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Page 2 of 4 event which would add up to be 5.12 acres, or 223,025 square feet. The retention basin was designed to retain all run-off generated from the site except run-off from the wood and yard waste composting area. The evaporation pond was sized for the wood storage and yard waste composting area where the quantity of run-off estimated to be generated is from a 100-year/24-hour precipitation event. Two feet of freeboard was part of the design criteria. During major events, if necessary, the pond will be pumped to maintain capacity. Reviewing Appendix E of the RFI, the composting area was expected to be 90,000 square feet. Operation Modifications: Figure 3 — RFI Amendment — Site Plan Modifications (March 2006) depicts the current operations over previous Figure 3- Preliminary Site Plan of 1993. The yard waste composting area and wood waste composting area have both been expanded and separated. The wood waste processing area has expanded into the area designated for future expansion, to total 108,070 square feet of operations area. The yard waste composting area now totals 150,000 square feet with a recent paving expansion just west of the evaporation pond. Regulatory Changes: Since 1993, there have been regulatory changes as well for wood waste processing and yard waste composting. Run-off from wood waste processing in considered an industrial activity needing a Stormwater Pollution Prevention Plan (SWPPP) with the use of best management practices to manage the run-off, but is not considered a leachate generating activity where the run-off would have to be collected in the lined pond. Yard waste composting is considered a potential threat to ground water, where containment is still required. Recently proposed Waste Discharge Requirements (WDRs) by the Central Valley Regional Water Quality Control Board is requiring to be contained. All run-off from the yard waste composting area have been collected since the start of operations, and will continue to be collected. Run-off from the wood waste processing area, with the move into the future expansion area, has not been collected in the evaporation pond. Evaporation Pond Capacity: The pond was designed for 90,000 square feet based upon the 100 -year, 24-hour storm where 20,000 cubic feet was designed to be contained with at least 2 feet of capacity. The approximate size of the evaporation pond was 200 feet wide and 70 wide. A copy of the As - Built Plan was obtained. The bottom of the pond slopes 0.5% with 3:1 slopes, scaled at 1 inch equals 30 feet. EBA Engineering, the original design engineers form 1993, reviewed the as-builts plans, and determine the pond has a total capacity of 57,500 cubic feet to the top of the lined pond (memo from August 1, 2006 is attached). Design Storm: The design storm from the 1993 RFI is 20,000 cubic feet based upon a water balance calculation for the most critical time period of December and January for 90,000 square feet, and was determined to be 17,000 cubic feet for the annual average. EBA determined that the 100 -year, 24-hour storm event can be maintained on-site with approximately 1.4 feet of freeboard for a design volume of 17,000 cubic feet. (Memo from August 1, 2006 attached). Edgar & Associates, Inc., a the design review engineer, used the SCS TR -20 model to determine the design storm over 150,000 square feet, based a 100 -year, 24-hour design storm event of 2.8 inches, the run-off amount totals 22,517 cubic feet, higher than the design storm of 17,000 cubic feet for the 90,000 square foot pad. The evaporation pond has adequate 9/25/2006