SITE INFORMATION AND CORRESPONDENCE

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STATE CF CALIFORNIA • . CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— FETE wI soN co e, o, CENTRAL VALLEY REGION - 3443 ROUTIER ROAD. SUITE A -'��`• SACRAMENTO, CA 95827-3098 Fy - PHONE: 1916) 361-5600 �(1r'H FAX (910"1367.5686 gip. T 5 July 1991 KivI V J U L 8 1991 I-NVIRONMENTAL HEALTH Mr. Abel Haines PERMIT/SERVICES Chief, Environmental Protection Office Defense Distribution Region West, Tracy Tracy, CA 95367-5000 REVIEW OF THE REMEDIAL INVESTIGATION/FEASIBILITY STUDY (RI/FS) REPORT, DEFENSE DISTRIBUTION REGION WEST, TRACY SITE, SAN JOAQUIN COUNTY We have reviewed the RI/FS Report submitted on 4 March 1991 by the Corps of Engineers for the Defense Distribution Region West (DORW) , Tracy Site (Tracy) . In general , Tracy has made considerable progress in the investigation and cleanup of the site. The RI Report documents the work that has been completed in the investigation and mitigation of the ground water contamination by volatile organic constituents (VOCs) . We are pleased that the extent of the VOC plume is nearly completely defined, that the Interim Remedial Measure (IRM) has been initiated and that the FS Report proposed an alternative to expand the remediation of the contaminated ground water to capture the plume off-site. Our review of the RI Report revealed there are other areas which need investigation and cleanup at the site. Our major areas of concern involve the expansion of the monitoring program to site-wide, the investigation of potential ground water and soil contamination in the southern portion of the site, the investigation and cleanup of the waste management units or potential source areas and the expansion of the ground water remedial measure. Enclosed is a memorandum which discusses these issues. In the past, these issues have had a lower priority than the definition of the VOC plume and installation of an IRM. Now that these tasks have essentially been accomplished, we believe that it is appropriate to change the focus of the site investigation and cleanup to address these issues. Our review of the FS Report revealed that the Toxic Pits Cleanup Act (TPCA) was not considered as an applicable or relevant and appropriate requirement (AKAR) . We plan to send Tracy additional information on our ARARs. The FS Report proposes the alternative consisting of 500 gallon per minute extraction, air stripping with in-situ biodegradation and reinjection as the remedial action for the cleanup of the ground water. We find the selection of this alternative to be acceptable. However, we are concerned that the existing IRM may not be used to its fullest, that shallow reinjection was the only proposed disposal alternative and that there is presently insufficient hydrogeologic information to support placement and design of the injection wells.