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4.-Miht <br /> ` THOMAS M.GAU P.O.BOX 1810-1810 E.HAZELTON AVENUE <br /> J. DIRECTOR STOCKTON,CALIFORNIA 95201 <br /> c• g L��E tq` (209)468-3000 FAX(209)468-2999 <br /> 4IFu, a 1 www.sjgov.org/pubworks <br /> Wn <br /> W <br /> FRITZ BUCHMAN <br /> DEPUTY DIRECTOR _ wm*ins YOU <br /> MICHAEL SELLING <br /> DEPUTY DIRECTOR <br /> JIM STONE <br /> DEPUTY DIRECTOR <br /> ROGERJANES <br /> BUSINESS ADMINISTRATOR October 1, 2013 <br /> Mr. Todd Del Frate <br /> California Regional Water Quality Control Board <br /> 11020 Sun Center Drive, #200 <br /> Rancho Cordova, California 95670-6114 <br /> SUBJECT: FINAL EVAPOTRANSPIRATION CLOSURE COVER REPORT <br /> 20012/13 WATER YEAR, FOOTHILL SANITARY LANDFILL <br /> Dear Mr. Del Frate: n <br /> Enclosed, please find the Annual Foothill Landfill Evapotranspiration Test Pad <br /> Assessment for the 2012/2013 rain season. This report also includes the results of <br /> monitoring beginning with the rain season of 2008/2009. <br /> We are most pleased to report that, once again, the data demonstrates success of the <br /> evapotranspiration (ET) closure cap at the Foothill Landfill. The ET cap performed better <br /> than a prescriptive closure cap (California Code of Regulations Title 27, Section <br /> 21090(a)(2)) with an intact clay barrier 10-6 cm/sec permeability, as predicted by the <br /> HELP model. <br /> As agreed between County and RWQCB staff when the ET closure method was <br /> proposed by the County, the ET test pad would be monitored for five consecutive rainy <br /> seasons, beginning with and including 2008/09. The portion of the landfill on which the <br /> ET cap was installed would be accepted as "closed" if the results of the ET test pad <br /> during that time showed that the ET closure cap met the predicted performance of the <br /> prescriptive cap. <br /> This recently-monitored rain year (2012/2013) concludes that five-year period. During <br /> that time the ET closure cap has met and exceeded the acceptance criteria each year <br /> without exception. In fact, in the five years of operation the average measured seepage <br /> was approximately 12% of predicted seepage through an intact prescriptive cap. <br /> Therefore, it appears that the criteria for acceptance has been met and that this portion of <br /> the landfill can be accepted as "closed" as of the date of this report (August 30, 2013). If <br /> you agree, then this will be our final report on this issue. <br />