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Frontier Transportation, Inc. Well Installation Work Plan July 30, 2008 Page 1 1.0) INTRODUCTION Biophysics Environmental Assessments, Inc . (BEA) was contracted by Frontier Transportation, Inc. to prepare a work plan to further delineate the extent of dissolved phase MTBE plume identified at 425 Larch Road, Tracy, California (See Figure 1, Site Location Map). The proposed work will consist of the installation of one ( 1 ) shallow monitoring well. The additional site assessment work was requested by the San Joaquin County Public Health Services, Environmental Health Division (SJCPHS-EHD), by Victoria L. McCartney, Senior REHS in a letter dated May 21 , 2008. 2.0) SITE LOCATION AND HISTORY The site is located in Tracy, California at 425 Larch Road in the northwest quarter of section 16, Township 2 South, Range 5 East, Mount Diablo Baseline at Meridian. The site consists of a trucking facility with one metal frame building and all parking and work areas capped by cement and/or asphalt. The site is located in an industrial park. Six (6) underground fuel storage tanks (USTs), three diesel tanks located northeast of the terminal and three gasoline tanks located southeast of the terminal, were removed from the site on July 21 , 1995 . Soil sample analysis identified total petroleum hydrocarbons as gasoline (TPH-g) and total petroleum hydrocarbons as diesel (TPH-d) in the gasoline tank excavation at maximum concentrations of 9, 800 mg/kg and 120 mg/kg, respectively. Groundwater sample analysis identified dissolved phase TPH-d in the diesel excavation pit at a maximum concentration of 17200 µg/L. In August of 1996, Twinning Laboratories, Inc. (Twinning) advanced six vertical soil borings (B- 1 , B-24 1 MW- IRA, MW- IRB, and MW-2RA) and one angle boring (B-4) to depths between 1 and 1 4& below grade surface (bgs) to assess subsurface conditions near the northeastern excavation. In addition, two hand augers (S- 1 and S-2) were advanced to 3 ' bgs to assess subsurface conditions beneath the dispenser and product lines and three groundwater monitoring wells, MW-1 through MW-3 , were drilled to approximately 25' bgs to assess the subsurface water. Initial subsurface water was encountered at 10. 5 ' bgs. Boring B-4 located northwest of the former USTs identified maximum TPH-g, BTEX (Benzene, Toluene, Ethylbenzene, and Xylene), and MTBE (Methyl-tert Butyl Ether) as 1 ,300 mg/kg, 180. 7 mg/kg, and 110 mg/kg, respectively at 10.2' bgs. Groundwater samples were collected from monitoring