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• Evaporation Pond The evaporation pond will be constructed to Class III Landfill standards pursuant to CCR, Title 23. The top of the pond will measure 66 by 162 feet. The evaporation pond will extend to a maximum depth of 6 feet (including 2 feet of freeboard) with 2:1 sideslopes and pond bottom sloping at I%. The evaporation pond liner system will consist of four feet of compacted clay material having a permeability of less than 1x10 cm/sec. Monthly precipitation and evaporation data used in the design of the evaporation pond are summarized in Table C-2. Based on the low moisture content of the anticipated compost material, it is estimated that approximately 100 gallons of water will need to be added to each ton of incoming green waste. Based on the estimated incoming tonnage and windrow dimensions, approximately 7.5 gallons or 1 cubic foot of water will need to be applied to each square foot of each new windrow. In order to meet these water requirements, an estimated 10 to 90 thousand cubic feet of water will be required each month. This quantity is nearly 10 times the amount of runoff generated from the entire composting operation. Therefore, the criteria used in the design the evaporation pond • included the volume required for a two month storage, in the event that there is no incoming compost, and the volume required to contain the 100-year, 24-hour storm event. The evaporation pond was designed to contain precipitation generated during the most critical two month period (December and January) when the composting area is expected to be at its maximum size (90,000 square feet). The water balance (precipitation minus evaporation) for this time period is estimated to be approximately 20,000 cubic feet and will be contained within the pond with at least 2 feet of remaining freeboard. The two feet of freeboard will provide an additional 20,198 cubic feet of storage in order to contain the volume of runoff estimated from the 100-year, 24-hour storm event (16,935 cubic feet). Water balance calculations were modeled on a monthly basis by summing runoff generation, direct rainfall on the pond surface, and evaporation from the corresponding water surface area. The volume of runoff at the end of a month was then correlated to a specific depth based on the pond geometry. The following evaporation pond spreadsheets and backup calculations provide a detailed description of the methods used to design the evaporation pond. L:NPROJECR39TMRF%RC[-4.?CY C-3 Dwember 16,1993