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y <br /> Draft Final FS Report and PP Memo -2- 12 November 1992 <br /> DDRW, Tracy <br /> standards (or effluent limits) because the numbers for each constituent are the <br /> usually the same. <br /> Aquifer cleanup levels for dieldrin, carbon tetrachloride and chloroform should <br /> not be established for OU-1 at DDRW, Tracy because either the source of the <br /> contamination is unknown or there are confirmed off-site sources (i .e. , the <br /> contamination may not be attributable to waste discharges from the depot) . <br /> However, effluent treatment standards must be established for dieldrin, carbon <br /> tetrachloride and chloroform because these contaminants are present in the <br /> ground water and the discharge of the treated ground water must not degrade the <br /> quality of the receiving water. <br /> In general , we concur with the proposed aquifer cleanup levels for 1, 1- <br /> dichloroethylene (DCE) at 6 µg/l , PCE at 0.7 µg/l and TCE at 2.5 µg/l . <br /> However, the effluent treatment standards should be based on best available <br /> technology (BAT) because it is available and cost effective. Therefore, except <br /> for dieldrin, the treatment standards for the VOCs should be 0.5 µg/l , which <br /> reflect BAT. The effluent treatment standards for other VOCs and dieldrin <br /> should be BAT or background. We have attached hand written corrections to a <br /> copy of Table 2.2-6 to reflect these changes. <br /> The confusion between the aquifer cleanup levels and the effluent treatment <br /> standards must be clarified in Table 2.2-6 by inserting the terms "aquifer" and <br /> "effluent" in text references. With respect to the effluent treatment <br /> standards, numerical limits based on BAT will be established in either the Waste <br /> Discharge Requirements (WDRs) or Substantive WDRs for discharges to land of the <br /> treated ground water. <br /> 3. We have several comments on the ARARs tables (Tables 2.2-3 and 2.2-4) . Our <br /> comments are presented as hand written comments on copies of the Tables and are <br /> attached to this memorandum. Our more significant comments are briefly <br /> discussed below. <br /> a. The Safe Drinking Water Act is applicable because the ground water is a <br /> source of drinking water. The Rose residence on Banta Road uses a domestic <br /> well for drinking water and has been contaminated by TCE. <br /> b. National Secondary Drinking Water Standards are ARARs. The Basin Plan for <br /> the Central Valley Region establishes water quality objectives including <br /> narrative standards to protect beneficial uses, such as taste and odor <br /> objectives. The Basin Plans are adopted for each Regional Board in <br /> compliance with the Water Code and the Clean Water Act. <br /> Table 2.2-5 lists the state and federal drinking water standards for the <br /> chemicals of concern identified in the Risk Assessment. We have provided hand <br /> written corrections to a copy of this Table. <br /> 4. The evaluation of disposal alternatives does not appear to be thoroughly <br /> investigated. The Draft Final FS Report still indicates the recommended <br /> disposal alternative for the treated ground water is by installing 31 new <br /> injection wells. Although we approve of reinjection as a disposal alternative <br /> for treated ground water because of the restoration to the resource, reinjection <br />