CORRESPONDENCE_2003-2004 - Laserfiche WebLink

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2. Final Closure of Crest of Module"I" The flat areas (slope less than 6:1) of Module"I"will receive final closure cap. The County intends to evaluate the use of an evapo-transporative(ET) cover for closure. The design effort will include: A. Investigation of on-site borrow sources for the evapor-transporative (ET) cover, in particular, the soil in the area of Module 2 and the stockpile placed during the excavation of Module 1. This investigation will include: • Historical Meteorological Data, and extract daily data for critical(wetter than normal) years. • ASTM D422—Grain Size • ASTM D4318 —Atterberg Limits to make a preliminary determination of the suitability of select on-site sources Apparently suitable soils will be further tested by: Standard Proctor test(ASTM D698) Saturated hydraulic conductivity(ASTM D5084) Soil water characteristics curve (SWCC) (ASTM D6836), Methods A and D applicable to coarse grained soils. B. Seeking clarification of acceptance criteria for ET covers from RWQCB staff C. Preliminary calculations to determine likely thickness of ET cover, using the results of the above tests on suitable soils. D. Confirming or adjusting the ET cover thickness once the likely thickness is established using WIN UNSAT-H, for 5-year simulations. Two 5-year simulations will be preformed, as follows: • The highest annual precipitation for all 5-years. This scenario is unlikely but represents "worst case" scenario • The historic highest precipitation occurring in the 2nd year,with other years receiving average precipitation. The above work will result in the criteria that will be used to compare an ET cover with a prescriptive cover. The County will then compare the cost of the ET cover to a typical engineered alternative closure(two-foot foundation layer, GCL as barrier layer, one-foot vegetative layer). If the cost of the ET cover is favorable and if the study demonstrates acceptability in accordance with RWQCB acceptance criteria,then the County will submit this evaluation for RWQCB review. 3. Landfill Gas (LFG) System Collecting LFG directly from the refuse of Module "I" is required because Module "I"is unlined; however, once a LFG system is required, San Joaquin Valley Unified Air Pollution Control Foothill Sanitary Landfill-Site Improvement Strategy 2 Department of Public works/Solid Waste February 2,2004 County of San Joaquin