Laserfiche WebLink
Pre -Development Hydrology <br />Drainage <br />Existing <br />Existing <br />Runoff <br />Runoff <br />Composite <br />Existing <br />Drainage <br />Area <br />Pervious <br />Impervious <br />Coefficient <br />Coefficient <br />Runaff <br />Discharge <br />Areas <br />Size (SF) <br />Surface (SF) <br />Surface (SF) <br />(Pervious) <br />(Impervious) <br />Coefficient <br />(Q EX, cfs) <br />A-1 31877 <br />13206 <br />1 18671 <br />0.3 <br />0.9 <br />0.65 <br />0.81 <br />Qex1=0.65 X1.7x 0.73=0.81cfs <br />Post -Development Hvdroloev <br />QPD1=0.72x2.2x0.73=1.16cfs <br />Discharge Calculation Method: Rational Method <br />Q=CiA, where ip-=1.7 in/hr (10year 10 minute) and iP-=t= 2.2 in/hr (30 <br />year 10 minute) <br />Post -Development Stormwater Storage: Attachment O <br />Volume Stored = (QPD - QEX) x (3/2)Tc, Tc =10 minutes <br />Detention Volume Summary Table <br />Pipe <br />Rock <br />1730 N. FIRST ST. <br />Storage Volume <br />Basin <br />Post - <br />Drainage <br />New <br />New <br />Runoff <br />Runoff <br />Composite <br />Required <br />Drainage <br />Diameter <br />Areas <br />Detention <br />20166162 <br />Volume <br />me <br />Deve I opme <br />A-1 <br />Area <br />Pervious <br />Impervious <br />Coefficient <br />Coefficient <br />Runoff <br />SHEET EX—B5 OF <br />Areas <br />(lu <br />319 <br />694 <br />152 <br />243 <br />ntDischarge <br />Size (SF) <br />Surface (SF) <br />Surface (SF) <br />(Pervious) <br />(Impervious) <br />Coefficient <br />(CLPD, ds) <br />A-1 <br />31877 <br />9385 <br />22492 <br />0.3 <br />0.9 <br />0.72 <br />1.16 <br />QPD1=0.72x2.2x0.73=1.16cfs <br />Discharge Calculation Method: Rational Method <br />Q=CiA, where ip-=1.7 in/hr (10year 10 minute) and iP-=t= 2.2 in/hr (30 <br />year 10 minute) <br />Post -Development Stormwater Storage: Attachment O <br />Volume Stored = (QPD - QEX) x (3/2)Tc, Tc =10 minutes <br />Detention Volume Summary Table <br />V1 = (1.16 — 0.81) X 3/2X10x60=319ft3 <br />Pipe Storage Volume =193ft * pi * 0.5A2 sf =152 CF <br />Rock Section Volume = 694 sf * 0.35=243 CF <br />Orifice Sizing Calculation: where <br />Q =4C.DZ 2gh Q = flow rate <br />Cd = discharge coefficient (0.611), <br />D _ 4Q g = gravitational acceleration (32.2 ft/1z}, <br />Cd 2gh h = depth of orifice <br />Orifice Sizing <br />Pipe <br />Rock <br />1730 N. FIRST ST. <br />Storage Volume <br />Basin <br />Q(Existing <br />Total <br />SUITE 600 <br />Storage <br />Section <br />Cd <br />Required <br />Surface <br />Diameter <br />Areas <br />Detention <br />20166162 <br />Volume <br />me <br />Vome <br />A-1 <br />(CF) <br />Area (SF) <br />32.2 <br />4 <br />Volume (CF) <br />SHEET EX—B5 OF <br />(lu <br />(lu <br />319 <br />694 <br />152 <br />243 <br />394 <br />V1 = (1.16 — 0.81) X 3/2X10x60=319ft3 <br />Pipe Storage Volume =193ft * pi * 0.5A2 sf =152 CF <br />Rock Section Volume = 694 sf * 0.35=243 CF <br />Orifice Sizing Calculation: where <br />Q =4C.DZ 2gh Q = flow rate <br />Cd = discharge coefficient (0.611), <br />D _ 4Q g = gravitational acceleration (32.2 ft/1z}, <br />Cd 2gh h = depth of orifice <br />Orifice Sizing <br />4 x 0.81 <br />D1=x12=3.9" <br />0.611x,,r 2x32.2x4 <br />! <br />1730 N. FIRST ST. <br />Orifice <br />Drainage <br />Q(Existing <br />SUITE 600 <br />BASIN DETENTION CALCULATIONS <br />Cd <br />g <br />h(ft) <br />Diameter <br />Areas <br />Discharge) <br />20166162 <br />(inch) <br />A-1 <br />0.81 <br />0.611 <br />32.2 <br />4 <br />3.9 <br />4 x 0.81 <br />D1=x12=3.9" <br />0.611x,,r 2x32.2x4 <br />! <br />1730 N. FIRST ST. <br />Subject <br />EXHIBIT B5 <br />SUITE 600 <br />BASIN DETENTION CALCULATIONS <br />BKF <br />SAN JOSE, CA 95112 <br />Job No. <br />20166162 <br />408-467-9100 <br />By <br />Date 06-25-19 Chkd. <br />(rt E�o��s liurvEro� �PwllExs <br />Ie� <br />408-467-9199 (FA41ge 7 of 7 <br />SHEET EX—B5 OF <br />REV: 07-25-19 DZ <br />