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l� CLEARWATER ✓ G R O U P, I N C 10 Environmental Services — GROUNDWATER MONITORING REPORT , SECOND QUARTER 2001 Bames Trucking Facility - 1817 South Fresno Avenue, Stockton, California June 8,2001 BACKGROUND The Barnes Trucking Facility is located adjacent to the southwest corner of the intersection of Charter Way (State Highway 4) and South Fresno Avenue (Figure 1) The property is located approximately 15 miles south of the Port of Stockton Turning Basin and 0 9 mile east of the San Joaquin River (Figure 2) Currently,the site is used as a truck dispatch center and parking area There are no fuel dispensing facilities stored or operating at the site In letters dated September 18, 1992 and April 30, 1996, the EHD indicated that additional investigation of this site was required because petroleum hydrocarbons were detected in soil samples collected from an underground storage tank (UST) excavation According to an April 30, 1996 EHD letter, two USTs were removed from the site on June 15, 1992 Both USTs were 10,000-gallon capacity tanks that had been used to store diesel fuel Four soil samples were collected from the bottom of the excavation at a depth of approximately 16 feet below ground surface (bgs) Soil samples were analyzed for total petroleum hydrocarbons as gasoline (TPHg) as diesel fuel (TPHd), as kerosene (TPHk), and as motor oil (TPHmo) Samples were also analyzed for benzene, toluene, ethylbenzene, and xylenes (BTEX) The highest concentrations of TPHg, TPHd, and BTEX were detected at 5,700 milligrams per kilogram(mg/kg)TPHg,50 mg/kg TPHd, and 48 mg/kg benzene TPHk and TPHmo were not detected in any of the four samples On September 25, 1997, Clearwater Group (Clearwater) supervised the drilling of six soil borings to depths from 32 to 38 feet bgs Three of the borings were converted to groundwater monitoring wells (MW-1 through MW-3) Soil samples collected from four of the six borings contained detectable concentrations of petroleum hydrocarbons The highest concentrations of TPHg(570 mg/kg) and benzene (4 0 mg/kg) were detected in the sample from SB-2 at a depth of 25 feet bgs Groundwater samples collected September 29, 1997 from all three monitoring wells contained detectable concentrations of dissolved petroleum hydrocarbons The highest concentrations of TPHg (32,000 micrograms per liter [µg/L]) and benzene (2,200 lig/L) were detected in the sample from monitoring well MW-1 Low concentrations of TPHd were detected in soil samples from SB-5 (11 mg/kg) and SB-6 (2 mg/kg), and in the groundwater sample from MW-1 (300µg/L), however, subsequent groundwater sample results have been non-detect for all three wells, and with approval from the EHD, analysis for TPHd has been discontinued Results of these efforts were presented in Clearwater's Subsurface Investigation Report, dated November 20, 1997 Based on these initial investigation results, the EHD requested additional monitoring wells be installed to better define the areal extent of soil and groundwater contamination After discussion with Lon Duncan of the EHD, Clearwater submitted the Workplan for Site Investigation dated November 18, 1998 An addendum to the workplan, dated December 10, 1998, was submitted in response to EHD comments The workplan and addendum were approved by the EHD on December 15, 1998 520 Third Street,Suite 104 • Oakland,California 94607 • Telephone 510-893-5160 + Fax 510-893-5947