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v A S S O C I A T E S I N C im groundwater samples collected from the vicinity of the former 10,000-gallon UST contained elevated concentrations of petroleum hydrocarbons. F In August 1998, ATC personnel supervised the advancement of three soil borings at the site. Drilling was performed using hollow stem auger. In accordance with the approved workplan, the soil borings were completed as groundwater monitoring wells MW1, MW2, and MW3. Soil samples contained detectable concentrations ofetroleum hydrocarbons. The p y groundwater monitoring wells were subsequently developed and the groundwater samples contained detectable concentrations of total petroleum hydrocarbons as diesel (TPHd). Field activities �" were summarized in ATC's Summary Report of Additional Subsurface Investigation, dated October 19, 1998. I` 2.0 METHODS AND PROCEDURES All field activities were performed in accordance with ATC's Workplan for Additional Subsurface Investigation at Continental Grain, 1805 Harbor Street, Stockton, California, dated ' June 28, 1999; ATC's Workplan Addendum for Additional Subsurface Investigation at L_ Continental Grain, 1805 Harbor Street, Stockton, California, dated April 3, 2000; and ATC's Workplan Addendum for Additional Off-Site Subsurface Investigation at Continental Grain, 1805 Harbor Street, Stockton, California, dated May 12, 2000. These workplans and addendums were approved by PHS/EHD. 2.1 Geo robe® Drilling Activities On April 20, 2000, an ATC geologist supervised the advancement of two soil borings, SB8 and : S139, to 20 feet bgs and one soil boring, SB 10, to 30 feet bgs. Soil boring SB 10 was advanced to LM 30 feet bgs at the request of Mr. Jeff Wong of PHS/EHD. A site plan with soil boring locations ir is shown on Figure 2. Fisch Environmental, California License C57 683865, advanced the borings using a truck mounted GeoprobeO narrow diameter rig employing direct push technology. Soil samples were collected from borings SB8, SB9, and SB10 at five-foot intervals in acetate sampling tubes and were described according to the Unified Soil Classification System. Descriptions of soil types encountered and sample collection intervals are presented on the boring logs contained in Appendix A. 4W 2.2 Soil Sampling and Analysis f Each soil sample was field screened with a Flame Ionization Detector (FID) for the presence of L. volatile organic compounds. Sample tubes were then sealed at each end using Teflon tape and plastic end caps, labeled, and placed on ice. Selected soil samples were kept on ice and delivered under chain-of-custody documentation to State-certified Argon Laboratories Inc. (FLAP Cert. No. 2358) in Ceres, California for chemical analysis. Selected soil samples were analyzed by Argon for TPHd and total petroleum w:%54.625001reportslsumi5,doc 2 i