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GEOMATRIX SOIL MANAGEMENT PLAN Westside Channel Outfalls System Tracy, California ' 1.0 INTRODUCTION Geomatrix Consultants, Inc. (Geomatrix), has prepared this soil management plan (SMP) on behalf of Chevron Environmental Management Company(ChevronTexaco) to address issues associated with residual crude oil in soil along a historic pipeline right-of-way that may be ' encountered during development, improvement, or maintenance activities within the project area of the proposed City of Tracy Westside Channel Outfall System (WCOS). The project ' area incorporates primarily Byron and Lammers Roads in Tracy California(Figure 1). Construction activities associated with the installation of the WCOS include excavation, dewatering, grading, paving, and installation of subsurface utilities. Subsurface utilities will ' include large diameter(i.e., 48-, 60- and 84-inch-diameter)reinforced concrete pipe. The project also includes construction/installation of retention basins and box culverts. During ' these or any other unforeseen activities, soil affected by degraded crude oil may be encountered between 5 to 25 feet below ground surface (bgs) at several locations along the pipeline. ' ChevronTexaco has evaluated the potential human health risk posed by the residual petroleum constituents associated with former ChevronTexaco operations as part of previous environ- mental investigations at six sites within the project area (Figure 1). ' Potential human health risks were evaluated using the methodology presented in the Human Health Screening Evaluation of the Preliminary Endangerment Assessment Guidance Manual (PEA; Cal-EPA, 1994) and/or through a comparison of site data to established human health screening criteria, such as preliminary remediation goals (PRGs; U.S. Environmental Protec- tion Agency,Region 9, 2002). Based on the results of these evaluations, residual petroleum constituents detected in soil and groundwater that may be encountered should not pose an un- acceptable risk to human health or to the environment, under the conditions evaluated. Results of the human health risk assessments were submitted to the appropriate regulatory agencies for review. Documentation regarding regulatory closure of each site may be obtained from ChevronTexaco or the respective regulatory agency upon request. I:\Doc_Safe\6000s\6447.006\WC0S SMP.doc 1