SITE INFORMATION AND CORRESPONDENCE

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I41,1111Cnt trt I u�l� tillh�t,ul�� „ntrtrl a, Itll � l I 'ru� lin A�.I . tiuilc WindonII Ilick.,e ti.n:1a11WHI, t 1111''r111.1 1) tieen-fai I, r lir:ft Ua�e; t;mcrnor Invimm�lcnl:Il Prok•cnun July 30, 1999 Commander ASCE-BE (Mr. Dale Clemons) Activity Services Center West Defense Depot San Joaquin, Tracy Site Building S-108, Sharpe Location P.O. Box 960001 Stockton, California 95296-0250 DRAFT REMEDIAL ACTION SOIL VAPOR EXTRACTION SITES 60 % DESIGN WORK PLAN FOR DEFENSE DEPOT SAN JOAQUIN, TRACY SITE Dear Mr. Clemons: The Department of Toxic Substances Control (DTSC) has completed their review of the above mentioned document dated May 1999. U.S. Environmental Protection Agency Remedial Design guidance indicates that the design should include a schedule and updated cost information, which may differ significantly from that contained the Feasibility Study (FS). Although a schedule is contained in Volume 3, Section 13, the cost information is not included in this design document and needs to be provided. The FS cost estimate is generally accurately to +50 to -30%, however, by the time the 100% Remedial Design is complete, the estimated cost figures should probably be within+/- 10 to 15% of the actual costs. Using the mass estimates included in the 60% design document and cost figures included in the FS, the cost per pound for the proposed actions range from—$4K to —$296K per pound. (SWMU 1, $70K/Ib; Area 1 - Building 237, $28K/Ib; Area 3, $4k/lb; SWMU 20/23 S296K/lb; SWMU 24 - Building 247, no TPH mass estimate). Given the relatively low level of contaminant mass at some of these sites, it is difficult to determine whether the clean-up is cost effective relative to the potential benefit. In the event that the cost effectiveness was not fully evaluated in the FS, the RD provides the opportunity to do so. California Hnvironmental Protection A,anc. Printed on Recycled Paper HM.dm HMSI W.O"