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' Geo"' icaf?echnics Inc. Page 2 Bank of Stockton(Airport) t Project No. 827.2 October 17, 1999 ' 3. A truck scale is located in the northeast portion of the Parcel along the driveway into the Property. An interview with the owner revealed that a former underground tank was located under the current truck scale facility. 4. A truck repair facility (owned by Billy Wong) is located along the north boundary of the parcel. Some spillage of motor oil has occurred in and around the opening of the shop. The shop has a concrete floor and the area out front of the shop entrance is asphalt for ' some distance. However, some oil and wastewater has run off the asphalt and stained the soil to the west of the shop. 5. It is recommended that the soil under the area where these tanks were located should be ' tested for petroleum fuel compounds. 2.0 PROPOSED INVESTIGATION To determine if soil has been contaminated by release of petroleum hydrocarbons from the previous USTs on this Property, Geological Technics Inc. proposes drilling several boreholes ' using GeoProbe direct push methods. 2.1 Borehole Drilling & Soil Sample Collection The Site Map in Figure 2 shows the locations of the proposed boreholes. The borehole will be drilled with a GeoProbe rig owned and operated by V&W Drilling of ' Rio Vista, CA (C574 720904). The GeoProbe advances a coring tool with a pneumatic hammer to a selected depth. Upon reaching that depth the coring tool is opened and advanced further to fill the core barrel. The soil sample enters an acetate cylinder contained in the coring tool. Upon filling, the coring tool is pulled from the hole and the cylinder is removed. The cylinder is then cut and the selected interval is preserved for laboratory analysis. The remainder is used for geologic logging. All soil samples will be sealed with Teflon, capped with plastic end caps, labeled and placed in a cooler at 4° Celsius for transport to the laboratory following Chain of Custody protocol. The GeoProbe borings will be advanced to approximately 15 feet bgs. Soil samples will be collected at five-foot intervals for geologic logging and laboratory analyses. One to two soil samples from each borehole will be submitted to the laboratory for analysis. Since only selected samples will be submitted for laboratory analysis, a screening process ' will be used to gather additional information through field observation. This information will assist in determining which samples will be analyzed. The bottom core sample will be submitted to the lab for analysis and if groundwater is encountered, the capillary fringe ' samples will be tested. Evidence of elevated contaminant concentrations as detected by field screening will be used ' to determine if additional samples should be tested. The following characteristics will be noted in the screening process: • sediment type, especially grain size and clay content ' • moisture content • visible evidence of contamination, i.e., color change due to reduction of iron or discoloration from hydrocarbons and other pollutants • readings above background on a organic vapor meter(OVM) 1