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I GEOMATRIX the City of Tracy (either building or public works departments) and the PHS EHD when approving permits for.construction or excavations. BACKGROUND 1. The area of the Nicholaw ropertYaddressed by this plan the"project area") is located.adjacent to West Byron Road. Pipelines, operated by CPL and other oil companies from approximately the early 1900s to the late 1956s, ran parallel to the northern edge of the Nicholaw property along West:Byron.Road (Figure 2). These pipelines carried crude oil:and Bunker Coil and were buried at a depth of approximately.3 feet below ground surface (bgs). Since 1990, soil and.groundwater investigations have been conducted at the Nicholaw property on behalf of CPL. The investigations have been reviewed by the PHS-EHD. The results of these 1 ' investigations indicate that limited amounts of petroleum hydrocarbons are present.in subsurface soil along the northern edge of the Nicholaw property that fronts West Byron Road, apparently the petroleum is likely de aded crude oil or Bunker C. result of releases from the pipelines. The petro y gr Total petroleum hydrocarbons (TPH) have been reported to be present in soil in I of 16 soil samples collected in 1994, at a concentration of 2700 milligrams per kilogram (mg/kg). Xylenes Lhave been detected at concentrations up to 0.23 mg/kg in 8 of 16 soil samples collected in 1994. E The affected soil occurs between the depths of approximately 1 to 5.5 feet bgs. The lateral Edistribution of petroleum hydrocarbons in soil is limited and does not appear to extend more than 50 feet southeast of the property boundary. The sample location where TPH-affected soil on the Nicholaw property was encountered is shown on Figure 2. The subsurface soil at the project area is predominantly silt and clay, with isolated sandy lenses, to a depth of at least 20 feet. The water table.is approximately 7 to 9 feet bgs. Based on the groundwater investigations performed to-date, shallow groundwater beneath the site has not been affected by the degraded crude oil. It has been determined by the PHS-EHD that the degraded. �4 crude oil is not a threat to groundwater quality. It should be noted that shallow groundwater ]:1WPD0CSIC3499WCH0SMP.DOC 2