SITE INFORMATION AND CORRESPONDENCE

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ChevronTexaco—Vernalis Pump Station,Vernalis,CA. Project No. 06-6102-00-6369-201 June 29,2004 Page 4 of 7 Previous sampling and chemical test results summarized and presented in the most recent Report of Soil and Groundwater Investigations(Geomatrix, January 2004)indicated the presence of residual petroleum in the soil to depths ranging mainly between 20 and 60 feet(Appendix B). Based upon this information, the soil borings will be advanced to a target depth of approximately 70 feet bgs. SAIC will attempt to collect soil samples from the depths that coincide with affected intervals observed in previous borings in accordance with the Second Draft Revised Technical Approach to Site Evaluation and Decision Making, Old Valley Pipeline Sites(CTA; Geomatrix, 2002), or from the most affected intervals. Grab groundwater samples will be collected from the strata containing first-encountered groundwater. TASK 1 —PRE-FIELD ACTIVITIES Prior to conducting field activities, SAIC will obtain boring and well permits from the San Joaquin County Public Health Services (SJCPHS) and the Stanislaus County Department of Environmental Resources (SODER), and, if warranted, obtain an encroachment permit from Caltrans. Several proposed boring and well locations on private properties would require access agreements,to be secured by ChevronTexaco. Prior to advancing the proposed borings, SAIC will conduct a site visit to mark the proposed boring and well locations and perform a high-level site reconnaissance noting any potential aboveground or belowground obstructions. SAIC will also subcontract with a private utility locator to perform an underground utility clearance at each boring location. Following SAIC's initial site visit and utility clearance,Underground Service Alert(USA)will be notified 48 hours in advance of field activities. If an encroachment permit is required from Caltrans, SAIC will prepare a traffic-control plan in general accordance with Caltrans guidelines for work along Highway 33. The encroachment permits,private property access agreements, and traffic-control plan will be submitted to the proper agencies or property owners, if required, for approval prior to field activities. TASK 2—WELL SEARCH AND SURVEY SAIC will conduct a search of DWR files to obtain information on water production wells used for domestic, irrigation,municipal, and/or other uses within a 2,000-foot radius of the site. A copy of the Well Completion Report Release Agreement—Agency Form will be forwarded to the RWQCB for authorization and signature. Following this search, SAIC will prepare a table containing the State Well Number, location,and water use(if available),which will be included in the soil and groundwater investigation report. TASK 3—FIELD ACTIVITIES Geoprobe or hollow stem auger-type equipment will be used to advance the proposed soil borings. During drilling activities, soil samples will be collected in general accordance with SAIC field procedures and the CTA. Drill cuttings will be drummed on site and will be properly disposed of by ChevronTexaco. During drilling activities, a continuous coring device will be used to collect soil samples. The samples will be field screened using photoionization detection(PID) equipment to detect the presence of residual petroleum in soil. The soil will also be logged in general accordance to the Unified Soil Classification System(USCS)as presented in ASTM 2488-90 under the supervision of a California Registered Geologist. Between borings,the down-hole equipment will be cleaned using a Liquinox/water solution to prevent the possibility of cross contamination between consecutive boring locations. The locations of proposed soil borings are shown on Figure 2. Soil borings will be advanced to a target depth of approximately 70 feet bgs, as per the attached Table 1. SAIC will attempt to collect soil samples from depths that coincide with affected intervals observed in previous borings or from the most affected soil interval observed. If primary soil borings appear to be affected by residual petroleum,based on visual and PID readings, SAIC will destroy the boreholes