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. 45 E Harding Way, Stockton, California March 14, 1994 Chevron USA Products Company Page 3 On April 24, 1989, a soil vapor extraction test on V-3, V-4, and V-5 revealed total volatile hydrocarbons (IVH) concentrations from 4,500 to 16,000 ppm Operation of a vapor extraction and treatment system (VETS) began on November 15, 1990 Further information regarding assessment work conducted by EA Is provided in their report, Work Plan To Investigate Groundwater dated April 16, 1991 On July 16, 1991, Chevron contracted Groundwater Technologyto drill and install one groundwater monitoring well at the site In the area of the former tank field (MW-9) Highest TPH-G concentrations in soil samples collected during drilling were detected at 26 feet (3,900 ppm) Analyzed groundwater samples contained 1,900 ppb TPH-G Information regarding the drilling and installation of MW-9 is provided in the Environmental Assessment Repo dated August 21, 1991, prepared by Groundwater Technology On May 11 and 12, 1992, two groundwater monitoring wells (MW-10 and MW-11), and one vapor extraction well were installed TPH-G concentrations from soil samples ranged from below method detection limn (MDL) to 730 ppm in VW-6F Benzene ranged from below MDL to 0 12 ppm in VW-6F Additional information is provided in the Environmental Assessment Report dated July 1992, prepared by Groundwater Technology On June 29, 1993, two additional soil borings were drilled lust east of the site in El Dorado Avenue and were converted into groundwater monitoring wells (MW-12 and MW-13) The drilling results and installation of these two wells are described in the Environmental Assessment Retort dated September 1, 1993, prepared by Groundwater Technology The groundwater beneath the site was monitored and sampled at quarterly intervals from January 1989 through January 1994 A historical summary of monitoring and sampling data is summarized in Table 2 ' GROUNDWATER 4995SUM RPT ❑0❑ TECHNOLOGY