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• MEMORANDUM • <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION <br /> 3443 Routier Road, Suite A Phone: (916) 361-5600 <br /> Sacramento, CA 95827-3098 ATSS Phone: 8-495-5600 <br /> TO: Antonia K. J. Vorster FROM: Camilla Williams <br /> Senior WRC Engineer Engineering Geologist <br /> DATE: 7 August 1992 SIGNATURE: Z�///[GGGci/Lt/GEGGOVY�/w <br /> SUBJECT: DRAFT PROPOSED PLAN FOR OPERABLE UNIT NO. 1, DEFENSE DISTRIBUTION REGION <br /> WEST (DDRW), TRACY, SAN JOAQUIN COUNTY <br /> I have reviewed the Draft Proposed Plan (PP) for Operable Unit No. 1 (OU-1) at DDRW, <br /> Tracy submitted on 10 June 1992. Some of my comments are the same as for the DDRW, <br /> Sharpe Draft PP. Major and minor comments are discussed separately below. <br /> Major Comments <br /> 1 . Disposal of the treated ground water through injection wells is considered a <br /> waste discharge to land. The use of additional injection wells for the <br /> discharge of the treated ground water must meet the substantive requirements of <br /> our Waste Discharge Requirements (WDRs) . The Interim Remedial Measure (IRM) at <br /> the site has an existing permit for the disposal of the treated ground water. <br /> The existing permit will be revised to include the expanded extraction, <br /> treatment and injection system. <br /> One of our concerns with an injection disposal system, is that pollutants <br /> extracted from one water bearing zone, or pollutants resulting from treatment, <br /> are not to be discharged into a different water bearing zone (receiving water) <br /> which is of better water quality than the treated effluent. Should this occur, <br /> the injected water would degrade the water quality of that receiving water. <br /> DDRW, Tracy must provide the documentation to demonstrate that degradation by <br /> other pollutants than volatile organic constituents (VOCs) will not occur with <br /> this method of disposal . <br /> 2. We are concerned that the Draft OU-1 PP confuses the terms "cleanup level " with <br /> "treatment standard" as evidenced by the definition provided for cleanup level . <br /> These terms are not interchangeable. The cleanup level is the contaminant <br /> concentration remaining in the aquifer at the completion of remediation; <br /> whereas, the treatment standard is the contaminant concentration in the <br /> effluent which is reduced by treatment. Normally, the treatment standard for <br /> VOCs is best available technology (BAT) , which can meet the detection limit of <br /> 0.5 micrograms per liter (µg/1 ) using Method 601 for analysis. <br /> 3. Numerical aquifer cleanup levels for all of the constituents of concern should <br /> be stated in the OU-1 PP. Article 5, Chapter 15 of the California Code of <br /> Regulations and State Board Resolution 92-49 require aquifer cleanup to <br /> background concentrations or the lowest concentrations for each individual <br /> pollutant which are technologically and economically achievable. In addition, <br /> the cumulative cancer risk must be considered in developing final aquifer <br /> cleanup levels. <br /> 4. Some of the alternatives include semi-annual monitoring for the majority of the <br /> duration of the remedial action. We do not concur with this proposal because <br />