Recommendation for No Further Investigation at Study Area 6 (SA 6), McClellan Air Force Base, California

摘要

The purpose of this report is to document the effectiveness of soil remediation at SA 6 and to provide data to support an NFI decision for the site. SA 6 is located in the southwestern portion of the base within Operable Unit B (OU B) (Figure 1.1), south of Building 656, and west of Building 655 (Figure 1. 2). The site is the former location of a gasoline service station (Building 657) and its associated underground storage tanks (USTs) which were located immediately east of the former building. The site is currently near the center of a large, paved parking lot. The former service station operated from 1955 until 1990. The two gasoline USTs and twO diesel USTs which supplied the station were removed in 1990 and 1991. Initial investigations conducted by the Base determined that the USTs had leaked and contaminated the soil. Subsequent investigations conducted at SA 6 identified fuel hydrocarbons, volatile organic compounds (VOCs) including benzene, toluene, ethylbenzene, and xylenes (BTEX), and halogenated VOCs in soil, soil vapor, and groundwater (ES, 1994; Radian, 1995). Although halogenated VOCs (chlorinated compounds) have been detected at SA 6, the Remedial Investigation Characterization Summary (RICS) (Radian, 1995) concluded that the source of these compounds is Investigation Cluster 7 (IC 7), another OU B site northwest of SA 6. Because only petroleum hydrocarbon contamination is attributed to the former gasoline service station, the RICS concluded that only total petroleum hydrocarbons (TPH) and BTEX were contaminants of potential concern (COPCs) at SA 6.