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• at the AASF and CSMS, but do not appear to be present in actionable concentrations. <br /> Groundwater does not appear to be actionably impacted by a release from former USTs <br /> containing petroleum hydrocarbons at the AASF. Objects potentially representing reportedly <br /> buried tear-gas canisters were located by remote-sensing methods in an unpaved area east of the <br /> Armory. Unidentified features potentially responsible for pavement uplift were detected by <br /> remote sensing methods in the vehicle storage area east of the CSMS building. <br /> 5.1 AASF <br /> Soil, soil vapor, and groundwater samples were collected at the AASF to assess the impact of <br /> past and present AASF activities on shallow soil and groundwater. Minor impacts to soil from <br /> petroleum hydrocarbons was detected in shallow soil in the areas of the former clarifier/washrack <br /> (boring B-3) and the former secondary clarifier near the fueling area (boring B-1). Elevated <br /> concentrations of zinc were also detected at boring B-1. The zinc concentration is well below the <br /> total threshold limit concentration (TTLC), defining a California hazardous waste, of 5,000 <br /> mg/kg. Concentrations of COCs were not detected in soil and soil vapor elsewhere during this <br /> investigation. <br /> Trace concentrations of benzene, MTBE and total xylene isomers were detected in two <br /> groundwater monitoring wells located around the former location of jet fuel USTs. The <br /> concentration of benzene (1.1 12g/L) is slightly greater than the drinking water standard for <br /> . California. Six monitoring events over a period of seven years suggest that groundwater has not <br /> been actionably impacted by the release of jet fuel from the former USTs, and that detections of <br /> trace concentrations of COCs are ephemeral. <br /> 5.2 CSMS <br /> Soil, soil vapor, and groundwater samples were collected at the CSMS to assess the impact of <br /> past and present CSMS activities on shallow soil and groundwater. Minor impacts to soil from <br /> petroleum hydrocarbons was detected in shallow soil in the areas of the washrack inside the <br /> CSMS building (boring B-7), the washrack near the carpenter shop building (boring B014), and <br /> the location of former hazardous materials storage in the vehicle and equipment storage yard east <br /> of the carpenter shop building (boring B-10). The impacts were related to oil-weight petroleum <br /> hydrocarbons, and ranged in concentration from 123 mg/kg to 1,630 mg/kg. <br /> Petroleum hydrocarbons were also encountered in surficial soil samples collected from a <br /> shallow, unlined ditch providing drainage from the unpaved and paved vehicle and equipment <br /> storage areas east of the CSMS and Armory. A release of oil-weight petroleum hydrocarbons to <br /> the ditch is apparent, likely the result of petroleum hydrocarbon-containing runoff from vehicle <br /> storage. <br /> Composited surficial soil samples contained concentrations of petroleum hydrocarbons ranging <br /> • from 76 mg/kg to 475 mg/kg. The impacts were related to oil-weight petroleum hydrocarbons, <br /> 2187-01/3134-100/MAY26'00 14 <br />