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J S Site Assessment Report`,. Former Texaco Service Station Chevron Site ID 309075 March 18, 2010 3.1 SOIL BORINGS Prior to drilling, the boring locations were cleared using a hand auger to the utility clearance depth of 8 feet 1 inch bgs. Boring MW-6 was advanced using an 8-inch outer diameter (OD) HSA to approximately 75 feet bgs. To minimize the potential for cross contamination between the shallow and deep water-bearing zones, MW-6D was double-cased with steel conductor casing using 15-inch OD HSA to approximately 78 feet bgs. The space between the wall of the borehole and the outside of the conductor casing was sealed at the base of the casing with approximately 2 feet of bentonite chips. Grout was then tremied into the annular space to seal the remainder of the casing to approximately 1 foot bgs. Once the casing was set and sealed, an 8-inch diameter borehole was advanced through the conductor casing to approximately 120 feet bgs. The soil borings were completed as monitoring wells. 3.1.1 Soil Sampling, Screening, and Analysis r Soil samples were collected continuously at boring MW-6D using a California-modified split spoon sampler from approximately 10 feet bgs to total depth. Soil samples were collected continuously at boring location MW-6 using a California-modified split spoon sampler from approximately 60 feet bgs to total depth. The samples were logged for soil characteristics and screened for the presence of volatile organic compounds (VOC) using photo-ionization detector (PID). Twelve soil samples collected from MW-6D were packed on ice, cooled to approximately 4 degrees centigrade (°C), and shipped under appropriate chain-of-custody protocols, to Lancaster Laboratories Incorporated (Lancaster) of Lancaster, Pennsylvania for analysis. Soil samples were analyzed for the following: • TPH-GRO (C6-C10) by United States Environmental Protection Agency (USEPA) Method 8260B • Total petroleum hydrocarbons in the diesel range [TPH-DRO (C1Q-C28)], total petroleum hydrocarbons as motor oil (TPH-MO) [C16-C36], and methanol by USEPA Method 8015B • Benzene, toluene, ethylbenzene, and total xylenes (BTEX) by USEPA Method 8260B r • Methyl tertiary butyl ether (MTBE), ethanol, di-isopropyl ether (DIPE), ethyl tertiary butyl ether (ETBE), tertiary amyl methyl ether (TAME), tertiary butyl alcohol (TBA), 1,2-dichloroethane (1,2-DCA) and ethylene dibromide (EDB), also known as 1,2-dibromoethane, and ethanol by USEPA Method 8260B All down-hole drilling and sampling equipment was steam-cleaned following the completion of each soil boring. Down-hole equipment was washed in a tri-sodium phosphate solution between soil samples and rinsed with distilled water. Soil analytical results are included in Table 3. Analytical results for the soil samples collected by ARCADIS are included in Attachment E. \\CA5FMData\Aproject\ENV\CHEVROM309075\6 Deliverables\Reports\DG Wells Assessment\Pssessment Report 4741010950.doc 3 v