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Treadwell&Rollo <br /> • pore saturation, and the volume, viscosity, and density of the hydrocarbon. Refined <br /> hydrocarbons, such as the diesel and gasoline found at OU 2,will move through soil to the <br /> groundwater if an adequate source of the hydrocarbon is present and the soil is sufficiently <br /> permeable. Information presented in this RI suggests that,with the possible exception of <br /> portions of Area 15, all source areas(i.e. USTs and heavily contaminated soil) have been <br /> removed. This will minimize further transport of petroleum hydrocarbon to the groundwater. <br /> Completion of the remedial activities at Area 16, and the possible initiation of remedial activities <br /> at Areas 15 and 21 will further diminish the possible transport of petroleum hydrocarbons to the <br /> groundwater. <br /> 5.1.2 Potential Migration Pathways of Groundwater Contaminants <br /> Groundwater at the study area is known to contain dissolved-phase fuel hydrocarbons, PAHs, <br /> and low levels of chlorinated hydrocarbons. Dissolved-phase metals do not appear to be present <br /> in statistically significant quantities. Dissolved-phase contaminants in groundwater can be <br /> • transported as part of the normal groundwater flow regime of the study area, or when withdrawn . <br /> from the soil during such actions as construction dewatering or other groundwater withdrawal <br /> activities. <br /> There is no evidence that significant concentrations of contaminants are moving in the dissolved- <br /> phase through groundwater flow at OU-1. At OU-2 significant concentrations of petroleum <br /> hydrocarbons and some VOCs are present in groundwater,but groundwater monitoring data <br /> indicates that significant concentrations are not migrating off site. It is unlikely that <br /> contaminants in groundwater are transported to the Stockton Ship Channel as groundwater flow <br /> is away from the channel. <br /> Given the depth to groundwater, the absence of extraction wells in the immediate vicinity of the <br /> study area, and the geotechnical constraints on construction that would likely preclude deep <br /> foundations, it is unlikely that contaminants in groundwater will be exposed to the surface in an <br /> uncontrolled manner. <br /> 31 <br /> 25970309.DGD 24 August 2000 <br />