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1 <br /> Quarterly Groundwater Ge Monitoring Report <br /> Frontier Transportation <br /> 0399-085 <br /> April 5, 1999 <br /> ' 1.0) INTRODUCTION <br /> BIakely Environmental Investigations, Inc. (BEII) was contracted by Frontier <br /> ' Transportation, Inc. ((909) 590-8200) to perform quarterly groundwater monitoring at the <br /> Frontier Transport facility, 425 Larch Road, Tracy, CA (See Figure 1, Site Location Map). <br /> Quarterly groundwater sampling was requested by the San Joaquin County Public Health <br />' Services, Environmental Health Division (PHS/EHD), Carrol Oz, Senior REHS. <br /> 2.0) SITE LOCATION AND HISTORY <br /> The site is located in Trac California at 425 Larch Road in the northwest quarter of <br /> Y <br /> section 16, Township 2 South, Range 5 East, Mount Diablo Baseline at Meridian. The site <br /> consists of a trucking facility with one metal frame building and all parking and work areas capped <br /> by cement and/or asphalt. The site is located in an industrial park. <br /> Six (6) underground fuel storage tanks (USTs), three diesel tanks located northeast of the <br /> terminal and three gasoline tanks located southeast of the terminal, were removed from the site on <br />' July 21, 1995. Soil sample analysis identified total petroleum hydrocarbons as gasoline (TPH-g) <br /> and total petroleum hydrocarbons as diesel (TPH-d) in the gasoline tank excavation at maximum <br /> concentrations of 9,800 mg/kg and 120 mg/kg, respectively. Groundwater sample analysis <br /> identified dissolved phase TPH-d in the diesel excavation pit at a maximum concentration of <br /> 1,200 gg/L. <br />' In August of 1996, six vertical soil borings (B-1, B-2, B-3, MW-IRA, MW-IRB, and <br /> MW-2RA) and one angle boring (B-4) were advanced to depths between i 0.5' and 12.5' below <br /> grade(bg) to assess subsurface conditions near the northeastern excavation by Twinning <br /> Laboratories, Inc. In addition, two hand augers (S-I and S-2) were advanced to 3' bg to assess <br /> subsurface conditions beneath the dispenser and product lines and three groundwater monitoring <br /> wells, MW-I through MW-3, were drilled to approximately 25' bg to assess the subsurface water <br /> beneath the site. Initial subsurface water was encountered at 10.5' bg. Boring B-4 located <br /> northwest of the former USTs identified maximum TPH-g, BTEX (Benzene, Toluene, <br /> Ethylbenzene, Xylene), and MTBE (Methyl-tert Butyl Ether) as 1,300 mg/kg, 180.7 mg/kg, and <br />' 110 mg/kg, respectively at 10.2' bg. <br /> Groundwater samples were collected from MW-1, MW-2, and MW-3 on August 30, 1996 <br />' and April 21, 1997 by Twinning.- Results are presented in Table 1. <br /> In January of 1998, BEII advanced four (4) groundwater monitoring wells (MW-4 <br /> through MW-7) to assess the extent of subsurface contamination beneath the site (See Figure 2, <br /> 1 <br />