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Q LAO 0,6 ' 2101 Webster Street 12th Floor Oakland, CA 94612 (5 10) 663-4100 • FAX (51 O) 663-4141 GEOMATRIX February 11,2003 Project 6447.001 Ms. Penny Fottrell Chevron Environmental Management Company P.O. Box 6012 San Ramon, California 94583 Subject: Off-Site Soil and Groundwater Investigation Work Plan U.S. Can/Welty Road 35275 Welty Road, Vernalis, California Dear Ms. Fottrell: Geomatrix Consultants, Inc. (Geomatrix),has prepared this Soil and Groundwater Sampling Work Plan on behalf of Chevron Environmental Management Company(ChevronTexaco) for the U.S. Can/Welty Road Property in Vernalis, California(the Site; Figure 1). The Work Plan was prepared in response to the Regional Water Quality Control Board's (RWQCB)Novem- ber 5, 2002 review of the August 6, 2002 Report of Soil and Groundwater Investigation (Report). The proposed scope of work has been prepared in accordance with ChevronTexaco's revised Consistent Technical Approach(CTA; second draft December 2002). This work plan includes advancing two soil borings to a maximum depth of 90 feet below ground surface(bgs)to delineate the lateral and vertical extent of petroleum hydrocarbons in groundwater downgradient of the site. Groundwater samples will be collected and submitted for laboratory analyses to assess off-site water quality. Additionally, soil samples will be col- lected from each boring at depths to evaluate the presence of petroleum hydrocarbons within the soil column. A description of proposed site investigation activities is provided herein, along with a brief site background summary. BACKGROUND The site is located at 35275 Welty Road and is bounded by Welty Road to the southeast and Byron Highway(Highway 33)to the northeast. The former Old Valley Pipeline(OVP)was located along the northeastern side of the site,parallel to the Union Pacific railroad tracks. The pipeline transmitted crude oil from Bakersfield to Richmond from the early 1900s to the 1930s. The site is currently used to manufacture containers;historical uses included the pro- duction of cans. The site is located in a rural area used for light industrial activities. EXISTING SOIL AND GROUNDWATER CONDITIONS In previous investigations, Geomatrix has identified the approximate extent of petroleum hydrocarbon-affected soil as being limited to two areas, as shown on Figure 2. Geomatrix has defined the lateral and vertical extent of affected soil in both the western and eastern affected areas, as defined in the August 2, 2002 Report(Figure 2). In the western affected area, the vertical extent of total petroleum hydrocarbons quantified as crude(TPHc) is defined by Geomatrix Consultants, Inc. Engineers, Geologists, and Environmental Scientists