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(VYATC ' • December 1995 - Groundwater Monitoring and Sampling - In order to establish site conditions at the time of their lease termination, OIT contracted Smith Technology to sample monitoring wells MW3 and MW5, located downgradient and upgradient of the former MQUAD anodization and wastewater treatment system located immediately east of the main building (Figure 2). Collected water samples were analyzed for pH, nitrate, sulfur, copper, lead, and nickel. Laboratory results indicate nitrate was present above the MCL in sample collected from well MW-3 at a concentration of 53 ppm. No other constituents tested were detected above their respective MCLs. • September 1997 - Groundwater Monitoring and Sampling - Smith Technology performed monitoring and sampling activities for wells MWI, MW2, MW3, MW5, and MW6. The depth to water ranged from 13.91 to 17.10 feet below top of well casing elevation. Groundwater in the uppermost aquifer beneath the site was determined to flow in a westerly direction. The average hydraulic gradient on September 11, 1997 was calculated to be 0.004 ft/ft or about 21 feet/mile. Well MW4, southwest of the wastewater treatment system, was not located during site activities. It is believed that MW4 was destroyed during construction activities associated with improvements to the wastewater treatment system. Groundwater samples collected from wells MWI, MW2, MW3, MW5, and MW6 contained concentrations of nitrate and sulfate ranging from nondetectable to 120 ppm and 30 ppm to 100 ppm, respectively. Groundwater samples collected from wells MWI and MW2 contained no detectable concentrations of VOCs. Groundwater samples collected from wells MW5 and MW6 contained toluene at concentrations of 0.71 ppb and 0.51 ppb, respectively. The groundwater sample collected from well MW3 contained chloroform, 1,1-dichloroethene, 1,1,1- trichloroethane, and freon 113 at concentrations of 0.89 ppb, 0.83 ppb, 2.5 ppb, and 2.9 ppb, respectively. Groundwater samples collected from wells MW2 and MW3 contained no detectable concentrations of SVOCs. Well MW2 contained arsenic and copper a concentrations of 0.21 ppm and 0.1 ppm, respectively. Zinc was detected in both wells but was also detected in the method blank. Nitrate exceeded the MCL in wells MWI, MW2, MW3, and MW6. Nitrate concentrations were highest in upgradient well MW6 indicating that the nitrate was likely coming from an off-site source. No other constituents were reported above MCLs in any of the wells. • Closed UST - The PHS/EHD file contained documentation of a UST near the northwest corner of the main building. This UST was originally installed in 1980 to supply fuel to the facility's backup emergency generator. However the tank was never utilized and remained empty until it was abandoned-in-place in 1992. The UST was filled with 16 cubic yards of pea gravel by Cen-Cal Services Inc. of Manteca, California. No testing of the underlying and adjacent soils and groundwater was W:\16962\REPORTS\WORK_PLN.DOC 4