ARCHIVED REPORTS_2003 FEASABILITY STUDY REPORT AND SITE ASSESSMENT WORK PLAN

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S E C O R • 2003 Feasibility Study Report and Site Assessment Work Plan July 18, 2003 Page 5 The following is a brief chronology of past work performed at the facility. ■ In December of 1983, Groundwater Technology, Inc. (GTI) installed groundwater monitoring wells MW-1 through MW-7 in the vicinity of the above-ground tanks and pump islands (PEG, 1995). ■ In November of 1984, GTI installed wells T-1 through T-3 in the area of an underground diesel storage tank (PEG, 1995). • In October of 1988, EA Engineering, Science, and Technology (EA) installed groundwater monitoring wells MW-8 through MW-11 on the periphery of the property boundaries (PEG, 1995). • During November of 1988, EA advanced shallow exploratory soil borings B-1 through B-9 along the northern property boundary(PEG, 1995). ■ During January through April of 1988, EA conducted a soil vapor survey in the impoundment area (PEG, 1995). ■ In May of 1989, Dames and Moore (D&M) installed monitoring wells (MW-12 and MW-13) to • a depth of approximately 60 feet bgs. The wells are screened from 48 to 50 feet bgs in a presumed lower water bearing zone (PEG, 1995). ■ In May of 1990, EA prepared a Problem Assessment Report (PAR) and Work Plan (PEG, 1995). The PAR, included a '/2 mile radius well search, fate and transport modeling, and summary of previous site work. ■ In July of 1993, Geraghty and Miller, Inc. (Geraghty) installed five extraction wells (MW-14 through MW-16, MW-18 and MW-19) and three groundwater monitoring wells (MW-17, MW- 20, and MW-21). Wells MW-14 through MW-16 were used for separate phase hydrocarbon (SPH) recovery and wells MW-18 and MW-19 were used for hydraulic containment (PEG, 1995). ■ In August of 1993, Geraghty & Miller, Inc. (G&M) performed a site assessment. Twenty soil borings were drilled in the farm field adjacent to the site. The results of groundwater samples collected from all 20 borings indicated total petroleum hydrocarbons as diesel (TPHd), total petroleum hydrocarbons as gasoline (TPHg), benzene and toluene concentrations were all non-detect (PEG, 1995). ■ In January of 1994, a groundwater remediation system was installed at the site for SPH recovery and hydraulic containment. The remedial system was initiated in February of 1994 and continued until February of 1996. During this time period, groundwater was extracted from wells, MW-18 and MW-19 (for hydraulic containment of groundwater) and SPH was recovered from wells, MW-14, MW-15, and MW-16 (PEG, 1995). • In June 1994, Touchtone Development observed the removal of one 10,000-gallon double walled fiberglass UST, pump island, and associated piping form the Keylock Terminal Area. I:\Chevron\1001621\REPORTS\2003\2003FS\FS..2003_revD.doc