FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

No Further Action Required Request Report US Can—Welty Road September 24,2013 The hydrocarbons in the subsurface are not very mobile. At least 40 years have passed since the pipelines were decommissioned; thus the extent of residual hydrocarbons in the subsurface is unlikely to increase. Significant changes of plume size or COPC concentrations, if measurable, would not be expected on a quarterly, semi-annual,or even an annual basis. The concentrations of COPCs do not pose a threat to human health or the environment, and it is expected that they will decrease to background levels over time. 12. Provide isoconcentration contour maps of contaminants of concern to define the lateral and vertical extent of contaminants remaining in soil and groundwater. The contour maps should present and estimated "zero zone"of contaminant concentrations both on site and off site. SAIC compared the sample analytical results for the COPCs to the lowest, most conservative ESLs and RSLs or WQOs, and concluded that the lateral extent of crude-oil affected soil and groundwater has been delineated as indicated on Figure 3. The investigation of off-site areas northwest of the former US Can property(including borings SB-38 through SB-41 and SB-43)is ongoing as part of the adjacent Ahern Road–Vernalis site. 13.Provide a summary of the remedial method(s) used to clean the site. Include the calculated zone of influence, assumptions used to design the remedial systems(s), and the duration of remedial activities. Soil was removed by WHF in 1996 as part of the waste/bum pit investigation. No remediation has been conducted as part of HPP-BTR investigation activities. 14.Provide a discussion of whether background is unattainable using best available remediation method(s). SAIC and Geomatrix Consultants, Inc. (Geomatrix)evaluated available remediation technologies for potential applicability to sites associated with former HPP-BTR operations,which is consistent with Section IIIA through C of SWRCB Resolution No. 92-49. SAIC prepared a report of findings(SAIC, 2005). Available removal technologies were compared to in-place management of SPO,using the evaluation criteria of effectiveness, implementability, and cost. The following removal technologies were evaluated: bailing; passive and active in-well skimming; belt skimmers; excavation; in situ flushing with surfactants and co-solvents; vacuum- enhanced recovery(bio-slurping); groundwater drawdown pumping; in situ heating at low and high temperatures; short-term, multi-phase extraction; and pressure-pulse technology. SAIC and Geomatrix found that very little of the SPO encountered at former OVP and TAOC sites can be recovered due to its high viscosity and the low hydraulic conductivity of fine-grained Central Valley soils. SAIC and Geomatrix also found that threats to water quality,human health, and the environment are essentially the same whether free product is actively removed or not; either way, significant percentages of free product will remain. SAIC and Geomatrix concluded that all of the remedial technologies—with the exception of excavation at some sites—are ineffective, not easily implemented, and/or disproportionately costly in comparison to benefits. Therefore, and in consideration of Section IIIA through C of SWRCB Resolution No. 92-49,active removal of the affected soil and groundwater is considered technologically and economically infeasible for this Site. Unlike removal technologies, natural attenuation in conjunction with an SGMP is a viable approach for the Site. Natural attenuation will degrade the residual crude oil and limit the lateral 9 SAIC.