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MEMORANDUM CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 361-5600 Sacramento, CA 95827-3098 ATSS Phone: 8-495-5600 TO: Antonia K. J. Vorster FROM: Camilla Williams Senior WRC Engineer Engineering Geologist DATE: 7 August 1992 SIGNATURE: SUBJECT: REVIEW OF DRAFT OPERABLE UNIT NO. I (OU-1) FEASIBILITY STUDY (FS) REPORT, DEFENSE DISTRIBUTION REGION WEST (DORM), TRACY, SAN JOAQUIN COUNTY I have reviewed the Draft FS Report. for OU-1 at the DDRW, Tracy site. The Draft FS Report was submitted on 9 June 1992 and was prepared by Woodward-Clyde Consultants for the Corps of Engineers. Overall , the Report is well organized and as with previous reports, Woodward-Clyde has done an excellent job of summarizing the information in tables and maps. These summaries help to expedite the review of the document and are valuable for future referencing. DDRW, Tracy should emphasize to the new contractor for the site-wide Remedial Investigation/Feasibility Study (RI/FS) the need to summarize data in tables. The Draft OU-1 FS Report evaluated seven treatment alternatives (Table 3.3-1) for the volatile organic constituent (VOC) ground water contamination: 1 . No action with the Interim Remedial Measure (IRM) at 120 gallons per minute (gpm) ; 2. Full design IRM at 340 gpm; 3. Pump and treat at 930 gpm using air stripping and vapor phase granular activated carbon (GAC) ; 4. Pump and treat at 930 gpm using GAC; 5. Pump and treat at 930 gpm using ultraviolet/ozone oxidation; 6. Pump and treat at 930 gpm using air stripping, vapor phase GAC and in-situ biological treatment; and 7. Pump and treat at 930 gpm using a bioreactor. The Draft OU-1 FS Report evaluated nine disposal alternatives (Table 2.4-2) : 1 . Discharge to a publicly operated treatment works (POTW); 2. Spray irrigation; 3. Storage and reuse for irrigation; 4. Evaporation ponds; 5. Discharge to surface water; 6. Spreading basin; 7. Injection trench; 8. Shallow ground water injection; and 9. Deep ground water injection. Based on my review of the Draft OU-1 FS Report, it appears that treatment Alternatives 3 or 6 with disposal by reinjection is preferred in the Report. My major concern with the Draft OU-1 FS Report involves the disposal of the treated ground water. In general , I do not concur with the expectation that all of the treated ground water will be able to be disposed of through shallow reinjection.