IRP Site. 18 Site 18 includes Sump 66 located on the northern side of former Building 88, which collected wastewater from the dry cleaning operation (see Figure 3). This sump was removed in May 1990. Excavated soils were stockpiled for treatment with other contaminated soils from NAS Xxxxxxx Field. Sample data from the excavation did not indicate significant contaminant levels, with PCE detected in only one of three soil samples at a concentration of 0.02 mg/kg; however, previous investigation of this area indicated concentrations of PCE as high as 6.9 mg/kg (PRC, 1991b). Tank 67 was a 20,000-gallon UST used to store fuel oil for the Building 88 boiler (see Section 2.4.4.2). It was removed in 1990 and no visible contamination was observed in the excavation. Confirmation soil sampling data from the excavation indicated low concentrations of TCE (0.01 mg/kg) (PRC, 1991b). Tank 68 was a UST of unknown composition and capacity located adjacent to the east side of former Building 88 (see Section 2.4.4.2). This tank may have stored waste solvents and petroleum products generated by operations in Building 88 and was reportedly closed in place. Samples collected from slant soil borings drilled below the tank in 1990 were found to contain low concentrations of VOCs including PCE and TCE (maximum concentration of 0.14 and 0.028 mg/kg respectively) (PRC, 1991b). A remedial action was conducted at Building 88 in 1994 and 1995. The building, foundation, underground piping, Tank 68 and Sump 91 (a sump located on the northern side of former Building 88 which collected water from the building’s floor drains) were demolished and removed. Confirmation sampling after the removal of Tank 68 and Sump 91 did not indicated any significant contamination. Low residual VOC concentrations were detected in soil samples collected from the Tank 68 (maximum PCE concentration of 0.130 mg/kg) and Sump 91 (maximum PCE concentration of 0.003 mg/kg) excavations. Therefore, no additional soil removal was performed in these areas (PRC, 1995c). Approximately 400 cubic yards of contaminated soil were excavated and treated from two areas after removal of the floors, foundation and underground piping of Building 88. The primary source of contamination was believed to be associated with floor drains in the building. PCE was detected in soil samples collected from below the building at concentrations up to 1 mg/kg. Areas where PCE concentrations were greater than 0.5 mg/kg were designated for excavation, base...
IRP Site. 19 IRP Site I9 includes four former USTs (Tanks 2, I4, 43, and 53) that are found at various locations around former NAS Xxxxxxx Field. Only Tank 14 is located within the NRP area (Figure 3). Tank 14 was a 1,100-gallon diesel fuel storage tank for the backup generator in Building 158, the operations building. This tank was removed and soil and groundwater was sampled during May and June 1990. Soil in the excavation was visibly stained and its distribution and the condition of the tank (i.e., there was no indication of leaks) suggested tank overfilling may have caused the contamination. Based on results of initial soil sampling of the excavation (4,400 mg/kg TPHd), additional soil was excavated and disposed off-site. The confirmation sample collected from the north wall of the enlarged excavation contained 1,700 mg/kg TPHd; other confirmation samples indicated negligible amounts (<25 mg/kg) of TPHd and TPH as motor oil (PRC, 1991a). Additional soil sampling was conducted in May 1992 to assess the extent of soil impacted by TPHd near former Tank 14. Soil samples were collected from three locations near the northern boundary of the 1990 Tank 14 soil excavation. None of the six soil samples collected contained detectable concentrations of TPHd (PRC, 1993). The Navy submitted a request for closure for Tank I4 to the RWQCB for review in December 2000 (Tetra Tech, 2000b).
IRP Site. 24 Site 24 includes the Hangar I fuel pits, high-speed fuel hydrants, and the fuel pier. Only the Hangar I fuel pits are located within the NRP area. During construction of Hangar I, three aviation gasoline dispenser pits and three aviation gasoline valve pits were installed in the floor of the hangar to service dirigibles. The pits are now covered by concrete or offices. In 1987, the Navy installed a new concrete floor in the southern half of the building. As a result, the location of the third pit could not be identified and no investigation of this former pit was conducted. Two soil borings were advanced through two of the pits and soil and groundwater samples were collected. Purgeable TPH was not detected in any of the soil or groundwater samples collected. Low concentrations of VOCs (less than 0.011 mg/kg of PCE, TCE, 1 ,2-DCE, and toluene) were detected in soil samples, as well as in groundwater samples. PRC concluded that the detection of chlorinated VOCs is likely the result of the underlying regional groundwater VOC contamination (PRC, 1996). Based upon the results of a risk assessment, the Navy has recommended closure of Site 24 with no additional remediation (Tetra Tech, 2003a).
