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2101 Webster Street 12th Floor Oakland, CA 94612 (51 O] 663-4100 + FAX (51 O) 663-4141 GEOMATRIX March 22, 2000 Project 6115.007 Ms. Katie Hower Chevron Environmental Management Compariy P.O. Box 6012 San Ramon, California 94583 Subject: Work Plan for Off--Site Investigation Burns Property (San Joaquin County APN 232-170-05) Tracy, California Dear Ms. Hower: Geomatrix Consultants, Inc. (Geomatrix), has prepared this work plan for additional investi- gation of petroleum hydrocarbons in the subsurface near the Burns Property(Figure 1). Soil and groundwater investigations were conducted at the Burns property by Earth Systems Con- sultants and Geomatrix in July and September 1999, respectively. The results of these inves- tigations indicate the presence of petroleum'hydrocarbons in the subsurface of the property (Figure 2). The off-site lateral extent ofpetroleum hydrocarbon-affected soil and groundwater quality have not been assessed. The vertical extent of the petroleum hydrocarbon-affected soil has been assessed. Geomatrix proposes advancing up to four off-site soil.borings downgradient of the petroleum hydrocarbon-affected soil on the Burns property(Figure 3). Two soil borings will be ad- vaned to an approximate depth of 15 feet below ground surface (bgs) in the West Side Irri- gation District Easement north of the site, and-if necessary, two additional (step-out)borings will be advanced in the residential neighborhood north of the easement. Per City of Tracy requirements, Geomatrix will remove and.replace sections of sidewalk at step-out boring locations. Prior to drilling, Underground Service Alert(USA)will be notified, the soil boring locations will be cleared by a private underground utility locator. Borings will be advanced using a hy- draulically driven, direct-push core barrel and drive sampler.. Soil recovered from continuous cores 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 for chemical analyses from each boring at either the area of soil core most visibly affected with petroleum hydrocarbons;or from just above the ground- water table if petroleum hydrocarbons are not identified visually or through screening using an organic vapor meter. Soil samples 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. I i Geomatrix, Consultants, Inc. i Engineers, Geologists, and Environmental Scientists `l