ARCHIVED REPORTS_PRELIMINARY ASSESSMENT_SITE INVESTIGATION REPORT

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• samples collected from the remediation excavations verified removal of the contaminants, and the excavations were backfilled with the authorization of the CVRWQCB. 2.2 CSMS One 2,000-gallon sump located on the east side of the CSMS building was removed in July 1987 (Placer Tractor Service, 1987). The sump was mistakenly removed in place of a 500-gallon waste oil tank located on the north side of the OMS. A soil sample collected when the sump was removed was tested for benzene, toluene and xylenes, PCBs and organochlorine pesticides (EPA Method 8080.3), purgeable halocarbons (EPA Method 80 10) and total volatile petroleum hydrocarbons (analytical method not indicated) (Canonie, 1987). Analytical data from the soil sample indicates that no release occurred from the sump. In 1992, 75 gallons of diesel fuel was spilled onto an asphalt-paved area during fuel cell loading (CA ARNG , 1992). The spill was cleaned up, and an incident report prepared. The county and state offices of emergency services were notified of the incident. The location of the release was not described. 2.3 OMS The USTs at the OMS were used for OMS operations vehicle fueling and comprised a dispenser island with two dispensers, one 5,000-gallon diesel UST, and one 10,000-gallon gasoline UST. The UST were removed in April 1996 (Seward Schreder Construction, 1996). Releases of diesel fuel and gasoline appeared to have occurred from the two UST, although benzene and toluene were not detected in the soil samples. The highest concentrations of TPH-d and TPH as gasoline (TPH-g) in soil were 12,000 mg/kg and 7,100 mg/kg, respectively. The highest concentrations of the aromatic hydrocarbons, ethylbenzene and total xylene isomers, detected in soil were 6.2 mg/kg and 580 mg/kg, respectively. No MTBE was detected in a soil samples collected from the Site. The highest lead concentration detected in soil was 10 mg/kg. Evidence that the 500-gallon waste oil tank has been removed was not located in the files reviewed by Versar. Removal of the waste-oil UST was rebid by the Office of the State Architect on behalf of the CA ARNG in 1987 (OSA, 1987). There is a reference to the removal of a 500-gallon waste oil tank in a 1991 environmental inspection checklist(CA ARNG ECAS Audits, 1991). 3.0 SITE INVESTIGATION This section describes the methodology used in further evaluating the condition of the subsurface in the areas of concern at the AASF, CSMS, and OMS. Included in this section are descriptions of the field methods and procedures, laboratory analyses, and storage and disposal of investigation derived wastes (IDW). 2187-01/3134-100/MAY26'00 4