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n <br />March 12, 1992 <br />Project 939-03.15 <br />Mr. Robert Evans <br />California Regional Water <br />Quality Control Board <br />Central Valley Region <br />3443 Routier Road <br />Sacramento, California 95837-0398 <br />Re: Confirmation Monitoring of Volatile Organic Compounds (VOCs) in <br />Well MW -5, Corral Hollow Sanitary Landfill, San Joaquin County <br />Dear Mr. Evans: <br />On behalf of the San Joaquin County (County) Department of Public <br />Works, EMCON Associates would like to submit the results of the verifica- <br />tion sampling and analysis event for ground -water monitoring well MW -5 <br />at Corral Hollow Sanitary Landfill. The data are being submitted in compli- <br />ance with Section C.7 of waste discharge requirements order no. 89-046, <br />dated April 5, 1989. Two VOCs were detected at low concentrations in a <br />ground -water sample from well MW -5. The ground -water sample was <br />collected on December 16, 1991, and analyzed using Environmental <br />Protection Agency (EPA) Method 624. The two compounds detected were <br />trichlorofluoromethane (Freon 11) and tetrachloroethylene (PCE) at con- <br />centrations of 2 and 4 micrograms per liter (µg/I) respectively. These <br />results were reported in the fourth quarter and annual 1991 monitoring <br />report for Corral Hollow Sanitary Landfill dated February 5, 1992. <br />Based on these results, the County directed EMCON Associates to <br />resample monitoring well MW -5 to confirm the results of the annual <br />monitoring program. Well MW -5 was resampled on February 12, 1992, <br />and a ground -water sample was analyzed for VOCs by EPA Method 624. <br />The analytical results of the February sampling event confirmed the results <br />of the previous sampling program. Freon 11 and PCE were detected at <br />pj9\939\9390316a <br />