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CLEARWA_ <br /> TE <br /> Environmenlnl Services <br /> located approximately 1.5 miles south of the Port of Stockton Turning Basin and 0.9 mile east of <br /> the San Joaquin River (Figure 2). Currently, the site is used as a truck dispatch center and <br /> parking area. There are no fuel dispensing facilities stored or operating at the site. <br /> .;--a <br /> 1.3 Previous Investigations <br /> In letters dated September 18, 1992 and April 30, 1996, the SJCEHD indicated that additional <br /> investigation of this site was required because petroleum hydrocarbons were detected in soil <br /> samples collected from an underground storage tank (UST) excavation. According to an April <br /> 30, 1996 SJCEHD letter, two USTs were removed from the site on June 15, 1992. Both USTS <br /> were 10,000-gallon capacity tanks that had been used to store diesel fuel. Four soil samples were <br /> collected from the bottom of the excavation at a depth of approximately 16 feet below ground <br /> surface (bgs). Soil samples were analyzed for total petroleum hydrocarbons as gasoline (TPHg) <br /> as diesel fuel (TPHd), as kerosene (TPHk), and as motor oil (TPHmo). Samples were also <br /> analyzed for benzene, toluene, ethylbenzene, and xylenes (BTEX). The highest concentrations <br /> of TPHg, TPHd, and BTEX were detected at 5,700 milligrams per kilogram (mg/kg) TPHg, 50 <br /> rymg/kg TPHd, and 48 mg/kg benzene. TPM, and TPHmo were not detected in any of the four <br /> samples. <br /> On September 25, 1997, Clearwater Group (Clearwater) supervised the drilling of six soil <br /> borings to depths from 32 to 38 feet bgs. Three of the borings were converted to groundwater <br /> monitoring wells (MW-1 through MW-3). Soil samples collected from four of the six borings <br /> ' .; contained detectable concentrations of petroleum hydrocarbons. The highest concentrations of <br /> TPHg (570 mg/kg) and benzene (4.0 mg/kg) were detected in the sample from SB-2 at a depth of <br /> 25 feet bgs. Groundwater samples collected September 29, 1997 from all three monitoring wells <br /> i <br /> contained detectable concentrations at ons of dissolved petro <br /> Ieum hydrocarbons, <br /> The highest <br /> t <br /> 1 ='; concentrations of TPHg32,000 micrograms per liter and benzene 2,200 /L were <br /> ( P [µgr-7) ( 1�g ) <br /> detected in the sample from monitoring well MW-1. Low concentrations of TPHd were detected <br /> is <br /> ' in soil samples from SB-5 (11 mg/kg) and SB-6 (2 mg/kg), and in the groundwater sample from <br /> =' MW-1 (300 ICg/L), however, subsequent groundwater sample results have been non-detect for all <br /> ZB 178E iSOC System Installation/start-up 2 Nov.24,2004 <br />