-10-       -Millcreck Township                     Flooding                             Walnut Creek                   Volume                                                 < I per year                  I                    C                Reroute stor.m sewer
                                         PP- I I        Millcreek Township                    Flooding                             Walnut Creek                   Volume                                                 < I per year              2-10                   R_,.C             -Dredge Beaver Run
                                         PP- 12         Millcrcek Township                    Flooding                             Walnut Creek                   Volume                                                 < I per year              2- 10                  R, P               Stormwater detention, revamp storm

                                                                                                                                                                                                                                                                                               sewers
                                         PP- 13         Millereek Township                    Flooding, erosion,                   Scott Run                      Volume, velocity, driection,                           < I per year              2- 10                  U. C               Improve stream channel or install storm
                                                                                               Landslide                                                            obstruction
                                                                                                                                                                                                                                                                                             sewers-
                                         PP-. 14        Millcreck Township                    Flooding                             Cascade Creek                  Volume, obstruction                                    < I per year              > 10                     R                Revamp channel and son in sewer
                                         PP-15          Millcreek Township                    Flooding                             Cascade Creek                  Volume, obstruction                                    < I per year              2- 10                    C                Enlarge box culvert
                                         PP- 16         Millcreck Township                    Flooding                             Cascade Creek                  Volume, obstruction                                    < I per year              2- 10                    C                Enlarge storm sewer
                                         P P- 17        Millcreek Township                    Flooding                             Cascade Creek                  Volume, obstruction                                    > I per year              2- 10                  R, C               Install storm sewer & add downstream
                                                                                                                                                                                                                                                                                             capacity
                                         PP- 18         Millcreck Township                    Flooding, sedimentation              Cascade Creek                  Volume, obstruction                                    > I per year              2-  10                   C                Clear channel
                                         PP-19 -Millcreck Township                            Flooding                             Cascade Creek                  Volume. obstruction                               __?@ I  per year               2-  10                   C                Clcarchannel-
                                         PP-20 __       Milicreek.Township---                 Flooding                             Cascade Creek                  Volume                                                 < Iper year               2-  10                   R                Install storm sewer system
                                         PP-.21        -Millcreek Township                    Erosion, landslide                   Cascade Creek                  Volume, velocity                                       > Iper year               2-  10                 R.. P              Siabilize slopes and channel
                                         PP-22          Millcreek Township                    Flooding                             Cascade Creek                  Volume, obstruction                                    > I per year              2-  10                   R                Add detention capabilities and clear
                                                                                                                                                                                                                                                                                             obstructions from culvert
                                         PP-23        -Millcrcek Township                     Flooding                             Marshall Run                   Volume, obstruction                                    < I per year              2-10                     R                Provide detention & revamp storm sewer
                                         PP-24          Millereek Township                    Flooding, erosion,                   Unnamed                        Volume, velocity, obstruction                          > I per year              2- 10                    R                Clear basin and outlet
                                                                                              sedimentation
                                         PP-25          Millcreek Township                    Flooding, sedimentation              Marshall Run                   Volume, obstruction                                    > I per year              2- 10           _R                        Revamp channel
                                         PP-26          Millcreek Township                    Flooding                             Marshall Run                   Volume, obstruction                                    > I per y -               2- 10                    R                Install storm sewer system
                                         PP-27          Millcreek Township                    Flooding                             Marshall Run                   Volume, obstruction                                    > I per year                  - 10                 C                Provide detention       facilities
                                         PP-28          Millcreek Township                    Flooding                             Marshall Run                   Volume, obstruction                                    > I per year       I      > 10                   R, C               Revamp storm sewer system or provide


















                                                                                                                                                                        Table 111-3
                                                                                                                                             Summary of Reported Stormwater Problems




                                                                                                                                                                                                                                Number of             Types of
                                          Map                                                                                                                                                                                   Properties            Properties
                                          Code                Municipality                      Description                   Stream/Location                       Reported Causes                        Frequency             Affected             Affected                          Proposed Solutions
                                                                                                                                                                                                                                                                            detention
                                       PP-29         Millcreek Township                 Flooding                           Marshall Run                 Volume, velocity                                   > I per year            2- 10                   C, I             Revamp storm sewer system or provide
                                                                                                                                                                                                                                                                            detention
                                       PP-30         Millcreek Township                 Erosion, sedimentation             Marshall Run                 Sedimentation                                      > I per year                 I                  R_               Clear basin and outlet structure--
                                       PP-31         Millcreck Township                 Flooding                           Marshall Run                 Volume, obstruction                                > I per year            2- 10                   R                Revamp storm sewers
                                       PP-32         Milicreek Township                 Flooding                           Marshall Run                 Volume, velocity, obstruction                      > I per year                 n/a           Roadway               Increase sic
                                                                                                                                                                                                                                                                                        Win sewer capacity
                                       PP-33       -Millcreek Township                  Flooding                           Marshall Run                 Volume, obstruction                                > I per year            2- 10                   R                Divert stormwater, install storm sewer
                                       PP-34         Millcreek Township                 Flooding, erosion                  Marshall Run                 Volume, velocity, obstruction                      > I per year            2- 10                   C                Install debris deflector, extend storm

                                                                                                                                                                                                                                                                            sewer
                                       PP-35         Millcreck Township                 Erosion                            Unnamcd                      Velocity                                           > I per year                 I                  R
                                       PP-36         Millcreck Township                 Flooding                           Wilkins Run                  Volume, obstruction                                > I per year-           2-   10                 C                Provide drainage
                                       PP-37-        Millcreek Township                 Flooding,                          Wilkins Run                  Volume, obstruction                                < I per year            2-   10                 C
                                       PP-38         Millcreck Township                 Erosion                            Unnamed                      Volume, velocity                                   > I *pcr year           2-   10                 R                Install storm sewers, stabilize banks
                                       PP-39         Millcreck Township                 Flooding                           Unnamed                      Volume                                             < I per year            2-   10                 R. C             Revamp storm sewers, install channel
                                       PP-40         Millcreek Township                 Flooding                           Unnamed                      Volume                                             < I per year            2- 10                   R. C             Revamp storm sewers, install channel
                                       PP-4 I.       Millcreck Township                 Flooding                           Unnamed                      Volume, obstruction                                < I per year            2- 10                                    Revamp storm sewers


                                       PQ            North East Borough                 None reported


                                       PR- I         N        EastTownship              Flooding                           Sixteen Mile Creek           n/a                                                    ft/a                     n/a                n/a              n/a
                                       PR-2          North East Township                Flo6ding                           Sixteen Mile Creek           Volume                                                 n/a                      n/a                n/a              n/a
                                       PR-3          North East Township                Flooding                           Sixteen Mile Creek           Volume                                                 n/a                      n/a                n/a              n/a
                                       PR-4          North East Township                Flooding, erosion                  Sixteen Mile Creek           Volume, obstruction                                    n/a                      n/a                n/a              _n/a
                                       PR-5          North East Township                Flooding, erosion                  Sixteen Mile Creek           Volume, obstruction                                    n/a                      ft/a               n/a              Improve driveway sluice pipes
                                       .PR-6         North East Township                Sedimentation                      Sixteen Mile Creek           Volume, direction                                  < I per year            2- 10                   A,R,C            -Divert flow------


                                       PS            Platea Borough                     None reported


                                       FT            Springfield Township               No response


                                       PU I          SummitTownship                     Flooding                           Walnut Creek                 Volume                                             > I per year            2- 10                   R,C              n/a


















                                                                                                                                                       Table 111-3
                                                                                                                               Summary of Reported Stormwater Problems




                                                                                                                                                                                                         Number of           Types of
                                      Map                                                                                                                                                                Properties          Properties
                                      Code             Municipality                   Description                Stream/Location                   Reported Causes                    Frequency           Affected            Affected                      Proposed Solutions


                                  Pv           VenangoTownship                None reported


                                  Pw           Washington TownsNp             None reported


                                  PX           Waterford Township             No response


                                  Py- I        Wesleyville Borough            Flooding                        Fourmile Creek            Volume, velocity                              > I per year           n/a         -n/a                   ftha
                                               Westeyville Borough            Flooding                        Fournaile Creek           Volume, velocity                              > I per year           n/a                 n/a            nh
                                  PY-3         Wesleyville Borough            Flooding                        Fourmile Cfeek             Volume, velocity                             > I per year           n/a                 n/a            n/a



                                             Types of Properties Affected:


                                               A       agricultural
                                               C      commercial
                                               I = industrial
                                               R = residential
                                               U = undeveloped










             Development in Flood Hazard Areas

             Stream reaches identified as being prone to flooding under 100 year storm conditio       ns in
             Flood Insurance Studies are identified previously in Plate 111-3. Development in the areas
             adjacent to these flood prone areas were characterized by analyzing the current land use
             within 100 feet of the identified flood prone stream reaches. This was accomplished by
             calculating the amounts land occupied by various land use classes that lie within the areas
             within 100 feet of each side of the identified stream reaches. This technique produced the
             approximate distribution of land use activities that lie in proximity to stream reaches
             identified as flood hazard areas in the Flood Insurance Studies.         This information is
             summarized in Table 111-4.



             Information obtained from the watershed municipalities through the municipal questionnaire
             also provides an indication of the nature of development in areas affected by stormwater
             drainage problems.     The municipalities were asked to indicate the types of properties
             affected by reported stormwater drainage problems and to estimated the approximate number
             of properties affected. Residential properties were identified as being affected by 76% of the
             problems for which the data was reported. Commercial properties were associated with 33%
             of the problems, agricultural or undeveloped in 20% of the cases, and industrial in 7% of the
             cases. Approximately 80% of the problems were reported to affect 10 or fewer properties
             and 20% were reported to affect more than 10 properties.



                                                      Table 1111-4

                                   Distribution of Land Use in Flood Prone Areas




                                                                     Percent of Total Area
                                 Land Use Classification            Adjacent to Flood Prone
                                                                        Stream Reaches


                          Residential

                          Commercial / Industrial

                          Mixed Residential    Commercial

                          Agriculture

                          Forest


                          Barren






             Lake Erie SWMP                            1111-15
             4026-02





















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

                    Stream     obstructions are defined as structures                    or assembly of materials which may impede,
                    retard or change flood flows. Typical obstructions include bridge crossings, culverts, piers,
                    suspended pipelines, etc..                  Information describing the dimensions, condition and flow
                    capacity of approximately ????????? separate stream obstructions was assembled during the
                    preparation of this plan. The approximate locations of these obstructions are illustrated in
                    Plate 111-4 (located in the map pocket appended to this report). The prior 1981 Stormwater
                    Management Plan served as the primary source of information describing the size and
                    configuration of obstructions. This information was supplemented by field investigations
                    and site visits to 77 obstruction locations.



                    The capacities of the obstructions were estimated based upon field measurements and the
                    application of procedures outlined in the U. S. Department of Transportation's publication
                    Hydraulic Design of Highway Culverts. The estimated capacities represent submerged but
                    not surcharged conditions with inlet control. Calculated obstruction capacities are presented
                    in Table A-1, located in Appendix A. Capacities are presented in terms of adequacy as
                    compared to estimated flood peaks at each location for various flood return frequencies. The
                    flood peaks were estimated using the PSU IV Method for                                          estimating flood peaks in
                    ungauged Pennsylvania streams.




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


                    Existing and Proposed Flood Protection Facilities

                    The eleven existing and thirteen proposed existing flood protection facilities reported in the
                    watershed are listed in Table 111-5.                        The approximate locations of these facilities are
                    illustrated in Plate 111-5 (located in the map pocket accompanying this report). There are no
                    regional flood control projects within the study area. The existing flood protection facilities
                    are designed to provide localized                 flood protection and include stream channelization, stream
                    bank protection, storm sewers and debris racks. The proposed facilities would also address
                    localized flooding problems and include stream channel improvements, stream bank
                    protection, and debris rack construction.









                    Lake Erie SWMP                                               111-16
                    4026-02




















                                                                                                         Table M-5
                                                                                            Reported Flood Control Projects


                                            Map                                                                  Year
                                            Code        Tvpe of Flood Control Project           Status           Built                 Owner                       Reported Bv

                                      FC- I          Millcreek Tube stream pipe               Existing           1919         Erie City                  Erie City
                                                     channel

                                      FC-2           Garrison Run Tube stream pipe           -ffx@tsting   -     1919         Erie City                  Eric City
                                                     channel


                                      FC-3           Drift catcher (debris catch er)                        Before 1915       Erie City                  Erie Citv

                                      FC-4           Pipe (36")                               Existing           1991         Erie City                  Erie City

                                      FC-5           Storm sewer                              Existing           1991         Erie City                  Erie City

                                      FC-6           Storm sewer                              Existing           1991         Erie City                  Erie City

                                      FC-7           Storm sewer                              Proposed           1993         Erie City                  Erie City

                                      FC-8           Pipe channel                             Proposed           n/a          n/a                        Fairview Borough

                                      FC-9           Pipe channel                             Proposed           1994         Fairview Twp.              Fairview Township

                                      FC-10          Pipe channel                             Proposed           1993         Fairview Twp.              Fairview Township

                                      FC-1 I         Channel realignment                      Proposed           1993         Private                    Fairview Township

                                      FC- 12         Channel realignment                      Proposed           1993         Private                    Fairview Township

                                      FC-13          Pipe channel                             Proposed           1994         Fairview Twp.              Fairview Township

                                      FC-14          Pipe channel                             Proposed           1994         Fairview Twp.              Fairview Township

                                      FC- 15         Gabions                                  Proposed           1994         Private                    Fairview Township

                                      FC-16          Pipe channel                             Proposed           1995         Fairview Twp.              Fairview Township

                                      FC-17          Pipe channeftation, riprap               Existing           1992         Private                    Fairview Township

                                      FC-18          Channel excavation, riprap               Existing           1992         Private                    Fairview Township

                                      FC-19          Creek stabilization                      Proposed           n/a          Lake City Borough          Lake City Borough

                                      FC-20          Flood walls                              Existing       1940-1950        n/a                        Lawren  cc Park Township

                                      FC-21          Debris rack                              Proposed           n/a          Lawrence Park Tw           Lawrence Park Township

                                      FC-22          Channel excavation     widening          Proposed           1996         MiUcreek Township          MWcreek Township

                                      FC-23          Retaining wall                           Existing           1956         Penn DOT _                 Wesleyville, Borough

                                      FC-24          Bank Protection                          Existing           1959         Wesleyville Borough        PA DER















                                               .. .... .. ......
                                                . ............... .... . .
                                                                   ........ .. ........
                               @Sys


             Existing and Future Storm Sewer Systems


             The approximate locations of areas served by storm and combined sewer systems are
             illustrated on Plate 111-5. @ As one would expect, the areas served by piped stormwater
             collection systems largely correspond to the most densely developed areas of in the
             watershed.



             The construction of storm sewers has been identified in the municipal questionnaires as a
             suggested solution to stormwater drainage problems in Fairview Township, and Millcreek
             Township. While some storm sewer construction can be expected to occur in these and other
             currently developed areas in order to address localized stormwater drainage problems, most
             of the future storm sewer construction will occur as new areas of the watershed are
             developed. Therefore, future storm sewer system construction will occur as residential and
             commercial development progresses. The locations of such future storm sewer systems will
             correspond to the locations of future residential and commercial development.



             Financing Storm Sewer Construction

             Under current practice, storm sewer construction in currently developed areas is generally
             financed by the municipality in which the construction occurs. Usually, storm sewer
             construction in newly developing areas is financed privately by the land developer.



             Amendments to the Pennsylvania Infrastructure Investment Authority (PENNVEST) make
             -certain municipalities eligible to receive financial assistance from PENNVEST to construct
             stormwater management improvements. Eligible municipalities are those which are located
             within watersheds for which stormwater management plans have been approved by the
             Pennsylvania Department of Environmental Reso        'urces and which have enacted, or will
             enact, stormwater ordinances consistent with the approved plans. Examples of eligible
             stormwater projects include construction of detention / retention basins, upgrades of existing
             storm sewer systems and the installation of new storm sewer systems.



             Municipalities considering the construction of such facilities should investigate the potential
             for the receipt of funding assistance through the PENNVEST program.






             Lake Erie SWMP                             111-18
             4026-02
















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


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


                  Existing and Future Stormwater Control Facilities

                  The survey of Lake Erie Area watershed municipalities conducted during the preparation of
                  this plan requested information relative. to current and planned storinwater control facilities.
                  Reported stormwater control facilities are listed in Table 111-6. The approximate locations of
                  these facilities are illustrated on Plate 111-5. A total of 3@ and 21 proposed stormwater
                  control facilities were reported. Nine municipalities reported either existing or proposed
                  stormwater control facilities. Over 90 percent of the facilities reported control stormwater
                  runoff by using detention / retention techniques.                         The majority of these facilities are
                  stormwater basins or ponds. However, the use of parking lot ponding storage techniques was
                  reported. Stormwater control through the use of facilities to induce ground water infiltration
                  was reported in several instances. The relatively widespread use of stormwater control
                  facilities is significant because it demonstrates that stormwater management requirements are
                  being enforced in the watershed and indicates                  that the use stormwater control             techniques is
                  not foreign to developers in the area.





                                                                                     .......                         ... . . .
                                                                                                             .. . .............
                                                                                                                . ............
                                                       ......... I I                                            . .............
                                                        ..............I ...............  .......                   . ............
                                                                                                                    ...............

                  Existing land use          land cover patterns        are   displayed on Plate HI-6           and the distribution of
                  land cover types in the Erie County portion of the watershed is summarized in Table HI-7.
                  This information was determined based upon the analysis of satellite imagery obtained.in
                  1993.

                                                                        Table IH-7

                                           Distribution of Existing Land Use in the Watershed

                                            Land Use Classification                       Percent of Watershed Area


                                   Residential

                                   Commercial / Industrial

                                   Mixed Residential          Commercial

                                   Agriculture

                                   Forest

                                   Barren







                  Lake Erie SWMP                                          111-19
                  4026-02




















                                                                                                               Table IH-6
                                                                                               Reported StorMW2ter Control Projects


                                               Map                       Type of                                        Year
                                               Code           Stormwater Control Project             Status             Built                  Comments                        Reported By

                                        SC-1             Retention basin                           -Ex-isting           1992         Existing storm system              Erie City
                                                                                                                                     overloaded
                                        SC-2             Retention basin                            Existing            1987                                            Erie City
                                        SC-3             Dry well                                   E ' ti              1993                                            Erie City
                                                                                                                        1987         New dev                            Erie City
                                                                                                                                     reduce flows to stream
                                        SC-4             Retention basin                           i=                                          elopment to

                                        SC-5             Dry well                                   Existing            n/a                                             Erie City
                                        SC-6             Dry well                                   Existing            n/a          Parking lot drai age               Erie City
                                        SC-7             Retention basin                            Proposed            1994                                            Erie City
                                        SC-8             Retention basin                            Existing            1992                                            Fairview Township
                                        SC-9             Infiltration device                        Proposed            1994         Perforated storm sewer             Fairview Township
                                        SC-10            Detention/retention pond                   Existing            1987         Mobile home park                   Girard Township
                                        SC-1 I           Detention basins                           Existing        1990-1992        Behrend   College                  Harborcreek Township
                                        SC-12            Detention basin                            Existing            1992         Subdivision                        Harborcreek Township
                                        SC-13            Detention basin                            Existing            1987         Shopping plaza                     Harborcreek Township
                                        SC-14            Detention basin                            Existing            1993         Tire center                        Harborcreek Township
                                        SC-15            Infiltration basin                         Existing            1990         Garden center                      I-larborcreek Township
                                        SC-16            Detention basins                           Proposed            1997         Subdivision                        Harborcreek Township
                                        SC- 17           Detention basin                            Proposed            1994         Subdivision                        Harborcreek Township
                                        SC-18            Detention basin                            Proposed            1993         Commercial development             Harborcreek Township
                                        SC-19            Detention basin                            Proposed            n/a          Subdivision                        Lake City Borough
                                        SC-20            Detention basin                            Proposed            n1a          Subdivision                        Lake City Borough
                                        SC-21            Detention basin                            Proposed            n1a          Subdivision                        Lake City Borough
                                        SC-22            n/a                                        Proposed            n/a          Subdivision                        Lake City Borough
                                        SC-23            Detention basin                            Proposed            n/a          Subdivision                        Lake City Borough
                                        SC-24            Underground storage                        Existing            1989         Industrial                         Millcrrek Township
                                        SC-25            Detention basin (dry)                      Existing            1982         Subdivision                        Mfllcreck Township
                                        SC-26            Detention basin (dry)                      Existin             1993         Subdivision                        Millcreck Township
                                        SC-27            Detention basin (dry)                      Existing            1991         Sui;!-v-ision                      Millcreek Township
                                        SC-28            Detention basin (dry)                      Existing            1990         Subdivision                        Millcreek Township
                                        SC-29            Detention basin (dry)                      Existing            1992         Subdivision                        MfflcreckTownship
                                        SC-30            Detention basin (dry)                      Proposed            1995                                            Millcreek Township
                                        SC-31            Detention basin (dry)                      Proposed            1997                                            Millcreek Township
                                        SC-32            Detention basin (dry)                      Proposed            1997                                            Millcreek Township
                                        SC-33            Detention basin (dry)                      Proposed            1994                                            Millcreek Township
                                        SC-34            Detention basin (dry)                      Proposed            1995                                            Millcreek Township
                                        SC-35            Detention basin (dry)                      Proposed            1997                                            Millcreek Township
                                        SC-36            Detention basin                            Existing            1991         Subdivision                        North East Township
                                        SC-37            Detention basin                            Existing            1993.        School                             North East Township
                                        SC-39            Detention basin                            Existing            1990         School                             North East Township
                                        SC-39            Detention basin                            Existing            1993         Subdivision                        North East Township
                                        SC-40            Detention basin                            Existing            1992         Commercial                         North East Township
                                        SC-41            Detention basin                            Pro osed            1994         Subdivision                        North East Township
                                        SC-42            Detention basin                            Pro sed             1994         Subdivision                        North East Township
                                        SC-43            Detention basin                      ---   Proposed            1994         Subdivision                        North East Township
                                        SC-44            Detention basin                            Proposed            1994         Subdivision                        North East Township
                                        SC-45            Infiltration, Underground Tanks            Existing            1992         Commercial                         Summit Township
                                        SC-46            Detention basin                            Existing            1990         Commercial                         Summit Township
                                        SC-47            Detention basin                            Existing            199 1        Commercial                         Sununu Township
                                        SC48             Underground tanks                          Existing            1992         Commercial                         SurnmitTownship
                                        SC-49            Parking lot ponding                        Existing            1993         Commercial                         Summit Township
                                        SC-50            Detention basin                            Existing            1990         Commercial                         Summit Township
                                        SC-51            Detention basin                            Existing            1990         Church -                           Summit Township
                                        SC-52            Detention basin                            Existing            1993         Commercial                         Summit Township
                                        SC-53            Detention basin                            Existing            1992         Subdivision                        Summit Township
                                        SC-54            Underground     tanks                                          1993         Commercial                         Summit Township
                                        SC-55            Detention basin                            Existing            1992         Commercial                         SummitTownship
                                        SC-56            Detention, sedimentation ponds             Existing            1972         Landffll                           SummitTownship
                                        SC-57            Detention basin                            P posed             1994         Commercial                         Summit Township
                                        SC-58            Farm pond                                  Existing            1960                                            Venango Township
                                        SC-59            Pond                                       Existing            1980                                            Venango Township
                                        SC-60            Pond                                                           1986                                            Venango Township









                High density residential, commercial and industrial land use classes predominate in the
                northern areas of the watershed and in the areas immediately adjacent to the Lake Erie Area.
                The density of commercial and residential development generally decreases as one moves
                                                                                     0
                southward and away from the banks of the Lake Erie Area. In the upper reaches of the
                south-most portions of the watershed, open space and agricultural land uses predominate.



                Table 111-8 contains 1990 U.S. Census population densities for each of the municipalities in
                the watershed. The data presented therein is indicative of the wide variation in development
                density in the watershed.





                                                                Table 111-8

                                                  Municipality Population Densities



                                                            Population                                     Population
                                                               Density                                       Density
                                 Municipality           (persons / sq. mi.)       Municipality          (persons / sq. mi.)
                          Conneaut Township                    44.7           McKean Borough                  697.6
                          Elk Creek Township                   50.2           McKean Township                 123.0
                          Erie City                            4,941.7        Millcreek Township             1,587.1
                          Fairview Borough                     1,420.0        North East Borough             3,551.5
                          Fairview Township                    282.0          North East Township             148.2
                          Franklin Township                    49.6           Platea Borough                  141.5
                          Girard Borough                       1,199.6        Springfield Township            85.4
                          Girard Township                      149.0          Summit Township                 221.1
                          Greene Township                      132.2          Venango Township                51.3
                          Greenfield Township                  52.4           Washington Township             91.0
                          Harborcreek Township                 441.8          Waterford Township              67.9
                          Lake City Borough                    1,399.4        Wesleyville Borough            7,310.0
                          Lawrence Park Township               2,268.4




                Potential future land development patterns in the Erie County portion of the watershed were
                o"btained from-the Erie County Department of Planning. Projected future land use / land
                cover patterns are indicated on Plate RI-7.               Projected future land cover statistics are
                presented in Table IR-9.








                Lake Erie SWMP                                   111-21
                4026-02













                                                  Table 111-9

                               Distribution of Future Land Use in the Watershed




                               Land Use Classification        Percent of Watershed Area

                        Residential

                        Commercial / Industrial

                        Mixed Residential  Commercial

                        Agriculture

                        Forest


                        Barren










































            Lake Erie SWMP                         111-22
            4026-02











                                       LAKE ERIE AREA WATERSHED
                                   STORMWATER MANAGEMENT PLAN
                                                    SECTION IV
                          WATERSHED TECHNICAL ANALYSIS - MODELING






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

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

                 The requirement   for assessing the watershed  wide  impact of the implementation of
                 stormwater runoff controls demands the use of computerized hydrologic modeling
                 techniques to estimate stormwater runoff rates under various conditions.        Digital
                 computer modeling refers to the use of sets of mathematical expressions (algorithms) to
                 reproduce key behavioral aspects of the natural system.       This section contains a
                 discussion of the modeling approached used in the preparation of the  Lake Erie Area
                 Watershed Stormwater Management Plan.




                                              .... . ..........
                                                ...........
                                              .. .............. ... ...... . . ............
                                                                      .. :- .. .. .....
                                           .... 11  ................. . .... ....... ... 11 . .......
                                                 ..... ......... .

                 There  are a number of hydrologic      modeling. techniques  available for estimating
                 stormwater runoff based upon ground cover and precipitation conditions. The Penn State
                 Runoff Model (PSRM) wa's selected for use in the Lake Erie Area Watershed. PSRM
                 was selected for use in this watershed for a number of reasons, including:



                     1. PSRM offer   *s the ability to analyze the timing of flow combinations
                        originating from various locations throughout a watershed. This capability is
                        particularly important in the evaluation of the effects of various stormwater
                        control techniques throughout a watershed.



                    2. PSRM is suitable for use for both urban and rural watersheds.



                    I PSRM offers flexible data input and output modes.









                                                          IV- 1

                 Lake Erie SWMP
                 4026-02









                     4. PSRM is has generally been         the model of choice for use throughout
                         Pennsylvania for the preparation of watershed stormwater management plans
                         under Act 167.



                     5.  Continuing development of PSRM and training.in its use is supported by the
                                                                        I
                         Pennsylvania Department of Environmental Resources and the Pennsylvania
                         State University.



                                                                     M.


                 Overview


                 Input data requirements for PSRM include the following parameters:



                     1. Watershed Representation Data
                         A. Tributary Area (Subbasin) Physical Features

                             1. Tributary land areas

                             2. Land slopes

                             3. Overland flow lengths

                         B.  Tributary Area (Subbasi n) Hydrologic Features

                             1. Composite runoff curve numbers

                             2. Percentage imperviousness

                             3. Initial abstraction estimates

                         C.  Drainage (Reach) System Features

                             1. Conv  eyance system (streams- and conduits) capacities

                             2. Conveyance system travel times

                         B.  Rainfall Inputs

                             1. Rainfall volumes

                             2. Rainfall distribution




                 Lake Erie SWMP                             IV-2
                 4026-02












                        Subbasin Physical Features

                        PSRM develops runoff hydrographs for individual portions (subbasins) of a
                        watershed which are then routed and combined in a manner corresponding to the'
                        network of streams that link the subbasins. Consequently, the initial task in the
                        development of the modeling data base was the delineation of subbasins within
                        the watershed. The designated Lake Erie Area watershed actually consists of a
                        number of small to moderately sized streams which drain to Lake Erie and areas
                        along and near the shore of the lake which drain directly to the Lake Erie
                        essentially through overland flow. Therefore the overall watershed was first
                        divided into subwatersheds. These subwatersheds, in turn, were further divided
                        into subbasins. Subwatersheds were delineated based upon topographic features
                        so as to 1) define the major stream drainage basins; and 2) accurately represent the
                        topology of the watersheds.                  Delineated subwatersheds and selected
                        characteristics are listed in Table IV-1 and delineated in Plate IV-1. Plate IV-1 is
                        Appended to the rear of this report.



                                                                  Table IV- I
                                                         Delineated Subwatersheds


                                           Drainage                             Drainage                             Drainage
                                             Area                                 Area                                Area
                      Subwatershed          (Acres)         Subwatershed         (Acres)        Subwatershed         (Acres)
                    Cascade Creek                6,650   Sixmile Creek               12,220   10.0 Mile Run *             3,540
                    Crooked Creek                13,600  Sixte'enmile Creek          12,100   11.5 Mile Run *             1,270
                    Eightmile Creek              4,510   Trout Run                    4,080   26.9 Mile Run *                880
                    Elk Creek                   57,960   Turkey Creek                 31440   29.0 Mile Run *             1,260
                    Fourmile Creek               7,280   Twelvemile Creek             9,310   39.9 Mile Run *             1,280
                    Garrison Run                 1,360   Twentymile Creek            22,080   40.9 Mile Run *            .1,340
                    McDaniel Run                 2,000   Walnut Creek                24,430   41.5 Mile Run *             2,850
                    Mill Creek                   8,750   3.2 Mile Run *                 560   Direct Runoff              19,700
                    Raccoon Creek                5,000   3.9 Mile Run *               1,250
                    Sevenmile Creek              5,430 , 6.7 Mile kun *               1,600


                              Note:    Unnamed tributaries that have been designated with the distance of their
                                       mouths from the western boundary of Erie County

                   Subbasin boundaries comprising the modeled subwatersheds were defined so as to as
                   closely as practical produce hydrologically homogeneous areas as well as to adequately
                   model hydrologically significant features such as tributaries, major storm sewers, and
                   significant obstructions. A total of 1,498 subbasins were delineated.


                   Lake Eric SWMP                                     IV-3
                   4026-02










                 Subbasin boundaries comprising the modeled subwatersheds were defined so as to as
                 closely as practical produce hydrologically homogeneous areas as well as to adequately
                 model hydrologically significant features such as tributaries, major storm sewers, and
                 significant obstructions. A total of 1,498 subbasins were delineated.



                 United States Geological Survey (U.S.G.S.) 7.5 minute quadrangle topographic mapping
                 and local storm sewer facilities maps were used as the basis for defining subwatersheds
                 and subbasins. The subbasin boundaries were delineated on the U.S.G.S. base and
                 digitized to facilitate subsequent analysis. Once digitized, the subbasin areas were
                 calculated. Subbasin areas average 133 acres in size.



                 Stream locations were digitized and added to the data base. Representative overland
                 flow widths for each subbasin were calculated based upon an analysis of the digitized
                 stream locations and subbasin boundaries.



                 Digital Elevation Model (DEM) data obtained from U.S.G..S. served as the source of
                 digital terrain data used to produce slope summaries for each subbasin.               DEM
                 quadrangles were mosaicked to fully cover the watershed. Slope in percent and aspect in
                 degrees were calculated from the raw elevation data and were used to determine
                 representative ground slopes for each of the subbasins.



                 Subbasin Hydrologic Characteristics

                 The principal subbasin specific hydrologic characteristics of interest in this analysis are
                 the composite Soil Conservation Service (S.C.S.) runoff curve number and percentage of
                 impervious area for each subbasin. Percent of impervious area is defined as the
                 percentage of the total subbasin area covered by surfaces which are essentially
                 impermeable to  'water. The runoff curve number is a indication of the amount of surface
                 runoff which may be expected to be produced as a result of a storm event. This runoff
                 potential is influenced by land cover and soil conditions.         The determination of
                 impervious 'percentages and curve numbers required the classification of land cover and
                 soil types.






                 Lake Erie SWMP                             IV-4
                 4026-02










                     Land Cover/ Land Use Classification

                     Landsat thematic mapper multispectral digital data      was used to provide the
                     necessary land use and land cover information.




                     Impervious Area Statistics

                     Impervious area statistics for each subbasin were estimated based upon the land
                     cover and land use through the relationships of impervious area components of
                     various land use / land cover classes developed and published by the U.S. Soil
                     Conservation Service.




                     Soils Group Classifications

                     The spatial distribution of soils (aggregated by S.C.S. hydrologic soil groups) was
                     defined through the use of S.C.S. soils maps and reports for Erie County and
                     Chautauqua County in New York. The various soil types were scan digitized into
                     the geographic information system database.         The various soil types were
                     aggregated the appropriate hydrologic soil groups based upon U.S. Soil
                     Conservation Service (S.C.S.) procedures. This procedure produced the data set
                     used to create the hydrologic soil group map presented previously in Section III,



                     Calculation of Runoff Curve Numbers

                     The factors that determine runoff curve numbers (CN) are the hydrologic soil
                     group and land cover type and condition. The S.C.S. has developed and
                     published tables which provide runoff curve numbers for each intersection of
                     hydrologic soil group and land cover type.



                     Geographic Information system     (GIS) methods were    used  to digitally combine
                     the land use / land cover and hydrologic soil group themes to yield a set of
                     associations between surface type and soils units.       These associations were
                     referenced to the S.C.S. information to attach the      appropriate runoff curve
                     number. Further processing within the GIS determined composite runoff curve
                     numbers for each of the subbasins in the watershed.



                 Lake Erie SWMP                              IV-.5
                 4026-02












                     Modeling Subbasin Data File Production

                     All of the subbasin information necessary for PSIZIM modeling was represented in
                     the GIS system as digitized themes. Once these data were resident in the GIS, the
                     necessary analyses were performed to develop the required PSRM input data set.
                     This data set is common to all subwatersheds and subbasins in the watershed and
                     is keyed to assigned subbasin identification numbers. The version of PSIUM used
                     in this modeling effort has the capability of reading the appropriate individual
                     subbasin characteristics data directly from the common subbasin data file.



                 Stream Reach Hydraulic Characteristics


                 Important input data requirements of the PSRM are estimates of the times of travel in
                 each of the modeled stream reaches and the bankfull capacity of each reach.




                     Travel Time Estimates


                     Travel time is calculated as the length of the reach divided by the average
                     velocity. Stream reaches were defined in conjunction with the delineation of
                     watershed subbasins as described previously. The length of each reach was
                     determined by direct measurement from the U.S.G.S. maps. Stream reach
                     velocity estimates were based upon cross section information available from
                     Flood Insurance Studies (FIS) completed within the watershed. This data was
                     used in conjunction with empirical relationships between stream cross section
                     measurements, discharge and mean velocity to produce velocity estimates for
                     stream reaches for which no FIS information is available.         Velocities for
                     channelized stream segments, major storm sewers, and long culverts were
                     calculated based upon reported and/or field'measured dimensional information.



                     Estimated velocities were divided by measured lengths to produce estimates of
                     times of travel for each stream reach for input into PSRM.









                                                          IV-6

                 Lake Erie SWMP
                 4026-02











                     Bankfull Capacity Estimates

                     The estimation of bankfull capacities in the natural stream reaches in the     Lake
                     Erie Area watershed was performed based upon information reported in the
                     literature which essentially states that bankfull capacities in natural streams
                     approximate the 2-year return -frequency flood discharge rate (Leopold, 1953;
                     Brush, 196 1; Harvey, 1969; and Brown, 1979). The estimates of the 2-year flood
                     for each stream reach were using. Procedure PSU-IVfor Estimating Design Flood
                     Peaks on Ungauged Pennsylvania Watersheds. Discharges calculated using this
                     procedure were used as initial bankfull capacity estimates for natural stream
                     reaches.



                     Full flow capacities for improved stream reaches and major storm sewer pipes or
                     culverts were calculated based upon slope and dimensional information.



                     -Modeling Stream Reach   Data File Production

                     The stream reach data required for PSRM modeling of the watershed was
                     compiled into a single reach data file. This input file contains stream time of
                     travel and capacity data keyed to each of the identified reaches modeled during
                     this planning effort.



                Rainfall Characteristics


                     Rainfall Intensity-Duration-Frequency

                     Rainfall depth-duration-frequency (DDF) values for the Lake Erie Area
                     watershed are summarized in Table IV-2.



                     These data were calculated using the charts describing rainfall intensity-duration-
                     frequency JDF) data presented in the Pennsylvania Department of Transportation
                     IDF Field Manual. This document divides the state of Pennsylvania into five
                     regions of relatively uniform rainfall patterns. Intensity-duration-frequency and
                     depth-duration-frequency (DDF) relationships for each of the five regions ar       .e
                     presented in the form of design charts. The Lake Erie watershed lies in Region 3.


                Lake Erie SWMP                             IV-7'
                4026-02












                                                             Table IV-2
                                           Rainfall Depth - Duration - Frequency Data



                   Return Period          Rainfall           Rainfall           Rainfall           Rainfall
                      (Years)            (3-hour)            (6-hour)          0 2-hour)          (24-hour)
                      2 - year          1.54 inches        1.84 inches        2.20 inches        2.62 inches
                      5 - year          1.84 inches        2.21 inches        2.65 inches        3.15 inches
                      10 - year         2.22 inches        2.70 inches        3.23 inches        3.75 inches
                      25 - year         2.54 inches        3.13 inches        3.84 inches        4.61 inches
                      50 - year         2.99 inches        3.68 inches        4.48 inches        5.34 inches
                     -100 - year        3.37 inches        4.18 inches        5.14 inches        6.19 inches


                      Rainfall Distribution


                      The   distribution of rainfall within the overall storm event is relevant to the
                      modeling effort. The U.S. Soil* Conservation Service (SCS) has developed
                      synthetic rainfall distribution patterns which include maximum rainfall intensities
                      for the selected design frequency arranged in a sequence that is critical for
                      producing peak runoff. SCS has developed four synthetic distributions from
                      available National Weather Service data that are applicable in various areas of the
                      United States. The SCS Type 11 distribution represents design storm conditions
                      appropriate for the region in which the Lake Erie Area Watershed is located.



                      Since the SCS Type II storm distribution is supported by significant research
                      activity, is widely used in stormwater runoff calculations throughout the area and
                      its use is incorporated directly in the frequently employed SCS stormwater runoff
                      computational procedures it was selected for use in the Lake Erie Area Watershed
                      model.




                            @.C4LL6M:jq"/;VERLF'ICA                                  .. ......
                                                        ............

                  As was discussed in Section III, there are three gauging stations that are operated by the
                  U.S.G.S. located in the Lake Erie Area Watershed. The gauges are located on Raccoon
                  Creek, Brandy Run (a tributary of Elk Creek), and Mill Creek. The. Mill Creek and
                  Brandy Run gauges provide peak discharge estimates for.strearn flows suitable for use in
                  calibrating the model. Peak discharge data were obtained for the Brandy Run gauge for a
                  storm that occurred on, August 28, 1990 and for the Mill Creek gauge for a storm that





                                                                IV-8

                  Lake Erie SWMP

                  4026-02









                  occurred on October 18, 1988. Hourly rainfall records for these     dates as reported at the
                  Erie Airport were also obtained.



                  The Penn State Runoff Model was loaded with the observed hourly rainfall records and
                  the model peak strearnflow estimates were compared to the observed results. Initial
                  estimates for the Manning's "n" values for pervious and impervious surfaces were
                  adjusted until optimal calibration was obtained. The model calibrated to values of 0.22
                  for the Manning's "n" value for pervious surfaces and 0.08 for the Manning's "n" value
                  for impervious surfaces. The literature reports that values for Manning's "n" range from
                  0.03 to 0.45 for pervious surfaces ranges and from 0.01 to 0.013 for impervious surfaces.



                  The calibrated model estimates a peak discharge of 930 cubic feet per second (cfs) for
                  the August 28, 1990 storm at the Brandy Run gauge. The reported gauged peak
                  discharge for this storm is 836 cfs. The model, therefore, predicts the storm peak flow to
                  within I I percent of the reported value for this actual event. The model estimates a peak
                  discharge of 2,317 cfs for the October 18, 1988 storm at the Mill Creek gauge. The
                  reported gauged peak discharge for this storm is 2,550 cfs. The model, therefore,
                  predicts the stonn peak flow to within 9% of the reported value for this actual event.
                  The August 28, 1990 storm produced 3.29 inches of rain over an eleven hour period.
                  This approximates an I I year return frequency event. The October 18, 1988 storm
                  produced 2.89 inches of rain over a six hour period. This approximates a 16 year return
                  frequency event. The ability of the model to predict actual observed peak discharges to
                  within approximately 10 percent for these relatively rare events indicates acceptable
                  model caliabration.





                  N


                  Existing Conditions

                  Runoff and streamflow rates- were estimated under current conditions using the PSRM
                  for each of the subwatersheds selected for detailed modeling. The model was run for the
                  mean annual, 5, 10, 25, 50 and 100 return frequency volumes associated with 3, 6, 12
                  and 24 hour duration storm events. In all, model output was developed for 24 storm
                  conditions for each of the 24 subwatersheds included in the modeling program. The
                  results of this modeling effort are summarized in Appendix B.




                  Lake Erie SWMP                             IV-9
                  4026-02










                 In reviewing the model results, it is important to recognize that the strearnflow estimates
                 developed as part of this plan have been developed by modeling the runoff produced by
                 rainfall volumes with a range of return frequencies distributed according to the SCS Type
                 II Distribution. Since this distribution is designed to maximize runoff from any given
                 rainfall volume, this procedure produces conservatively high runoff rate estimates
                 suitable for the design of local controls. As a result, the strearnflow estimates contained
                 in Appendix B are likely to be higher that estimates produced using other methods that
                 employ statistical analyses of reported flood frequencies.




                 Future Conditions


                 The PSRM wa     s used to estimate runoff and strearnflow rates under projected future
                 development conditions. This was accomplished by revisin       g the S.C.S. runoff curve
                 number and percent impervious estimates in the model subbasin database to reflect the
                 projected future land use / land cover characteristics as presented in Section III. The
                 model was then run under these conditions to produce estimates of future runoff and
                 strearriflow rates for the 24 hour, 50 year return frequency storm. Model output for each
                 of the modeled subbasins is provided in Appendix B and summarized at the mouth of
                 each subwatershed in Table IV-3.






                                                       TABLE IV-3

                          COMPARISON OF EXISTING AND FUTURE PEAK DISCHARGES

                                      (24 HOUR, 50 YEAR FREQUENCY EVENT)




















                                                           IV-10

                 Lake Erie SWMP

                 4026-02
















                   "W
                                        LAKE ERIE AREA WATERSHED
                                    STORMWATER MANAGEMENT PLAN
          AU                                           SECTION V

                    DEVELOPMENT OF WATERSHED TECHNICAL STANDARDS
                                                    AND CRITERIA



                 EUROD.UCHON.

                 As was discussed previously in Section 1, the basic standard for stormwater management
                 as established by Act 167 is that those involved in activities which can generate
                 additional stormwater runoff, increase its velocity, or change the direction of its flow
                 must be responsible for controlling and managing the runoff so that these changes will
                 not cause harm to other persons or property throughout the watershed. This mandate
                 requires comprehensive storinwater planning at a watershed level and the development of
                 standards and criteria for managing stormwater to prevent adverse impacts, both at a
                 particular site and anywhere downstream where the potential for harm can be reasonably
                 be identified.



                 Specifically, the primary prerequisite for effective stormwater management in the
                 watershed is the development of standards which specify allowable stormwater
                 discharges from land development activities. Standards must also be developed which
                 address issues associated with the control of velocity, direction and quality, if
                 appropriate. The standards must be accompanied by associated criteria which for the
                 basis for the design and assessment of activities instituted to comply with those standards.



                 :.CVN2W                           Ev..@-Y     ClUTER-M.
                      ..........

                 A key element in the development of this stormwater management study is the definition
                 of the characteristics of the rainfall events against which the developed control standards
                 must be Applied. Specifically, the rainfall events which the stormwater control measures
                 must adequately handle need to be defined. The objective of the analyses discussed in the
                 following paragraphs was to describe characteristics of storm events which will serve as
                 the basis for the evaluation and design of effective control measures in the Lake Erie Area
                 Watershed.







                                                            V - 1
                 Lake Erie SWMP
                 4026-02












                  The critical rainfall event characteristics are as follows:



                      1. An identified duration or length of the particular rainfall event.
                      2. An identified rainfall intensity or distribution or pattern of precipitation falling
                           over the duration of the event.

                      3. An identified frequency of     occurrence or the expected time interval between
                           occurrences of the given precipitation event.

                      4. An identified volume or total amount of rainfall that can be expected for the
                           particular event.




                  Storm Distribution


                  The selection of the appropriate distribution of rainfall within the overall storm event was
                  discussed in Section IV. For the reasons specified therein, the Soil Conservation Service
                  (SCS) Type II rainfall distribution was selected for application to the development of
                  control standards and the design of actions to be taken to satisfy those standards.




                  Storm Duration


                  Storm duration refers to the length of time over which the specified amount of
                  precipitation falls. This factor is of concern because rainfall duration has a direct effect
                  upon the resulting runoff volume and peak rate of discharge. The length of the rainfall
                  period contributing to the peak runoff rate is related to the time for runoff to travel from
                  the hydraulically most distant point of the watershed to a point of interest (time of
                  concentration).   In general, largest peak discharges result when the storm duration
                  roughly equals the time of concentration in the watershed.



                  In small watersheds the critical storm duration may be measured in minutes, while in
                  large watersheds or basins the time of concentration may be measured in days. In the
                  Lake Erie watershed, the appropriate storm duration for use in the development and
                  application of control standards was selected using the hydrologic model. The PSRM
                  was used to estimated peak discharge rates throughout the watershed for the mean annual,
                  5, 10 25, 50 and 100 year return frequency storms of the following candidate durations: 3
                  hour, 6 hour, 12 hour and 24 hours. The model runs produced estimates of the peak
                  discharges at 1438 points throughout the watershed for each of the four candidate


                  Lake Erie SWMP                             V-2
                  4026-02










                durations. For 86% of the 1438 subbasins modeled in the watershed, the 24 hour durati      on
                storm produced the largest peak rate of discharge. The 6 hour and 3 hour storms
                produced the largest peak rate of discharge for 13% and 1% of the subbasins,
                respectively. Moveover, the 24 hour duration storm is the critical event for 22 out of the
                27 modeled subwatersheds which drain approximately 95% of the study area.



                A supporting consideration in the selection of the storm duration for use in the Lake Erie
                Area Watershed is the fact that the popular Soil Conservation Service Technical Release
                55 Urban Hydrology for Small Watersheds procedure for estimating runoff and peak
                discharges is based upon a 24-hour storm, duration. This procedure is extensively used
                within the region and nationally in the production of stormwater control plans for
                proposed land development. Adoption of a storm duration criteria other than 24 hours
                would effectively preclude the use of this most popular computational procedure.



                For the reasons discussed above, 24 hours has been selected as the appropriate storm
                duration criteria for application throughout the watershed. It is recognized that the use of
                shorter durations will be appropriate and permissible in the design of stormwater
                collection facilities. However, the selection and application of controls to the discharge
                of runoff from developing sites will be based upon the 24-hour storm duration criteria.



                Storm Return Frequencies and Precipitation Volumes


                    General


                    Storm return frequency refers to the average interval in years over which a storm
                    event of a given precipitation volume can be expected to recur. For example,
                    reference to a "10-year" storm with an associated 3.75 inch 24 hour duration
                    storm volume indicates that a storm producing 3.75 inches of rainfall over a 24
                    hour period on-the average can be expected to occur approximately every ten
                    years. Another way to consider this storm is that, on the average, a storm
                    producing 3.75 inches of rainfall over a 24 hour period has approximately a ten
                    (10) percent chance of occurring in any given year. Storm duration and volumes
                    for return frequencies ranging from 2-years to 100-years were presented
                    previously in Section IV of this report (Table IV-2). This data is presented
                    graphicall y below in Figure V- 1.






                                                            V-3

                Lake Erie SWMP

                4026-02








                                         Figure V-1: Precipitation Volumes
                               8.0

                        CIO



                                                                               ..............*............
                               6.0                                          ........
                                                                 ..............0.....
                                                                              ................ . ...........
                                                                  ..........................
                        ct
                       .1-4    4.0
                        CIA


                               2.0                           storm Duration
                                               3-Hour     6-Hour 12-Hour 24-hour


                               0.0
                                   0         20          40         60         80         100        120
                                                  Retum Period (Years)



                     As is indicated in Figure V-1, precipitation amounts increase with increasing
                     return periods reflecting the obvious fact that the larger the rainfall event the more
                     infrequent the occurrence. As one would expect, larger rainfall amounts produce
                     larger stream discharges. This is illustrated in Figure V-2 for various streams in
                     the watershed. The estimates of stream discharges reflected in Figure V-2 were
                     produced using the Penn State Runoff Model developed for the Lake Erie Area
                     Watershed.



                     The Pennsylvania Department of Environmental Resources "Storm Water
                     Management Guidelines" describe design frequencies as the peak rates of
                     discharge for which the components of drainage systems are designed.
                     Reoccurrence intervals used for design typically range from 2 to 100 years.
                     Individual drainage system components are generally assigned design storm
                     frequencies based upon an evaluation of such factors as the size of the area
                     drained and the potential for damage produced as a result of inadequate drainage
                     as characterized by the size of the affected area, the nature and characteristics of
                     land use in the affected area (i.e., residential, commercial, industrial uses).
                     Components of the initial drainage system such as storm sewers and inlet



                 Lake Erie SWMP                               V-4
                 4026-02









                     structures generally a designed for relatively high frequency events ranging
                     upwards to the 10-year storms. Major drainage system components are generally
                     designed for less frequent, larger storms such as the 25-year and 50-year events.
                     Flood protection projects typically are designed to accommodate conditions
                     produced by the I 00-year storm events.



                     Design frequency criteria for the construction of conveyance facilities such as
                     storm sewers, pipes, culverts, bridge openings and spillways are contained in a
                     number regulations and design manuals, including: regulations produced relative
                     to the Pennsylvania Dam Safety and Encroachments Act, and the Pennsylvania
                     Flood Plain Management Act; Pennsylvania Department of Transportation design
                     criteria; Pennsylvania Soil and Erosion Control Manual; and the Water Pollution
                     .Control Federation Manual of Practice No. 9: Design and Construction of
                     Sanitary and Storm Sewers. These references provide ample guidance under the
                     law and standard engm*eenng practice to permit local municipalities to establish
                     local requirements for traditional stormwater facilities design commensurate with
                     local conditions. There are, however, no state level criteria for stormwater
                     discharges as they relate to total discharge volumes and rates from new land
                     development. Moreover, unlike the generally site specific conduit construction
                     criteria, site runoff criteria must be established based upon watershed wide
                     considerations.   Consequently, this watershed plan presents specific criteria
                     relative to storm frequencies to be used in controlling total stormwater discharge
                     volumes and rates from new site development.



                     Upper and L*ower Storm Frequency Criteria Limits

                     For this study the design storm frequency criteria were selected to respond to
                     watershed conditions and to meet the objective of Act 167 to minimize
                     stormwater damage now and in the future. The following example serves to
                     illustrate the design storm frequency criteria selection rationale. The following
                     table contains pre-development and post-development peak rates of discharge for
                     a hypothetical development.












                                                           V-5

                Lake Eric SWMP

                4026-02














                                                         Table V- I
                                    Hypothetical Storm Discharge Rates Under Various
                                                Return Frequency Conditions


                                                                       Design Storm

                                 Condition              2 - Year         10 -Year        100 - Year

                         Pre-development                 50 cfs           75 cfs          100 cfs
                         Post-development                100 cfs          150 cfs         200 cfs



                    Two conclusions may be drawn for the data presented in this table:



                         1.  If the design storm frequency criteria require that only the 100-year event
                             be used as a point of control, the post-development discharge for the 2-
                             and 10-year storms will be greater that the pre-development rate and-
                             runoff from the development may cause downstream harm at the more
                             frequent storm events.



                         2.  If the criteria require that only the 2-year event be applied, damage ma   y
                             result from increased runoff during the less frequent storm conditions.



                    If the stormwater conveyance system from this hypothetical development site to
                    the river were capable of accommodating flows generated under 100-year return
                    frequency storm conditions controlling discharges under simply a I 00-year storm
                    freque *ncy criteria would be acceptable. However, information obtained from
                    local municipal questionnaires and data produced through an analysis of existing
                    obstruction capacities identified a number of locations where flooding occurs as
                    frequently as-once per year. The municipal questionnaires identified 5.0 locations
                    within the watershed at which flooding occurs on average at least once per year
                    (Table 111-5). In addition, it.is generally accepted that the, bankfull capacity of
                    natural stream channels approximates the mean annual flood. As a result, flows in
                    excess of the mean annual flood frequently produce localized flooding.
                    Consequently, the mean annual (2-year) event has been selected as the lower limit
                    design storm frequency criteria.




                                                            V-6
                Lake Erie SWMP
                4026-02












                     The I 00-year frequency storm was selected for use in the watershed for the
                     following reasons.



                         1. The survey of obstructions identified 52 obstructions with capacities less
                             than the 100-year flood (Table A-1). A failure to control runoff under
                             storms of these frequenci 'es would exacerbate flooding conditions at these
                             sites as well as those sites with even smaller capacities.



                         2.  Control of the 100-year frequency runoff would serve to preserve the 100-
                             year flood plain and floodway boundaries as defined in the flood insurance
                             studies completed in the watershed. These boundaries provide the basis
                             for on-going flood plain management in the area. Permitting increased
                             runoff at the 100-year return frequency conditions would result in an
                             expansion of the flood zones and substantially increase the potential for
                             damage.



                         3.  The use of a 100-year frequency for the upper limit of the criteria would
                             afford a high degree of protection commensurate with the highly
                             developed urbanized areas existing at the base of most of the watersheds.



                     Intermediate Frequency Criteria

                     In setting the upper and lower limit for return frequency storms to be controlled, it
                     is assumed that runoff produced from discharges occurring events occurring at all
                     intermediate frequencies will also be controlled. In other words, the stormwater
                     control facilities would regulate discharges such that the post-development
                     discharges would match the pre-development discharges at the 3-year, 4-year, 5-
                     year frequency storms and so on through the 100-year frequency event. Since it
                     would clearly be impractical to design for such a multitude of conditions and
                     cumbersome to review managen ent plans produced on such a basis.


                     Intermediate return frequency events were selected as reasonable points at which
                     to verify that the runoff control system performance will generally parallel pre-
                     development conditions between the 2- and 100-year limits. The selected check




                                                             V-7
                Lake Eric SWMP
                4026-02









                     points and the manner in which they approximate modeled actual runoff rates at
                     various return frequencies are illustrated in Figure V-3.

                                                       Figurie V-3
                                           Design Storm Control Points
                           16,000

                           14,000
                      C4                                                    .......... ..
                           12,000                                  ...........
                       a)         -
                           10,000

                           8,000
                                                                 Actual Discharges
                           6,000                                 Control Point Approximations

                           4,000
                           2,0001
                                 0         20        40         60        80         100       120
                                              Storm Return Frequency (Years)


                     The following storm frequency check points have been selected for inclusion in
                     the stormwater management criteria:



                           1. 2-year frequency storm;

                           2. 1 0-year frequency storm;

                           3. 25-year frequency storm; and

                           4. 1 00-year frequency storm.



                     The rationale for the selection of the upper and lower check points was described
                     previously. The reasons for selecting the 10-year and 25-year frequency storm
                     intermediate check points are as follows:



                         1. The use of these two intermediate points are effective in producing a curve
                             of runoff rate verses storm return frequency which reasonably closely







                 Lake Erie SWMP

                4026-02










                                    approximates the observed modeled relationship between the two variables
                                    (as illustrated in Figure V-4).



                               2.   The 10-year and 25-year events are the most frequently referenced
                                    recommended design storm for a wide range of stormwater drainage
                                    facilities.




                          Precipitation Volumes

                          Precipitation volumes to be used in the design and evaluation of stormwater
                          control measures in the Lake Erie Area Watershed are presented in Table V-2.



                                                                        Table V-2
                                                              Design Rainfall Volumes
                                                             (24 - Hour Storm Durations)


                                                                                    Volume
                                                            Mum Period              (Inches)
                                                           2 - year                   2.62
                                                           10 - year                  3.75
                                                         1 25 - year                  4.61
                                                           10 - Ye                    6.19



                                              Ms
                                                     ..T @-D.'     :.S
                                            .............
                      ............... ...                      ...... .. ....                      .. . ....... .............


                     General Approach


                     The basis for the establislunent of runoff control standards is contained in the Storm
                     Water Management Act. The statement of legislative findings contained in the Act
                     (Section 2 of the Act) presents the following findings:



                                    "(1) Inadequate management of accelerated runoff of storm water
                                    resulting from development throughout a watershed increases flood
                                    flows and velocities, contributes to erosion and sedimentation,
                                    overtaxes the carrying capacity of streams and storm sewers,
                                    greatly increases the cost of public facilities to carry and control
                                    storm water, undermines flood plain management and flood control


                     Lake Eric SWMP                                        V-9
                     4026-02










                             efforts in   downstream communities, reduces ground water
                             recharge, and threatens public health and safety.



                             (2) A comprehensive program of storm water management,
                             including reasonable regulation of development and activities
                             causing accelerated runoff, is fundamental to the public health,
                             safety and welfare and the protection of the people of the
                             Commonwealth, their resources and the environment."



                 Section 3 of the Act defines the duty of persons engaged in the development of land as
                 foll ows:



                             "Any landowner     and any person engaged in the. alteration or
                             development of land. which may affect storm water runoff
                             characteristics shall implement such measures consistent with the
                             provisions of the applicable storm water plan as are reasonably
                             necessary to prevent injury to health, safety or other property.
                             Such measures shall include such actions as are required:



                                 (1) to assure tlaat the maximum rate of storm water runoff is
                                 no greater after development than prior to development
                                 acfivities; or



                                 (2) to manage the quantity, velocity and direction of
                                 resulting storm water runoff in a manner which otherwise
                                 adequately protects health and property from possible
                                 injury.11



                 The most effective method means of safisfying the Act based         upon the statements of
                 legislative findings and definition of duty would be to control land development activities
                 such that both the total volume and rate of runoff from new development are identical to
                 that which occurred before development i.e., post-development runoff volume and rates
                 identical to pre-development conditions. If this could be accomplished, stormwater
                 runoff from the new development would not produce any effect on downstream flows,
                 eliminating any concern relative to the creation of downstream damage potentials.


                 Lake Erie SWMP                             V - 10
                 4026-02










                 Unfortunately, however, most land development activities involve the conversion of land
                 use from a type which exhibits a relatively low runoff potential to a higher runoff
                 potential type. This factor produces a typical effect upon runoff as illustrated in Figure
                 V-4. As is indicated in Figure V-4, land development typically produces increases in
                 both total runoff volumes and peak rates of discharge.



                 As is indicated in Figure V-5, measures can be taken to manage stormwater runoff by
                 reducing the increase in total runoff volume and/or control peak rates of discharge.
                 Techniques which may be used to minimize the increase in total runoff volume are
                 described in Section VI of this report. These techniques generally consist of measures
                 which minimize the extent of land cover changes from pervious to -impervious areas
                 and/or artificially induce infiltration to ground water. While these measures can be
                 effective in reducing increases in runoff volumes, it is usually impractical to entirely
                 avoid runoff volume increases attendant with most land development activities.
                 Consequently, as indicated in Figure V-5, post-development hydrographs produced
                 through the implementation of runoff volume reduction measures typically produce
                 hydrographs with peak rates of discharge and total volumes falling between pre-
                 development and uncontrolled post-development conditions. Because it is impractical to
                 entirely avoid increases in total runoff volume, the inevitability of some degree of runoff
                 volume increases must be accepted and the primary emphasis of the stormwater control
                 criteria must be placed upon the control of peak discharge rates. In order to minimize the
                 potential for damage, the basic, minimum stormwater runoff control criteria to be applied
                 in the watershed is that post-development peak discharges rates must not exceed pre-
                 development peak discharge rates. Methods of controlling peak discharge rates from new
                 development are presented in Section VI of this report. In general, they consist of
                 measures which essentially retain and delay the controlled release of runoff so as not to
                 exceed pre-development rates.



                 The typical results of the application of peak discharge control measures in addition to
                 feasible runoff volume reduction provisions are illustrated in Figure V-5. As is indicated
                 in Figure V-5, although the post-development total runoff volumes fall between pre-
                 development and uncontrolled post-development volumes, the peak rate of discharge
                 approximates the pre-development peak rate. This is accomplished by extending the time
                 duration of time the peakrate of discharge occurs. Instead of an instantaneous peak as
                 occurs in the pre-development condition, the peak discharge occurs over an extended
                 period of time. This characteristic attenuation of peak discharge rates necessitates the
                 development of additional standards designed to avoid the development of associated
                 downstream problems. The derivation of these sup        plemental  standards is discussed
                 below.





                                                           V - I I

                 Lake Erie SWMP

                 4026-02







                            Figure V-4                                            Figure V-5
                       Uncontrolled Runoff                                   Controlled Runoff


                       Runoff Hydrographs                                   Runoff Hydrographs

                                 Post-Development                                     Post-Development
                                 (uncontrolled)                                       (uncontrolled)
                                                                                      Post-Development
                                                                                       (volume reduction)
                                  Pre-development                                      Pre-development
                                                                                       Post-Develoy-ment
                                                                                        (volume re uction
                                                                                         and peak discharge
                                                                                         control)
                                                                                         %


                                                                                           %


                   Elapsed Time                                          Elapsed Time

                      Total Runoff Volumes                                 Total Runoff Volumes

                                                                 Pre-development          -----------
                                                                 Post-Development
                                        -----------              (uncontrolled)
             Pre-development                                     Post-Development
                                     --------------              (volume reduction)
            Post-Development                                     Post-Development
            (uncontrolled)                                       (volume & peak
                                     Total Volume                controlled)             Total Volume      oil.










                   Release Rate Percentage Concept


                       General Concept

                       It is through the development and application of release rate percentage based,
                       peak discharge standards that the stormwater management plan truly assumes a
                       watershed wide status. The investigations which serve as the basis for the
                       establishment of release rate percentage represent the principal means through
                       which the watershed wide implications of control strategies are evaluated,
                       considered and incorporated into specific control standards.



                       T he general concepts behind the development and application of release rate
                       percentage based stormwater management criteria are discussed below through
                       the use of the hypothetical watershed illustrated in Figure V-6. Figure V-7
                       contains the total hydrograph for flows at the point of interest as well as the
                       hydrographs for flows generated in each of the five (5) subbasins as they reach the
                       point of interest. As is illustrated in Figure V-7 and summarized in Table V-3, the
                       peak discharge at the point of interest is sum of the discharges originating from
                       each of the upstream subbasins as they coincidentally reach the point of interest.



                                                                Table V-3
                                                  Example Hydrograph Combination
                                                      Pre-Development Conditions

                                                 Peak Discharge at                   Discharge at Point of Interest
                                                  Subbasin Mouth                       During Wa rshed Peak
                          Subbasin           Time              Discharge              Time              Discharge
                           Number          (Minutes)                fs)             (Minutes)              (cfs)
                               1               20                  200                 70                   0
                               2               50                  650                 70                  650
                               3               40                  500                 70                  400
                               4               50                  500                 70                  300
                               5               30                  300                 70                  150
                            Total                                                                          1,500









                   Lake Erie SWMP                                  V - 13
                  4026-02











                           HYPOTHETICAL WATERSHED


                                          I
                                        %2
                                                3


                                           %  4
              Point of Interest               5           FIGURE V-6

                                 SUBBASIN HYDROGRAPH
           1,600 -
                                    1,500 cfs       Watershed Peak
                                                    Rate of Runoff
           1,400-
                 -Total Flow Hydrograph

         -731,200-

         con
           W                                                  lb
          0 1,000 -
           02 800-                                650 cfs
                                    '50
                                       0 cfs


             600-
         cy                        ,-500 cfs


         0
                                                  400 cfs
         ;-T 400-
                  3
                   00 cf s


                                          00 cfs 1200 cf@-,--.
             200
                   5      4       3   2-   cfs--/. I.,          ........
               0
                 0   10  20  30   40  50  60  70   80  90 100 110 120
                                         @0


                                        50 cf
                                  2/1


                                     Time in Minutes      FIGURE V-7









                       The potential effects of land development occurring in Subbasin 3 upon the runoff
                       hydrographs for Subbasin 3 and the e.,-,tire hypothetical watershed are illustrated in
                       figure V-8 and are tabulated in Table V-4. Figure V-9 illustrates the effects of
                       the institution of stormwater controls which serve to limit post-development peak
                       discharge rates to the pre-development discharge rate through flow detention. As
                       is indicated by the hydrographs presented in Figure V-8, limiting the peak
                       discharge in this manner would serve to extend the period over which the pre-
                       development discharge occurs. The result of this flow attenuation is described by
                       the data presented in Table V-4. Following development and the institution of the
                       specified controls, Subbasin 3 would contribute 500 cfs to the watershed peak at
                       the point of interest rather than the 400 cfs contributed in the pre-development
                       state. This would produce a 100 cfs increase in the watershed peak despite the
                       control of Subbasin 3 peak discharges to pre-development levels.



                                                                Table V-4
                                          Example Watershed Impacts of Flow Attenuation
                                                              (Subbasin 3)


                                                                         Peak       Contribution to     Watershed
                                                                       Runoff       Watershed Peak         Peak
                                         Condition                       (Cfs)           (cfs)             (cfs)
                         Pre-development                                 500             400               1,500
                         Post-development (uncontrolled)            1      10            490               1,590
                         Post-development (100% Release Rate)            500             500
                         Post-development (Reduced Release Rate)         400             400               1,500


                       This situation can be avoided if the post-development runoff rate is controlled so
                       that the peak rate of runoff does not exceed the rate of flow contributed to the
                       watershed peak.



                       The effects of controlling peak rates of runoff in the example situation are
                       presented graphically in Figure V-9 and in tabular form in Table V-4. As is
                       indicated, selection of the proper allowable post-development peak discharge rate
                       in consideration. of contribution to downstream flows can avoid unintentional
                       increases in peak stream discharges as a consequence of efforts to limit runoff
                       from the new development(s). The methodology used to determine the allowable
                       peak rate of post-development discharge in the previous example can be
                       generalized as follows:
                                                                                                       @1.500










                  Lake Erie SWMP                                  V - . 15
                   4026-02










                                     SUBBASIN HYDROGRAPH (100% RELEASE RATE)
                         1,800  -   NOTE: Only Subbasin No. 3 is shown.                          Watershed Peak
                                                                                                 Rate of Runoff
                         1,600-                Watershed Peak                                    Post-development
                                -              Rate of Runoff                                    (100% release rate)
                                               Pre-development                                     Q=1,600 cfs
                         1,400-
                                               Q=1,500 cfs
                     C4
                     '05 1,200-

                                                                                                           1b
                         1,000-    Uncontrolled                           7 10 cfs
                                -  Post-Development
                          800-     Runoff                                                Post Development with
                     U
                                                                          lb             discharge from
                          600   -                                                        Detention Basin       500 cfs


                     C,   400-
                          200-                                           .500 cfs:   Pre-development
                                                             3                       Runoff
                             0                               1                                   1 . I          I .
                                0       10    20     30     40'    50     60 -    70     80      90        100 110 ' 120
                                                                       Time in Minutes                     FIGURE V-81
                       1,600       SUBBASIN HYDROGRAPH (REDUCED RELEASE RATE)
                                - NOTE: Only Subbasin No. 3 is shown.                              Watershed Peak
                                                                                                   Rate of Runoff
                       1,400-                                                                      Post-development
                                                                                                   (reduced release
                                -        Watershed Peak
                     0                            Runoff
                     U
                                         Rate of                                                      rate)
                       1,200                                                                         %
                                         Pre-development                                                   =1,500 cfs
                                                                                                           %
                                          Q=1,500 cfs                                                      %
                     0-1,000-
                                                                                                                %
                                 Uncontrolled                             710 cfs:
                     .2  800     Post-Development
                                                                                          Release Rate from
                     U           Runoff
                                                                                          Detention        400 cfs
                         600    -                                          lb

                                                                                             Post-Development
                         400-
                         200-                                                         ':: @Pr ed"e'v`el'o`p` m* e n t
                                                            3
                           0 r
                                                                                                 Po
                                                                                   .%%%          ' I
                                                                                                   st-dev

                                                                                                           0
                                                                                                           e
                                                                                                            'o me
                                                                                                                 r
                                                                                                                   nt
                                                                            @4*@,OOL7                      re ease ate,
                                                                                                   Q       1600 cfs





                                                                          7 10 cfs














































                                0    10      20     30      40     50     60      70     80                100 110 120
                                                               Time in Minutes                             FIGURE V-9












                                                        EQUATION 1
                                             Pre-development Subbasin Peak Discharge
                                                Contribution to Watershed Peak
                                             Pre-development Subbasin Peak Discharge
                                     r 7-Assigned Release Rate Percentage


                                                        EQUATION 2
                                             Pre-development Subbasin Peak Discharge
                                       X     Assigned Release Rate Percentage
                                             Allowable Post-development Peak Discharge


                    The application of these two equations to the determination of appropriate post-
                    development peak discharge rates defines the release rate percentage concept of
                    stormwater management. This concept was developed to be fully responsive to
                    the intent and requirements of Pennsylvania Act 167. The release rate percentage
                    concept provides performance standards for storm drainage control in a
                    watershed. The significance of this approach lies in the fact that the concept
                    provides an effective tool for comprehensive watershed stormwater management.



                    Determination ofRelease Rate Percentages

                    The previous paragraphs introduced the release rate percentage concept using a
                    simplified example, The following discussion presents the general strategy that
                    was used to apply this concept in the Lake Erie Area watershed.



                    The intent of the release rate percentage concept is to identify the general
                    characteristics of subbasin interactions and combinations and defin e their relative
                    impacts on total stream flows. This information is used to calculate the assigned
                    release rate percentages as described previously. For areas modeled, the general
                    approach employed in the Lake Erie watershed was to establish release rate
                    percentages for each subbasin by determining the peak rate of runoff from the
                    subbasin and its contribution to peak discharges in downstream reaches. This was
                    accomplished using the Penn State Runoff Model described in Section IV of this
                    report. The specific steps in the approach are as follows:




                Lake Erie SWMP                            V - 17
                4026-02









                         1. Perform overall watershed modeling u    sing the Penn State Runoff Model.
                         2.  Identify the modeled flow contribution that a particular subbasin
                             contributes to each of the modeled downstream reaches.

                         3.  Calculate the release rate percentage for each subbasin at each downstream
                             reach.

                         4.  Assign a single release rate percentage for each subbasin which will
                                                                     I
                             adequately protect all downstream reaches.



                     Areas not included in the modeling effort   were assigned a release rate percentage
                     of 100%. In these areas, which were previously identified in Chapter IV, runoff
                     drains essentially directly to Lake Erie.       Due to these circumstances, the
                     stormwater management goals can be achieved through the application of a
                     uniform standard requiring that post-development peaks shall not exceed the pre-
                     development peak discharge rates (i.e., a release rate percentage of 100%).



                 Assigned Release Rate Percentages

                 Assigned releas e rate percentages for the Lake Erie Area watershed are tabulated in Table
                 V-5 and illustrated in Plate V-1. Please note that in both Table V-5 and Plate V-1, the
                 subbasins have been aggregated into "Release Rate Percentage Areas".



                 Application of the Assigned Release Rate Percentages

                 As indicated previously, the release rate percentage concept is a tool for watershed level
                 stormwater management, developed to ensure that the application of runoff control plans
                 for individual sites consider downstream stormwater runoff implications. As such, the
                 release rate percentage fanctions as a performance standard; that is, it defines an end
                 result which is to be attained. Under this approach, an individual developer can select
                 and design those drainage control measures that are mostappropriate to the site as long as
                 the applicable release rate percentage for the subbasin.is met. It is important to note that
                 the assigned release rate percentages must be applied only to actions which control peak
                 runoff through detention, retention or other methods which attenuate runoff discharges.
                 Applicable stormwater control techniques are discussed in. Section VI of this report.







                                                            V_ 18
                 Lake Erie SWMP
                 4026-02









                   Table V-5 Assigned Release Rate Precentages
























































                                                                     V- 19
                   Lake Erie SWMP
                   4026-02









                 In order to use the release rate for a particular site in one of the delineated release rate
                 percentage areas, the developer should follow the following general sequence of actions.



                 1.  Compute the pre-development and post-development runoff for the specific site using
                     an approved method for the 2, 10, 25 and 100 year storms, using no stormwater
                     management techniques. If the post-development peak rate is less than or equal to the
                     pre-development rate, the requirements of Act 167 and this plan have been met. If the
                     post-development runoff rate exceeds the pre-development rate, proceed to Step 2.



                 2.  Apply on-site stormwater management techniques to increase infiltration and reduce
                     impervious surfaces. Recompute the post-development runoff rate for the 2, 10, 25
                     .and 100 year storms; and if the resulting post-development rate is less than or equal to
                     the pre-development rate, the requirements of this plan have been met. Otherwise,
                     stormwater detention or retention will be required and the developer should proceed
                     to Step 3.



                 3.  Multiply the assigned release rate percentage for the area times the pre-development
                     peak runoff rate to determine the allowable total peak runoff rate from the
                     development.     Design the necessary detention/retention facilities to meet the
                     allowable peak runoff rate standard.



                 It should be noted that stormwater storage can be provided on or off site. The possibility
                 for regional or off-site facilities is an option which can be considered as a means to more
                 efficiently provide the needed facilities, in terms of both cost and land requirement
                 considerations. In many areas, the best solution may.be for several development sites to
                 share ajoint facility.



                 Municipalities may also benefit from this approach. They may maximize development in
                 prime development areas by providing regional or distributed storage through the use of
                 natural or artificial takes, floodplains and steep sloped valleys which are unsuitable for
                 development. However, where off site storage is to be used, the developer must ensure
                 that no flooding or harm will be caused by runoff between the new development and the
                 off site storage area. This may require the protection of the stream channel or the
                 construction of a storm sewer to convey runoff to the storage site.




                 Lake Erie SWMP                             V-20
                 4026-02











                  PERMISSIBLE RUNOFF COMPUTATIONTECIEVIQUES


                  GENERAL


                  A number of techniques and methods have been developed and are used to estimate rates
                  and volumes of runoff from land. Runoff computation techniques permissible for use in
                  developing runoff control plans pursuant to the requirements of this Plan have been
                  identified. It is recommended that municipalities require land developers to limit the
                  computation techniques employed to one or more of those listed. The list of permissible
                  techniques includes a cross section of the most commonly used computation methods
                  entailing a range of approaches, levels of effort and required access to computer, facilities.
                  The list affords developers the opportunity to select from a suite of techniques. At the
                  same time, the number of techniques which the local reviewing engineer must be familiar
                  with is kept to a manageable number. In addition, the use of inapplicable, unproven or
                  inaccurate techniques is prohibited.




                  PERMISSIBLE       RUNOFF COMPUTATION
                  TECHNIQUES

                  The recommended permissible runoff computation techniques are as follows.



                          Soil Conservation Service Urban Hydrology Method (TR-55)

                      2. Soil Conservation Service Model (TR-20)
                      3. U. S. Army Corps of Engineers Flood Hydrograph Package (HEC-1)

                      4. Penn State Runoff Model



                  Engineers involved in the preparation of stormwater control plans and reviewers of such
                  plans should review the pertinent information relative to the use and applicability of each
                  of these methods. It is important that the assumptions implicit and explicit in each of the
                  techniques be understood and that the techniques are properly applied.







                  Lake Erie SWMP                              V - 21
                  4026-02












                                        LAKE ERIE AREA WATERSHED
                                    STORMWATER MANAGEMENT PLAN
             4:U                                      SECTION VI
                              STORMWATER MANAGEMENT TECHNIQUES



                 JrNTRODUCTION

                 One of the key features     of the Stormwater   Management Act 167 is       its mandate   to
                 implement comprehensive stormwater runoff control practices.            The Act requires
                 stormwater planning at the watershed level in such a manner that adverse impacts of
                 storm runoff are prevented,   both at a particular site and at every potential flood prone
                 location downstream from      the watershed. Therefore, any stormwater management
                 technique must consider runoff impacts on the watershed.



                 St udies in recent years have identified a number of methods of reducing the impact of
                 development on storm peaks. Many management practices indicate the ingenuity of the
                 planning, engineering and regulatory agencies. In particular, the publications of Soil
                 Conservation Service (SCS) of Department of Agriculture (USDA), U.S. Environmental
                 Protection Agency (EPA) and American Public Works Association (APWA) are quite
                 comprehensive and aid in expanding some of the management practices reported in this
                 section.



                 The present-day emphasis. on detention or reduction of urban runoff within the
                 contributing source area represents a remarkable shift in runoff control strategy that h  as
                 occurred only just recently [Kibler and Aron, 1980]. This trend toward on-site runoff
                 abatement includes control measures that either reduce the runoff directly at the source or
                 delay the arrival of runoff contributions at some critical points downstream. Attesting to
                 the strength of this trend is the large 'and growing number of publications describing
                 various on-site control measures. Notable contributions    in thi s regard include those by
                 Poertner [1974, 78] on stormwater detention practices; Becker et al. [1973] on rooftop
                 storage; Aron et al. [1976] on general runoff abatement measures including infiltration
                 trench design; Montgomery County Soil Conservation District on storage detention
                 ponds; ASCE, The Urban Land Institute, and the National Association of Homebuilders






                                                            vi-I

                 Lake Erie SWMP
                 4026-02











                        [1976] on residential runoff abatement measures; and Field [1978] and Field and Lager
                        [1975] for comprehensive reviews of structural and nonstructural measures.



                        Methods applicable to almost all watersheds are based on the principles of velocity
                        reduction, -infiltration enhancement, detention and retention storage, etc. However, site-
                        specific conditions in a given watershed may lead to the development of innovative
                        control measures. All the methods are designed to control sediment, pollution and
                        stormwater within the watershed. Although the design of stormwater control facilities is
                        usually completed by engineers and landscape architects, key policy questions should first
                        be answered by local officials. Preferences of. local residents concerning level of
                        protection, aesthetics, m          aintenance . responsibilities, and cost allocation should be
                        assessed by local officials, not professionals. After community stormwater management
                        policies have been established, detailed design or design review of particular controls and
                        measures can be carried out [Clinton River Watershed Council, 1984]. Where practical,
                        control measures should be designed to exploit the beneficial uses of the stormwater such
                        as recreational and aesthetic benefits and recharge of underground aquifers. In many cases
                        this can be the decisive factor in approval of a new land development. The intent of this
                        chapter is to review the existing storm water management techniques and make
                        recommendations on their applicability, from many different perspectives such as
                        suitability for the study watershed, cost, effectiveness, advantages, disadvantages and
                        maintenance.etc.



                                                                                                              ...............
                                                                                                    . ..............................
                                                   ............. .... . .....                  ....... .. . ....  -1 ...I. .....
                                                                                                         . .........-... _ _
                                                                                                    ............ .........
                                                                                                  .......... .
                        EVNCEff Of             7V"W4                                                                  .......
                                                              TER@                            .. .......
                                                                                                    I.....  ---- ............. ...........
                                                                                                   .............  I------ .....................
                                                                                               ........ ..... .. .......................
                                                                                    ... .......                   .......
                             ... ...........             ...... -1 ............. .... ...... ...................... I------ ...... ......_...... ........ ....
                        Early stormwater management efforts concentrated on transporting the runoff as quickly
                        as possible from a storm location, by routing it through storm sever systems. As the
                        urban development increased in the watershed, such a flood control effort resulted in the
                        worst flooding conditions downstream, due to increased total flow, peak flow rate, stream
                        velocity and flow depth. Land development causes an increase in the rate of runoff from
                        the site, resulting in an increased peak flow rate. Changing a natural channel to a
                        concrete-lined ditch or a storm sewer system increases the velocity and reduces the travel
                        time to downstream locations. A reduction in the travel time may make the peak flow
                        rate from one watershed, to contribute or in the worst case to coincide with the peak flow
                        rate of some other watershed(s). This again results in an increased peak flow rate.
                        Detaining the storm water and releasing the maximum rate over a longer period of time
                        may also induce the same adverse effect.






                                                                                VI-2

                        Lake Erie SWMP

                        4026-02













                 It ishow recognized due to above mentioned problems that, the most logical and effective
                 approach to control the storm runoff is to maintain the natural runoff flow characteristics.
                 This can be accomplished in general by maximizing natural infiltration processes,
                 reducing impervious surfaces, preserving floodplains, and controlling storm runoff in the
                 watershed. There are numerous, technically acceptable techniques which have varying
                 degrees of applicability in the . study area, depending on the site and watershed
                 characteristics. Some of the most widely used ones will be described here, along with a
                 brief discussion of their key- features, advantages and disadvantages, and typical costs. It
                 will be up to each individual developer to select the techniques that are most appropriate
                 to the project and site. It is most likely that in most situations, a combination of on-site
                 controls will be the most appropriate and least costly stormwater management system.
                 Nevertheless, some alternatives must be carefully analyzed. For example, when several
                 detention basins are used, their interaction must be considered, since a combination of the
                 timing of their releases could aggravate downstream flooding father than alleviating it.
                 Also, the efficiency and costs of many of management alternatives vary from one location
                 to another. Many of the alternatives, such as on site storage basins, erosion control, and
                 flow reduction alternatives, may be feasible only for areas of new development [Kibler,
                 1982].



                 To determine the most appropriate set of techniques for a particular site, several factors
                 should be evaluated-



                     1. Soil characteristics (i.e. soil permeability, erodibility)

                     2. Topography

                     3.  Subsurface conditions

                     4.  Drainage patterns (i.e. proximity to stream flooding problems)

                     5.  Proposed land uses

                     6.  Costs

                     7.  General advantages and disadvantages of each technique.








                                                             VI-3

                 Lake Erie SWMP

                 4026-02














                 STORMWATER RUNOFF PROBLEMS,


                 FLOODING

                 During high intensity, or long duration storms the existing infiltration capacity of soils
                 mav be exceeded and surface storage filled to capacity. Once this happens, runoff occurs
                 in 'the form of overland and channel flow. During some high runoff and relatively
                 infrequent storm events, if the existing watercourses have insufficient capacity to convey
                 surface flows, they get flooded. Natural floodplains provide some benefits by serving as
                 reservoirs, natural recharge basins, collectors of pollutants, wildlife habitats etc. As
                 floodplain or upstream areas are developed, this natural beneficial phencimenon, becomes
                 a disaster due to its increased frequency and magnitude. Thus, new developments
                 increase the flood problems and damage downstream as compared to predevelopment.



                 There are many ways to reduce the impact of new development on flooding. Some
                 general concepts to consider in determining which solutions are applicable to a study area
                 are listed below:



                     1. Limit development of floodplains and prohibit development in floodways

                     2. Increase infiltration

                     3. Reduce runoff rates

                     4. Store precipitation and runoff where it falls and release it slowly
                     5. Keep water confined in adequate pipes or channels

                     6. Protect areas subject to flood damages

                     7. Build flood control measures

                     8  Limit erosion and sediment transport




                 EROSION AND SEDIMENTA TION

                 When raindrops hit bare soil, the cumulative effect is the splashing of the hundreds of
                 tons of soil into the air. , Some particles are washed into streams or downstream areas





                                                           VI-4

                 Lake Erie SWMP

                 4026-02











                  unless the velocity is very low or the soil is protected by some means. This phenomenon
                  is called erosion. The runoff from new land developments can result in erosion both on-
                  site and off-site. Once soil erosion begins, the soil particles transported by runoff and
                  water currents begin to settle down in downstream drainage ways, which is called
                  sedimentation. Sedimentation may result in blockages of natural watercourses, plugging
                  of culverts and storm sewers, smothering of vegetation, filling of reservoirs, etc. The
                  sedimentation occurs at increased rates during and following land development because
                  graded areas are left in an unprotecte*d state. Data collected by Brandt [1972] shows that
                  erosion rates on land undergoing development can be 2,000 times the erosion rate of
                  forested lands.



                  Erosion problems in the Lake Erie Area Watershed are particularly significant in the
                  vicinity of the bluffs along the Lake Erie beach.          Unless properly collected and
                  transported, runoff in the vicinity of the bluffs can collect on the surface of the bluffs,
                  near the crest. As the collected water percolates into the ground, it moves out through the
                  bluff face. This excess water adds extra weight and stress to the bluff, causing erosion
                  and extreme slumping. This ultimately can lead to loss of property and threats of damage
                  to residential, commercial, and industrial properties.



                  General concepts to be followed for minimizing erosion and sedimentation include the
                  following:



                      1. Protect the soil surface to withstand effects of rainfall and runoff

                      2. Limit soil erosion through site management practices

                      3. Store rainfall and runoff where it originates and release it slowly

                      4. Catch sediment before it enters natural drainage ch  annels



                  Activities specifically appropriate to drainage in the vicinity of the shore line bluff areas
                  include.-











                                                              VI-5
                  Lake Erie SWMP

                  4026-02











                     1. Collection of surface runoff in properly designed stormwater collection and
                         conveyance systems.

                     2.  Conveyance of surface water runoff to the base of the bluffs thorough outfalls
                         equipped with energy dissipation devices.




                 POLLUTANT TRANSPORT

                 Runoff from developed areas contains more pollutants than from natural watersheds.
                 These pollutants include heavy metals, BOD, and high concentration of suspended
                 solids. Heavy metals and BOD generally increase as the area is developed and reach a
                 plateau when the development has stabilized. Suspended solids increase during first two
                 years following the disturbance of land for development. The impacts of these pollutants
                 depend on the existing quality and use of the receiving waters. If the newly developed
                 area drains into a supply reservoir, an increase in the amount of pollutants could be very
                 significant. In other cases, the impacts may be difficult to determine and are often long-
                 term, subtle, and persuasive rather than immediate.




                                             ... ... .....
                                             EL      IWM                            .......
                 OMMM swww4m. @ @.. I I OT
                                   . ......... . ............. .... ..
                 Many methods are available to alleviate the impact of urbanization on the quantities and
                 rates of stormwater runoff. Maryland Interim Watershed Management Policy [APWA,
                 198 1 ] states, "When engineering a site for stormwater management, two overall concepts
                 must be considered: 1) the perviousness of the system should be maintained or enhanced,
                 and 2) the rate of runoff should be slowed. Land development methods which tend to
                 reduce the volume of runoff are preferred over methods which tend to increase the
                 volume of runoff." Many of the steps taken to reduce flooding also have significant
                 effects in reducing erosion, sedimentation and stream pollution and may reduce the need
                 for capital-intensive storin sewer systems.


                 All things considered, the most advantageous means o f* controlling stormwater runoff
                 from new developments is by minimizing the amount -of increased runoff volumes
                 produced. If it were possible to complete the new development in a manner such that
                 there would be no change in either the volume or peak rate of discharge after
                 develo pment   there would be essentially no stormwater related impacts. While it is





                                                            VI-6

                 Lake Erie SWMP

                 4026-02










                  recognized that, in most cases, it may not be possible to accomplish the goal of making
                  both post-development runoff volumes and peak rates of runoff match pre-development
                  conditions, reasonable efforts should be made to minimize increases in total runoff
                  volumes prior to the design of supplemental controls designed to control peak discharge
                  rates.



                  It is recommended that land developers be encouraged to take reasonable and applicable
                  steps to incorporate features into their developments which will serve to minimize
                  increases in stormwater runoff volumes.




                  R UNOFF VOL UME RED UCTION MEASURES

                  Following are brief descriptions of measures which may be taken to limit increases in
                  total runoff volumes resulting from new developments. The applicability of these
                  measures is highly site specific and dependent upon the nature of the development.
                  However, it is recognized that the potential application of these techniques be seriously
                  considered early in the design of land development activities.



                     Limit the Amount ofLand Disturbed

                     The added volume of runoff produced' as a result of the development of "virgin"
                     land is directly related to the amount of land cover changed from its natural state
                     to a more impervious condition (usually paved). Consequently, increases in
                     runoff volumes can be minimized to the extent that land cover disturbances can be
                     minimized.     Individuals involved in land development activities, should,
                     therefore, be encouraged to optimize their development activities from the
                     standpoint of accomplishing the basic objectives of the development while
                     minimizing the amount of paved areas used and natural areas disturbed.














                                                            VI-7

                  Lake Erie SWMP

                  4026-02











                     Utilize Terraces, Contoured Landscapes, Runoff Spreaders,
                     Diversions and Grassed or Rock-Lined Waterways

                     These measures increase the time of concentration by increasing length of
                     overland flow, and thus lowering the flood peak. They will provide the additional
                     benefit of reducing total runoff by infiltration if the site has well-drained soils.
                     Runoff spreaders spread runoff or direct it into a system of terraces. Terraces are
                     more suitable for reducing erosion from agricultural and non-urban areas and
                     conserving soil moisture.       They reduce effective slope length and runoff
                     concentration. About 90% of the soil that is moved is deposited in the terrace
                     channels. In contouring, crop rows follow field contours to prevent erosion and
                     runoff. It can reduce average soil loss by 50% on moderate slopes and less on
                     steep slopes. It must be supported by terraces on long slopes. There are no soil or
                     climatic limitations on practicing contouring, but it is not feasible on very
                     irregular topography.     Grassed waterways or swales stabilize vegetation on
                     drainage channels.     For"velocities of up to 8 ft/sec runoff is reduced by grass
                     channels, if correctly graded and stabilized. Detailed design information for this
                     category of alternatives can be obtained from the Soil Conservation Service's
                     Engineering Field Manual for Conservation Practices.



                     Use of Infiltration Devices

                     Infiltration devices are used to reduce flood peaks by releasing all or part of the
                     stored runoff into the ground water. The infiltrated water may appear a short
                     distance downstream as surface water at a later time. However, the runoff
                     hydrograph at the outlet point should be much lower and.drawn out in time than
                     that from runoff delay techniques [Aron, 1975J. An example application of
                     infiltration storage techniques is provided in Figure VI-I.

















                                                             VI-8

                 Lake Erie IWMP

                 4026-02









                                                  Figure VI-1
                                     Example Application of Roof
                                and Parking Lot Infiltration Facility







                                                     Irv
                              Von


                                                                                 Drain Pipes

                                                          0
                                                                                           Storinwater
                                      Roof                                                 Infiltration
                                                                                           Facility


                                                                                          Overflow to
                                                          0                               Detention
                                                      Downspouts                          Facility



                     Soils comprised of sands and/or silty sands have high infiltration capacities, and
                     therefore are well suited for infiltration storage. Soils comprised of fine silts and
                     clays have low infiltration capacities and therefore, are not suitable for
                     constructing infiltration devices over them. Deep soil sampling should be
                     performed to assess the feasibility  'of water loading the various geological strata
                     for purposes of stormwater disposal. Percolation tests, pumping tests, and soil
                     sampling should provide useful data about the depth, size, and location where
                     subsurface storage Js practical. In the Lake Erie Area Watershed, a number of the
                     soils have properties which can limit the applicability of infiltration storage.
                     Therefore, this alternative should be used with caution. If this method is proposed
                     as the primary means to reduce runoff, for large development sites or for sites
                     located in landslide-prone soil locations, a soil engineer's report should be
                     obtained. Moreover, infiltration systems should not be used where there is a
                                                  <































                                                             VI-9
                 Lake Erie SWMP
                 4026-02











                      reasonable probability the runoff may be contaminated (e.g. industrial sites,
                      commercial parking lots, etc.).



                      The following techniques for stormwater control are based on the principle of
                      encouraging infiltration to ground water.



                          Seepage or Recharg, e Basins

                          Figure VI-2 shows a typical design of a seepage or recharge basin. In this
                          method, runoff is collected in various storm drainage systems and then
                          passed into large excavations called seepage or recharge basins designed
                          to allow a large percentage of annual rainfall to recharge an underlying
                          aquifer. In addition to reducing runoff volumes, this method offers to put
                          the stormwater to beneficial use by allowing a large percentage of runoff
                          to recharge an aquifer.


                                                            Figure VI-2
                                                   Seepage or Recharge Basin


                            Surface Runoff via
                            Graised Swile    Bypass tbr Excess Runoff



                                                                           E.mergency
                           Stormwater                                       Overflow
                           Drainage
                           system
                                             WW

                                     Sediment Trap
                                                                   Splash Pad




                                                                               2" Coarse Sand



                          Generally, the infiltration basins must be located in aquifer recharge areas,
                          but they may be used whenever the water table is more than 48", below the
                          ground surface. If they are used as the only means of stormwater control,
                          their size must be sufficient to store the area's maximum design rainfall






                                                              VI-10

                  Lake Erie SWMP
                  4026-02












                            from all paved 'areas.          However, seepage or recharge basins are
                            economically more feasible if designed to recharge a limited amount of the
                            runoff that is produced by rainfall events and to overflow relatively early
                            during intense rainfall events. Control of this overflow may require the
                            use of additional stormwater management facilities. As indicted above,
                            when seepage basins are used there is a need to consider the impacts of the
                            type and quality of runoff being infiltrated; e.g., water quality impacts on
                            ground water, and possibility of the pit being sealed by the salts in the
                            water. Seepage basins should not be used where there is a significant
                            potential for pollution of the ground water. In order. to maintain good
                            infiltration rates, the bottom of the basin should be kept silt free by using a.
                            sediment trap. In addition, an
                            emergency overflow structure is                                  6Figure 0M-3
                            required     to    bypass      excess                           Seepage Pits
                            runoff.


                                                                                                                  Seepage Pits or Dry Wells                                                                

                                                                                                                                                                                                           
                            Seepage       pits     are      small                                                                    excavations        designed         to
                            overflow during intense storms,
                            but reduce flood peaks by
                            encouraging       infiltration      to
                            ground water.        They can be                                
                                                                                                                       effectively used at the sites                                  
                            where soil permeability is over                                                           0. 15 ft/day and water table is
                            more than 48" below the bottom
                            of the pit.        There are two
                            important design considerations
                                                                                                                                       associated with seepage pits: (1).                                                   RA" Sofid Lim
                            the minimum size                                                                                                                             depends, on porosity of the soil                                              How                                                                                                  Map
                                                                             








                                                                   

                   Lake Erie SWMP

VI-II
4026-02


 










                         porosity of the soil and design storm) should be sufficient to maintain
                         predevelopment infiltration rate; (2) side area should be at least two times
                         larger than the bottom area. Figure VI-3 shows three seepage pit designs
                         each with an alternative overflow mechanism.




                         Seepage Beds or Ditches

                         Seepage beds dispose of runoff by infiltration it into the soil through a
                         system of perforated pipes laid in ditches. The runoff should be allowed
                         to pass through a sediment trap as shown in Figure 1, with a bypass
                         structure to drain runoff from extreme rainfall events. They are not
                         suitable for sites with water tables less than 48" deep and extremely low
                         permeability. A typical design of a seepage bed is shown in Figure VI-4.




                                                             Figure Vi-4
                                                             Seepage Bed
                                               I Alit,                 r                                @dh
                                                                                        2" Straw
                                                  12" Topsoil                           or Paper


                                             10A. 12" Gravel
                                                                                            (0


                                           1.    18" Gravel



                                                          10 Foot Minimum Separation






                         Dutch Drains

                         Dutch drains are employed in residential developments. They are simply
                         ditches either filled entirely with gravel or covered with top -soil and
                         seeded. Very wide drains are usually covered with brick lattice or porous
                         block as shown in Figure VI-5. The drains may either be located directly






                                                            VI-12

                 Lake Erie SWMP

                 40 26-02











                          under the roof eaves along the length of a building, or runoff can be routed
                          from downspouts to the dutch drain.



                                                                  Table VI-5
                                                                Dutch Drains
















                                         Brick Lattice               Porous Block                    Grass




                          If dutch drains are the        only   means of stormwater disposal in a
                          development, they should be able to drain area's design rainfall alone, and
                          therefore their siz e will be quite large. More often two to four feet drains
                          are combined with other control alternatives for partial stormwater
                          management using dutch drains.

                                                                                 


                          Porous Pavement                                     

                          Porous pavement        is  a   special
                          asphalt mixture designed to pass
                          water at a high rate to a specially
                                                                                         
                          prepared subbase.       The special
                                                                                         
                          subbase is thicker than a normal                                    
                          gravel subbase and is composed         ZARIN                                       of coarse graded stone supplying                               SIB
                          large    void    spaces    to    store                        






                                                                VI-13

                  Lake Erie SWMP
                 4026-02
 









                         runoff. Figure VI-6 shows a typical porous pavement cross-section. The
                         base aggregate is designed to have about 40% voids ratio.



                         Regardless of design traffic number (DTN), a minimum surface thickness
                         of 4" should be provided. Also, the combined surface and base thickness
                         should not be less than anticipated frost penetration. Porous pavements
                         have shown very positive results in regard to permeabilities, wear
                         resistance and freezing - thawing effects. However, the main problem
                         with porous pavements is that of pore clogging by muddy tires.




                 PEAK DISCHAR GE CONTROL DEVICES

                 Peak discharge control devices are those which control peak discharges rates by either
                 lengthening the runoff path of the storm water or storing it and releasing it at a controlled
                 rate. The runoff delay may vary between 15 to 30 minutes for very small areas to several
                 hours for drainage basins of larger extent. A common goal of delay devices is, however,
                 the disposal of all stored water before a second storm might hit. The stored water must be
                 allowed to release at a flow rate that is designed not to cause harm.



                 Delay of runoff is accomplished by two basic principles of detention and retention.
                 Detention is defined as detaining a large portion of the runoff from a storm, for a time
                 period approximately equal to the natural runoff duration. Retention, on the other hand,
                 is defined as holding of runoff for some time period longer than the natural runoff period.
                 There are following alternatives available based on the principle of runoff delay.



                 There are a number of on-site locations for temporary storage of precipitation and runoff
                 are generally considered:



                     1. Storage in ponds and lakes

                     2.  Rooftop storage

                     3. Underground storage






                                                             VI-14

                 Lake Erie SWMP

                 4026-02











                     4. Parking lot storage

                     5. Blue-green storage

                     6. Multiple use storage areas



                  In. planning on-site storage methods, one should consider existing physical, social and
                  economic limitations of the area. What may be a good solution at one site, may be
                  inappropriate at another.




                  Detention and Retention Basins

                  Detention and retention basins take a variety of forms. Some are wet (filled with water
                  all of the time) and some are dry (filled with water only during storms).



                  Some are designed as a continuation of a stream or river (on-strearn basins) while others
                  are separate from the river (off-site basins). Off-strearn basmis are usually connected to
                  the water course by pipes or swales.



                     Dry Ponds

                     As the name implies, dry ponds are designed to be normally dfy with the ability
                     store a portion of the stormwaterduring a storm event and then release the stored
                     volume slowly and safely. Typically they are used in areas where runoff volume
                     has been increased and it is desirable to reduce the runoff rate.



                     Retention basins are used when extreme limits on downstream flow rate or
                     velocity are required. The outflow rate'will be relatively low and extended over a
                     longer period of time as compared to the outflow period of detention basin. This
                     requires large amounts of storage for detaining stormwater for periods greater than
                     24 hours. Figure VI-7 shows a typical detention basin design. One detention
                     basin can be designed to control the stormwater from 2, 10, 25 and 100-year







                                                            VI-15
                  Lake Erie SWMP
                  4026-02











                        design storm events, by constructing multi-stage outlet structures. The outlet flow
                        discharge rate from the basin will depend on the return period of the design storm.




                                                                  Table V1-7
                                                    1@pical Detention Basin Design


                                                                     Upper Outlet        Top of Dam
                                             Water Surface During Design Storm                 Spillway Elevation
                               ChanneIInlet"__--'--------._ _.@                              A,


                                                                   Lower Outlet                    Q+:11*.ng Basin

                                  Extra Excavation for Wet Basin
                                                                    I Elevadon
                                 Pipe Inlet          Rip Rap                            opo Dam


                                                           Extent of Inundation
                                                           During Design Storm
                                                                 Upper Outlet

                               Channel Inlet        .---Low Flow Channel

                                                                  Lower Outlet
                                                                      Trash Rack               Stilling Basin

                                                                                                 Emergency
                                                                                                 spillway
                                                                  Plan







                        RooftopRetention

                        Rooftop retention utilizes the built-in structural capabilities       of rooftops to store a
                        certain amount of rainfall that falls on them. In many cases, existing roof
                        structures require little modification to function as retention structures. On fla             t
                        rooftops, drains must be designed with proper outlet capacities to control release






                                                                    VI-16

                   Lake Erie SWMP
                   4026-02










                                          rates to the design level. Overflow                                                                      Figure VI-8
                                          mechanisms should be provided to                                                        Examples of Rooftop Detention
                                          preclude danger from overloading.                                                                            Devices


                                                                                                                                                                   
                                          Special considerations of roof                                                                                         
                                                                                                                                       4qU Roof Drain                                                       water tightness may be necessary                                                                 Typical Roof Systern with Controlled
                                          when water is to be detained for                                                                 Release Drain and Overflow Scupper
                                          longer time periods or where                                                      Drain Hole
                                          frequent freezing and thawing are                                                                Strainer                                
                                                                                                                                                     
                                          prevalent. Figure VI-8 illustrates
                                          several types of roofto'p retention                                                                                                                            devices.               On sloping roofs, the                                                          
                                                                                                                                           Pipe
                                          retention can be achieved by                                                                                     Showing Inlet Hole
                                          providing findams. Findams are
                                          actually about 4" high gravel                                                                                Table V1-9
                                          ridges at 15 to 30 ft spacing as                                                          Roof Ponding With Gravel Dikes
                                          shown in Figure VI-9. Individual
                                          wedge-shaped ponds would build                                                               Coarse Gravel Blanket                        Ponded Stornswater
                                          UP behind. these                               "minidikes".                                                    Fine Gravel Dike
                                          Through laboratory studies it was
                                          found that a series of five dikes of                                                                                      Sloping Roof
                                          1/4 inch gravel placed on roofs of                                                Downspout
                                                                                                                           Draining onto                         BUILD]NG
                                          1% slope will cut the peak runoff                                              



                                          runoff rate by 50% and extend the runoff time by about 30 minutes [Aron, 1975].
                                          Finer gravel would naturally delay the runoff further. The effectiveness of the
                                          rooftop storage is a fimction of the actual area affected by such storage. It is most
                                          effective when used as an integral part of a larger stormwater runoff control plan.
                                          Detailed structural analyses of the structure should be completed to assure that the
                                          added roof load represented by stored water can be safely supported. Moreover,
                                          additional maintenance -should be anticipated on roofs subject to leaf
                                          accumulation.
                                                                                                                                                        
                                                                                                                                   
                                                                                                                                    































                                                                                                                       VI-17

                                  Lake Erie SWMP
                                  4026-02
 













                      Wet Ponds

                      Permanent or wet ponds are detention/retention structures filled with water all the
                      time with adequate detention capacity to store the design floods above normal
                      ponds level. Overflow spillways must be provided to bypass or discharge flows
                      into floodways on the peripheries of the ponds so that safe water-storage
                      elevations are not exceeded nor banks breached.



                      For extremely large ponds, adequate design precautions should be taken to
                      minimize possible shoreline erosion due to ice, wind and wave action. Sediment
                      accumulation and water pollution due to roadside accumulations of salts, copper,
                      and asbestos from brake linings, grease, oil, and heavy metals, are the
                      disadvantages associated with wet ponds. Such deleterious material should be
                      screened out from the drainage system by interception and. disposition before it
                      reaches stormWater storage ponds. In some locations municipal, state or federal
                      safety standards regarding the depth and volume of water will have to be met.
                      These ponds are unquestionably more aesthetically appealing than a typical dry
                      detention basin. In addition, they can be designed to provide some recreational
                      benefits. North Park Lake is an example of a permanent pool. Figure 10 shows
                      some suitable locations in a site plan for a residential development [Becker et al.,
                      1973].



                      The main difficulty with wet ponds lies in the frequent unavailability of land. Dry
                      ponds can be made rather inconspicuous as an integral part of the landscaping or
                      as lawn areas for office buildings. For example, depressed front lawn areas can
                      be designed to detain runoff from intense storms and to serve as building's green
                      space in dry season. The outlet pipes allow the ponds to drain in 12 to 24 hours,
                      and a certain amount of water undoubtedly filters into the ground [Aron, 1975] -
                      thus drying the areas and returning them to a suitable condition for dry weather

                      uses.


















                                                             VI-18

                 Lake Erie SWMP

                 4026-02












                        Underground DetentionlRetention Tanks

                        This alternative involves the construction of underground holding tanks or large
                        sized pipes as a means of providing controlled runoff from the site. In areas
                        where land is expensive or surface topography is not suitable, these tanks can
                        serve the same function as basins, while conserving land area. Outflow control
                        devices may consist of small gravity pipes, or weirs. In some applications
                        pumping may be required to discharge the stored runoff. This method can be
                        quite expensive because of high material construction costs and possible pumping
                        requirements; however, they may be appropriate in situations where land area is at
                        a premium. An example general design of an underground stormwater detention
                        facility is illustrated in Figure VI- 10.

                                                              Figure VI-10
                                                 Underground Detention Facility



                                                                                      Parking Lot
                                    Parking Lot                                         Surface
                                      Surface
                                                                                     Inlet Grates



                                                          Ac ess Pit
                                    Inlet Grates     F     7,
                            . . .......... . .... . . . .....  Outlet
                                                              Pipe
                                     Slop%..
                                                                                                        Access
                                                                                                          Pit

                                                             Oriface                 Slope
                                 Oversized Pipe              Plate
                                                                            Oversized --144           @hce
                                    C6                                        Pipe
                                    0                                                              Plate
                                                                                                         Outlet
                                                                                                          Pipe

                                                                                        Proffie
                                                                                        View
                                     Plan
                                    View














                                                                   VI-19

                   Lake Erie SWMP

                   4026-02












                     Parking Lot Detention

                     Parking lots cover a major portion of commercial developments and are,
                     therefore, large contributors of stormwater runoff. Stormwater runoff can be
                     detained on parking lot sites by shallow basins or swales. If properly designed,
                     this measure can be quite effective. Initial construction costs implementing these
                     measures are only a small percentage above the construction cost of conventional
                     parking lots. Arrangements of areas in a parking lot to accept ponding should be
                     planned so that pedestrians are inconvenienced as little as possible. A 7" design
                     depth is not unreasonable for parking locations in the remote areas of lots
                     [APWA, 198 11. The facility should be designed to drain completely and avoid
                     formation of ice.



                     Design considerations should recognize the possible use of porous asphalt,
                     provided the subgrade has an adequate infiltration capability. Expansive and/or
                     collapsing type soils may preclude this solution. An alternative to impervious
                     paving of parking areas is the substitution of grassy strips. The ground surface of
                     the planting strip is depressed and driving lanes are graded to direct the storm
                     runoff into the depressions. The strips. should be filled with pervious soil to allow
                     a maximum of infiltration, and planted with a Fescue-type grass which is both
                     resistant to occasional swamping and dry soil conditions. The strips should be
                     oriented perpendicular to the parking lot slope and surrounded by broken curbs to
                     protect them from being overrun by cars.



                     Blue-Green Storage

                     Incorporation of stormwater storage in urban drainage ways traversing roadways
                     is a version of detention ponding that has been identified as the blue green
                     concept. Topographical characteristics of many land areas adjacent to roadway
                     embankments make them very much adaptable for use as detention facilities.
                     This can be achieved by designing the culverts to pond where appropriate, as
                     shown in Figure VI- 11. Many drainage structures can be designed to operate in
                     this fashion. Roadway embankments at control points should be stabilized and
                     protected to minimize erosion effects of retained water.







                                                             VI-20

                 Lake Erie SWMP

                 4026-02










                                                             Figure VI-11
                                        Road Embankment Stormwater Detention




                                  Stormwater
                                 Impoundment


                                                                                                  Stream-@
                                                        A Q'S

                                                                        ......         . . . . . .
                                    A
                                                                                                                 A





                                                                       PL4N


                                                                         Roadway


                               Stormwater       Culvert
                              Impoundment                                                       Embanlanent


                                                                                                          WrA

                                                                         Secdon A-A                               J



                       Detention within Pedestrian Plazas and Malls

                       On-site detention in heavily congested areas can be incorporated effectively in the
                       design of pedestrian plazas, malls, and other similar type developments. The
                       ponding requirement can be accomplished at selected locations with very shallow
                       depths (I to 3 in) to avoid public inconvenience. Frequent maintenance and
                       suitable discharge control devices designed to satisfy the architectural objectives
                       of the land development are necessary in developments of this type.












                                                                 VI-21

                  Lake Erie SWMP

                  4026-02












                       Multiple Use Impoundment Areas

                       These areas utilize sites having primary functions other than runoff control. In
                       new developments, such multiple use should be incorporated into the primary
                       design.   For example, open space and grassed areas provided in the land
                       development to enhance the aesthetic appeal can also be used as storinwater
                       detention facilities. This can be accomplished by providing stormwater release
                       controls such as weirs, orifices, small diameter pipes and gates etc.



                       A hard-surface basketball or tennis court can be designed to drain adjacent
                       grassed or paved areas. The stormwater would collect in grass swales around the
                       edge of the court, seep through a gravel drain to retain the sediment load, and
                       discharge onto a porous asphalt surface. Some type of emergency drain should be
                       provided. Positive drainage toward the control devices is essential to avoid the
                       swampy conditions, weed growth and increased maintenance costs. For optimum
                       operation of control structures, it is also essential to screen out the floating debris
                       from the inlet stormwater.




                   RELA TIVE AD VANTA GES AAD DISAD VANTA GES



                   Table VI- I gives a brief summary of principal urban runoff abatement practices and their
                   associated relative advantages and disadvantages. As was expressed previously, the
                   runoff volume reduction measures which simultaneously reduce runoff peaks offer
                   significant advantages from the perspective of both local and watershed wide effects.
                   However, since there are limitations inherent in the volume reduction techniques, it is
                   likely that an overall storrawater control plan will include a combination of applicable
                   volume reduction features and peak discharge control features (i.e. detention and/or
                   retention facilities).



                   Selection of the best combination of techniques to be used in a particular instance should
                   be made by the developer in consultation, or at least with the concurrence, of the
                   municipal reviewer.







                                                               VI-22

                   Lake Erie SWMP

                   4026-02















                                                                                          TABLE VI_ I


                                               ADVANTAGES AND DISADVANTAGES OF ON-SITE CONTROL METHODS
                                          METHOD               T                  ADVANTAGES                                     DISADVANTAGES

                                                              REDUCTION OF RUNOFF / INFILTRATION STORAGE

                                Dutch Drains                        - Reduces the total volume                        - Looses efficiency if
                                                                       of runoff.                                        intensive storms follow in
                                                                    - Reduces the peak runoff                            rapid succession.
                                                                       discharge rate.                                - Subject to clogging by
                                                                    - Enhances the groundwater                           sediment.
                                                                       supply.                                        - Limited to application
                                                                    - Provides additional water                          for small sources of run-
                                                                       for vegetation in the                             off only, i.e., roof
                                                                       area.                                             drains, small parking
                                                                    - Reduces the size of down-                          lots, tennis courts.
                                                                       slope stormwater control                       - Maintenance is difficult
                                                                       facilities.                                       when the facility becomes
                                                                                                                         clogged.
                                                                                                                      - Limited application in
                                                                                                                         poor infiltration soils.


                                Porous Pavement                     - Reduces the total volume                        - More prone to water
                                                                       of runoff.                                        stripping than conven-
                                                                    - Reduces the peak runoff                            tional mixtures.
                                                                       discharge rates.                               - Subject to clogging by
                                                                    - Enhances the groundwater                           sediment.
                                                                       supply.                                        - Water freezing within the
                                                                    - Provides additional water                          pores takes longer to thaw
                                                                       for vegetation in the                             and hirnits infiltration.
                                                                       area.                                          - Motor oil drippings and*
                                                                    - Reduces the size of down-                          gasoline spillage may
                                                                       slope stormwater control                          pollute groundwater.
                                                                       facilities.                                    - Limited application in
                                                                    - Less costly than conven-                           poor infiltration soils.
                                                                       tional pavements for most                      - recent studies suggest
                                                                       applications.                                     that porous pavement's
                                                                    - Safety features - superior                         advantage will reduce
                                                                       skid resistance and visi-                         withtime.
                                                                       bility of pavement
                                                                       markings.
                                                                    - Provides pavement drainage
                                                                       without contouring.

















                                                                                  TABLE Vl- I


                                          ADVANTAGES AND DISADVANTAGES OF ON-SITE CONTROL METHODS
                                      METHOD                               ADVANTAGES                 T_ DISADVANTAGES
                                                               Prevents puddling on the
                                                                surface.


                              Seepage/Recharge                - Reduces the total volume                 i    Must be fenced and
                              Basins                            of runoff.                                    I ugularly maintained.
                                                              - Reduces the peak runoff                       If porosity is greatly
                                                                discharge rates.                              reduced, it maybe
                                                              - Enhances the groundwater                      necessary to bore seepage
                                                                supply.                                       holes or pits in the base.
                                                              - Construction borrow pits                      No filtering supplied by
                                                                often can be converted to
                                                                                                              the topsoil.
                                                                a large seepage basin to                   - Usefulness limited in poor
                                                                serve multiple areas.                         infiltrations soils.


                              Seepage Pits                    - Reduces the total volume                   - Looses efficiency if
                                                                of runoff.                                    intensive storms follow in
                                                              - Reduces the peak runoff                       rapid succession.
                                                                discharge rates.                           - Subject to clogging by
                                                              - Enhances the groundwater                      sediment.
                                                                supply.                                    - Maintenance is difficult
                                                              - Provides additional water                     when the facility becomes
                                                                for vegetation in the                         clogged.
                                                                area.                                      - Limited utility in poor
                                                              - Reduces the size of down-                     soils.
                                                                slope stormwater control
                                                                facilities.


                             Seepage Beds/Ditches             - Reduces the total volume                   - More expensive than other
                                                                of runoff.                                    infiltration techniques.
                                                              - Reduces the peak nmoff                     - Replacement of entire
                                                                discharge rates.                              system if clogging by
                                                              - Enhances groundwater                          sediment should occur.
                                                                supply.                                       Maintenance of sediment
                                                              - Reduces the size of down-                     traps must be frequent and
                                                                slope stormwater control                      consequently more
                                                                facilities.                                   expensive.
                                                              - Distributes stormwater
                                                                over a larger area than
                                                                other infiltration
















                                                                              TABLE VI-I


                                        ADVANTAGES AND DISADVANTAGES OF ON-SITE CONTROL METHODS




                                    METHOD                             ADVANTAGES                               DISADVANTAGES
                                                              techniques.
                                                              May be placed under paved
                                                              areas if the bearing
                                                              capacity of the paved area
                                                              is not affected.
                                                              Safer than seepage or
                                                              recharge basins.


                            Terraces, Diversions,             Increases the overland                      On poorly drained soils,
                            Runoff Spreaders,                 flow time, increasing the                   these techniques may leave
                            Grassed Waterways,                time of concentration and                   ground waterlogged for
                            and Contoured Land-               allowing for increased                      extended periods after
                            scapes                            infiltration.                               storms.
                                                           - Vegetative swales are                        vegetative channels may
                                                              less expensive than curb                    require more maintenance
                                                              and gutter systems.                         than curb and gutter
                                                                                                          systems.
                                                                                                          Roadside swales become
                                                                                                          less feasible as the
                                                                                                          nuniber of driveway
                                                                                                          entrances requiring
                                                                                                          culverts increase.


                                                                          DELAY OF RUNOFF
                            Rooftop Retention              - No additional land                        - Leaks may cause damage to
                                                              requirements.                               buildings and contents.
                                                           - Not unsightly or a safety                 - Stored runoff will greatly
                                                              hazard.                                     increase the load imposed
                                                           - May be adapted to existing                   on structural support.
                                                              structures.                                 This increased construc-
                                                                                                          tion expense may be
                                                                                                          greater than the savings
                                                                                                          resulting from reducing
                                                                                                          the size of downslope
                                                                                                          stormwater management
                                                                                                     i    facilities.
















                                                                                    TABLE VI_ I


                                           ADVANTAGES AND DISADVANTAGES OF ON-SITE CONTROL METHODS
                                       METHOD              T                ADVANTAGES                    -7 DISADVANTAGES
                               Parking Lot Detention           - Adaptable to both                             - May cause an inconven-
                                                                   existing and proposed                         ience to people.
                                                                   parking facilities.                        - Ponding areas are prone
                                                               - Parking lot storage is                          to icing, requiring more
                                                                   usually easy to incorpo-                      frequent maintenance.
                                                                   rate into parking lot
                                                                   design and construction.


                               Multiple Use                      Serves more than one                           Difficult to maintain the
                                                                   purpose. Employing areas of                   porosity of multi-use areas.
                                                                   grass, a certain amount of
                                                                   stormwater will infiltrate
                                                                   and improve the quantity
                                                                   of water recharged by
                                                                   natural filtering processes.
                                                                 If porous pavement is used
                                                                   on basketball or tennis
                                                                   courts, additional infil-
                                                                   tration will be provided.


                               De.tention/Retention            - Offers design flexibility for                  Facilities that empty out
                               Basins                              adapting to a variety of uses.                completely can have an
                                                               - Construction of ponds is                        unsightly nature and be a
                                                                   relatively simple.                            detriment to the developments.
                                                               - May allow significant                          Difficulty in establishing a
                                                                   reduction in the size of                      regular maintenance program.
                                                                   downslope stormwater                         In a residential development,
                                                                   management facilities.                        it may be difficult to
                                                               - May have some recreational                      determine whose responsi-
                                                                   and aesthetic benefits if                     bility it is to pay for the
                                                                   runoff is not carrying                        maintenance program.
                                                                   heavy sediment loads.                        Consumes land area which
                                                                                                                 could be used for other

                                                                                                                 purposes.
















                                                                                TABLE VI- I


                                         ADVANTAGES AND DISADVANTAGES OF ON-SITE CONTROL METHODS
                                     METHOD                              ADVANTAGES                  T_ DISADVANTAGES
                             Permanent Ponds                  Will provide both a                          Stormwater runoff having a
                                                               reduction in peak runoff                     high sediment or pollutant
                                                               rates and a source of                        load should not be controlled
                                                               recreation in any residential                in existing ponds because of
                                                               area.                                        its adverse impact on the
                                                            - Only minor modifications may be               natural conditions.
                                                               required to adapt an existing
                                                               pond for use as a permanent
                                                               stormwater management facility.
                                                            - Wildlife habitat and wetlands
                                                               may be preserved


                             Underground                    - Minimal interference with                    Subsurface excavation
                             Retention/                        traffic or people.                           could be extremely expen-
                             Detention Tanks                - Can be used in existing as                    sive depending upon the
                                                               well as newly developed                      type and amount of rock
                                                               areas.                                       encountered.
                                                            - Potential for using storm-                   Access for maintenance
                                                               water for nonpotable uses.                   may be difficult if proper
                                                                                                            design features are not
                                                                                                            provided.














                 STPRMWA TER QUALITYBESTMANAGEIVENT PRAC77CES

                 The volumes and rates of stormwater runoff from land developments are a major concern
                 in stormwater management. However, they are not the only consideration. The impacts
                 of stormwater runoff upon water quality are becoming of increasing concern. The
                 predominant categories of pollutants that have been identified in stormwater runoff from
                 developed areas are listed below.



                                   sediments                   9 organic enrichment
                                   nutrients                   9 toxic pollutants
                                   pathogens                   0 salts


                 There are a number of methods through which the negative effects of stormwater runoff
                 pollution can be minimized. These. methods are generally referred to as best management
                 practices for stormwater quality control (BMPs). These best management practices are
                 generally low cost, relatively low technology methods of reducing the pollutant contenf
                 of stormwater runoff. The following sections describe the most commonly employed
                 stormwater quality BMPs. As is indicated by the following information, most of the
                 stormwatcr quality BMPs also are effective in controlling the volumes and rates of
                 stormwater runoff produced by new land developments and were presented previously in
                 the context of stormwater flow control. It is fortunate that the most effective stormwater
                 management controls have the dual benefits of reducing stormwater quantities and
                 improving runoff quality.



                 Vegetative Best Management Pracdces

                 All of the following practices rely on various forms'of vegetation to enhance the pollutant
                 removal, habitat value, or appearance of a development site. Although in practice each
                 technique, by itself, is usually not capable of entirely controlling increased runoff and
                 pollutant export for A development site, they can improve the performance and amenity
                 value of other BMPs. These practices, therefore, should be considered as an integral part
                 of every development site plan.







                                                           VI-28

                 Lake Erie SWMP
                 4026-02












                      Limiting the Amount of Land Disturbed (Urban Forestry)

                      Limiting the amount of land disturbed and/or replanting         vegetation following
                      completion of construction can reduce pollutants in stormwater runoff in several
                      ways: 1) through plant uptake and storage, 2) by reducing the volume of
                      stormwater runoff and the associated pollutants, 3) through filtering, and 4) by
                      preventing soil erosion. With careful landscape design, as much as 50% of a
                      residential lot can be converted into an attractive natural setting of trees, shrubs,
                      and ground covers. The extent to which pervious, vegetated areas can be
                      preserved and/or created will have a direct effect upon the volume of stormwater
                      runoff and the quantities of associated pollutants that will be produced.
                      Moreover, the cost of maintaining the vegetated areas is relatively low and the
                      aesthetic value to the overall development can be quite high.

                      Grassed Swales                                                   Figure VI-12
                      Grassed swales are typically applied in              Illustration of Grassed Lined Swale
                      residential developments and highway
                      medians as an alternative to curb and
                      gutter drainage systems.       Figure VI-12
                      presents an example of a grassed swale.
                      Grassed swales remove pollutants throu
                                                                  gh
                      the filtering action of the grass, deposition
                      in low velocity areas, and by infiltration
                      into the subsoil. These mechanisms are
                      most effective in removing particulate
                      effective in removing particulate pollutants                    Figure VI-13
                      and have a negligible effect on soluble             Illustration of Rock Lined Channel
                      pollutants.    Swales are generally less
                      expensive to construction than curb and
                      gutter. systems and maintenance is
                      relatively low cost, generally consisting of
                      normal lawn maintenance activities such
                      -as mowing and watering as needed.











                                                              VI-29

                  Lake Erie SWMP

                 4026-02











                                 A variation to grassed swales is a rock lined waterway (Figure VI-13). A rock
                                 lined waterway consists of a channel lined with rock. These channels are
                                 generally less effective that grassed swales in the removal of pollutants due to a
                                 reduced filtering through the grass. However, some suspended pollutants are
                                 removed through deposition in low velocity areas.



                                 Filter Strips

                                 Filter strips are similar to grassed swales in many respects. However, they differ
                                 in that they are designed to only accept overland sheet flow and are not intended
                                 to serve a dual purpose as a conveyance facility. In practice, runoff from an
                                 adjacent impervious area is evenly distributed across the filter strips. To perform
                                 properly, a filter strip must be: 1) equipped with some sort of level spreading
                                 device; 2) densely vegetated with a mix of erosion resistant plant species that
                                 effectively bind the soil; 3) graded to a uniform, even, and relatively low slope,
                                 and 4) be at least as long as the contributing runoff area. Filter strips are
                                 especially effective when constructed as a buffer between the development
                                 activities and adjacent streams, curbs, and swales. They can also be used to
                                 protect surface infiltration trenches from clogging by sediment. An example of an
                                 application of filter strips is presented in Figure VI-14.

                                                                                         Figure VI-14
                                                       Example Application of Vegetated Filter Strips



                                                                                    Top elevationof strips                   Berms placed perpendicular
                                                                                    oi s6r6e conto6i, 'and                   to top of strip to prevent
                                                                                    directly abuts trench                    concenWated flows







                                                                                                                          WMded
                                                                                                                          Off sui




                                                                                                         rauss
                                                                                                         er s



                                                                                 Stone trench
                                                                                 acts as               5% strip slope or less
                                                                                 levelspreader





                                                                                              VI-30
                           Lake Erie SWMP

                           4026-02











                    The pollutant removal mechanisms in filter strips are similar to those presented
                    previously for grassed swales. As is the case with grassed swales, filter strips are
                    particularly effective in removing particulate pollutants such as sediment, organic
                    material, and many trace metals.        Filter strips are relatively inexpensive to
                    establish and cost almost nothing if preserved during site development. A
                    creatively landscaped filter strip can become a valuable community amenity,
                    providing wildlife habitat, screening, and stream protection. The open space
                    created by the filter strips can also be applied toward meeting established
                    development density limitations that may be contained in local ordinances.




                    Constructed Wetlands

                    There are two prevalent types of constructed wetlands in use:            1) shallow
                    constructed wetlands (Figure VI- 15) and 2) wet detention systems (Figure V1- 16).
                    Constructed wetland systems perform a series of pollutant mechanisms, including
                    sedimentation, filtration, adsorption, microbial decomposition, and - vegetative
                    uptake to remove sediment, nutrients, oil and grease, bacteria, and metals. While
                    constructed wetlands can be very effective in the removal of the broad range of
                    pollutants encountered in stormwater runoff, it is important that they be properly
                    designed, sited, and maintained.        The critical design consideration is the
                                                      Figure VI-15
                                 Schematic of a ShaHow Constructed Wetland




                                                VL
                                                                     6 inches deep
                               Inflow              6 inches           r less
                                                  or less
                     Levelspreader      Forebay                                   2-31%
                     mechanism          (3 ft deep)        0 - 12 inches          deep          Outflow


                                               fit.                Gradual slope













                                                           VI-31

                Lake Erie SWMP

                4026-02










                     maximization of the detention time in the wetland through proper sizing and
                     configuration to prevent short circuiting.

                                                     Figwe VI-16
                               Example Wet Detention Wetland S-Ystem




                                            Baffle or
                                             Skimmer                                         Outflow
                             0   ---------- - -----------        r --- 2R
                        Inflow   ---------        Treatnientvolunie..,_                  0 Ar-OR / grease
                                                        littoral,                              skimmer
                                                        zone (3.5ft)           Slope (10:1 desirable;
                                 Sediment sump                                 4:1 minimum)
                                                         Deeper area



                     Siting of wetlands can be difficult due to the importance of soil properties (chiefly
                     permeability) to performance, size requirements, and concerns relative to potential
                     nuisance insect breeding. In addition, created wetlands become a resource area
                     that will subsequently be protected by federal and state laws.



                 InfilOation Facilities

                 Infiltration facilities permanently capture runoff so that it soaks to the ground water. As
                 was presented previously, to the extent of their capacity to handle the volumes of
                 stormwater runoff produced, they are very effective in controlling stormwater runoff
                 flows. They also can be very effective in removing pollutants. Pollutant removal in these
                 BMPs occurs primarily through infiltration, which eliminates the runoff volume or lowers
                 it by the capacity of the facility. Currently, the three types of facilities commonly
                 employed to remove pollutants from stormwater runoff through infiltration are: 1)
                 infiltration'basins; 2) infiltration trenches / dry wells; and 3) porous pavements (grassed
                 swales, which also promote infiltration were discussed previously under vegetative
                 practices).
                                                e or

                                                    r


                         fl
                                 ........    77
                        n   ow                            -tto
                                                        = @(35ft)        @@@op







                                                            VI-32

                 Lake Erie SWMP

                 4026-02














                         Infiltration Basins

                         Infiltration basins are similar to dry ponds, except that infiltration basins have
                         only an emergency spillway and no standard outlet structure (see Figure VI-17).
                         All flow entering an infiltration basin (up to the capacity of the basin) is retained
                         and allowed to infiltrate into the soil.               Infiltration basins provide pollutant
                         removal through volume. reduction, filtration, and settling. They are particularly
                         effective in removing bacteria, suspended solids, insoluble nutrients, oil and
                         grease, and floating wastes. They are less effective in removing dissolved
                         nutrients, some toxic pollutants, and chlorides. Therefore, infiltration basins
                         should not be used in cases where the runoff can be suspected to contain
                         significant amounts of those pollut-rtnts.


                                                            Figure VI-17
                                         Example Infiltration Basin Layout






                                                        Flat basin floor with
                                           M'.          dense grass turf                                          Inlet
                                                                                       Rip-rap
                                                                                      settling basin and
                         Riprap
                                                                                      level spreader
                         outfall
                         protection                                  Back-up underdrain
                                                       Emergency spillway





















                                                                        VI-33
                    Lake Erie SWMP

                    4026-02











                     Infiltration basins often have relatively large land requirements and require a
                     suitable soil to be effective. Accumulating runoff must be able to infiltrate the
                     soil in the bottom of the basin. Typically sand and loam, with infiltration rates
                     greater that or equal to 0.27 inches per hour are the preferred soils. Soils with
                     percolation rates meeting this criteria exist throughout the watershed. However,
                     high or seasonally high water tables predominate throughout most of the
                     watershed. For infiltration to occur, ground water levels should be located at least
                     2 to 4 feet below the bottom of the basin. Consequently, the use of infiltration
                     basins will not be practical throughout most of the Lake Erie Area Watershed.



                     In
                       filtration Trenches IDry Wells

                     Subsurface infiltration practices, such as infiltration trenches or dry wells force
                     rtmoff into the soil to recharge ground water'and remove pollutants. Filtration is
                     the primary pollutant removal mechanism active in these facilities.              They
                     effectively remove suspended sediments, floating materials, and bacteria.. They
                     are less effective at removing dissolved materials.



                     The soil infiltration rate and structure size are the most important considerations
                     in the design of infiltration structures. The soils underlying the structures must be
                     tested to determine their infiltration capacity and the ground water level. The soil
                     must neither be too impermeable to runoff nor to rapidly permeable. Moreover, a
                     distance of at least 2 feet should be maintained between the bottom of the
                     infiltration structure and the mean high ground water elevation. Due to the nature
                     of prevailing conditions in the area, siting of infiltration facilities must be made
                     carefully throughout the Lake Erie Area Watershed.




                     Porous Pavement

                     By allowing. stormwater to infiltrate into the soil, porous pavements can reduce
                     runoff volume and pollutant discharge. Porous pavements can remove significant
                     amounts of both soluble and particulate pollutants. Porous pavement is primarily
                     designed to remove pollutants deposited from the atmosphere, as coarse solids can








                                                             VI-34

                 Lake Erie SWMP

                 4026-02











                      clog the pavement pores. As a result, porous pavements are generally designed
                      into parking areas that receive light traffic.



                      As is the case with all of the infiltration systems, the effectiveness of porous
                      pavements for pollutant removal is highly dependent upon soil characteristics and
                      ground water levels. The soils under the pavement system must produce adequate
                      infiltration and ground water levels should be 2 to 4 feet below the bottom of the
                      paving and subbase system.         Proper maintenance of porous pavements is
                      important and can be extensive. The pavement must be kept free of coarse
                      particles that can clog the pavement and prevent runoff from infiltrating. The
                      pavement must, therefore, be regularly inspected and cleaned with a vacuum
                      sweeper and high pressure jet.




                  Detention Facilities

                  One of the most common structural methods of controlling runoff is through the
                  construction of ponds to collect runoff, detain it, and release it to receiving waters at a
                  controlled rate. Pollution reduction during the temporary period of runoff storage results
                  primarily from the settling of solids. Detention facilities, therefore, are most effective at
                  reducing the concentrations of solids and the pollutants that adhere to solids, and less
                  effective at removing dissolved pollutants.



                  The three types of detention facilities commonly used to remove pollutants from
                  stormwater runoff are extended detention dry ponds, wet ponds, and constructed
                  wetlands. The first two types of facilities are discussed below. Constructed wetlands
                  were introduced previously under the topic of vegetative methods.



                      Extended Detention Dry Ponds

                      As was discussed previously in regard to flow control devices, dry ponds are
                      frequently used to control peak discharges by temporarily detaining runoff. They
                      are designed to completely drain at the conclusion each rainstorm event. When
                      designed to achieve pollutant load reductions, the design of the ponds are






                                                             VI-35

                  Lake Erie SWMP

                  4026-02











                       modified to achieve longer detention times than are necessary solely to adequately
                       control peak discharges. Generally, the ponds are designed to retain a specified
                       runoff.volume for a period of time sufficient to achieve the desired pollutant
                       removal. This requires sufficient storage volume and an outlet flow control
                       devices to accomplish the desired flow detention. Dry ponds should also include
                       a low flow channel designed to reduce erosion; vegetation on the bottom of the
                       pond to promote filtering, sedimentation, and uptake of pollutants. In addition,
                       dry pond designs frequently include upstream structures to remove coarse
                       sediments and reduce sedimentation and clogging of the outlet. An example of a
                       layout of an extended detention pond is illustrate in Figure VI- 18.


                                                                Figure VI-18
                                       Schematic of a Dry Extended Detention Pond



                                                                                  Lower Stage
                                                                                                         Embanlanent


                                                Top Stage
                                                                                          @Wer

                                                                               Extended
                                                                               Detention                       ZV
                                                                               Control Device
                                                                                                           Emergency
                                                             ew                 . . . . . . .              Spillway

                                                           10 Year Water Surface Elevation
                                                        2Year-




                                                               Riprap
                                                               Apron
                                                                    Gravel                                ei
                                           Plan View






                       Maintenance of water quality dry ponds is important.                       Regular mowing,
                       inspection, erosion control, and debris and litter removal are necessary to prevent
                       excessive sediment buildup and vegetative overgrowth. Also, periodic nuisance






                                                                    VI-36

                   Lake Erie SWMP

                   4026-02












                   and pest control could be required. The primary constraints to siting dry ponds
                   are land requirements, topography, and depth to bedrock.




                   Wet Ponds

                   The design of wet ponds is similar to that of dry ponds. In wet ponds, however,
                   stormwater runoff is directed into a co nstructed pond or enhanced natural pond, in
                   which a permanent pool of water is maintained. Once the capacity of a wet pond
                   is exceeded, collected runoff is discharged through an outlet structure or
                   emergency spillway. An example of a wet pond sys  tem is presented in Figure 0VI-
                   19.


                                                Pond


                                                                                                                                    




                                                                                     



                                             
                                                      
                                    
                                                                         




                                                                                            
                                                                                           


                                                                                  
                                                    

                                                              




                                                
                                                                                                                                            


                                                    






                                                        VI-37

               Lake Erie SWMP

               4026-02
 









                     The primary pollutant removal mechanism in wet ponds is settling. The ponds are
                     designed to collect stormwater runoff during rainfall and detain it until additional
                     stormwater enters the pond and displaces it. While the runoff is detained, settling
                     of particulates and associated pollutants takes place in the pond. Wet ponds can
                     also remove pollutants from runoff through vegetative uptake. Wet ponds should
                     be vegetated with native emergent aquatic plant species, which can remove
                     dissolved pollutants such as nutrients from the runoff before it is discharged to the
                     receiving water.



                     Wet ponds are typically designed with a number of different water levels. One
                     level has a permanent poll of water. The next level periodically is inundated with
                     water during storm. This level should be vegetated and relatively flat to promote
                     settling and filtering of sediments and vegetative uptake of nutrients. The highest
                     level will be inundated only during extremely heavy rainfall. This level should
                     also be vegetated. Sizing of wet ponds is determined by requirements for storage
                     volumes and desired detention times.



                     Maintenance requirement for wet ponds include periodic sediment removal
                     (approximately once every 10 to 20 years), mowing, and litter removal. Factors
                     affecting siting include land requirements, soil conditions (soils should not be
                     excessively porous and ground water tables should be relatively high), and
                     topography.



                 Summary of Water Quality Best Management Practices

                 As was indicated in the preceding discussion, there are a number of techniques that
                 represent best management practices for reducing pollution associated with stormwater
                 runoff. These techniques all also have application in efforts to control runoff volumes
                 and peak rates of dicharge.          Consequently, appropriately designed stormwater
                 management facilities can improve runoff water quality while achieving the required
                 control of stormwater discharge flows. Table IV-2 contains a comparison of the pollutant
                 removal effectives for the range of BMPs discussed under various design approaches. As
                 is indicated in Table VI-2, the effectiveness of the BMPs varies. It is important, however,
                 to recognize the water quality benefits that are offered and to consider these benefits in
                 the overall selection and design of stormwater management controls.





                                                            VI-38

                 Lake Erie SWMP
                 4026-02












                                                                                                                    Table V1-2
                                       Comparative Pollutant Removal of Stormwater BMP Designs



                                          Best Management                                              V   Z6                                                   Overall
                                          Practice / Design                                                                                                Effectiveness                                   Key

                                          Grassed Swale
                                                                     Design 1              00000 e                                                       Low                           0          0 to 20% Removal
                                          Filter Strip               Design 2                       (@       (@       (@       0                         Low                           (@         20-to 40% Removal
                                                                     Design 3                       0 0 0                                                Low                           C)         40 to 60% Removal
                                                                     Design 4                                                                            Moderate                                 60 to 80% Removal
                                          Porous Pavement                                                                                                                              a
                                                                     Design 5                                                                            Moderate                                 80 to 100% Removal
                                                                     D    .esign 6                                                                       High                                     Insufficient Knowledge
                                                                     Design 7                                                                            High
                                          Infiltration Basin
                                                                     Design 5                                                                            Moderate
                                                                     Design 6              0        3        (3       (A       0         (a              High                          Source: DER Special Protection
                                                                                                                                                                                       Waters Implementation
                                                                     Design 7                                                                            High                          Handbook
                                          Infiltration Trench
                                                                     Design 5                                                                            Moderate
                                                                     Design 6              Q1 (3             3        Q1       0         Q1              High
                                                                     Design 7                                                                            High
                                          Wet Pond
                                                                     Design 8                                                                            Moderate
                                                                     Design 9              0 0 C@                              Q0        (D              Moderate
                                                                     Design 10             0        QO       (3       3        (a        (9              High
                                          Extended Detention Pond
                                                                     Design I I                                                          (D              Moderate

                                                                     Design 12                                                                           Moderate
                                                                     Design 13                                                                           High




                                       Design 1:  High dope swales with no check dams                                             Design 8: Permanent pool equal to 0.5 inch storage par a  .ropervious acre
                                       Design 2:. Low gradient swales with check don                                              Dmiga9: permanent pool equal to 2.5 (Vr); -bote, Vr equals the mean storm nmoff
                                       Design 3:  20 foot wide turfstrip                                                          Design 10: permanent pool equal to 4.0 (Vr); where, Vr equals the mews stom nmoff
                                       Design 4:  100 foot wide forested strip with lavel spreader                                Design 11: First - flush runoffvolume detamed 6-12 hours
                                       Desiga5: facility emiltrates first -flush: 0.5 inch mnoff/ imperviotni sere,               Design 12: Runeff volume produced by 1.0 inch dawned for 24 hours
                                       Design 6:  Facility exfilaztes we inch rveall'volume per impervious acre                   Design 13: As in design 12, but with sh"ou, marsh, in bottom stage
                                       Design 7:  Facility exfiltrates all rueoff up to 2 year design storm







                                                                                                                                  VI-39
                                    Lake Erie SWMP
                                     4026-02














                 EROSIONAND SEDIMENTA77ON CONTROL MEASURES

                 The ability of storm water runoff to transport material is a function of flow velocity and
                 the erosion resistance of the material. As stormwater runoff flow rates increase, the flow
                 velocity increases and more eroded.material is transported. As the water travels down the
                 watershed, channel gradients reduce flow velocity and sediment begins to be deposited in
                 streams and storm sewers. This process, known as sedimentation, continues as the flow
                 rate and flow velocity reduces. New developments further increase the sedimentation
                 problem by removing natural vegetation and making the bare ground susceptible to
                 erosion.



                 The following principles should be practiced for urban soil erosion and sedimentation
                 control.



                 I .Keep disturbed areas small: Areas vulnerable to erosion should be disturbed the
                    minimum amount possible. As much natural cover as possible should be retained and
                    protected. The construction plan should be phased whenever possible in small units
                    and in sequence such that only the area being developed is exposed. All other areas
                    should have a good cover of vegetation or mulch.



                 2. Stabilize and Protect Disturbed Areas: Mechanical and/or structural methods and
                    vegetative methods are available for stabilizing disturbed areas. These methods
                    include seeding, mulching, sodding, retaining walls, terracing, use of chemical
                    stabilizers, and others.



                 3. Keep Runoff Velocities Low: Removal of existing vegetative cover and the resulting
                    increase in impermeable surface during development increase both the volume and
                    velocity of runoff. Short slopes, low gradients and the preservation of natural
                    vegetation cover help to keep stormwater velocities low and thus limit soil erosion.











                                                          VI-40
                 Lake Erie SWMP

                 4026-02












                       4. Protect Disturbed Areas from Runoff. Protective measures that can be utilized to
                            prevent water from entering and running over disturbed areas are diversions,
                            waterways, structures etc.



                       5.   Retain Sediment within the Site Area: Sediment can be retained by two methods:
                            filtering runoff as it flows, and detaining sediment laden runoff for a period of time
                            large enough to allow the soil particle settle. Sediment basins, vegetative filter strips,
                            terraces and sediment barriers may be used to retain sediment. However one should
                            not rely solely upon vegetation filter strips, since sediment may rapidly render such
                            areas useless by killing the vegetation.



                       6.   In-stream Control: After precipitation and runoff has concentrated, an outlet channel
                            is needed for safe release of the water off the site. This outlet channel needs to be
                            protected from erosion.            A wide, shallow grassed water way can be a very good
                            method. Channels with steeper gradients need structural protection along with, or
                            instead of vegetative measures. Typical structural measures include: earth dams with
                            a full flow pipe through the fill, weirs, flood gates, and check dams. In designing
                            such facilities, it is important to consider the effects of the dam or embankment on
                            upstream properties. The design must include safety features in the form of spillways
                            and bypasses to prevent overtopping which can cause embankment failure.



                       The details on the design and implementation of practices described above and many
                       others can be obtained from the Soil Conservation Service and the County Conservation
                       District.




                       @[email protected]@@@VE.RS.US.STO                      TEA.    .. .....
                                    .. .. .....
                                                                                                           . . ........
                                                               :TIVES
                              AGEMENT
                                                        "A
                             .... .. .... . . . .. ...                    ........... ....           ... . ..

                       It was mentioned earlier that the soil characteristics at the development site, such as soil
                       permeability, water capacity, frost penetration etc. play ail                 'important role in the selection
                       of gtormwater management alternatives. This section gives specific soil information for
                       the Lake Erie Area Watershed and discusses the soil characteristics and their impact on
                       alternative storinwater management techniques.






                                                                               VI-41
                       Lake Eric SWMP

                       4026-02












                 Soil information for Erie County can be obtained from the publications, "Soil Survey of
                 Erie County, Pennsylvania". These publications are prepared by Soil Conservation
                 Service of U.S. Department of Agriculture. The survey has a general soil map showing in
                 color, the soil associations in the county. A soil association is a landscape that has a
                 distinct pattern of soils in defined proportions. The soil association map should not be
                 used to determine the soil type, for selecting stormwater water management alternatives.
                 The reason is that, a general soil map is intended to be a general guide in evaluating large
                 areas such as a watershed, or in county-wide planning for community development. It is
                 not a suitable map for selecting a site for locating a stormwater detention or retention
                 facility. For example, this map can be used to establish a generalized idea, that Ellery
                 and Alden Silt Loam s    'oils. constitute a major soil type in the Lake Erie Area Watershed.
                 Also, the survey tells that these soils have seasonal high water tables ranging from 0 to 10
                 inches below the surface, thus having severely limited application for infiltration storage.
                 Thus, a general rule can be established that infiltration storage alternative should not be
                 approved in the Ellery and Alden Silt Loam soils unless the occurrence of the ground
                 water table at shallow depths has been ruled out by on-site engineering tests.



                 Table VI-3 presents some relevant properties of the Lake Erie Area Watershed soils
                 significant to the use of various stormwater management techniques. Table VI-4
                 indicates the suitability of the soils for some generalize construction activiities associated
                 with stormwater management alternatives. General conclusions that can be drawn from
                 the information contained in Tables VI-3 and VI-4 include the following.



                     1. Activities designed to minimize the creation of impervious surfaces will be
                         appropriate throughout the watershed.
                     2.  The construction and operation of dry and wet ponds will generally be feasible
                         throughout the watershed, although consideration must be given to site          specific
                         soil conditions.

                    .3.  The use of large scale induced infiltration systems will generally be limited by
                         soil and ground water conditions that frequently are not suitable for those
                         techniques.









                                                              VI-42

                 Lake Erie SWMP

                 40 26-02













                                                                         Table VI-3
                                                             Lake Erie Area Watershed
                                                                  Relevant Soil Properties

                                                           Depth to Seasonal           Depth To
                                                          High Ground Water             Bedrock             Percolation Rate
                                  Soil Name                       (Inches)              (Inches)             (Inches/Hour)
                       Allis Silt Loam                            0-12                      18                  0.2-2.0
                       Beach and Riverwash                          0                     >48                     > 8.3
                       Beach Sand (stabilized)                    0-24                    >120                    > 6.3
                       Berrien Fine Sandy Loam                    9-28                    > 120                 0.2-2.0
                       Birdsall Silt Loam                         0-18                    >120                  0.2-0.63
                       Candice Silt Loam                          0-18                    > 120                 0.2-0.63
                       Caneadea Silt Loam                         12-30                   >72                   0.2-2.0
                       Chagrin Silt Loam                          0-30                    >72                   0.63-6.3
                       Chagrin Very Gravelly Loam                 12-36                   >72                   2.0-20.0
                       Conotton Coarse Sandy Loam                 18-72                   >120                  0.2-6.3
                       Dune Sand                                  >24                     >72                     >20.0
                       Dalton Silt Loam                           18-72                   >120                  0.2-20.0
                       Ellery and Alden Silt Loam                 0-10                    >72                   0.2-2.0
                       Erie Silt Loam                             6-18                    >96                   0.2-2.0
                       Fredon Loam                                -0-18                   >72                   0.2-6.3
                       Halsey Loam                                0-12                    >120                  0.2-6.3
                       Howard Gravelly Silt Loam                  >24                     > 120                 0.63-6.3
                       Langford Silt Loam                         18-30                   >120                  0.63-2.0
                       Lobdell Silt Loam                          0-18                    >48                   0.2-6.3
                       Mahoning Silt Loam                         18-30                   >120                  0.2-0.63
                       Manlius and Lordstown                      >24                     >30                   0.2-2.0
                       Mardin Gravelly Silt Loam                  18-30                   >120                  0.2-2.0
                       Miner Silt Loam                            0-6                     >72                   0.2-0.63
                       Muck and Peat                              >24                     >48                     <0.2
                       Ottawa Fine Sandy Loam                     >24                     >120                  <0.2 - 2.0
                       Ottawa Loamy Fine Sand                     >24                     >120                  0.2-6.3
                       Phelps Gravelly Silt Loam                  18-30                   >120                  0.2-0.63
                       Platea. Silt Loam                          6-18                    >120                  0.2-2.0
                       Rimer Fine Sandy Loam                      0-30                    >120                  0.2-0.63
                       Scio Silt Loam                             18-30                   @-72                  0.2-2.0
                       Sloan Silt Loam                            0-10                    >72                   0.2-0.63
                       Sloan Silty Clay Loam                       0                      >72                   0.2-0.63
                       Trumbell Silt Loam                         0-18                    >120                  0.2-0.63
                       Unadilla Fine Sandy Loam                   >24                     >72                   0.63-2.0
                       Volusia, Gravelly Silt Loam                0-18                    >96                   0.2-2.0
                       Volusia Silt Loam                          0-18                    >96                   0.2-2.0
                       Wallingion Fine Sandy Loam                 0-18                    >120                  0.2-0.63
                       Wallinkton Silt Loam                       0-18                    >120                  0.2-0.63
                       Wauseon FIne Sandy Loam                    0-18                    >72                   0.2-2.0
                       Wayland Silt Loam                          0-18                    >72                   0.2-2.0
                       Williamson and Collamer                    18-30                   >120                  0.2-2.0
                       Wooster Gravelly Silt Loam                 >24          T-->i2o                          2.0-6.3













                                                                         Table VI-4
                                                                 Lake Erie Area Watershed
                                                      Limitations to Suitability of Soils for Stormwater
                                                                 Management Alternatives


                                Soil Name                    Ponds                    Building Sites            Diversion Terraces
                        Allis Silt Loam             Shallowness               High water table; shallow       Shallow to bedrock
                                                                              to bedrock
                        Beach and Riverwash         Rapid permeability        Flooding                        None
                        Beach Sand - Stabilized     Rapid permeability        Flooding                        None
                        Berrien Fine Sandy          Rapid permeability        Seasonally high water table;    None
                         Loam                                                 Unstable substratum
                        Birdsall Silt Loam          None                      High water table                None
                        Canadice Silt Loam          None                      High water table; unstable      None
                        Chagrin Fine Sandy          None                      Unstable                        None
                        Conotton Coarse Sandy       Rapid permeability        Flooding                        None
                        Dalton Silt Loam            None                      Seasonally high water table;    None
                                                                              unstable substratum
                        Dune Sand              -    Rapid permeability        Unstable                        Rapid permeability
                        Ellery and Alden Silt       None                      High water table                None
                        Erie Silt Loam              None                      Seasonally high water table     None
                        Fredon Loam             -   Quicksand                 High water table                Quicksand
                        Fresh Water Marsh           Flooding                  FGding                          Flooding
                        Halsey Loam                 Ouicksand                 High water table                None
                        Howard Gravelly Silt        Rapid permeability        None                            None
                        Langford Silt Loam          None                      High water table                None
                        Lobdell Silt Loam           None                      High water table                None
                        Mahoning Silt Loam          None                      Seasonally high water table     None
                        Manlius and Lordstown       Shallowness               Shallow to bedrock              Shallow to bedrock
                        Mardin Gravelly Silt        None                      None                            None
                         Loam
                        Mardin and Volusia          None                      Seasonally high water table     None
                         Gravelly Silt Loams
                        Miner Silt Loam             None                      High water table                None
                        Muck and Peat               Unstable                  Unstable                        Unstable
                        Ottawa Fine Sandy Loam      Rapid permeability        None                            None
                        Ottawa Loamy Fine           Rapid permeability        Unstable                        None
                         Sand
                        Phelps Gravelly Silt        None                      None                            None
                         Loam
                        Platea Silt Loam            None                      Seasonally high water table     None
                        Rimer Fine Sandy Loam       Quicksand                 Seasonally high water table     None
                        Scio Silt Loam              None                      Seasonally high water table     None
                        Sloan Silty Clay Loam       None                      Flooding                        None
                        Trumbull Silt Loam          None                      Seasonally high water table     None
                        Unadilla Fine Sandy         None                      None                            None
                         Loam
                        Volusia Gravelly Silt       None                      Seasonally high water table     None
                         Loam
                        Wallington Fine Sandy       Quicksand                 Seasonally high water table     None
                         Loam
                        Wallington Silt Loam        None                      Seasonally high water table     None
                        Wauseon Flne Sandy          Quicksand                 Seasonally high water table     None
                         Loam
                        Wayland Silt Loam           None                      Flooding                        None
                        Williamson and Collamer     Quicksand                 Seasonally high water table     None
                         Fine Sandy Loarns                                                                 I
                        Williamson and Collamer     None                      Seasonally high water table     None
                         Silt Loams
                        Wooster Gravelly Silt       Rapid permeability        None                            None
                         Loam













                 OPERATION AND MAINTENANCE CONSIDERATIONS

                 Most stormwater control facilities or systems must be monitored and maintained
                 regularly following construction to assure effective operation, long life and compatibility
                 with the local setting. Table VI-5 contains a summary of key operation and maintenance
                 considerations for the storrawater management alternatives discussed previously.



                 As is indicated in Table VI-5, there is range of operation / maintenance items which must
                 be performed depending upon the type of stormwater management techniques employed.
                 It is recommended that individual municipal stormwater management ordinance require
                 that the enumeration of specific recommended operation and maintenance activities be
                 be outlined by the design engineer at the time applications for permit approval are made.
                 The designer of the facilities should be in the best position to define the maintenance
                 requirements associated with the facilities being proposed. However, operation and
                 maintenance plan should be reviewed in consideration of the general requirements
                 presented in Table VI-5. The approved set of operation and maintenance activities should
                 then be used as the basis of an on-going operation and maintenance plan. Also,
                 provisions should be made in the appropriate ordinances or regulations to provide for
                 effective mechanisms through which the completion of critical maintenance can be
                 assured.




                   11BLIC VCEPTAN-.CE:@.                        TEN TION:
                                                        .......... ... ...... ...... .........

                 On-site detention, also has the disadvantage of not having wide               spread public
                 acceptance. This is mostly because the individuals have to spend extra dollars to satisfy
                 the runoff control regulations. Also, they are concerned about the safety of their children
                 also, which are usually attracted toward the ponds. Therefore, it is highly recommended
                 to. employ multi-purpose use of detention facilities. In the minds of a community, the
                 multi-purpose use of such a detention facility greatly improves the perception that such a
                 facility is a justifiable expense by the public or by the private developer [APWA, 198 1
                 Detention ponds are excellent examples of multi-purpose adaptability. When conceived
                 and designed artistically, they can support different kind of activities throughout the year,
                 such as, water sports and fishing. During winter months, shallow detention ponds with a
                 permanent pool of water provide opportunities for ice skating in some parts of the
                 country.







                                                            VI-45
                 Lake Erie SWMP

                 4026-02













            6                                                          0                                    Pu        0         PO       0-0      110       u        0
                                                                      @u        0                           a                            o-       0         0        CO
                                                              CD       a                                              CD        0                 0
                                                                                0                           CL

                                                                                                                                0        (M
                                                                                                                                                            0        0
                                                                                          0        0                  W                  t-4
                                                                                                            Cr
                                                    Q.                                             En                           CD
                                                    CD        rA                                                      tv                 u                  CD       CD
                                                                                                                                CD
                                              a     rA                          CD                                    CD                 CD                 CD       CD
                                              Ch    ca.                         0         rA
                                              UQ    r-                                             Gn                 CD                 CD
                                                                                                                                                            0
                                              w                                                                       0                  0
                                              CD                                                            CD
                                              I=.
                                                                                                            CD

                                                                                                                                                            rA


                                              0     CD
                                              0     CD


                                                    UQ
                                                    a
                                              CL
                                                                                                                                                                               Dredging
                     @-4                      0

                                              CD
                     a-,                            a                                                                                                                          Debris / Sedimentation Removal
                                                    CD
                                                    10
                                                                                                                                                                               Weed Control
                                                    CD


                                                    .A                                                                                                                         Insect Control


                                                                                                                                                                               Mechanical Maintenance


                                                                                                                                                                               Mowing

                                                                                                                                                                               Cleaning

                                                                                                                                                                               Repair

                                                                                                                                                                               Inspection










                  A detention basin that. is dry between runoff events can be used for field sports such as
                  football, soccer, baseball, and various passive recreational pursuits such as badminton,
                  model airplane operation, shuffleboard, croquet, and picnicking. Some detention basins
                  may double as tennis or baseball courts. It might be difficult to convince some
                  developers that the benefits derived from recreation outweighs the cost of the land plus
                  construction costs. However, should the recreation area be redesigned as a multi-purpose
                  recreational/detention basin, the cost would look insignificant compared to the cost of
                  upgrading a storm drainage system or the amount of potential flood damages.



                  Detention facilities may also contribute to the protection and preservation of wildlife
                  habitats and other natural resources. , One example is a 602 ha (244 ac) tract in Chester
                  County, Pennsylvania, where 315 homes were to be constructed. Approximately 84 ha
                  (34 ac) of open space were provided containing two detention ponds designed to store
                  runoff from the 100-year rainstorm. One year following the completion of the detention
                  ponds, wildlife was observed returning to its former habitat. Geese have nested and fish
                  have returned to the streams and newly constructed channels. The dual purpose
                  utilization of stormwater detention facilities as wetlands represents a potential useful
                  means of coping with the increasingly stringent wetland protection requirements and
                  associated wetland replacement activities.



                  Although multiple uses are a better alternative for securing the community acceptance,
                  maintenance costs for such facilities may be higher. Therefore, when considering
                  multiple uses, it is important to look at all the associated costs and intangible benefits, to
                  determine if it is practical to proceed with the multiple use concept.




                     -:XX

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

                  A survey conducted by APWA in 1980, based on 325 respondents, revealed that there
                  have been two -drownings reported at the detention facilities. It is therefore, very essential
                  to take precautions in design and selection of storm water management alternatives, to
                  minimize hazards. Embankment slopes, railings, fencing and other features are obvious
                  considerations.    The importance of designing and constructing outflow structures and
                  dams with safety considerations in mind should never be ignored. In general, the
                  approa&es that can be used to promote safety are [APWA, 198 1






                                                              VI-47
                  Lake Erie SWMP

                  4026-02












                      1.    Keep people off the detention facility site

                      2.    Provide escape aids

                      3.    Make the onset of the hazards gradual

                      4.    Eliminate the hazards



                  The designers and reviewers of stormwater control facilities, particularly those using
                  detention / retention facilities should pay particular attention to incorporating appropriate
                  safety features in the design of the facilities.



                  Special attention must be given to the design of outflow structures to satisfy the safety
                  considerations. Water currents constitute a distinct hazard to persons who enter a
                  detention pond or basin during periods when stormwater is being discharged. The force
                  of the currents may push a person into an     outflow structure or may hold a victim under
                  the water where a bottom discharge is used. Several features designed to either eliminate
                  or reduce such hazards are illustrated in Figures VI-20 and VI-21.



                  Figure VI-20 illustrates two versions of desi  gns for non-submerged outlets: 1) curvilinear
                  trash/safety racks for standard flared end sections and 2) narrow flume outlets. Both of
                  these designs represent methods which tend to reduce the potential for persons to be
                  drawn into or trapped against the outlet devices.



                  Figure  VI-21 presents suggested safety features for submerged outlets:            1) outflow
                  velocities and hence the associated hazards can be reduced through the use        of a porous
                  dam type of outlet facility; and 2) the illustrated safety rack for submerged outlets reduces
                  the entrapment potential and provides a means of egress from the basin. As is also
                  illustrated in Figure VI-2 1, drowning hazards can also be reduced by using a floating inlet
                  for a ba'sin outlet structure. The floating inlet -reduces the drowning hazard by eliminating
                  the water force which could trap a person at the outflow structure.








                                                              VI-48

                  Lake Erie SWMP

                  4026-02












                                                            Table VI-20
                             Suggested Safety Features for Non-Submerged Outlets


                                                                                fill 111111               10
                                                                                           Plan View







                                     Plan View                                             Elevation



                                                                                                   A




                     A-

                                      Elevation





                                                                                Isometric Detail of Louver









                                                                                        Section A - A
                                    Section A - A


                     Curvilinear Trash/Safety Rack                          Narrow Flume Outlet For
                   for Standard Flared End Sections                                Detention Ponds













                                                                VI-49
                   Lake Eric SWMP

                  4026-02












                                                                 Figure VI-21
                                         Suggested Safety Features for Submerged Outlets


                                                                   Ladder Rungs   -low,




                                                                                    Flow Control





                                                       Safety Rack for Submerged Outlets








                                                                             Holes to fill
                                                                             Receptacle
                                                                  Runott     and Initiate
                                                                             Floating
                     A,ttinuated
                                               Detention
                      Runoff

                                                          Filter Fabric
                                    Rock


                                           4W
                                          Infiltration



                            Porous Dam for Detention Ponds
                            With Low Velocity Discharge



                                                                                             Floating Inlet With
                                                                                       Recessed Receiving Receptacle






                                                                                . .. ...... .... ...... ..... . ......... .
                    DISM        LAE A     T6


                    GENERU

                    The stormwater management techniques discussed thus far. have been geared primarily to
                    on-site control methods. It is likely that on-site controls will be the predominant form of
                    stormwater management in the Lake Erie watershed. Off-site, distributed storage is,





                                                                      VI-50

                    Lake Erie SWMP

                    4026-02










                 however, an alternative or adjunct to on-site control techniques which should be
                 recognized and considered for use where appropriate. Simply defined, distributed storage
                 is the process of utilizing the most suitable site or sites for regional detention facilities.



                 The combination of on-site detention and distributed storage approaches may
                 significantly improve the capability of land developers and communities to control
                 stormwater on a watershed basis.        Distributed storage may also offer a means of
                 accommodating development in a manner which minimizes total costs and optimizes land
                 utilization through the sharing of a single, strategically located detention or retention
                 facility. Finally, the use of distributed storage may increase the feasibility of dual or
                 multi-purpose facilities. For example, certain recreation areas might easily be used to
                 provide temporary stormwater storage; natural or artificial ponds and lakes can serve both
                 recreation and stormwater management objectives; and stormwater management facilities
                 may be constructed as replacement wetlands.





                      .... ... ...

                 The institution of stormwater management regulations throughout the watershed will
                 require that land developers include provisions in their land development plans to limit
                 increases in the volume of runoff and to control peak rates of stormwater discharges to
                 levels specified in the local ordinances.        These standards will be presented as
                 performance standards. That is, the standards will set limits on the peak rate of discharge
                 permitted from the development site without specifying the exact methods to be used in
                 order to meet the standards. The owner of the development will be affor*ded a high
                 degree of flexibility in the selection and design of the specific measures to be
                 incorporated into the design of the development. This will permit the developer to select
                 and arrange the various available control techniques in a manner that is most efficient for
                 the particular information and that best accommodates the intended use of the
                 development.
                 Nevertheless, the various stormwater control techniques offer differing degrees of benefit.
                 For example, measures such as the preservation of pervious areas, the use of filter strips
                 and buffers, and the use of vegetated swales offer the following significant advantages:



                     1. Minimization of total runoff volumes






                                                            VI-51

                 Lake Erie SWMP

                 4026-02











                     2. Promotion of aquifer recharge

                     3. Stormwater pollution reduction

                     4. Ease of construction and maintenance

                     5. Low construction and maintenance costs

                     6. Preservation of open space



                 The opportunity for realizing these benefits is lost if no effort is made to utilize these
                 techniques and the stormwater performance standards are satisfied solely through the
                 construction of detention facilities. It is important, therefore, that the land developers be
                 encouraged to make use of the fall range of available control techniques in an integrated
                 approach that maximizes the attributes of each. To that end, the municipal stormwater
                 ordinances should encourage the land developers to select the general types of stormwater
                 controls used in his/her stormwater management plan in the general order of preference:



                     1 . Maximization of infiltration on-site by minimizing land disturbance, maximizing
                          the amount of pervious surfaces incorporated in the development, and creating
                          vegetated strips and buffer areas.
                     2.  Flow attenuation through the use of operi'vegetated swales, rock lined channels,
                          and natural depressions

                     3.  Stormwater detention / retention structures (dry, wet, multi-purpose)



                 An example of a land development that employs the broad range of applicable. control
                 techniques is present in Figure VI-22. Tlie concept illustrated in Figure VI-24 is an
                 approach to providing stormwater management techniques in a manner that incorporates
                 them into the overall design of the development while using the flow and pollution
                 control capabilities of each technique in an integrated stormwater management and
                 overall land development plan.











                                                            VI-52
                 Lake Erie SWMP
                 40  26-02





                                                                                             Figure VI-22
                                                Example of Development Integrating Variety of Stormwater
                                                                                       Control Techniques



                                                                   r


                                                                                              e
                                                                                    Ir























                                A


                                                          4A







                                                                                                   Techniques Employed

                                                    A:       Wet detention pond                                              F:       Multi-use dry detention area
                                                    B:       Grassed swale                                                   G:       Dutch drains under roof eves
                                                    C:       Oringinal growth woodlands preserved                            H:       Pervious surface walkways
                                                    D:       Rock-lined channel                                              1:       Parking lot detention storage
                                                    E:       Grassed strips                                                  J:       Grassed strips in parking area



                                                                                                                             .   @ NOAA COASIAL SERVICES CTR LIBRARY             I
                                                                                                                             ! 3 6668 14111483 7                                 1
                                                                                                                                                                                 1
                                                                                                                                                                                 1
                                                                                                                                                                                 1
                                                                                                                                                                                 1
                                                                                                                                                                                 1
     1.                                                                                                                                                                          I
                                                                                                                                                                                 I
                                                                                                                                                                                 I
                                                                                                                                                                                 I
                                                                                                                                                                                 I
                                                                                                                                                                                 I
                                                                                                                                                                                 I
                                                                                                                                                                                 I
                                                                                                                                                                                 I
                                                                                                                                                                                 I
                                                                                                                                                                                 I
                                                                                                                                                                                 I