SITE INFORMATION AND CORRESPONDENCE_FILE 1

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EA ENGINEERING, SCIENCE. AND TECHNOLOGY, INC. Laurie L. Cotulla 2 February 1988 San Joaquin Local Health District Page 2 If ground water is not encountered within 45 feet, the bore hole will be resealed with cement grout . However, when water is encountered the bore holes will be completed as monitoring wells with PVC screen (4-inch diameter, 0.020-inch slot, Schedule 40) from 5 feet above to 20 feet below the static water level or to the competent clay layer (Figure 2) . Above the screen to the surface, Schedule 40 blank PVC casing will be installed. Each well will be equipped with a bottom threaded plug and a well cap. The annular space from the bottom to approximately 1 foot above the screen will be filled with clean Monterey or Lapis Luster sand. The sand pack will be sealed with 1 foot of bentonite pellets and a neat cement grout to the surface. The well will be secured with a water-tight monitoring well cover that can be opened only with a special wrench, to protect the well from unauthorized entry. Each well will be equipped with a well tag containing pertinent information. After completion, each well will be developed using either a submersible stainless steel pump or a PVC bailer (depending on yield) until the water is free of sand. All drilling and well construction activities will be supervised by a qualified geologist or engineer. All ground-water sampling will be done by a trained geologist or a trained environmental scientist. Before sampling, each well will be purged by removing four or five casing volumes of water with a precleaned bailer. Purged water will be filtered through activated carbon and then put into 55-gallon drums. A sample of the filtered water will be taken for total petroleum hydrocarbon analysis . All drums will be stored in EA' s warehouse until sample results are received. Ground-water samples will be collected with precleaned Teflon bailers. All water samples will be collected in appropriate containers with Teflon-lined caps and preserved with either hydrochloric or sulfuric acid. All samples will be labeled, placed on ice, and shipped under chain of custody to the state- certified laboratory. Samples will be analyzed for TPH and VOA using the modified EPA Methods 624, 8010, 8020, 8240, and 8015, as appropriate. In addition to these field activities, sufficient information on regional geology and hydrogeology will be collected, and on the basis of all data available the problem assessment report will be developed according to the Guidelines For Site Assessment, Cleanup, and Underground Storage Tank Closure of the State Water Resources Control Board (July 1982) . EXX10:73R