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quay y l THOMAS M.GAU P.O.BOX 1810.1810 E.HAZELTON AVENUE DIRECTOR STOCKTON,CALIFORNIA 85201 c• (209)468-3000 FAX(209)468-2999 c4c F oaawww.sjgov.org/pubworks FRITZ BUCHMAN E` DEPUTY DIRECTOR wormng for YOU MICHAEL SELLING DEPUTY DIRECTOR STEVEN WINKLER DEPUTY DIRECTOR ROGERJANES BUSINESS ADMINISTRATOR January 22, 2012 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 2011 GROUNDWATER AND SURFACE WATER MONITORING REPORT; FOOTHILL SANITARY LANDFILL Dear Mr. Del Frate: Enclosed is the Second Semester and Annual 2011 Groundwater and Surface Water Monitoring Report for the Foothill Sanitary Landfill. Groundwater monitoring continues on a semi-annual basis in accordance with our WDRs. Samples take in the second semester indicate that, with the exception of one well, the groundwater general water quality parameters were within acceptable limits. Two VOCs below 2 ppb (one above "trace") were reported in well MW-3. The reoccurrence of these compounds after years of non-detection is troublesome, especially when many of those years were without a LFG collection system. These detections are approximately five years after the placement of HDPE over refuse, consistent with a five-year lag time between action on the surface and effects seen in the groundwater. The County continues to be concerned that installation of impermeable liner over refuse seals the refuse from the air and increases the potential for contamination of groundwater even when a LFG collection system is operating. In response to these detections, the County continues to increase corrective action, primarily improvements to the LFG collection system completed in the second semester 2011. A replacement well GX-2A was installed, and the LFG pipe size to wells GX-1, -3, -6, -7 and -9 were increased. These improvements were viewed during your inspection in December 2011. Collection of LFG from wells that may affect the pressures beneath the liner is increased weekly, and will continue until overdraw is noticeable. The Evapotranspiration (ET) closure cover test pad continues to show that our ET cover performs twice as well as an intact prescriptive cover. Neither surface water or storm water were available due to lack of rain.