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Preliminary Endangerment Assessment Page 5 Former Haley's Flying Service GPE Project 474.2 3.0 SAMPLING ACTIVITIES AND RESULTS The sampling strategy and protocols are described in the Work Plan for this PEA, entitled Work Plan Addendum — Preliminary Endangerment Assessment, Former Haley's Flyin Service, 21,000 Paradise Road, Tracy, CA (Geo-Phase Environmental, 2006b). There were few deviations from the Work Plan(see Section 3.5). 3.1 Groundwater Sampling and Analysis The installations suspected to be the primary sources of pesticide contamination are the washout pit and nearby loading dock. Groundwater samples were collected from 6 points around this area (see Figure 2). Power-Probe TM soil borings (designated B-3 through B-8) were advanced to a depth sufficient to penetrate the groundwater surface, and a sample of the shallow groundwater was collected from each of the borings. An additional sample of groundwater from the onsite domestic water production well was also collected and tested. On May 12, 2006, the Power-Probe TM soil borings were installed using 1.5-inch outside diameter, Power-ProbeTM drilling equipment owned and operated by RSI Drilling (C-57 License #802334). The borings, (B-3 thru B-8) were advanced to a depth sufficient to penetrate the groundwater surface, which was found at approximately 8 to 9 feet below grade. The Power-Probe TM uses direct-push methodology in which the drilling tools are pushed directly into the ground using a hydraulic ram and hammer system. The drilling process involved the use of a duel-tube drill stem in which the outer drill string acts as a temporary casing while soil and groundwater samples are collected through the inner tube. In a further attempt to reduce the risk of cross contamination, the inner drill string and sampling equipment was removed from each boring at the approximate depth of the groundwater surface, and then steam cleaned prior to advancing the boring to its total depth and collecting the groundwater sample. The soil at the level of the groundwater surface consists of poorly permeable clay and silt. In order to obtain adequate water entry for suitable water samples, the borings were advanced to depths of 16 to 20 feet below grade. During drilling, a log was made of each boring. Information noted includes such data as sample depths, horizons of detectable contamination (detected by field methods), soil classification utilizing the Unified Soil Classification System and sediment description (color, texture, composition, hardness, moisture content, and post-depositional changes that have occurred in the sediments). The boring logs are attached as Appendix B. Upon reaching total depth of the each boring, a groundwater sample was collected. The inner drill string was removed, and 3/4-inch diameter, new, dedicated, flush joint PVC tubing was lowered to the groundwater through the temporary casing. The lead 5 or 10 feet of PVC tubing was slotted with 0.010-inch openings, thus creating a temporary well. The groundwater sample was then collected with a stainless steel bailer that was carefully steam- 2937 Veneman Avenue,Suite B240 Geo-Phase Environmental Inc. Phone: (209)569-0293 Modesto,Ca 95356 Fax: (209)569-0295