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Californiaional Water Quality Con Board <br /> log Central Valley Region a <br /> Robert Schneider,Chair <br /> Linda S.Adams Arnold <br /> or Sacramento Main Office <br /> I �Q Schwarzenegger <br /> Secreta <br /> Environmental 11020 Sun Center Drive!4200,Rancho Cordova,California 95670.611 Governor <br /> Protection Phone(916)464-3291 •FAX(916)464-4645 <br /> http://www.waterboards.ca.gov/centralvalley / <br /> ' 4 <br /> June 30, 2006 rTyf,�rr <br /> Mr. Mark Adams <br /> Lincoln Center Environmental Remediation Trust <br /> 137 Park Place <br /> Point Richmond, CA 94801 <br /> CONCURRENCE WITH DRAFT PROPOSED PHASE IV INTERIM REMEDIAL ACTION <br /> DETAILED PLAN, LINCOLN CENTER, STOCKTON, SAN JOAQUIN COUNTY <br /> Staff of the California Regional Water Quality Control Board, Central Valley Region (Regional <br /> Water Board) has reviewed the Draft Proposed Phase IV Interim Remedial Action (IRA) <br /> Detailed Plan, for the Lincoln Center Site (the Site), Stockton. The document is dated June 8, <br /> 2006, and was received by the Regional Water Board on June 15, 2006. Your environmental <br /> consultant, LFR Inc., of Emeryville prepared the plan on your behalf. <br /> Former dry cleaning operations at the Site have resulted in the presence of tetrachloroehtene <br /> (PCE) in soil and groundwater. Due to rising groundwater elevations of approximately 20 feet <br /> from 1996 to present, a re-saturated zone of PCE contamination has been created in low <br /> permeability sediments situated above the historical water table. It is staffs understanding <br /> that the purpose of the Phase IV IRA is to verify remediation of the Re-saturated-Zone <br /> sediments is achievable with the Proposed Phase IV IRA. In previous phases of assessing <br /> remedial alternatives, the Re-saturated-Zone sediments in the Historical Source Area have <br /> responded more slowly to remedial measures. A Draft Feasibility Study (FS) was submitted to <br /> the Regional Water Board in August 2002, followed by three phases of IRAs. <br /> In support of the Phase IV IRA, two preparatory filed activities were conducted. First, in <br /> August 2005, LFR conducted an air sparging pilot test to determine if air-sparging technology <br /> was a viable remdial measure to deliver air followed by ozone into the Re-saturated-Zone <br /> sediments and the Historical Source Area. Five lines of evidence were used to confirm that air <br /> sparging would be a viable option: air entry pressures, tracer gas distribution, tracer gas <br /> recoveries, decrease in volatile organic contaminant (VOC) concentrations, and groundwater <br /> level responses. Second, in January 2006, a focused Membrane Interface Probe (MIP) <br /> investigation was conducted to aid in the design an effective air/ozone delivery system. The <br /> MIP technology provided enhanced assessment of Iithology and the lateral and vertical extent <br /> of VOC concentrations. Based on the results of the MIP investigation, the number of wells, <br /> their distribution, screen intervals and depths for sparging were proposed. <br /> The Regional Water Board staff concurs with the Draft Proposed Phase IV IRA as submitted, <br /> and beginning the 45-day public comment period. Staff appreciates the opportunity to have <br /> reviewed the Draft Proposed Plan before distribution to recipients and beginning the public <br /> California Environmental Protection Agency <br /> �a Recycled Paper <br />