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Californi egional Water Quality Co of Board <br />i1l�; Central Valley Region <br />Karl E. Longley, ScD, P.E., Chair <br />Linda S. Adams Sacramento Office Arnold <br />Secretaryfor 11020 Sun Center Drive #200, Rancho Cordova, California 95670.6114 Schwarzenegger <br />Environmental Governor <br />Protection Phone (916) 464-3291 FAX (916) 464-4645 <br />http://www.waterboazds.ca.gov/centralvalley (��('' " <br />7 October 2009 t1 �l�V� v LSD <br />OCT 0 9 2009 <br />Kevin Basso, General Manager ENVIRONMENT E LT <br />Forward Inc. PERMIT/SERVICES <br />1145 West Charger Way <br />Stockton, CA 95206 <br />FINALALTERNATIVE rFILL COVER, EQUIVALENCE TO TITLE 27 PRESCRIPTIVE <br />COVER, FORWARD LANDFILL,•AQCOUNTY <br />Regional Water Board staff has reviewed the "Third Year Moisture Monitoring Performance <br />Report" (Report) submitted on 28 August 2009. The Report uses temperature, precipitation, <br />soil moisture and soil suction potential data collected over three years to demonstrate that <br />Forward's alternative ET cover performs as well as a prescriptive cover. <br />Forward constructed a minimum 4 -foot thick monolithic soil cover on the north slope of the <br />Austin Road landfill as an alternative final cover demonstration. The cover was constructed of <br />clayey silt from an onsite soil borrow area and was hydroseeded with native vegetation seed <br />mix. Two monitoring stations to collect soil moisture and soil suction potential data at 12 -inch, <br />24 -inch and 36 -inch depths were installed. The monitoring stations were installed in July 2006 <br />and have collected three years of cover performance data. Throughout the three year test <br />period rainfall has been below normal, so that in staff's opinion the cover has not been truly <br />tested in normal or above -normal rainfall conditions. <br />Based on the cover design model, the pre -construction materials testing, the cover <br />construction testing, the cover performance data and on other published alternative cover <br />performance results (information generated by the Alternative Cover Assessment Program <br />(ACAP) staff makes the following conclusions: <br />The ACAP testing has demonstrated that properly designed and constructed ET <br />alternative landfill covers perform as well and has some advantages over Title 27 <br />prescriptive covers in climates like California's Central Valley. <br />2. Design modeling indicates that a four -foot thick alternative ET cover constructed with <br />Forward's specific soils. and climatic conditions will outperform a prescriptive cover even <br />in high rainfall years. <br />3. The cover performance monitoring collected over a three year period demonstrates that <br />this cover performed as well as or better -than a prescriptive cover. Moisture did not <br />percolate through the cover into the waste and likely dry season evapotranspiration <br />exceeded wet season percolation (net negative flux). <br />California Environmental Protection Agency <br />Via, Recycled Paper <br />