Jamestown Public Schools Bush Elementary Addition and Alterations

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1 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

2 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 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

3 TABLE 3 RUNOFF - PROPOSED CONDITIONS I-YEAR 10-YEAR 100-YEAR PROPOSED STORM STORM STORM SUBAREA EVENT EVENT EVENT Pr Subarea # cfs 1.78 cfs 3.16 cfs Pr Subarea # cfs 0.78 cfs 1.06 cfs Pr Subarea # cfs 3.79 cfs 5.86 cfs Pr Subarea # 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) ANALYSIS YEAR YEAR YEAR CONDITION POINT # STORM STORM STORM EVENT EVENT EVENT Woods Existing Proposed English Existing Street Proposed 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 BUSHELEMADDillONSANDALTERATlONS

4 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 ac-ft and elevation of '. 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 ' and ', respectively. The peak storage capacity during the lo-year storm event is acre-feet and 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 ' with a 12" outlet pipe at an elevation of '. The outlet controls in the weir wall consist ofa 3" orifice at an elevation of ', a 7" orifice at an elevation of ', and a level weir wall at an elevation of 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 acre-feet and redevelopment area is 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 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 BUSH ELEM. ADDmONSAND ALTERATIONS

5 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 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 acre-feet being reduced from the 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 BUSHELEM. ADDmONSAND ALTERATIONS

6 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 TEL (716) FAX (716) 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 I DRAWING NUMBER I FIG-031

7 BY N"S"V DATE "1\ III \ I Clark Patterson Lee DE SIGN PROFE SS IONALS CHECKED BY DATE PROJECT Us.). 'S e.1.j CALC. NO. REV. SUBJECT VVt..o--tuS1.-t:) \NAc:...J; JO B NO. SHEET NO. (C SUI'-S) - \ c. r :) ) \00'. <!. O. C;-1.. ), ) D N(4 U"ro- J J-, 8"c? (2., 1;;/. 'fyl -V;b..::2 o.-k Ac:vtb (rz;.ju.rr..e..o A'0 1J1 7, o.j) 0.11 /1-'\'1' - 0.'7 \f-"\f> - Q c Gtr- 0.7 C, L A \J cf o. )M.f' - 0.0::< LA - O. 1(0 - \ '- Y'\ - 0.:2. \ QU' )

8 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 ( ) 1:48 PM 2/4/2014

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

10 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 Synthetic Curve Type II 24hr Synthetic Curve Type II 24hr 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 CHAMBERS IN POND CHAMBERS IN POND CHAMBERS IN POND CHAMBERS OUT POND CHAMBERS OUT POND CHAMBERS OUT POND Max Max WSEL Pond Storage ft ac-ft *ENGLISH ST JCT *ENGLISH ST JCT *ENGLISH ST JCT PR SUBAREA 1 AREA PR SUBAREA 1 AREA PR SUBAREA 1 AREA PR SUBAREA 2 AREA PR SUBAREA 2 AREA PR SUBAREA 2 AREA SIN: Bentley PondPack ( ) 1:48 PM Bentley Systems, Inc. 2/4/2014

11 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 PR SUBAREA 3 AREA PR SUBAREA 3 AREA Max Max WSEL Pond Storage ft ac-ft PR SUBAREA 4 AREA PR SUBAREA 4 AREA PR SUBAREA 4 AREA *WOODS JCT *WOODS JCT *WOOOS JCT SIN: Bentley PondPack ( ) 1:48 PM Bentley Systems, Inc. 2/4/2014

12 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 COMPOSITE AREA & WEIGHTED CN ---> (75) SiN: Bentley PondPack ( ) 1:48 PM Bentley Systems, Inc. 2/4/2014

13 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 COMPOSITE AREA & WEIGHTED CN ---> (98) ".""""."."""".... "."""""".. "" "... " "".. """ ""."""".,,.,, """"",,.,,",,.,,,,... "... ".. ". """".". ".. """"".".... ".. ".. """... "... ". " "."... "".,,""",,...,,."". SIN: Bentley PondPack ( ) 1: 48 PM Bentley Systems, Inc. 2/4/20l4

14 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 COMPOSITE AREA & WEIGHTED CN ---> (85) SIN: Bentley PondPack ( ) 1: 48 PM Bentley Systems, Inc. 2/4/2014

15 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.= ft.25 ft 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 Orifice-Circular > CO Weir-Rectangular WO ---> co Culvert-Circular CO ---> TW TW SETUP, OS Channel SIN: Bentley PondPack ( ) 1:48 PM Bentley Systems, Inc. 2/4/2014

16 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 ft.2500 ft.600 Structure ID Structure Type # of Openings Invert Elev. Diameter Orifice Coeff. = 01 = Orifice-Circular ft.5833 ft.600 Structure ID Structure Type # of Openings Crest Elev. Weir Length Weir Coeff. Weir TW effects = WO = Weir-Rectangular ft 4.00 ft (Use adjustment equation) SiN: Bentley PondPack ( ) 1:48 PM Bentley Systems, Inc. 2/4/2014

17 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 ft ft ft ft ft ft/ft OUTLET CONTROL DATA... Mannings n Ke Kb Kr RW Convergence (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 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 ft ---> Flow At T2 Elev = 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 ( ) 1: 48 PM Bentley Systems, Inc. 2/4/2014

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

19 STORMWATER MANAGEMENT CALCULATIONS Project Name: Date: By: Design Stonns Bush Elementary School 2/4/2014 (Revised) NJV 1-YEAR (in).1 10-YEAR (in) 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 _ I (FROM FIG. 4.1 OF NYSDEC MANUAL) _.5_27... I(FROM CALCULATION ABOVE) _.8... HAREA IN ACRES) o_.o_17...1iacre-feet OF STORAGE REQUIRED cUBIC FEET OF STORAGE Jamestown Public Schools Bush Elementary Addition and Alterations 2/4/2014

20 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) YEAR (in) 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 Using P and S values determine Q Q = (P -0.2S)2 1 (P+0.8S) Q VALUE =1..._ 0_ Jamestown Public Schools Bush Elementary Addition and Alterations 2/4/2014

21 STREAM CHANNEL PROTECTION VOLUME, Cpv CALCULATIONS Project Name: Date: By: Design Storms Bush Elementary School Feb-14 NJV 1-YEAR (in) 2.1 I YEAR (in) YEAR (in)i 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 SQ. MI RUNOFF CURVE NUMBER (CN) = INITIAL ABSTRACTION (Ia) FOR CN = la = (200/CN - 2) la VALUE = lalp lalp VALUE = 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 ac-ftl inl 0.22 cfsl Jamestown Public Schools Bush Elementary Addition and Alterations 2/4/2014

Summary of Detention Pond Calculation Canyon Estates American Canyon, California

July 15, 2015 Bellecci & Associates, Inc Summary of Detention Pond Calculation Canyon Estates American Canyon, California 1. Methodology: Method: Unit Hydrograph Software: Bentley Pond Pack Version 8i