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I. No other detections were made at or above the laboratory reporting limits for the remaining list of analytes included for the groundwater this assessment. 6.1.4 GEOPHYSICAL SURVEY The geophysical survey conducted at the site revealed at least four suspect anomalies (A-D) that could be interpreted as possible large buried metal objects (i.e. UST's). Only anomaly A was identified by both the GPR and MD, and is coincidentally located in the area identified by Ms. Schmiedt as once having USTs. The remaining anomalies (B-D) while displaying subtle characteristics typical of a UST did not display a significant response from the MD assessment and are not coincident with former UST locations. 6.2 CONCLUSIONS Soils The metal concentrations detected in soils were below the PRGs for each metal included in this assessment as referenced in the residential "Preliminary Remediation Goals, United States Environmental Protection Agency, 2002", with the exception of arsenic. The arsenic concentrations ranged from 1.6 mg/kg to 2.4 mg/kg in the shallow soil samples, and 1.0 mg/kg to 3.0 mg/kg in the monitoring well soil samples. The PRG for arsenic is 0.39 mg/kg (cancer end point) and 22 mg/kg (non-cancer end point). None of the soil samples exceeded the non-cancer end point. The metals concentrations detected in each of the soil samples were also compared to background naturally occurring concentrations within California as referenced from Bradford et. all, "Background Concentrations of Trace and Major Elements in California Soils", Kearney Foundation Special Report, UC Riverside and Cal-EPA DTSC, March 1996. The background average concentration of arsenic in soil in California is 3.5 mg/kg. None of the detected concentrations exceeded the average background levels see in California. It is Kleinfelder's opinion that the concentrations of arsenic found in the soil samples is representative of naturally occurring background conditions. The pesticides 4,4-DDD, 4,4-DDE, 4,4-DDT, Dieldrin, and Endosulfan I; and the Carbamate Oryzalin were detected in sporadic locations across the site as shown in the shallow soil and monitoring well soil sample analyses. There were no pesticides, organophosphates, or carbamates detected in the soil samples collected and analyzed from B-3 or B-4 (depression near the east edge of the site). As seen in the soil samples collected from the monitoring well borings, the concentrations of the detected pesticides generally decreased with depth, many to non-detectable concentrations (with the exception of 4,4-DDT in MW-2). The noted detected concentrations of pesticides and carbamate are all below the respective PRGs. The soil samples collected from the shallow soil borings B-1 (next to sump rinseate tank), B-7 (former fuel AST), and B-8 (beneath the washout pad) showed the concentrations of TKN, nitrate as NO3, and nitrate as N to be relatively higher than the other shallow soil sample locations. These 27125.E01 / STO4R181 Page 18 of 23 © 2004 Kleinfelder, Inc. February 13,2004 KLEINFELDER 2825 East Myrtle Street, Stockton, CA 95205-4794 (209) 948-1345 (209) 948-0621 fax