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Memorandum <br />Date: July, 2014 <br />From: Bruce J. Friedhoff <br />To: Sangeeta Lewis <br />RE: Forward, Inc. Compost Facility Stormwater Improvements <br />PROJECT UNDERSTANDING <br />Item H.8.H of Forward’s recently adopted Waste Discharge Requirements (WDRs) R5-2014-0006 <br />requires the submittal of a report by February 1, 2015 that demonstrates that the compost area meets <br />or exceeds the relevant facility specifications. The purpose of this memorandum is to document the <br />surface water design for the Compost Facility run-on and run-off controls for the following <br />requirements: <br />1.Compost Facility shall implement storm water BMPs so that run-off water does not adversely <br />affect the beneficial uses of any downstream water body; <br />2.The Discharger shall monitor leachate and water in the retention basin as required by MRP <br />R5-2014-0006 <br />3.The retention basin shall be equipped with a synthetic liner, shall maintain a minimum two <br />feet of freeboard and shall be designed and operated to minimize the downward percolation of <br />constituents; <br />4.The Compost and Compost storage pads shall be designed, constructed and maintained to <br />prevent to the greatest extent possible, ponding, infiltration, inundation, erosion, slope failure, <br />and washout; <br />5.The pad or pads shall have a minimum one percent slope; <br />6.The Discharger shall maintain an effective run-on control system and for the composting area <br />a run-off control system designed to withstand the maximum peak flow from a 25-year, 10- <br />minute storm; and <br />7.The retention basin shall be designed to accommodate all runoff and direct precipitation from <br />a 25-year, 24-hour storm and maintain two feet of freeboard. <br />WATER BUDGET <br />Monthly and annual precipitation data was downloaded from the California Department of Water <br />Resources, Flood & Safety, Climate Data, Precipitation, Monthly Historical Data, for Stockton AP, July <br />2014 Web Site. Monthly runoff from rainfall was computed using the SCS runoff equation and a Curve <br />Number of 88. Monthly evaporation data was down loaded from the Western Regional Climate Center, <br />July 2014. The monthly composed water demand was assumed to be 18.7 acres times the monthly <br />evaporation depth. The required monthly volume of storage for process water storage was computed by <br />subtracting the monthly runoff by the process water demand (but not less than zero). The difference <br />between demand and supply is assumed to be supplied by other sources. The maximum monthly storage <br />volume is 10.1 Acre Feet and occurs in January.