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THOMAS R.FLINN P.O.BOX 1810-1810 E.HAZELTON AVENUE DIRECTOR STOCKTON,CALIFORNIA 95201 • �Y aisw� (209)468-3000 FAX(209)468-2999 www.sjgov.org/pubworks THOMAS M.GAU CHIEF DEPUTY DIRECTOR � MANUEL SOLORIO WorkWg for YOU DEPUTY DIRECTOR STEVEN WINKLER DEPUTY DIRECTOR ROGER JANES BUSINESS ADMINISTRATOR July 25, 2009 Mr. Todd Del Frate California Regional Water Quality Control Board Central Valley Region 11020 Sun Center Drive, #200 Rancho Cordova, California 95670-6114 SUBJECT: FIRST SEMESTER 2009 GROUNDWATER AND SURFACE WATER MONITORING REPORT; FOOTHILL SANITARY LANDFILL Dear Mr. Del Frate: Enclosed is the First Semester 2009 Groundwater and Surface Water Monitoring Report for the Foothill Sanitary Landfill. Groundwater monitoring continues on a semi-annual basis in accordance with our WDRs. Wells MW-4 and MW-5 have been sampled four times since installation. Statistical analysis of well MW-5 data indicates exceedence of the concentration limit for sulfate (10.9 vs. 9.7 ppm). However, these statistical analyses at MW-5 are not valid with only four data points. It may be appropriate to use intra-well statistical evaluation for these wells due to their distance from the landfill and from the other three wells. Wells MW-3 and MW-4 show equal concentration of bicarbonate alkalinity (140 ppm), which is a modest exceedence of the concentration limit for that parameter (130 PPM). Because the well MW-4 is directly up-gradient of the landfill, we do not believe that these results indicate impact by landfill activity. Other results are unremarkable. All groundwater wells are free of VOCs. I feel it important that no VOCs have been confirmed in any groundwater well at the Foothill Landfill since October 2001, over seven years ago. The water level at MW-1 has dropped below an elevation where we can purge sufficiently. However, this well is now known to be cross-gradient from the landfill and is not the optimal reference well for this landfill. Recently-installed MW-4 is directly up-gradient, but the number of samples collected to date (four) is less than recommended for the statistical software (eight). To address this issue, we propose to increase sampling from MW-4 from semi-annual to quarterly to more quickly obtain the recommended number of samples, and use data from MW-4 in statistical analysis meantime. Well MW-1 would continue to serve as a groundwater elevation monitoring point, contributing to the data from which we draw groundwater contours. Sampling at MW-1 would resume if the groundwater elevation returns to sufficient elevation to allow adequate purging. Please let us know your thoughts on this proposal.