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April 19, 1988 <br /> Page 2 <br /> D. Site Map <br /> Figure 2 presents the general facility layout at the time the tanks were still <br /> in use. As stated above, the tanks, islands, and building have all been <br /> removed. <br /> III. FIELD WORK TO DETERMINE HYDROGEOLOGY <br /> A. Drilling Information <br /> 1. Type of Drilling <br /> In order to determine if hydrocarbon contamination exists at the site, <br /> four (4) soil borings are proposed by Chevron U.S.A. Inc., as specified on <br /> the attached Figure 2. The borings will be drilled with continuous <br /> flight, hollow-stem auger (8 inch) drilling equipment by a licensed well <br /> driller. If groundwater is encountered, the borings will be converted to <br /> three (3) inch diameter observation wells. <br /> 2. Depth of Borings <br /> Based on other groundwater investigations conducted in the area, <br /> groundwater is expected to be encountered between 10 and 20 feet below <br /> grade. Borings will be advanced approximately 20 feet beyond first <br /> encountered groundwater, making sure not to penetrate a 5 foot thick <br /> aquitard. <br /> 3. Date of Drilling <br /> The drilling should be scheduled within two (2) weeks of San Joaquin <br /> County Environmental Health Department's approval. <br /> 4. Soil Sample Collection and Classification <br /> During drilling, soil samples will be collected at five (5) foot intervals <br /> using a modified California split-spoon sampler equipped with clean brass <br /> tube inserts. The sampler will be driven a maximum of 18 inches, using a <br /> 140 pound hammer with a 30 inch drop. The number of blows per six (6) <br /> inches will be recorded. The lithology will be logged under the direction <br /> of a California Registered Geologist using the Unified Soil Classification <br /> System. Monitoring well specifications, moisture content and soil density <br /> will also be recorded in the logs. <br /> 5. Submission of Boring Logs <br /> After completion of field activities, a report will be prepared which will <br /> include copies of the boring logs. <br />