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26 October 2000 AGE-NC Project No 97-0333 Page 2 of 7 Total petroleum hydrocarbons quantified as gasoline and diesel (TPH-g and TPH-d, respectively) were detected beneath the east ends of the three USTs at concentrations as high as 2,600 milligrams per kilogram(mg/kg),beneath the west ends of the USTs at concentrations as high as 25 mg/kg, and beneath product piping at concentrations as high as 8,000 mg/kg Volatile aromatic compounds -benzene, toluene, ethylbenzene and xylenes (BTEX) were detected beneath the east ends of three USTs at concentrations ranging up to 340 mg/kg, beneath the west ends of the USTs at concentrations ranging up to 2 7 mg/kg, and beneath product piping at concentrations ranging to 880 mg/kg Fuel oxygenates (methyl tertiary butyl ether MTBE,tert-amyl methyl ether TAME and tert-butanol TBA) were detected beneath the east ends of the three USTs at concentrations ranging up to 16 mg/kg,beneath the west ends of the USTs at concentrations ranging up to 3 1 mg/kg, and beneath product piping at concentrations ranging up to 690 mg/kg Analytical results of soil samples collected during tank removal activities are summarized in Table 1 . 22 PREVIOUS SUBSURFACE INVESTIGATION The following is a brief summary of site assessment activities On 15 April 1999, a total of six soil probe bonngs (P-1 through P-6) were advanced at the site to assess the lateral and vertical extent of impacted soil A total of 17 soil samples and five grab ground water samples were collected during the investigation and submitted for laboratory analysis TPH-g and TPH-d were detected in soil samples at concentrations as high as 390 milligrams per kilogram (mg/kg) and in grab ground water samples at concentrations as high as 310,000 micrograms per liter (µg/1) BTEX compounds were detected in soil samples at concentrations as high as 51 mg/kg and in grab ground water samples at concentrations as high as and 48,000 µg/1 Methyl tertiary butyl ether (MTBE) was detected in selected soil samples and grab ground water samples at concentrations as high as 140 mg/kg and 810,000,ug/l, respectively Analytical results of soil and grab ground water samples collected during the April 1999 investigation are summarized in Tables 2 and 3 On 08 September 2000,a Sensitive Receptor Survey Report was submitted to the PHS-EHD The results of the survey located a non-operational City of Manteca municipal water well approximately 1,900 feet northwest of the site and an operational City of Manteca municipal water well located approximately 1,500 feet south of the site On 29 June and 07 July 2000, five ground water monitoring wells (MW-1, MW-2, MW-3, MW-4 and MW--5) were installed on-site to maximum depths of 32 feet bsg, on 1 I July 1dtiu)+ridG(obn%ironmem)I s.,