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%MOO *400 Work Plan for Additional Assessment ARCO Facility No.2 186 Stockton,California Page 4 • Secure well permits from San Joaquin County, • Secure an encroachment permit and a revocable permit from the City of Stockton, Dept. of Public Works to install the groundwater monitoring well located along American Avenue, • Execute an access agreement with the City of Stockton, Dept. of Parks and Recreation to install the two monitoring wells in Oak Park,and • Mark the proposed well location and notify Underground Service Alert, ARCO, and the PHS/EHD of the scheduled field activities. Task Z: Soil Borings and Monitoring Well Installation To characterize the extent of petroleum hydrocarbon impacted groundwater, three offsite soil borings will be advanced to a depth of approximately 80 feet bgs. Soil and groundwater grab samples will be collected during the advancement of the borings. The soil borings will be converted to groundwater monitoring wells. The monitoring wells will be constructed using 2-inch diameter polyvinyl chloride (PVC) casing. One well (MW-5) will be installed east-northeast (downgradient) of the site in the City right-of-way of American Ave. The second well (MW-6) will be located north-northeast of the site in Oak Park, approximately 20 feet north from the curb line. This proposed location is between the ARCO site and Oak Park's east agriculture water well. The third well (MW-7) will be located north-northwest of the site. This well will also be located in Oak Park, approximately 20 feet north from the curb line. The proposed location is between the ARCO site and Oak Park's west agriculture water well. Figure 3 presents the proposed locations of the monitoring wells. The initial 5 feet of each boring will be advanced with a hand auger and/or posthole digger to reduce the possibility of damaging underground utilities. Soil samples will be collected at 5-foot intervals during the advancement of the borings using a California-type, split-spoon sampler equipped with three precleaned brass tubes. The ends of the bottom-most, intact tube from each sample interval will be lined with Teflon TM sheets, capped, and sealed. Each sample will then be labeled, placed in a resealable plastic bag, and stored in an ice-chilled cooler. The samples will remain chilled until relinquished to a State-certified analytical laboratory. Strict chain-of-custody procedures will be followed from the time the samples are collected until the time the samples are relinquished to the laboratory. Soil contained in the remaining brass tubes will be screened for volatile organic compounds using field instrumentation equipped with a photoionization detector (PID). Delta will record PID readings, soil types, and other pertinent geologic data on the borehole log. A minimum of four soil samples will be submitted for chemical analysis from each boring and will include the sample exhibiting the highest PID response and the sample from just above first-encountered groundwater. Other samples will be selected based on soil type and field observations. Hydropunch sampling equipment will be used to collect groundwater grab samples at desired depths. The Hydropunch sampler will be pushed approximately 2 feet below the bottom of the borehole and the screen interval exposed to allow for the collection of discreet groundwater samples. Procedures pertaining to the use of the Hydropunch and collection of samples are detailed in Appendix A. A minimum of four water samples will be collected for laboratory analyses, beginning with first