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1U <br /> meter Manag t R wort <br /> Sturbridge Village, Phase II <br /> 1. <br /> Pre-Development ID-Year Peak Flow <br /> Post-Development 10-Year Peak Flow <br /> Recorme'ndat i ons to Detain Difference in 10-Year Flows <br /> II. Pre-Devel t Flow: <br /> Rational Method: Q = CIA <br /> tc = tp = 5min. <br /> C = 0.20 (Woodland) <br /> 1 = 7.5 in/hr <br /> A = 51.7 Ac <br /> Q = (.2)(7.5)(51.7) = 77.6 cfs <br /> III. Post-Dev 1 Flow: <br /> Proposed Use: Single Family Dwellings on 2- to 4-Acre Lots <br /> Impervious Surface: <br /> 1600' long, 20' wide public road = 32000 SF <br /> Avg. 1700 SF house, 1800 SF <br /> Driveway on 16 Lots <br /> s 56000 SF <br /> 88000 SF = 2.0 Ac <br /> Rational Method: Q = CIA <br /> C: <br /> Woodland Area C Wei ed C <br /> Impervious Area 53.1 .0 0.039 <br /> 3.9 1.0 0.039 <br /> Total =_-_=_ <br /> ------- <br /> 100.0 0.231 <br /> Q = (.231)(7.5)(51.7) = 89.6 cfs <br /> , IV. ention R uirements: <br /> Required Storage: 5 = (Q1 - Qo)tp <br /> Q = 89.6 - 77.6 = 12.0 cfs <br /> tp = 5 min = 300 sec <br /> Volume: 5 = (12.0)(300) = 3,600 cf <br />