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Mr. Ron Rowe September 4, 1997 Page 3 information provided by the Department of Water Resources. If aerial photographs are encountered during the well survey or other project research, they will be presented in the Soil and Water Investigation Report. 3.0 FIELD ACTIVITIES 3.1 Drilling and Soil Sampling The soil and water investigation proposed by SECOR includes a two phased approach. The first phase of the investigation will be to characterize the soil and groundwater conditions on-Site. The second phase will be to assess any off-Site migration(if needed)as soon as access agreements can be negotiated. The first phase will include the supervision and installation of six groundwater monitoring wells(MW-2,MW-3,MW-4,MW- 5,MW-6,and MW-7)at the locations shown on Figure 2. Wells MW-2,MW-3, and MW-4 will be installed at the anticipated cross-gradient and down-gradient property boundaries to determine if the impacted groundwater has migrated off-Site. Wells MW-5 and MW-6 will then be installed to characterize the middle portion of the property. Finally,well MW-7 will be installed in the former tank pit and continuously cored to depth to characterize the subsurface soils beneath the Site and provide vertical definition of the petroleum hydrocarbon impacted soil and groundwater beneath the Site. To facilitate the vertical definition of soil and groundwater at the Site,discrete soil and water samples will be collected during drilling of MW-7 within key lithologic units. The depth and well construction details for each of the proposed boreholes is presented in Table 1. Each boring will be drilled using a truck-mounted drill rig equipped with 8-inch diameter hollow-stem augers. Relatively undisturbed soil samples will be collected for lithologic description and possible chemical analysis at a minimum of 5-foot intervals using a California-modified split-spoon sampler lined with three 6-inch long brass tubes,with the exception of the boring proposed for well MW-7. Well MW-7 will be continuously cored to depth and soil and groundwater samples will be collected using a SimulProbe Technology,Inc. split spoon sampler. A SECOR geologist will describe the soil encountered according to the Unified Soil Classification System(USCS) and will maintain boring logs of these descriptions. Representative soil samples from each sample interval will be screened in the field for the presence of volatile organic compounds (VOCs) using a photoionization detector(PID). Screening results will be documented on each boring log. SECOR will select a minimum of two soil samples from each drilling location for chemical analysis,one from the vadose zone and one from directly above the first encountered groundwater with the exception of the boring proposed for well MW-7. In addition to the two soil samples mentioned above, a minimum of one additional soil sample will be collected from the saturated zone of boring MW-7. The ends of the brass tubes containing the soil samples will be covered with teflon sheeting, capped with plastic end caps, labeled, sealed in plastic bags, and stored in an ice-filled cooler. The samples selected for chemical analysis will be delivered to a California state-certified analytical laboratory with a completed chain- of-custody documentation. Before use and between advancement of boreholes,drilling equipment will be decontaminated using a steam cleaner. Soil sampling equipment will be washed in a laboratory grade soap and potable water solution and rinsed with potable water before use and between sample intervals. H:\SFFB\STOCKTON\.SFFBWKP.RVr