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SUBJECT: Foothill Sanitary Landfill 12/93 <br /> Storm Drainage Calculations <br /> Design Criteria: <br /> The flow velocity, depth of flow, and channel <br /> capacity are computed using Manning's Equation. <br /> V = 1. 486 Rzr3 SIn <br /> n <br /> V = Velocity, ft. /sec. <br /> n = Manning coefficient, no units <br /> R = Hydraulic radius, ft. <br /> S = Slope, ft. /ft <br /> The Manning Equation is modified to compute channel <br /> capacity. <br /> Q = VA = 1. 486 Rua S112 <br /> A = Area of flow, ft.'- <br /> The values of Manning's Coefficient '°n" are taken from <br /> San Joaquin County Department of Public Works' Manual <br /> for Storm Drainage Desian. <br /> Earthen Channel n = 0 . 030 <br /> The rainfall intensity-duration curve for the 100 year <br /> storm event has been developed using precipitation- <br /> frequency data supplied by the National Oceanic and <br /> Atmospheric Administration's Precipitation-Frequency <br /> Atlas of the Western United States . <br /> The intensity-duration curve is presented on the <br /> following page. <br /> Design flow rates are computed using the rational <br /> formula. <br /> Q = CIA <br /> Q = Design flow rate, f-t- .3/sec. (cfs) <br /> C = Coefficient of runoff, no units <br /> I = Rainfall intensity, inches <br /> A = Watershed area, acres <br /> The runoff coefficient used was 0 . 60 . <br />