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oY4�1{y, J THOMAS® M.GAU 4V P.O.BOX 1810-1810 E.HAZELTON AVENUE a. < ,t4 ,14t. STOCKTON,CALIFORNIA 95201 DIRECTOR (209)468-3000 FAX(209)468-2999 wwvw.sjgov,orglpubworks if- kA FRrrZ BUCHMAN DEPUTY DIRECTOR MICHAEL SELLING DEPUTY DIRECTOR ROGERJANES s LISINESS ADMINISTRATOR January 20, 2013 Mr. Todd Del Frate California Regional Water Quality Control Board Central Valley Region 11020 Sun Center Drive,#200 Rancho Cordova, California 95670-6114 SUBJECT: SECOND SEMESTER AND ANNUAL 2012 GROUNDWATER AND SURFACE WATER MONITORING REPORT; FOOTHILL SANITARY LANDFILL Dear Mr. Del Frate: Enclosed is the Second Semester and Annual 2092 Groundwater and Surface Water Monitoring Report for the Foothill Sanitary Landfill. This report presents data from July through December 2012. Groundwater monitoring continues on a semi-annual basis in accordance with our WDRs. The last monitoring report was submitted in July 2012, presenting data from January through June 2012. No VOCs were found in any well in this semester. Previous low detections(2 ppb or less) at one well have apparently subsided. I believe that the short-duration groundwater impact was the result of placing HDPE over refuse from mid-2006 until the LFG system was fully functioning in 2007. The time of low- level impact coincides with the approximately five-year delay from the event which caused it, a lag we have seen previously. Note that the LFG system was not installed until 2006, and was not needed to mitigate groundwater impact from November 2002 when impact ceased until after the placement of HDPE over refuse. The County continues to be concerned that installation of impermeable liner over refuse increases the potential for contamination of groundwater even when a LFG collection system is operating. The Evapotranspiration (ET) closure cover test pad continues to show that our ET cover performs at least twice as well as an intact prescriptive cover. Due to the small amount of rain received in the 2011/12 rain year, run-off from the test pad could not be measured. Equipment to measure smaller quantities of run-off was installed this summer, and is in place to measure this winter's run-off. General parameters, minerals and inorganic results are unremarkable. Surface water was collected in December. The up-stream and down-stream samples were comparable.