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GEOMATRIX <br /> HEALTH RISK SCREENING EVALUATION <br /> Surland Homes Property (Laurelbrook) <br /> Tracy, California <br /> ' EXECUTIVE SUMMARY <br /> On behalf of Chevron Environmental Management Company(ChevronTexaco), Geomatrix <br /> ' Consultants, Inc. (Geomatrix), has prepared this Preliminary Endangerment Assessment (PEA) <br /> for submittal to the California Department of Toxic Substances Control (DTSC) for the Surland <br /> 1 Homes Property(Laurelbrook) located in Tracy, California. This report is equivalent to a <br /> Preliminary Endangerment Assessment (PEA) and is being submitted in accordance with <br /> provision 3b of the Voluntary Cleanup Agreement between ChevronTexaco and the DTSC. <br /> ChevronTexaco's former Old Valley Pipeline(OVP)was located adjacent to the Union Pacific <br /> Railroad Company right-of-way which runs along the north side of West Byron Road, south of <br /> the Surland Homes residential subdivision which consists of more than 100 single-family <br /> homes. The former OVP transported heavy petroleum (crude and fuel oil) from Bakersfield to <br /> Richmond, California, from the early 1900s to the 1950s. Also present in the right-of-way was <br /> the former Associated Pipe Line(APL) Company's(predecessor to Texaco and now <br /> ChevronTexaco)pipeline that transmitted heavy crude from the Central Valley to the Bay Area <br /> from the early 1900s to the 1970s when it was decommissioned. <br /> Since 1998, Geomatrix has conducted soil and groundwater investigations on behalf of <br /> ' ChevronTexaco. Work plans and investigation results have been reviewed by the San Joaquin <br /> County Public Health Services - Environmental Health Department (SJCPHS-EHD) and the <br /> State of California Regional Water Quality Control Board, Central Valley Region(RWQCB). <br /> Results of the investigations indicate that limited amounts of petroleum hydrocarbons, <br /> specifically degraded crude or Bunker C oil, are present in subsurface soil along the OVP and <br /> that the lateral and vertical extent of residual petroleum in soil is constrained. <br /> Subsurface soil at the site is predominantly silt and clay,with isolated sandy lenses, to a depth <br /> ' of 16 feet. Groundwater occurs at a depth of approximately 5 to 7 feet below ground surface <br /> (bgs) and flows generally toward the north-northwest. Analytical results indicate that the <br /> residual petroleum in soil is not providing a significant source of dissolved petroleum <br /> constituents to groundwater. <br /> ' 1ADoc_SafcN6000sW647.007HRA\SurlandHRA.dm ES-1 <br />