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No Further Action Required Request Report <br /> Tracy Byron Road-Tracy,California December 1,2011 <br /> human health or the environment,and it is expected that they will decrease to background levels <br /> over time. <br /> 12. Provide isoconcentration contour maps of contaminants of concern to define the lateral <br /> and vertical extent of contaminants remaining in soil and groundwater. The contour maps <br /> should present an estimated"zero zone"of contaminant concentrations both on site and <br /> off site. I <br /> SAIC compared the sample analytical results for the COPCs from the borings advanced to <br /> delineate the lateral extent of the hydrocarbons to the lowest, most conservative ESLs and RSLs J <br /> or WQOs, and concluded that the lateral extent of crude-oil affected soil and groundwater has <br /> been delineated, as indicated on Figure 3. Although the screening levels used to delineate the <br /> extent of crude-oil affected soil and groundwater at the Site may have changed over time, it <br /> should be noted that all screening levels used were very conservative and are considered <br /> adequate for site delineation purposes. <br /> 13. Provide a summary of the remedial method(s)used to clean the site. Include the <br /> calculated zone of influence, assumptions used to design the remedial systems(s), and the <br /> duration of remedial activities. <br /> Remediation has not been implemented at the Site. I <br /> 14. Provide a discussion of whether background is unattainable using best available <br /> remediation method(s). <br /> Consistent with Section IILA through C of SWRCB Resolution No. 92-49, SAIC, in <br /> collaboration with Geomatrix Consultants, Inc. (Geomatrix), evaluated available remediation <br /> technologies for potential applicability to sites associated with former HPP-BTR operations. <br /> SAIC prepared a report of findings(SAIC,2005). Available removal technologies were <br /> compared to in-place management of separate phase oil (SPO), using the evaluation criteria of <br /> effectiveness, implementability,and cost. The following removal technologies were evaluated= <br /> bailing;passive and active in-well skimming; belt skimmers; excavation; in sitar flushing with <br /> surfactants and co-solvents; vacuum-enhanced recovery(bio-slurping); groundwater drawdown <br /> pumping; in situ heating at low and high temperatures; short-term, multi-phase extraction; and ' <br /> pressure-pulse technology. <br /> SAIC and Geomatrix found that very little of the SPO encountered at HPP-BTR sites is available <br /> for recovery due to its high viscosity and the low hydraulic conductivity of fine-gained Central <br /> Valley soils. The evaluation also found that threats to water quality, human health,and the <br /> environment are essentially the same whether free product is actively removed or not, because in <br /> each case, significant percentages of free product will remain. SAIC and Geomatrix concluded <br /> that all of the remedial technologies—with the exception of excavation at some sites—are <br /> ineffective, not easily implemented,and/or disproportionately costly in comparison to benefits. ' <br /> Unlike removal technologies, natural attenuation—,coupled with a soil and groundwater <br /> management plan—is a viable approach for the Site. Natural attenuation will degrade the <br /> residual crude oil and limit the lateral and vertical extent of dissolved hydrocarbons in , <br /> groundwater as well as any active remediation technology. Natural attenuation is a viable <br /> technology for weathered heavy crude oil with low concentrations of BTEX, and the extents of <br /> BTEX and associated TPH plumes in groundwater are generally limited to the area of SPO. The ' <br /> effectiveness, implementability, and cost-effectiveness of natural attenuation are summarized <br /> 8 , <br /> SAIE <br />