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Work Plan For Soil Sampling-Tosco (Former Unocal)#6981, 4707 Pacific Avenue, Stockton, CA March 7, 2000 August 1992 to evaluate the feasibility of utilizing groundwater extraction to remediate hydrocarbon- impacted groundwater. A vapor extraction system has operated at the site since September 1994. To date,approximately 12,000 pounds of gasoline hydrocarbons and 169 pounds of benzene have been extracted and treated. The VES is currently being operated on a periodic schedule in pulse mode. In February 1996,wells MW-3,MW-10,MW-12,and MW-13 were abandoned at the request of the city of Stockton. This work was performed to facilitate reconstruction of the intersection and widening of Pacific Avenue. To replace the abandoned wells MW-3, MW-10, MW-12, and MW-3, GR, in August 1999, installed three groundwater monitoring wells (MW-14, MW-15, and MW-16), one groundwater sparging well (VW-7), and advanced one soil boring (VW-9). The new monitoring wells and sparge well were subsequently added to the sites' quarterly monitoring program. SCOPE OF WORK GR will collect the required compliance samples from the UST pit, beneath the product piping, and beneath the dispenser islands. Groundwater is not expected to be encountered in the initial excavations. If impacted soil is encountered and Tosco elects to over-excavate the impacted soil,GR will observe the over-excavation activities and collect confirming soil samples. To implement this scope of work, GR proposes the following tasks: Task 1. Compliance Sampling The USTs, associated product lines and dispensers, and all above-ground structures will be removed by Tosco's contractor. The backfill will be removed from the UST pit and piping trench and will be stockpiled. Soil samples will be collected from the native soil beneath the ends of each UST. Soil samples will also be collected from the native soil beneath the product piping on the basis of one soil sample per 20 linear feet of piping, and from native soil from beneath the product dispensers. Soil samples will be screened in the field for the presence of volatile organic vapors using a photoionization detector. GR sample collection and handling procedures are described in Appendix A. Excavated backfill material will be stockpiled at the site pending disposal. The stockpile will be placed on and covered with plastic sheeting. Four discrete samples per 1,000 cubic yards of soil will be collected from the stockpile and submitted to the laboratory for compositing and analysis. These composite samples will be analyzed for TPHg, BTEX, MTBE and lead, as required for disposal at the Forward landfill in Manteca, CA. Compliance soil samples will be analyzed at Sequoia Analytical, a State-certified Hazardous Materials Testing Laboratory (ELAP#1210, #1271, and #1624). Soil samples from beneath the Stockton,to#6981.WP1 2