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Quarterly Groundwater Monitoring Report
<br /> • Frontier Transportation
<br />' 0998-011
<br /> October 16, 1998
<br /> 1.0) INTRODUCTION
<br /> Blakely Environmental Investigations, Inc. (BEI, Inc.) 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 Tracy California at 425 Larch Road in the northwest quarter of
<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 framed building and all parking and work areas
<br /> capped 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 pg/L,
<br /> ' In August of 1996, six vertical soil borings(B-1, B-2, B-3, MW-I RA, MW-IRB, and
<br /> MW-2RA) and one angle boring (B-4) were advanced to depths between 10.5' 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-1 and S-2) were advanced to T 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, BEI, Inc. 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,
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