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S E C O R U Ms. Anne Connor March 9, 2007 Page 2 u During the December 2005 investigation, additional information obtained by PG&E and/or U SECOR suggested that the older steel ASTs were not located at the ConVault location, but in a nearby structure identified historically as the heavy equipment storage shed. In May 2006, SECOR completed an additional subsurface investigation in the vicinity of the storage shed. Soil sample locations are illustrated on Figure 2. Using hand tools, seven soil borings were advanced to depths of approximately 3.3 to 3.8 feet bgs, where each of the soil borings encountered the hardpan layer reported during previous work at the Site. Thirteen soil samples were collected from representative depths above the hardpan and submitted for chemical analysis. Laboratory analytical results from the May 2006 investigation are summarized on Table 1. U Soil samples from four soil borings advanced in the vicinity of the former equipment storage shed and from two step-out borings advanced east of the shed, reported only very low concentrations of diesel-range hydrocarbons (up to 17 milligrams per kilogram or mg/kg). Soil samples from soil boring HA-5, advanced approximately 10 to 15 feet southwest of the shed, reported elevated concentrations of gasoline-, diesel-, and motor oil-range hydrocarbons, and detectable concentrations of ethylbenzene and total xylenes. Chemical impacts were observed to 3.5 feet bgs, where the hardpan layer was encountered. SECOR also sampled an adjacent domestic well which supplies the PG&E facility. The only constituent detected was 2,2-dichloropropane, which was reported at a concentration of 1.3 micrograms per liter (Ng/L). This constituent is not believed to be sourced from the '-' chemical impacts observed at boring HA-5. The construction of the well is not known. SCOPE OF WORK At PG&E's request, SECOR developed a scope of work to remove shallow soils impacted by petroleum hydrocarbons at the HA-5 location. The scope of work was based on the v assumption that the excavation would be relatively small, on the order of 5 to 10 feet square and approximately 5 feet deep, corresponding to removal of approximately 5 to 20 cubic yards of material to be removed and off-hauled for disposal. An important objective of the ►� remediation was the examination of soils beneath the hardpan layer encountered during previous work at approximately 3.5 feet bgs. SECOR proposed collecting four confirmation soil samples from the excavation and submitting the samples for laboratory analysis prior to U backfilling the excavation. The following sections describe the scope of work performed at the Site. I:\PG&E\French Camp\2007 Investigation\report\Excavation Report_Final.doc March 9,2007 Project No.050T.50351.00.0003 v