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Atlantic Richfield Company 2 ARCO Service Station#595,6100 North Highway 99,Stockton CA November 30 2000 Additionally, a domestic well supplying water to the service station is present in the southwestern portion of the property During September 1999, product lines and dispensers at the site were upgraded Soil samples collected from beneath the product lines, vapor lines, dispensers, and previously abandoned in place product lines indicated that petroleum hydrocarbons had impacted soil beneath the site The highest concentrations of hydrocarbons were found beneath the dispensers and product lines Approximately 189 tons of soil generated during the removal of the underground facilities and the trenching for new piping was disposed of at BFI Landfill in Livermore, CA In June 2000, three soil bonngs (B-1, B-2, and B-3) were drilled near the locations of the highest hydrocarbons concentrations in previous soil samples and four groundwater monitoring wells (MW-1 through MW-4) were installed at the site In each of the borings, primarily salty clay was present from the ground surface to approximately 48 to 59 bgs Beneath approximately 48 feet to 59 feet bgs, silty sand to sand was encountered First groundwater was encountered at approximately 58 to 62 feet bgs (within the sand layer) Underlying the sand at depth of 64 to 74 feet was silty clay, which was encountered to the bottom of the deepest boring at 75 feet bgs Groundwater levels stabilized between 56 and 59 feet bgs Based on monitoring data collected on June 16, 2000, groundwater flow was to northwest with a gradient of 0 007 Soil sampling results indicated minor detections of hydrocarbons (less than 0 5 ppm) in only five of 41 samples analyzed Initial groundwater sampling from wells MW-1 through MW-4 indicated that petroleum hydrocarbons had impacted the groundwater beneath the site A agency well survey performed by SECOR indicated a total of five wells were located within 1/2-mile of the site (Figure 1) An active domestic well is located on the southwestern corner of the ARCO property Construction details of the well are unknown PROPOSED SCOPE OF WORK The scope of work for this site assessment will include the installation of three groundwater monitoring wells, the drilling of two soil borings, and the performance of a 500-foot radius door-to-door well survey The wells and borings have been proposed to evaluate the vertical and lateral extent of petroleum hydrocarbons in soil and groundwater beneath the site and the proposed locations are shown on Figure 2 If the results indicated the need for deep, discretely screened monitoring wells, and addendum to the Work Plan will be submitted As required by the Occupational Health and Safety Administration (OSHA) Standard "Hazardous Waste Operations and Emergency Response" guidelines (29 CFR 1910 120), and by California Occupational Health and Safety Administration 077 43029 310/WPLAN Nov 2000 doc