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r CTATt: ASSOCIATES I N C . contained toluene (2.2 ppb), ethylbenzene (0.60_ ppb), xylenes (3.6 ppb), and MTBE (7.1 ppb). The sample from well MW-9 contained TPHg (54 ppb), toluene (2.3 ppb), xylenes (3.2 ppb), and MTBE (10 ppb). Groundwater levels collected during February 1999 indicated groundwater was at or near historically high levels (Gettler-Ryan Inc., February 1999). • The PHS/EHS file contained copies of correspondences dated from July 1998 to April 1999, between the SWRCB, the RWQCB, and PHS/EHD regarding concerns with UNOCAL's petition for closure. Most recently the RWQCB has advised the SWRCB that "In light of current concerns over the impacts of MTBE on groundwater, it seems prudent to us to continue monitoring at this site for one year to determine if the perceived "trends" noted by your staff are borne out by future data" (RWQCB, April 16, I999). SUMMARY AND REOMMENDATIONS A limited soil gas survey of the site's suspect areas, including the northeastern portion of the subject property bounding the former UNOCAL site and the southeastern portion of the property, was performed by ATC on June 7, 1999. Constituents of concern were not detected above laboratory method detection limits in any of the samples analyzed (Table 1). Furthermore, groundwater confirmation samples collected from the suspect areas did not contain any of constituents of concern above the laboratory method detection limits (Table 2). No additional investigation appears warranted at this time. A review of PHS/EHS files for the former UNOCAL site revealed that additional subsurface investigative activities have occurred as recently as February of 1999. The extent of petroleum hydrocarbons in soil and groundwater :appears to have been essentially defined. However the vertical' extent of groundwater impacts has not been "precisely defined". Nine years of groundwater analytical data has indicated the plume of petroleum in groundwater is stable and has not moved substantially. Also, the groundwater plume appears to be undergoing microbially mediated biodegradation. Groundwater samples collected on February 4., 1999 from wells MW-8 and MW-9, located on the - Bank of America property and immediately east of the Property, respectively, contained detectable concentrations of gasoline constituents. The MW-8 sample contained toluene (2.2 ppb), ethylbenzene (0.60 ppb), xylenes (3.6 ppb) and MTBE (7.1 ppb). The sample from well MW-9 contained TPHg (54 ppb), toluene (2.3 ppb), xylenes (3.2.ppb) and MTBE (10 ppb). Groundwater levels collected during February 1999 indicated groundwater was at or near historically high levels. A review of historical groundwater data contained in Gettler-Ryan's February 16, 1999 First Quarter 1999 Groundwater Monitoring&Sampling Report prepared for UNOCAL, "indicates the detection of toluene, ethylbenzene, or xylenes in wells MW-8 and MW-9 has not occurred since W:\17292.05\summaryrpt.doc 8 f