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STATE OF CALIFORNIA - Environmental Prot*Agency • PETE WILSON, Governor <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD �m,R <br /> CENTRAL VALLEY REGION <br /> 3443 Routier Road, Suite A <br /> Sacramento, CA 95827-3098w,F' <br /> PHONE: (916) 255-3000 <br /> DOD FAX: (916) 255-3052 <br /> 13 July 1994 <br /> Mr. Jim Pinasco <br /> Department of Toxic Substances Control <br /> 10151 Croyden Way, Suite 3 <br /> Sacramento, CA 95827-2106 <br /> DRAFT FINAL COMPREHENSIVE REMEDIAL INVESTIGATION/FEASIBILITY STUDY <br /> PHASE I SITE CHARACTERIZATION REPORT AND ANALYTICAL DATA REPORT, <br /> DEFENSE DISTRIBUTION REGION WEST (DDRW), TRACY, SAN JOAQUIN COUNTY <br /> We have reviewed the Draft Final Remedial Investigation/Feasibility Study (RI/FS), Phase I Site <br /> Characterization Report (Draft Final Phase I SCR) and Analytical Data Report for DDRW, Tracy <br /> submitted 13 June 1994. We have also reviewed the response to our comments on the Draft Phase I <br /> SCR submitted as part of the cover pages of the Draft Final Phase I SCR. We concur with the <br /> Analytical Data Report without comment. The Draft Final Phase I SCR was revised to incorporate <br /> the majority of our comments. However, we have some remaining concerns that may influence the <br /> scope of the Phase II RI/FS effort which are included in our comments on the Draft Final Phase I <br /> SCR as follows: <br /> GENERAL COMMENTS <br /> 1. Solid Waste Management Units (SWMUs): The Draft Final Phase I SCR does not <br /> graphically relate potential sources of contamination to the Operable Unit No. 1 (OUl) <br /> plume. The approximate location of the OU1 ground water plume is illustrated in <br /> Figure 1-3. However, this figure does not identify the SWMUs suspected as being source <br /> areas of the plume. A map illustrating the known extent of the OU1 plume, which includes <br /> the approximate locations and known areal extents of the potential source areas should be <br /> provided in the Final Phase I SCR. This comprehensive view would be useful in further <br /> characterizing the suspected source areas and in evaluating source removal remedial <br /> alternatives for these areas in completing the RI/FS. <br /> 2. Water Quality Assessments: We commend the efforts made by DDRW, Tracy and <br /> Montgomery Watson to conduct thorough Water Quality Assessments to determine site <br /> specific threats to water quality. The Water Quality Site Assessment information is <br /> extremely well organized and well presented in the Draft Final Phase I SCR. <br /> It is acceptable to use generic attenuation factors in the site-specific water quality assessments <br /> for metals at DDRW Tracy. However, the criteria for determining these factors are <br /> appropriate with the exception of the vertical distance to the water table as presented in <br />