SITE INFORMATION AND CORRESPONDENCE

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Former TAOC Pump station - 3 - 2 March 2004 990 Beechnut Tracy, San Joaquin Co. Soil One soil boring (GMX-17) was advanced to 53 feet (maximum exploration depth) to evaluate the vertical extent of impacted soil. According to visual observations, PID readings, and analytical results, the vertical extent of impacted soil attenuates with depth, terminating by 53 feet in boring GMX-17. TPH-c, BTEX, and PAHs were not detected in the soil sample collected beneath the affected soil in this boring at 52.5 feet. Borings were advanced at four different site locations to collect samples from shallow soil (5 feet) for the screening HRA. Soil staining and measurable PID readings were not observed. Samples were analyzed for BTEX and PAH compounds only. BTEX was ND and two samples reported low concentrations of PAHs at or slightly above lab reporting limits in two of the one-foot samples. Twenty-one shallow borings (6 to 7 feet) were advanced near former boring GMX-09, that previously reported elevated TPH-c and PAH constituents in a sample from 5.5 feet. The purpose was to assess the extent of PAHs in shallow soil near this boring. Thirteen borings reported measurable PID readings and some stained soil, generally in the uppermost five-feet. Stained soil and/or measurable PID readings were not reported for the remaining eight borings. PAHs were detected in 13 of 22 samples analyzed and the remaining nine were ND or slightly above the lab reporting limits. Soil Stockpile Two borings were advanced to 3 feet to evaluate the soil conditions in the stockpile. Concentrations of TPH-c, BTEX and PAH constituents were not detected in one boring. In the second boring, TPH-c was 950 mg/kg and BTEX was ND, with low concentrations of two PAH compounds reported at or slightly above the detection limits. Groundwater During the investigation, two borings were advanced approximately 150-feet north of the site to obtain grab groundwater samples. However, impacted soil was observed in the borings and no grab groundwater samples were collected. Additional downgradient delineation is needed. CONCLUSIONS The south-southeast and central portions of the site have not been significantly impacted by TPH compounds. However, the northeast, southwest, and northwest areas of the site, and extending offsite to the north, have been impacted by TPH compounds, including PAHs. With a few exceptions, the majority of impacted soil occurs from near surface to approximately 15 to 20 feet. The extent of TPH-impacted soil, within the pile as well as extending from approximately 20 to 53 feet, has been adequately delineated. According to the soil sample analyses, TPH compounds are present throughout the soil pile. Even though the property is fenced, the site is within a residential area and reportedly has been accessed by residents.