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Work Plan -Foimer Unocal Station No. 0187 October 9, 1997 SCOPE OF PROPOSED WORK TASK 1. WELL INSTALLATION To further assess the lateral extent of dissolved hydrocarbons in groundwater northeast of the subject site, GSI proposes to install one additional offsite groundwater monitoring well approximately 120 feet northeast of well U-9. As shown on Figure 3, the proposed location of this well is restricted due to the proximity of the surrounding buildings. GSI Field Methods and Procedures are presented in Appendix A. To perform this work, GSI will perform the following specific tasks: Task 1.1. Pre-Field Activities GSI will update the site safety plan. Underground Service Alert (USA) will be notified a minimum of 48 hours prior to initiating well installation activities. Unocal will secure an access agreement from the property owner. Task 1.2. Field Activities GSI will install one groundwater monitoring well at the location shown on Figure 3. Drilling and well installation will be performed by a California licensed well driller. The well boring will be drilled with eight-inch-diameter hollow-stem augers to a total depth of approximately 55 feet bgs. We estimate groundwater will be encountered at approximately 32 feet bgs. As previously discussed, the lowest depth to groundwater was recorded at approximately 48 feet bgs in August 1994. Groundwater has continued to rise from August 1994 to August 1997; a rise of approximately 16 feet in three years. To accommodate the historical low and high groundwater depths for this site, we intend to construct the proposed well with approximately 23 feet of screen within the saturated zone and 7 feet of screen extending above the saturated zone. San Joaquin County Public Health Services, Environmental Health Division (SJCPHS) has indicated in the past that the maximum screen interval for a groundwater monitoring well is 20 feet. This screen interval will not cover the historical low and high depths to groundwater. The proposed well construction is shown on Figure 4. A GSI geologist will monitor the drilling activities and prepare a log of the boring. Soil samples for description and possible chemical analysis will be obtained from the well boring at five-foot intervals, as a minimum. Soil from each sampled interval will be screened in the field for the presence of volatile organic compounds using a photoionization detector (PID). Although the actual number of samples submitted for chemical analysis will depend on site conditions and field screening data, we anticipate a minimum of two unsaturated samples from the boring will be submitted for chemical analysis as described in Task 1.5. Drill cuttings will be stored at the site pending receipt of chemical analytical data and disposal. The drill cuttings will be stockpiled on and covered with plastic sheeting. Soil samples will be collected from the drill cuttings as described in Appendix A. These samples will be submitted to the laboratory for compositing into one sample, and then analyzed as described in Task 1.5. Steam cleaning rinsate waste water will be stored at the site in properly labelled drums pending disposal. 48827.07.1 3