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California -gional Water Quality C ';rol Board Q <br /> Central Valley Region <br /> Katherine Hart, Chair <br /> 11020 Sun Center Drive,#200, Rancho Cordova, California 95670-6114 <br /> Linda S.Adams (916)464-3291 • FAX(916)464-4645 Edmund G.Brown Jr. <br /> Acting Secretary for http://www.waterboards.ca.gov/centraIvalley Governor <br /> Environmental Protection <br /> RECEIVED <br /> 17 March 2011 <br /> MAR 21 2011 <br /> Mr. James Diel ENVIRONMENTAL HEALTH <br /> Manager, Site Remediation PERMIT/SERVICES <br /> Union Pacific Railroad Company <br /> 9451 Atkinson Street, Suite 100 <br /> Roseville CA 95747-5528 <br /> BIOTREATMENT BEDS POST-REMEDIATION INVESTIGATION REPORT, UNION <br /> PACIFIC RAILROAD COMPANY FORMER TRACY MAINTENANCE FACILITY, 720 <br /> EAST 6TH STREET, TRACY, SAN JOAQUIN COUNTY <br /> The California Regional Water Quality Control Board, Central Valley Region (Central Valley <br /> Water Board) staff has received and reviewed the Response to Comments - Biotreatment <br /> Beds Post-Remediation Investigation Report (Comment Responses), dated 5 November <br /> 2010, prepared by ARCADIS U.S., Inc. (ARCADIS) on behalf of Union Pacific Railroad <br /> Company (UP). Central Valley Water Board staff provided comments on the Post-Remedial <br /> Investigation Report on 24 August 2010, and requested additional data to evaluate the <br /> effectiveness of the biotreatment remedy as described in Cleanup and Abatement Order <br /> (CAO) No. 92-707. <br /> UP implemented the biotreatment method in order to clean up Total Petroleum Hydrocarbons <br /> quantified as diesel (TPHd), polynuclear aromatic hydrocarbons (PAHs), and volatile organic <br /> compounds (VOCs) in sediment excavated from the former Toxic Pits Cleanup Act (TPCA) <br /> pond in 1987 and 1992. Three phases of biotreatment occurred from 1994 to 1997, <br /> including application of nutrients and water, soil tilling, and sampling for TPHd and PAHs. As <br /> of March 2010, soil samples in the biotreatment beds contained concentrations of up to 620 <br /> milligrams per kilogram (mg/Kg) TPHd. PAHs were below the cleanup goals by 1997. VOCs <br /> were not found to be associated with biotreatment bed soils. Monitoring and sampling of <br /> groundwater has produced no detections of TPHd or VOCs downgradient of the biotreatment <br /> beds since at least 2003, indicating that current soil levels are protective of groundwater <br /> beneficial uses. <br /> ARCADIS input site-specific parameters to the VLEACH model in order to predict <br /> groundwater concentrations derived from remaining soil TPHd. Results of the modeling <br /> indicate that the maximum observed soil concentration of 620 mg/Kg (March 2010) would <br /> result in a groundwater TPHd concentration of less than12 micrograms per liter (pg/L). <br /> Groundwater sampling in four monitoring wells in or near the biotreatment beds (MW-01A, <br /> MW-04A, MW-05A, and MW-26A) has not produced detections of TPHd since 2003. <br /> California Environmental Protection Agency <br /> ca Recycled Paper <br />