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CaliforniaWgional Water Quality Con&l Board <br /> <LN'i Central Valley Region <br /> QW; Karl E.Longley,ScD,P.E.,Chair (a <br /> Linda S.AdamsArnold <br /> Secretary for Sacramento Main Office Schwarzenegger <br /> Environmental 11020 Sun Center Drive 4200,Rancho Cordova,California 95670-6114 Governor <br /> Protection Phone(916)464-3291 •FAX(916)464-4645 <br /> http://www.waterboards.ca.gov/centralvalley i---,I- �f <br /> DEC 012007 <br /> 27 November 2007 ENVIPO{�VE�IT HEALTH <br /> Mr. Kevin Basso, General Manager <br /> Forward Inc. <br /> 1145 West Charger Way <br /> Stockton, CA 95206 <br /> REVIEW OF ALTERNATIVE FINAL COVER EQUIVALENCE DEMONSTRATION EXISTING <br /> AND FUTURE LINED AREAS, FORWARD LANDFILL, SAN JOAQUIN COUNTY <br /> Regional Water Board staff has reviewed the "Alternative Final Cover Equivalence <br /> Demonstration Existing and Future Lined Areas"(Demonstration) submitted on <br /> 1 November 2007. The Demonstration uses both theoretical (HELP model) and observed <br /> performance to compare a Title 27 prescriptive cover with Forward's alternative ET cover <br /> design. <br /> Theoretical infiltration rates were modeled for Forward's proposed alternative ET cover and a <br /> prescriptive final cover, the results indicate that the alternative cover will outperform the <br /> prescriptive cover. The alternative cover consists of four feet of soil; the design thickness was <br /> determined from LEACHM model runs using Forward's specific soil properties and local <br /> climatic conditions. <br /> An alternative cover test section was constructed and in the first year (2006/2007) moisture did <br /> not percolate through the cover (into the waste). The 2006/2007 rainy season was unusually <br /> dry (total rainfall 46% of average) and to date the cover's field performance has not been fully <br /> tested. <br /> Based on the Demonstration and on other published alternative cover performance results <br /> (information generated by ACAP) staff makes the following conclusions: <br /> 1. The ACAP testing has demonstrated that properly designed and constructed ET <br /> alternative landfill covers perform as well and may have some advantages over Title 27 <br /> prescriptive covers in climates like California's Central Valley. <br /> 2. Modeling results indicate that a four-foot thick alternative ET cover constructed with <br /> Forward's specific soils and under Forward's specific climatic conditions will outperform <br /> a prescriptive cover. Models are no better than the assumptions that go into them and <br /> a field test section was constructed to confirm the results. <br /> California Environmental Protection Agency <br /> �a Recycled Paper <br />