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Water Quality Peak Flow Calclations NYSDEC Water Quality Volume (WQv) & Water Quality Peak Flow (Qp) Calculation Worksheet (REQUIRED Qp) PROJECT INFORMATION Total Drainage Area A: 2.09 ac Impervious Area I: 1.90 ac Percent Impervious 90.9 % NYSDEC 90% Rainfall P: 1.00 in. Time of Concentration Tc: 0.27 hrs Rv: 0.87 WATER QUALITY VOLUME Water Quality Volume WQv=([(P)*(Rv)*(A)]/12)*43560 WQv: 6,587 cf WATER QUALITY PEAK FLOW (NEW DEVELOPMENT) Runoff Volume Q=WQv/(A*3600) Q: 0.87 in. 2 ½ CN=1000/(10+5*P+10*Q-10(Q +1.25*Q*P) ) CN: 98.80 CN Rounded CN: 99 CN < or = 98 CN: 98 Initial Abstraction (Ia=200/CN-2) Ia: 0.04 in. RATIO R=Ia/P R: 0.04 2 C0 = A*R +B*R +C C0: 2.54 2 C1 = A*R +B*R +C C1: -0.58 2 C2 = A*R +B*R +C C2: -0.17 2 Unit Peak Discharge qu=10^(C0+C1*Log(Tc)+C2*(log(Tc)) ) qu: 663.03 cfs/mi2/in Water Quality Peak Flow Qp=qu*A*Q/640 (100%) Qp: 1.88 cfs REDVELOPMENT Impeverious Area Reduction IC 0.00 % WQv Treatment by Standard Practice SP 0.00 % Runoff Reduction RR 0.00 % Req. WQv% By Alt. Practice AP=(25-(% IC+%SP+%RR))*3: AP 75.0 % Required Water Quality Peak Flow RD QP=(Qp*AP): RD Qp: 1.41 cfs Page 1 of 1 Page 175 of 1493