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f •.I THOMAS R. FLINN DIRECI OR' r ..J THOMAS M GAU CHH') Vy D7;RLCI'OR MICHAEL SELLING STEVEN WINKLER 01-FUTy DIRECT%a ROGER JANES BUS Ess ADUINIs-RA-OR October 21, 2010 Mr. Todd Del Frate California Regional Water Quality Control Board 11020 Sun Center Drive, # 200 Rancho Cordova, California 95670-6114 P 0. BOX 1810 - 1810 E. HAZELTON AVENUE STOCKTON CALIFORNIA 95201-3018 !2`.:91 4618-3000 FAX 'G 4i -'i8-2 ,,.,. _I r � � SUBJECT: THIRD QUARTER 2010 GROUNDWATER MONITORING REPORT, CORRAL HOLLOW SANITARY LANDFILL Dear Mr. Del Frate: Enclosed please find the Third Quarter 2010 Groundwater and Surface Water Monitoring Report for the Corral Hollow Sanitary Landfill. Monitoring was performed in accordance with the monitoring program included with the Waste Discharge Requirements (WDRs) approved by the Regional Water Quality Control Board for this site. Groundwater conditions remain consistent with those of the previous year. VOCs were not reported at shallow aquifer wells SB -1, MW -4 or at any deep aquifer well. Nine VOCs were reported in impacted well MW -5, five in trace concentrations, none above 9 ppb. Seven VOCs were reported in well MW -8, three in trace concentration. VOCs found in MW -8 were also found in MW -5. This quarter, general water quality concentration limits were not exceeded where they can be established, except for Bicarbonate Alkalinity in SB -1. Bicarbonate is not listed in the California drinking water standards, and is not considered a threat to human health and safety or to the beneficial use of this aquifer. TO -14 analyses of soil gas are included in this Report. Progress of Corrective Action Measures is submitted during the first and third quarters, and is therefore included in this quarterly report. Monitoring data indicates significant improvement in groundwater quality at well MW -5 (the impacted well) since operation of the LFG system in late 2001. The LFG wells installed in December 2008 continue to withdraw gas from the northern portion of the landfill, much of which is air pulled into the landfill in an attempt to mitigate the VOC impact. Inorganic parameters at MW4 continue to show the benefit of the grading improvements in late 2003. This improvement seems to indicate that the lack of closure cover over small portions of the refuse at the eastern edge of the landfill is not negatively impacting groundwater at this time.