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• k4 KLEINFELDER approximately limited to the respective depths and locations where these nine soil samples were collected, with the exception of PPI, at 19 feet. The estimated depths of petroleum impacted soil and anticipated future excavation depths as illustrated on Plates 3 and 4 were partly developed using data from these nine discrete soil samples. 4) Twelve discrete soil samples were collected and analyzed from perimeter pushprobe borings G2, G3 and G4 at depths ranging from 5 to 43 feet bgs. Based on this data, it is Kleinfelder's opinion that petroleum impacted soil has not migrated laterally a significant distance beyond the footprint area. Please note this finding does not include potential soil vapor migration of volatile compounds, since soil vapor sampling was not conducted as part of this assessment. 5) A total of four grab groundwater samples were collected one in the footprint area and three from perimeter locations. Relatively low concentrations of TPH-G (0.053 and 0.21 mg/1) 'l was detected in two groundwater samples. Benzene was detected from GI at a concentration I of 0.80 µg/1 and toluene was detected at 1.3 µg/1. Total xylenes were detected in the groundwater sample colleted from G1 at a concentration of 1.69 µg/1. TPH-G was the only 'r requested analyte detected in groundwater from the perimeter pushprobes, at location .G2. 1 The levels detected at the depths and locations in groundwater at the site are below State and Federal MCLs for drinking water. The extent and distribution of hydrocarbon in groundwater r{I is unknown at this time. It is Kleinfelder's opinion that the potential exists that the detections in groundwater may be a result of cross-contamination especially at location GI. The possibility of cross contamination was discussed during workplan preparation with the various parties involved [Chevron representatives (Cambria Environmental) and Kagehiro Ranch, hie. (Curtis and Arata Attorney's and Geocon Environmental)]. 6) Kleinfelder at this time does not recommend clean-up or additional groundwater monitoring activities related to petroleum constituents detected in groundwater, based on the relatively low levels detected and since applicable petroleum constituents are below drinking water standards (MCLs). If additional information is desired related to groundwater to assess potential risk, Kleinfelder recommends either installation of temporary or permanent groundwater wells to confirm the accuracy of the grab groundwater sampling results. 7) Kleinfelder recommends submitting a workplan to SJC/EHD detailing proposed remedial activities, potential profile soil sampling and analyses for disposal purposes and a confirmation soil sampling plan. 8) Kleinfelder recommends this report be submitted to San Joaquin County Public Health Services Department Environmental Health Division (SJC/EHD) for review and comment. This report, and the conclusions and recommendations presented in this Executive Summary, are subject to the "Limitations"presented in Chapter 7 of this report. Any other party(other than the Pegasus MH Ventures I), or regulatory agencies having enforcement jurisdiction for this site) ;J who would like to use this report shall notify Kleinfelder, Inc. of such intended use in writing for permission. ��. 44843.T03/ST04RIO25 Copyright 2004 Kleinfelder,Inc. page 14 of 16 91 August 6,2004