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KEI-P88-1013 .R4 October 27 , 1994 Page 2 approximately 3 , 500 feet northwest of the Mokelumne Aqueduct, and 5, 000 feet northwest of the Calaveras River. A Location Map is attached to this report. The site has been under investigation since mid-1985, when the station was closed and two 10, 000 gallon fuel storage tanks and one waste oil tank were removed from the site. The location of the former tanks and pump islands are shown on the attached Figure 2 , 3 , and 4 . soil contamination was discovered after the tanks were removed. Between mid-August 1985 and March 1988 , at least 19 soil borings (seven of which were apparently converted into vapor extraction wells) and ten monitoring wells were installed by Kleinfelder and Associates, as shown on the attached Figures 3 and 4 . The vapor extraction wells reportedly were never operated. These soil borings and wells apparently delineated the zone of soil contamination that was then present at the site. The extent of ground water contamination at the site, however, had not yet been completely defined. On January 19 , 1988 , and again on July 25 , 1988 , KEI submitted proposals for soil and ground water remediation at the site. A proposal was subsequently approved by Unocal and the pertinent regulatory agencies. Soil remediation excavation began on September 19 , 1988 , and was completed on December 12 , 1988 . The area excavated in relationship to the Kleinfelder and Associates soil borings is as indicated on the attached Figure 4 . A total of 28 soil samples were collected and analyzed from the excavation sldewalls and bottom. These samples were used to further delineate the zone of contamination and guide soil excavation. The excavation was terminated at the water table (at a depth of 53 feet) or at a shallower depth if pit bottom sample analyses indicated no detectable contaminant concentrations. Soil was excavated to a maximum depth of 53 feet below grade (the existing shallow water table depth) . During excavation, two monitoring wells (MW1 and MW7) and all seven vapor extraction wells were destroyed. Also during excavation, six of the remaining seven monitoring wells (MW2 , MW3 , MW4 , MW5 , MW8 , and MW9) suffered various amounts of wellhead damage. Documentation of the soil excavation methods, sampling techniques, and the analyti- cal results are presented in KEI ' s report (KEI-P88-1013) dated December 15, 1988 . As previously stated, during the excavation activities it was necessary to destroy two monitoring wells, MW1 and MW7 . The wells were destroyed on September 25, 1988 , after permits were obtained front the San Joaquin County Public Health Services (SJCPHS) . i