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M. Scott Mansholt _ Chevron - 2 8 July 2008 Tracy Byron Road The approximately 200-foot wide by 7,000-foot long City of Tracy storm drain project, completed in 2003, is located within a residential area of west Tracy, and extends from Corral Hollow Road on the east to Van Sosten Road on the west. The Catellus OVP/TAOC project, currently being characterized by Chevron, is adjacent to the west end of the project. Adjoining properties are developed with private residences, small commercial businesses, and/or agricultural parcels/residencies. Consequently, access to certain properties was time consuming and in some cases, not achieved. Some proposed boring locations had to be relocated to parcels or roadways where access could be obtained to accommodate the investigation schedule. Interstate Freeway 205 (1-205) crosses Byron Road near the west end of the project. The focus of the investigation was to further delineate affected soil and/or groundwater upgradient (south) of Byron Road and the former OVP/TAOC pipelines. Based on the findings of the storm drain project and subsequent investigation, we recommended an additional 8 to 10 borings be advanced upgradient of the areas of crude oil impacted soil/groundwater. Due to the difficulty of property access, only five of nine previously approved borings were completed. According to historical documents, soil and groundwater investigations were conducted on adjacent downgradient properties to the north. With the exception of the Surland Homes, between 1996 and 2002, No Further Action (NFA) determinations for the properties were approved by the San Joaquin County Environmental Health Department (SJCEHD) or the Sacramento office of the Regional Water Quality Control Board (RWQCB). The Surland Homes residential property is currently being addressed by Chevron. Additionally, part of the upgradient sites to the south, were issued NFA closures by the SJCEHD in 1996 and 1997. The recent and current investigations addressed areas where delineation was incomplete. Reports of the earlier investigations and response letters to Chevron are contained in the Regional Water Board project files. CURRENT INVESTIGATION During March 2007, SAIC completed soil borings SB-37 through 41. Soil and groundwater samples were collected and submitted for analysis of the petroleum hydrocarbon constituents of concern. The investigative findings addressed data gaps identified by the earlier characterization studies. Soil Five soil borings, advanced to depths of 24 to 32 feet, were completed along the south side of Byron Road at the west end near 1-205. Total petroleum hydrocarbon (TPH) affected soil was not observed. TPH as crude oil (TPHc), benzene, toluene, ethylbenzene, and xylenes (BTEX) was reported non-detect (ND) for all samples collected at depths of 5 to 24 feet. In addition, polynuclear aromatic hydrocarbons (PAHs) constituents were ND at their respective method detection limits (MDLs).