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concentration of 79 ug/L, TPHd in Well 3MW-1R at 120 ug/L and in MW-36 at 79 ug/L, and TPHo in Well 3MW-1R at 120 ug/L and in Well MW-36 at 71 ug/L. Benzene was reported in Well 3MW-1 at a concentration of 0.95 ug/L (14 October 1999). More recent (18 February 2004) sampling from Wells 3MW-1R and MW-36 were reported as non-detect for benzene. Recent sampling did not identify concentrations of N-propylbenzene above the MDL of 0.5 ug/L for both Well 3MW-1R (18 February 2004) and Well MW-36 (19 August 2003). The fuel oxygenate MTBE was reported at 10 ug/L in Well MW-1R (18 February 2004) and below the MDL of 0.5 ug/L in Well MW-36 (19 August 2003); TBA was not detected in either well for the same respective sampling periods. The metal As was reported in samples collected on 18 February 2003 from Wells 3MW-1R and MW-36 at concentrations of 6.3 ug/L and 9.2 ug/L, respectively. The metal Pb was not reported above the MDL of 3 ug/L for either well during the same sampling period. Groundwater grab samples from Boreholes DP-8, DP-9 and DP-21 were below MDLs for all COCs with the exception of TPHd reported from Borehole DP-8 at 27.5 feet with a concentration of 68 ug/L (September 2001) and Borehole DP-21 at 22 feet with a concentration of 103.5 ug/L (May 2002). 1.7 FORENSIC SOIL TESTING On January 26, 2005, five (5) soil samples were collected from the Worknet site (Parcel 3) and submitted to Friedman & Bruya, Inc. (2005) for forensic evaluation (Appendix G). The purpose of the evaluation was to define the age of the hydrocarbon to establish the age of the release to assist in evaluating if the release is ongoing (current), a recent release, or an older release; such as a release that occurred twenty (20) or more years ago. Two (2) of the samples, SB-5-ill and SB-5-21I were analyzed using a gas chromatograph with a flame ionization detector (GC/FID) and an electron capture detector (ECD). The results of the analysis indicated the hydrocarbon in the soil is a medium boiling point petroleum product such as heating oil #2. The normal alkenes were mostly absent but a dominant pattern of isoprenoids were present, suggesting the material had undergone a severe biodegradation. It was concluded that the material present is consistent with a release that occurred twenty (20) or more years ago. 1.8 CHEMICALS OF CONCERN Potential chemicals of concern (PCOCs) identified at the site include VOCs, SVOCs, TPHg, TPHd, TPHo, PCBs and metals. Based upon the reported data, the primary COC in shallow soils is Pb, and TPH in soil and groundwater. In the soils, the metal Pb, is generally found within five (5) feet of ground surface. Several of the PCOCs were not present at the reported detection limit. 1.9 PRELIMINARY ENDANGERMENT ASSESSMENT Work performed through August 2004 was reviewed as a Preliminary Endangerment Assessment (PEA) equivalent report by DTSC for the area designated Parcel 3 (Appendix H). The PEA was specific to human health and did not address surface water or groundwater. DTSC stated that the surface and groundwater regulatory oversight is currently being performed by the RWQCB. The metal Pb, as the primary COC, was reported at a maximum concentration of 710 mg/kg in a soil sample at a depth of one (1) foot bgs. DTSC's conclusion was that the level of Pb is unacceptable with the property's current unrestricted/unmonitored redevelopment status. DTSC suggested that institutional controls be implemented to prevent development of the property as residential. Additionally, DTSC stated that the level of Pb is not restrictive under a commercial office or construction worker scenario. Parcel 3 is zoned commercial. Golden State Environmental, Inc. - 8 - Los Angeles, San Diego and Houston Revised Work Plan — Soil and GW Characterization July 2006