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r <br /> E ORAND U <br /> DATE: August 1, 2006 <br /> TO: Evan Edgar, Edgar& Associates, Inc. <br /> FROM: Dale Solheim, EBA Engineering <br /> PROJECT: Tracy Material Recovery Facility JOB#: 06-1262 <br /> REFERENCE: Evaporation Pond <br /> The following is a summary of the criteria that was used for the design of the Evaporation Pond <br /> for the Tracy Material Recovery and Transfer Facility. The pond was intended to collect runoff <br /> from the wood and yard waste compost pad and was constructed according to the project plans at <br /> approximately 220 feet long by 70 feet wide at the top of the liner (elevation 114). The side <br /> slopes are 3:1, horizontal to vertical, and depth varies from 4.75 feet to 5.5 feet (bottom finish <br /> grade to top of liner). With these dimensions, the volume of the pond to the top of the liner <br /> calculates to approximately 57,500 cubic feet. <br /> The criteria used in the 1994 Report of Facility Information (Appendix C of the Report of <br /> Composting Site Information) for sizing the pond was to contain precipitation generated during <br /> the most critical two month period (December and January) when the compost area is expected <br /> to be at its maximum size of 90,000 square feet and have enough freeboard to also contain the <br /> 100-year, 24-hour storm event. The volume of runoff estimated from precipitation during this <br /> two month period from the pad and precipitation directly into the pond was calculated at <br /> approximately 20,000 cf. This includes evaporation from the pond during this period and is <br /> based on 90% runoff from half of the pad (bare concrete) and 50% runoff from the other half of <br /> the pad (assuming covered with compost). <br /> Based on a 90,000 sf pad, the remaining available pond volume of 37,500 cf(57,500 cf—20,000 <br /> cf) can contain the 100-year 24-hour storm event and still maintain approximately 1.4 feet of <br /> freeboard. The runoff from the 100-year, 24-hour storm event was calculated to be <br /> approximately 17,000 cf. <br /> CADOCUMENTS AND SETTINGS\NEIL EDGAR\LOCAL SETTINGS\TEMPORARY INTERNET FILES\OLKI AWEMO-EDGAR(05-04-06).130C <br />