SITE INFORMATION AND CORRESPONDENCE

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S � -STA E OF CALIFORNIA-Environmental Protectioenc PETE WILSON,Governor CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD CENTRAL VALLEY REGION 3443 Routier Road,Suite A a Sacramento,CA 95827-3098 -- PHONE:(916)255-3000 FAX:(916)255-3015 22 January 1996 RECEIVELi J AN 2.3 1996 Mr. Verrill Norwood ENVIRONMENTAL I-4EALTH NVIRONMETLTH Pioneer Chlor Alkali Company, Inc. PERMIT 1 SERVICES 700 Louisiana Street 4200 NCNB Center Houston, Texas 77002 GROUNDWATER INVESTIGATIONATALL PURE CHEMICAL COMPANY, TRACY As you are aware, the Board has previously requested All Pure Chemical Company (All Pure) to complete the investigation of ground water contamination at the Tracy facility. As the enclosed memo discusses, further investigation is needed to determine the sources and extent of volatile organic compounds (VOCs) in ground water at the facility. The Tracy Defense Depot(TDD) is installing a ground water infiltration gallery and ground water extraction and treatment system to the north of All Pure which is scheduled for startup in the fall of 1996. There is concern that the ground water extraction will pull the carbon tetrachloride and chloroform known to be present in the ground water beneath All Pure to the north. At least two domestic wells north of All Pure are known to have carbon tetrachloride at concentrations exceeding the maximum contaminant level for drinking water. Chloroform also is present at low concentrations in several domestic wells north of All Pure. The Board believes that All Pure is the likely source of both of these VOCs, since it is the only facility in the area where both carbon tetrachloride and chloroform are known to be present in the ground water. Although it appears that shallow ground water at the All Pure facility is being captured by the two production wells onsite, the construction and pumping history of these wells is unknown. Such information is necessary for the most accurate determination of ground water movement at the site. It is important that the investigation of the ground water contamination at All Pure be completed as soon as possible, since the TDD extraction system will be operating this fall. By 23 February 1996, please submit a work plan to complete the definition of soil and ground water contamination at the All Pure Tracy facility. The work plan should propose activities to determine the source(s) of VOC contamination, the lateral and vertical extent of contamination, and ground water flow directions, and include construction details and information on the pumping history of the two onsite production wells.