ARCHIVED REPORTS_REMEDIAL ACTION REPORT

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Tracy Pump Station Remedial Action Report January 4,2012 4. FINDINGS 4.1 SUBSURFACE CONDITIONS SAIC supervised the excavation of PAH-affected soil by RECON from October 21 through November 2, 2011. A total of 3,685.3 tons of hydrocarbon-affected soil were excavated and directly loaded into waste transport trucks or roll-off bins for disposal at the Altamont Landfill or Buttonwillow. An additional 157.5 tons of hydrocarbon-affected soil with debris containing asbestos were excavated and loaded into roll-off bins. Finally, 1.83 tons of large non-regulated debris were excavated and loaded into a roll-off bin. The depth of the excavation extended from 9 to 10 feet bgs according to the vertical extent of PAH-affected soil. Groundwater was encountered during excavation activities at approximately 8.5 feet bgs. 4.2 SOIL ANALYTICAL RESULTS Top soil analytical results for the COPCs are summarized in Tables 3 and 4. Copies of the soil ' sample laboratory analytical reports are included as a component of Appendix D. 5. CONCLUSIONS AND RECOMMENDATIONS SAIC excavated and removed soil with high concentrations of PAHs from the area of the former blow-off pond. SAIC concludes the following regarding the nature and extent of affected soil at the Site based on the results of this remedial action and previous site investigations: • A total of 29 borings were advanced, and 49 soil samples were collected and submitted for laboratory analysis within the excavation area to delineate the excavation and to provide post-excavation sidewall and excavation bottom sample results; • Approximately 3,842.78 tons of soil were excavated and transported off-site for disposal. Excavation depth averages 10 feet bgs; • Approximately 196,355 pounds of TPHc were removed from the excavated area. Calculations and assumptions are presented in Appendix I; and • All soil visually containing residual hydrocarbons was removed from the remediation area to a maximum depth of 10 feet bgs and properly disposed of at Chevron approved landfills. SAIC recommends performing a human health screening evaluation as a further step in the process of moving the Site toward no further action required status. & REFERENCES Department of Water Resources, 2006. California's Groundwater Bulletin 118, Update 2003. October(specific basin update January 20, 2006). EPA, 2008. Test Methods for Evaluating Solid Waste, Physical/Chemical Methods. UP date IV of the Third Edition. January. RWQCB (Central Valley Region), 2011. Review—Remedial Action Plan, Former Tracy Pump .Station, West Grant Line Road, Tracy, San Joaquin County. July. SAIC, 2011. Remedial Action Plan, Former Tracy Pump Station, Tracy, San Joaquin County, California. June. 1 5 SAIE I