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S ECOR <br /> Mr. Michael Infurna <br /> San Joaquin County Environmental Health Department <br /> March 27, 2007 <br /> Page 4of8 <br /> Task 2 — Geophysical Survey and Utility Clearance <br /> SECOR will subcontract with NORCAL Geophysical Consultants, Inc. (NORCAL) to <br /> perform a geophysical survey. The geophysical investigation area is illustrated on <br /> Figure 2, and extends approximately 75 feet into the Site from East French Camp Road, <br /> and approximately 110 feet into the Site from the property line shared by the adjacent <br /> residence to the north. The area of investigation encompasses the excavation area, <br /> both former AST locations, and the paved driveway portion of the Site. <br /> NORCAL will use magnetometer, ground-penetrating radar, and electromagnetic line <br /> locating methods to determine if any USTs or related piping are present in or near the <br /> area where SECOR has observed petroleum hydrocarbon-impacted soils. Features <br /> identified by NORCAL will be marked in the field using marking paint and recorded on a <br /> scaled site plan. NORCAL will also clear each of the proposed soil boring locations for <br /> detectable subsurface utilities. <br /> Task 3 — Soil and Groundwater Investigation <br /> SECOR proposes advancing four soil borings at locations surrounding the previous <br /> excavation. These soil borings will be located to delineate the extent and magnitude of <br /> impacted soils observed during previous investigations, and to assess groundwater <br /> conditions. Proposed soil boring locations are illustrated on Figure 3. In addition to <br /> these locations, SECOR may complete additional `step-out' soil borings as necessary to <br /> delineate the extent of impact to soil and/or groundwater. <br /> Soil Boring Advancement <br /> The soil borings will be advanced by Woodward Drilling (Woodward). The initial four soil <br /> borings will be advanced to first-encountered groundwater. Based on SECOR's review <br /> of regional hydrologic conditions, first-encountered groundwater is anticipated in the <br /> upper 35 feet bgs. Additional step-out soil borings will be advanced to depths deemed <br /> appropriate based on conditions observed in the initial soil borings. <br /> The upper 5 feet bgs of each soil boring will be cleared using a hand auger to confirm <br /> the absence of subsurface utilities, and soil borings will be advanced to total depth using <br /> a direct-push (i.e., GeoprobeTM) system. Continuous soil cores will be retrieved and <br /> examined by a SECOR geologist for lithologic characteristics and evidence of chemical <br /> impact. Representative soil samples will be screened for volatile organic vapors using a <br /> photoionization detector (PID). <br /> I:\PG&E\French Camp\additional 2007 investigation\work plan\2007 Investigation Work Plan_Final.doc March 27,2007 <br /> Project No.050T.50351.01 <br />