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Californiagional Water Quality Co of Board lo Central Valley Region Katherine Hart,Chair Linda S.Adams Arnold Secretary for 11020 Sun Center Drive#200,Rancho Cordova,California 95670-6114 Schwarzene er Environmental Phone(916)464-3291 •FAX(916)464-4645 Governor99 Protection http://www.waterboards.ca.gov/centralvalley 13 May 2010 MAY 1 44 its ENVIRONMEN T HEALTH! W. Michael Carroll PER I-f/ ERV#CES San Joaquin County Dept. of Public Works Solid Waste Division P.O. Box 1810 Stockton, CA 95201 NOTICE OF VIOLATION: REVIEW OF THIRD QUARTER 2009 GROUNDWATER AND SURFACE WATER MONITORING REPORT, CORRAL HOLLOW SANITARY LANDFILL, SAN JOAQUIN COUNTY Central Valley Water Board staff has reviewed the Third Quarter 2009 Groundwater and Surface Water Monitoring Report (Report) for the Corral Hollow Sanitary Landfill. The Report was prepared in accordance with Waste Discharge Requirements (WDRs) Order No. 5-01-176. The Monitoring and Reporting Checklist is attached for your review. Based upon review of the Report, staff finds that groundwater in the vicinity of wells MW-5 and MW-8 continues to be affected by a release from the landfill, which is a violation of the WDRs. Current data indicates VOC concentrations continue to affect groundwater in the vicinity of wells MW-5 and MW-8. Concentrations of Freon 11 and Freon 12 reported are consistent with past detections. The chlorinated series of tetrachloroethene (PCE), trichloroethene (TCE), and vinyl chloride were also detected at concentrations consistent with past results. 1,1-dicholoroethane was detected during this and the last monitoring event conducted. Although the number of VOCs initially reported since corrective action began 2001 is less than current VOCs reported, it appears that concentrations of VOCs have not been reduced by the additional landfill gas (LFG) extraction wells installed during December 2008. Although efforts have been made to increase collection of LFG, the plume continues to affect the underlying groundwater. Based on Figure 4 of the Report, it appears the recently installed LFG extraction wells envelop the northeastern boundary only, and it appears the wells are not influencing gas collection along the northern boundary in the vicinity of wells MW-5 and MW-8. The Evaluation Monitoring Program (EMP) requires the plume be defined in accordance with Title 27, §20425(b), but it may not be necessary at this time to investigate offsite. It is appropriate to begin this investigation by revising the initial Engineering Feasibility Study (EFS) to incorporate new site information. California Environmental Protection Agency �aRecycled Paper