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California9egional Water Quality Cool Board <br /> Central Valley Region <br /> '.. <br /> Linda S.AdamsArnold <br /> Karl E. Longley,ScD,P.E.,Chair <br /> Secreiaryfor Schwarzenegger <br /> Fnvironmentol 11020 Sun Center Drive 4200,Rancho Cordova,California 95670-6114 Governor <br /> Protection Phone(916)464-3291 •FAX(916)4644645 <br /> htip://w .waterboards.ca.gov/centralvalley <br /> RECE VMEDD <br /> 21 January 2009 JAN 2 2 2009 <br /> ENVIRONMENT HEALTH <br /> DESJC, M.BENSON PERMIT/SERVICES <br /> Defense Distribution Depot San Joaquin <br /> P.O. Box 960001 <br /> Stockton, CA 95296 <br /> REVIEW Or RESPONSE TO COMMENTS ON REGIONAL WATER BOARD <br /> 25 NOVEMBER 2008 REVIEW LETTER; UST 25 CLOSURE WORK PLAN, DEFENSE <br /> DISTRIBUTION DEPOT SAN JOAQUIN— TRACY, SAN JOAQUIN COUNTY <br /> California Regional Water Quality Control Board, Central Valley Region (Regional Water <br /> Board) staff has reviewed the Response to Comments (RTC) document that you sent to me <br /> by electronic mail on 19 December 2008. The Air Force Center for Engineering and the <br /> Environment (AFCEE) prepared the RTC on behalf of Defense Logistics Agency Enterprise <br /> Support San Joaquin, California (DESJC) for the Defense Distribution Depot (DDJC) Tracy <br /> site. The RTC responds to our 25 November 2008 letter review of the DESJC <br /> September 2008 Underground Storage Tank (UST) 25 Site Closure Work Plan (Work Plan). <br /> The RTC document is not responsive to the Regional Water Board staff comments in that it <br /> indicates groundwater monitoring wells will not be installed and that cone penetrometer test <br /> (CPT) borings will be advanced as was proposed in the Work Plan. The RTC document <br /> justifies this decision by stating that the Work Plan intent was to meet sample collection <br /> proposed in the October 2003 Final Preferred Alternative Analysis Report (PAR). Please <br /> note that in our September 2002 comment letter on the June 2002 Draft PAR, we indicated <br /> the need for groundwater monitoring wells. However, DDJC implemented monitoring plans <br /> at UST Site 25 proposed in the Draft PAR before it responded to our comments or submitted <br /> a Final PAR. In essence, the monitoring strategy for UST Site 25 was never agreed upon. <br /> As we indicated in our 25 November 2008 review letter, Regional Water Board staff does not <br /> concur with the strategy of monitoring with CPT borings because the magnitude and extent <br /> of groundwater contamination indicates the need for shallow monitoring wells screened <br /> across the water table. This is indicated by the concentrations of total petroleum <br /> hydrocarbons in the diesel range measured by laboratory chemical analyses of water <br /> samples collected beneath the site. The reported concentrations (up to 650,000 micro grams <br /> per liter) are indicative of liquid-phase petroleum hydrocarbons (LPH) floating on the water <br /> table. Natural attenuation processes are known to be slow at degrading LPH and this has <br /> been corroborated by the data collected between 1988 and 2003 at UST Site 25. Monitoring <br /> wells are necessary to aid in the assessment of the extent of LPH beneath the former UST <br /> and the existing building that the former UST was contiguous with. <br /> California Environmental Protection Agency <br /> ¢a Recycled Paper <br />