Jamestown Public Schools Bush Elementary Addition and Alterations

ADDENDUM TO THE STORMWATER POLLUTION PREVENTION PLAN For the Jamestown Public Schools Bush Elementary Addition and Alterations Jamestown, New York Chautauqua County February, 2014 Clark Patterson Lee DESIGN PROFESSIONALS

ADDENDUM TO THE STORMWATER POLLUTION PREVENTION PLAN FOR THE JAMESTOWN PUBLIC SCHOOLS BUSH ELEMENTARY ADDITION AND ALTERATIONS The following sections are updated per the revised plans developed in February of2014, which includes a larger classroom addition (0.13 ac to 0.17 acre) and a parent parking lot within the drop-off loop (0.11 acre of additional impervious in lieu of lawn). 4.0 HYDROLOGIC ANALYSIS OF PROPOSED CONDITIONS 4.1 Proposed Conditions Proposed Subarea #1 consists of open space and miscellaneous sidewalk areas. The total pervious and impervious areas are 1.39 acres and 0.09 acre, respectively. Stormwater runoff begins as sheet flow over lawns and impervious areas where it is collected by the existing diversion swale, which discharges directly to the wooded tree line. Proposed Subarea #2 consists of the building addition rooftop. The total impervious area is 0.17 acre. Stormwater runoff begins as sheet flow and is collected by the rooftop drains and conveyed to the underground stormwater management facility, which ultimately discharges to the wooded tree line. Proposed Subarea #3 consists of open space, the paved drop-off loop and parking area, and miscellaneous sidewalk areas. The total pervious and impervious areas are 0.8.3 acre and 0.76 acre, respectively. Stormwater runoff generally begins as sheet flow over lawn and impervious areas where it is collected by the proposed storm drainage system and conveyed to the underground stormwater management facility, which ultimately discharges to the wooded tree line. 4.2 Proposed Conditions - Hydrologic Analysis Results The following table, Table 3, summarizes the peak flow generated from the proposed drainage areas for the various storm events (see Appendix). STORMWATER POLLUTION PREVENTION PLAN ADDENDUM JAMESTOWN PUBLIC SCHOOLS -1 - BUSHElEMADDmONSANDALTERATlONS

TABLE 3 RUNOFF - PROPOSED CONDITIONS I-YEAR 10-YEAR 100-YEAR PROPOSED STORM STORM STORM SUBAREA EVENT EVENT EVENT Pr Subarea #1 0.47 cfs 1.78 cfs 3.16 cfs Pr Subarea #2 0.44 cfs 0.78 cfs 1.06 cfs Pr Subarea #3 1.54 cfs 3.79 cfs 5.86 cfs Pr Subarea #4 0.12 cfs 0.38 cfs 0.63 cfs The following table, Table 4, summarizes the peak runoff rates for existing and proposed conditions for the various design storm events. Under proposed conditions, the stormwater runoff from the drainage areas have been hydrologically added and routed through the proposed stormwater management facilities to allow for comparison of the existing and proposed stormwater runoff within this project area. computer calculations and results): The results are as follows (see Appendices for TABLE 4 OUTLFOW - EXISTING vs. PROPOSED CONDITIONS Peak Flow (cfs) 1-10- 100- ANALYSIS YEAR YEAR YEAR CONDITION POINT # STORM STORM STORM EVENT EVENT EVENT Woods Existing 0.83 3.15 5.62 Proposed 0.64 3.00 5.03 English Existing 0.36 1.25 2.16 Street Proposed 0.12 0.38 0.63 As a result of a properly sized stormwater management facility and designed outlet structure, the peak stormwater runoff rates have decreased under proposed conditions. STORMW ATER POLLUTION PREVENTION PLAN JAMESTOWN PUBLIC SCHOOLS - 2 - BUSHELEMADDillONSANDALTERATlONS

5.0 STORM WATER MANAGEMENT FACILITY HYDRAULIC SUMMARY 5.1 Stormwater Management Facility Results The proposed stormwater management facility is an underground infiltration basin, located in the southwest corner of the site. After performing the infiltration test, a peak infiltration rate of 0.90 inlhr was incorporated into the design, refer to Appendix I for infiltration testing results. The infiltration basin consists of approximately 120 underground stormwater chambers. This basin has a peak storage capacity of 0.290 ac-ft and elevation of 1594.75'. The peak outflows during the 10-year and 100-year storm events are 1.34 cfs and 2.26 cfs with a peak storage elevation of 1593.25' and 1594.29', respectively. The peak storage capacity during the lo-year storm event is 0.122 acre-feet and 0.185 acre-feet, during 100-year storm event. The outfall structure consists of a 5' diameter precast concrete manhole with weir wall. The structure has a rim elevation of 1596.25' with a 12" outlet pipe at an elevation of 1591.25'. The outlet controls in the weir wall consist ofa 3" orifice at an elevation of 1591.25', a 7" orifice at an elevation of 1592.25', and a level weir wall at an elevation of 1594.25. The outlet pipe discharges directly to the wooded tree line. 6.0 STORMWATER QUALITY MANAGEMENT 6.2 Stormwater Quality Analysis Data The proposed stormwater management facility was designed to temporarily store and treat or infiltrate the required water quality volume associated with this project. The required water quality volume for the new construction is 0.070 acre-feet and redevelopment area is 0.068 acrefeet (see proposed WQv Calculations in Appendix H). For the new construction, the required pretreatment volume for the infiltration practice is 25%, since the infiltration rate is below 2 inlhr, of the required water quality volume, which calculates to 0.017 acre-feet. Since proprietary flow through devices are proposed for the pretreatment of the new construction and treatment of the redevelopment area, the water quality volume needed to be converted to a flow rate. The calculated required flow rates are 0.22 cfs for the new construction and 1.23 cfs for the STORMW ATER POLLUTION PREVENTION PLAN JAMESTOWN PUBLIC SCHOOLS - 3 - BUSH ELEM. ADDmONSAND ALTERATIONS

redevelopment area. The minimum runoff reduction volume for this site is 30% based on the HSG rating ofc. 6.3 Stormwater Management Facilities Water Quality Design Feature The proposed underground infiltration basin provides a water quality treatment volume of 0.063 acre-feet utilizing infiltration. The pretreatment for the infiltration basin is provided utilizing a VortSentry HS36 that provides a treatment rate of 0.55 cfs, which is greater than the 0.22 cfs required. The treatment for the redevelopment area is provided utilizing a VortSentry VS50 that provides a treatment rate of 1.71 cfs, which is greater than the 1.23 cfs required. The runoff reduction is provided by the infiltration basin. According to the design manual, 90% of the volume infiltrated can be applied toward the runoff reduction. That results in 0.057 acre-feet being reduced from the 0.070 acre-feet of required water quality volume. This results in an 81% reduction which is greater than the minimum of 30% required for HSG C. STORMWATER POLLUTION PREVENTION PLAN JAMESTOWN PUBLIC SCHOOLS - 4 - BUSHELEM. ADDmONSAND ALTERATIONS

g Q) z.t "0 ;JI.. I jj '" a. j;;.q.le 0 " WATER RESERVO;!? ::;: Q. N '" @ 0: i 0 0 1;; Q Q) 8 I I I I 'f "0 Q. Q. Q) ;;;., B i5 «i5 «V c C>.,3 " E 8l.s; i5.g Q) CD E c: 0 0 ' z V; NO. O r O U CD 0 () Z..'" " REV ISIONS DAlE" BY HKED DESCRlPTION CLARK PATTERSON LEE DESIGN PROFESSIONALS 1279 NORTH MAIN STREET JAMESTOWN, NEW YORK 14701 TEL (716) 664-4710 FAX (716) 661-3429 www.clarkpafterson.com EXISTING SCHOOL BUILDING 1 Sty BRlCI( JAMESTOWN PUBLIC SCHOOLS CITY O F JAMESTOWN C HAUTAUQUA C OUNTY NEW YORK STATE DATE: 02/04/14 DRAWN: NJV DESIGNED: NJV CHECKED: NJV SCAlf: 1 "= 100', o BUSH ELEMENTARY SCHOOL PROPOSED DRAINAGE CONDITIONS PROJECT NUMBER 1 73651.01 I DRAWING NUMBER I FIG-031

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Job File: J:\PROJECTS\Jamestown PSD\Bush Elem\D Design\D08 CAD\AutoCAD\Civil\CO\PondPack\P Rain Dir: J:\PROJECTS\Jamestown PSD\Bush Elem\D Design\D08 CAD\AutoCAD\Civil\CO\PondPack\ JOB TITLE Project Date: 4/16/2013 Project Engineer: nvoit Project Title: Watershed Project Comments: SiN: Bentley Systems, Inc. Bentley PondPack (10.01.04.00) 1:48 PM 2/4/2014

Table of Contents i Table of Contents ********************** MASTER SUMMARY ********************** Watershed... Master Network Summary............ 1.01 ********************** CN CALCULATIONS ********************* PR SUBAREA 1.... Runoff CN-Area 2.01 PR SUBAREA 2.... Runoff CN-Area 2.02 PR SUBAREA 3.... Runoff CN-Area 2.03 ******************** OUTLET STRUCTURES ********************* Outlet 1...... Outlet Input Data.... 3.01 SIN: Bentley PondPack (10.01.04.00) 1:48 PM Bentley Systems, Inc. 2/4/2014

Type... Master Network Summary Page 1.01 Name... Watershed File... J:\PROJECTS\Jamestown PSD\Bush Elem\D Design\D08 CAD\AutoCAD\Civil\CO\PondPack\Pr MASTER DESIGN STORM SUMMARY Network Storm Collection: Chautauqua Count Total Depth Rainfall Return Event in Type RNF ID ------- -- ------ --------------- ---------------- 1 2.1000 Synthetic Curve Type II 24hr 10 3.6000 Synthetic Curve Type II 24hr 100 4.9000 Synthetic Curve Type II 24hr MASTER NETWORK SUMMARY SCS Unit Hydrograph Method (*Node=Outfall; +Node=Diversion;) (Trun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt) Return HYG Vol Qpeak Qpeak Node ID Type Event ac-ft Trun hrs cfs ----------------- ------ -------- -------- -- -------- 740 CHAMBERS IN POND 1.142 12.0500 1. 78 740 CHAMBERS IN POND 10.326 12.0500 4.21 740 CHAMBERS IN POND 100.500 12.0500 6.43 740 CHAMBERS OUT POND 1.079 12.4500.19 740 CHAMBERS OUT POND 10.233 12.3000 1. 34 740 CHAMBERS OUT POND 100.387 12.3000 2.26 Max Max WSEL Pond Storage ft ac-ft - ------- ------------ 592.20.058 593.25.122 594.29.185 *ENGLISH ST JCT 1.008 12.0000. 12 *ENGLISH ST JCT 10.023 12.0000.38 *ENGLISH ST JCT 100.038 12.0000. 63 PR SUBAREA 1 AREA 1.053 12. 2000.47 PR SUBAREA 1 AREA 10.169 12.1500 1. 78 PR SUBAREA 1 AREA 100.292 12.1500 3.16 PR SUBAREA 2 AREA 1.026 11. 9000.44 PR SUBAREA 2 AREA 10.048 11. 9000.78 PR SUBAREA 2 AREA 100.066 11. 9000 1. 06 SIN: Bentley PondPack (10.01.04.00) 1:48 PM Bentley Systems, Inc. 2/4/2014

Type... Master Network Summary Page 1.02 Name... Watershed File.... J:\PROJECTS\Jamestown PSD\Bush Elem\D Design\D08 CAO\AutoCAO\Civil\CO\PondPack\Pr MASTER NETWORK SUMMARY SCS Unit Hydrograph Method (*Node=Outfall; +Node=Oiversion;) (Trun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt) Return HYG Vol Qpeak Qpeak Node 10 Type Event ac-ft Trun hrs cfs --------- -------- ------ ---------- ------- ------ PR SUBAREA 3 AREA 1.115 12.0500 1. 54 PR SUBAREA 3 AREA 10.279 12.0500 3.79 PR SUBAREA 3 AREA 100.434 12.0500 5.86 Max Max WSEL Pond Storage ft ac-ft...------- ----- - ---- PR SUBAREA 4 AREA 1.008 12.0000. 12 PR SUBAREA 4 AREA 10.023 12.0000. 38 PR SUBAREA 4 AREA 100.038 12.0000. 63 *WOODS JCT 1.132 12.2000.64 *WOODS JCT 10.402 12.2000 3.00 *WOOOS JCT 100.679 12.2000 5.03 SIN: Bentley PondPack (10.01.04.00) 1:48 PM Bentley Systems, Inc. 2/4/2014

Type... Runoff CN-Area Page 2.01 Name... PR SUBAREA 1 File... J:\PROJECTS\Jamestown PSD\Bush E1em\D Design\D08 CAD\AutoCAD\Civi1\CO\PondPack\Pr RUNOFF CURVE NUMBER DATA............................ Soil/Surface Description CN Area acres Impervious Adjustment %C %UC Adjusted CN Open space (Lawns,parks etc.) - Goo 74 Impervious Areas - Paved parking 10 98 1. 390.090 74.00 98.00 COMPOSITE AREA & WEIGHTED CN ---> 1. 480 75.46 (75)............ SiN: Bentley PondPack (10.01.04.00) 1:48 PM Bentley Systems, Inc. 2/4/2014

Type... Runoff CN-Area Page 2.02 Name... PR SUBAREA 2 File... J:\PROJECTS\Jamestown PSD\Bush Elem\D Design\D08 CAD\AutoCAD\Civil\CO\PondPack\Pr RUNOFF CURVE NUMBER DATA ""."... """... ".. """".. "... "".. ".""""".. """"""",,.,,.,,.. """,,.,,""",,",,""",,.,,.. "".".. ".. "".""""""""""".. ""."...... "... "... "".. "... " " """"."..,,...,,",,.... Soil/Surface Description CN Area acres Impervious Adjustment %C %UC Adjusted CN Impervious Areas - Paved parking 10 98.170 98.00 COMPOSITE AREA & WEIGHTED CN --->. 170 98.00 (98) ".""""."."""".... "."""""".. "" "... " "".. """ ""."""".,,.,, """"",,.,,",,.,,,,... "... ".. ". """".". ".. """"".".... ".. ".. """... "... ". " "."... "".,,""",,...,,."". SIN: Bentley PondPack (10.01.04.00) 1: 48 PM Bentley Systems, Inc. 2/4/20l4

Type... Runoff CN-Area Page 2.03 Name.... PR SUBAREA 3 File.... J:\PROJECTS\Jamestown PSD\Bush Elem\D Design\D08 CAD\AutoCAD\Civil\CO\PondPack\Pr RUNOFF CURVE NUMBER DATA........................................................................... o...... Soil/Surface Description CN Area acres Impervious Adjustment %C %UC Adjusted CN Open space (Lawns,parks etc.) - Goo 74 Impervious Areas - Paved parking 10 98.830.760 74.00 98.00 COMPOSITE AREA & WEIGHTED CN ---> 1. 590 85. 47 (85)............................ SIN: Bentley PondPack (10.01.04.00) 1: 48 PM Bentley Systems, Inc. 2/4/2014

Type... Outlet Input Data Page 3.01 Name... Outlet 1 File... J:\PROJECTS\Jamestown PSD\Bush E1em\D Design\D08 CAD\AutoCAD\Civil\CO\PondPack\Pr REQUESTED POND WS ELEVATIONS: Min. Elev.= Increment = Max. E1ev.= 591.25 ft.25 ft 596.00 ft ********************************************** OUTLET CONNECTIVITY ********************************************** ---> Forward Flow Only (UpStream to DnStream) <--- Reverse Flow Only (DnStream to UpStream) <---> Forward and Reverse Both Allowed Structure No. Outfall E1, ft E2, ft ----------------- ------- --------- --------- Orifice-Circular 00 -> CO 591. 250 596.000 Orifice-Circular 01 ---> CO 592.250 596.000 Weir-Rectangular WO ---> co 594.250 596.000 Culvert-Circular CO ---> TW 591.250 596.000 TW SETUP, OS Channel SIN: Bentley PondPack (10.01.04.00) 1:48 PM Bentley Systems, Inc. 2/4/2014

Type.... Outlet Input Data Page 3.02 Name.... Outlet 1 File... J:\PROJECTS\Jamestown PSD\Bush Elem\D Design\D08 CAD\AutoCAD\Civil\CO\PondPack\Pr OUTLET STRUCTURE INPUT DATA Structure ID Structure Type # of Openings Invert Elev. Diameter Orifice Coeff. = 00 = Orifice-Circular 1 591. 25 ft.2500 ft.600 Structure ID Structure Type # of Openings Invert Elev. Diameter Orifice Coeff. = 01 = Orifice-Circular 1 592.25 ft.5833 ft.600 Structure ID Structure Type # of Openings Crest Elev. Weir Length Weir Coeff. Weir TW effects = WO = Weir-Rectangular 1 594.25 ft 4.00 ft 3.100000 (Use adjustment equation) SiN: Bentley PondPack (10.01.04.00) 1:48 PM Bentley Systems, Inc. 2/4/2014

Type.... Outlet Input Data Page 3.03 Name... Outlet 1 File... J:\PROJECTS\Jamestown PSD\Bush Elem\D Design\D08 CAD\AutoCAD\Civil\CO\PondPack\Pr OUTLET STRUCTURE INPUT DATA Structure ID Structure Type No. Barrels Barrel Diameter Upstream Invert Dnstream Invert Roriz. Length Barrel Length Barrel Slope = CO = Culvert-Circular 1 1.0000 591. 25 591.00 50.00 50.00.00500 ft ft ft ft ft ft/ft OUTLET CONTROL DATA... Mannings n Ke Kb Kr RW Convergence.0130.5000. 031274.5000.001 (forward entrance loss) (per ft of full flow) (reverse entrance loss) +/- ft INLET CONTROL DATA... Equation form Inlet Control K Inlet Control M Inlet Control c Inlet Control Y T1 ratio (RW/D) T2 ratio (RW/D) Slope Factor 1.0078 2.0000.03790.6900 1.133 1. 294 -.500 Use unsubmerged inlet control Form 1 equ. below T1 elev. Use submerged inlet control Form 1 equ. above T2 elev. In transition zone between unsubmerged and interpolate between flows at T1 & T2... At Tl Elev 592.38 ft ---> Flow At T2 Elev = 592.54 ft ---> Flow = submerged inlet control, 2.75 cfs 3.14 cfs Structure 10 Structure Type = TW = TW SETUP, OS Channel FREE OUTFALL CONDITIONS SPECIFIED CONVERGENCE TOLERANCES... Maximum Iterations= 40 Min. TW tolerance.01 ft Max. TW tolerance.01 ft Min. RW tolerance.01 ft Max. HW tolerance.01 ft Min. Q tolerance.00 cfs Max. Q tolerance.00 cfs SIN: Bentley PondPack (10.01.04.00) 1: 48 PM Bentley Systems, Inc. 2/4/2014

Appendix A A-1 Index of Starting Page Numbers for ID Names ----- 0 ----- Outlet 1... 3.01, 2.01, 2.02, 2.03 - - -- W ---- Watershed... 1.01 SiN: Bentley PondPack (10.01.04.00) 1: 48 PM Bentley Systems, Inc. 2/4/2014

STORMWATER MANAGEMENT CALCULATIONS Project Name: Date: By: Design Stonns Bush Elementary School 2/4/2014 (Revised) NJV 1-YEAR (in).1 10-YEAR (in) 3.6 100-YEAR (in) 4.9 WATER QUALITY DESIGN 1. COMPUTE WATER QUALITY VOLUME (WQv) - PRETREATMENT with PROPRIETARY SMP RUNOFF COEFFICIENT (Rv) = 0.05+(1)(0.009) -- I VALUE = I 531(% IMPERVIOUS COVER) Rv= WQv = «P)(Rv)(A»/12 P VALUE = RvVALUE = A VALUE = WQv = 25% required for pretreabnent 0.5271 0_.9...1 I (FROM FIG. 4.1 OF NYSDEC MANUAL) 1...- 0_.5_27... I(FROM CALCULATION ABOVE) 1...- 1_.8... HAREA IN ACRES) o_.o_17...1iacre-feet OF STORAGE REQUIRED 757.5521cUBIC FEET OF STORAGE Jamestown Public Schools Bush Elementary Addition and Alterations 2/4/2014

RUNOFF CURVE NUMBER (CN) AND RUNOFF (Q) Project Name: Date: By: Design Storms Bush Elementary School Feb-14 NJV 1-YEAR (in).1 2-YEAR (in) 2.5 10-YEAR (in) 3.6 100-YEAR (in) 4.9 COMPUTE RUNOFF (Q) 1. THE CN VALUE HAS BEEN DETERMINED USING THE COMPUTER PROGRAM POND PACK RUNOFF CURVE NUMBER (CN) = 2. DETERMINE THE RUNOFF (Q) VALUE RAINFALL, P (24-HOUR) P VALUE = I 0.90 inl S = 1000/CN - 10 S VALUE = I 1.491 Using P and S values determine Q Q = (P -0.2S)2 1 (P+0.8S) Q VALUE =1..._ 0_.1... 71 Jamestown Public Schools Bush Elementary Addition and Alterations 2/4/2014

STREAM CHANNEL PROTECTION VOLUME, Cpv CALCULATIONS Project Name: Date: By: Design Storms Bush Elementary School Feb-14 NJV 1-YEAR (in) 2.1 I---- 2-YEAR (in) 2.5 10-YEAR (in)i----3.6 100-YEAR (in)... 4_.9... COMPUTE PEAK DISCHARGE FOR WATER QUALITY VOLUME 1. DETERMINE THE VALUE OF THE UNIT PEAK DISCHARGE (qu) USING TR-55 AND TYPE III RAINFALL DISTRIBUTION AREA (A) = 1.76 acresl 0.0028 SQ. MI RUNOFF CURVE NUMBER (CN) = INITIAL ABSTRACTION (Ia) FOR CN = la = (200/CN - 2) la VALUE = 0.2991 lalp lalp VALUE = 1 0.1421 Time of Concentration Tc VALUE = 0.29 hrs.hfrom POND PACK CALCULATION) Using above data and Exhibit 4-11 from TR-55 (NRCS, 1986), qu = WQv = Use volume from previous calculation = WQv = in watershed inches = Qp = peak discharge in cfs =qu xaxwqv 680 csm/inl 0.017 ac-ftl 0.119 inl 0.22 cfsl Jamestown Public Schools Bush Elementary Addition and Alterations 2/4/2014