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w w Mr. Robert Mihalovich Chevron Environmental Management Company June 29, 2000 Page 2 direct-push core barrel and drive sampler containing brass liners to a depth of 15 feet bgs. The upper 5 feet of the boring will be advanced using a hand auger. Soil recovered from the continu- ous core will be examined and logged in accordance with the Unified Soil Classification System (USCS) as presented in the American Society of Testing and Materials Standard D2488-90. One soil sample will be collected from each boring for chemical analyses from the area of the soil core most visibly affected with petroleum hydrocarbons. If petroleum hydrocarbons are not identified visually or through screening using an organic vapor meter, the soil sample will be collected from just above the groundwater table. The soil sample will be collected in brass or stainless steel liners, sealed with Teflon sheets,plastic end caps, and tape, labeled, and stored in an ice-cooled chest. If no petroleum hydrocarbon-affected soil is observed in the soil core, a groundwater sample will be collected from boring GMX-29, 30, and 31. A temporary well consisting of 1-inch-diameter polyvinyl chloride (PVC)blank casing and 10 feet of 0.01-inch slot well screen will be placed in the borehole. The grab groundwater sample will be collected with a disposable bailer and will be decanted into 40-milliliter acidified volatile organic analysis(VOA)vials and 1-liter amber bottles. Sample containers will be labeled, sealed in plastic bags, and stored in an ice-cooled chest. Following collection of soil and groundwater samples, the casing will be removed and the borehole will be backfilled with cement grout. Geomatrix will submit the samples to a State of California certified analytical laboratory under Geomatrix chain-of-custody procedures. The soil sample will be analyzed for total petroleum hydrocarbons (TPH) as crude oil (C$to C36 carbon range)using EPA Method 8015; for poly- nuclear aromatic hydrocarbons(PAHs)using EPA Method 8270 SIM, and for benzene,toluene, ethylbenzene, and xylenes (BTEX) using EPA Method 8021B. The groundwater sample will be analyzed for TPH quantified as gasoline (C6 to C12 carbon range) and diesel (CIO to C24 carbon range)using EPA Method 8015 Modified; for BTEX using EPA Method 8021B; and for PAHs using EPA Method 8270 SIM. The laboratory will perform TPHd analyses both with and without a silica gel preparation procedure prior to analysis. The silica gel preparation procedure removes polar biodegradation byproducts from the sample extract. Pending subcontractor availability, the proposed field work will be scheduled within two weeks of approval of this work plan. Appropriate regulatory agencies will be notified at least 48 hours prior to implementation of field work or if there are any changes in the schedule. Please call Michael Keim at(510) 663-4107 if you have any questions. Sincerely, GEOMATRIX CONSULTANTS, INC. Michael R. Keim Gary R. Foote, R.G. Project Scientist Senior Geologist MRK/GRF/pp