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Ground Water FS Report -6- 16 September 1991 <br /> DDRW, Sharpe Site <br /> an automated ground water level measuring system is being used at the site, Sharpe <br /> should be using the wealth of historical ground water level data to evaluate the <br /> potential effects of season variations on the hydraulic system in order to <br /> optimize the effectiveness of the extraction system. Because of the existing <br /> historical data, the South Balloon Area extraction system should be used as a <br /> model for the development of the extraction systems in the North Balloon and <br /> Central Areas. <br /> GENERAL DISPOSAL <br /> 12. The Draft FS Report states that if water is disposed of in the same aquifer from <br /> which it was withdrawn, arsenic and selenium will not require removal , as the <br /> levels of these compounds in ground water are not considered to be high for the <br /> San Joaquin Valley (page 3-24) . This statement is incorrect and this issue is <br /> discussed in our identification of ARARs in the accompanying memorandum. <br /> Effluent from the ground water treatment systems which contain arsenic, nitrates <br /> and other inorganics may not be disposed of to ground water which has lower <br /> concentrations of each respective constituent. This may limit the alternatives <br /> available at the Sharpe Site for the disposal of the treated ground water. For <br /> example, considering that the 10-` cancer risk for arsenic is 0.03 µg/1 , this <br /> criteria may restrict Sharpe's land disposal options. In general , a waste may not <br /> be disposed of to land where the contaminant concentrations exceed background <br /> ground water concentrations. The Board considers the disposal to land of any <br /> treated ground water with elevated concentrations of any inorganics to be part of <br /> the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) <br /> Act. <br /> 13. Tables 3.2-2 and 3.2-5 of the Draft FS Report summarize the screening of <br /> technologies for remediation of VOC and arsenic-selenium contaminated ground <br /> water. These tables also summarize the different disposal options. The disposal <br /> alternative of discharge to the local Publicly Operated Treatment Works (POTW) was <br /> not retained as an applicable disposal alternative. The local POTW was not <br /> identified but the reason for the disqualification from continued screening is <br /> listed as an inadequate capacity. There is little to no benefit of disposing of <br /> the treated ground water to a nearby POTW, regardless of the available capacity, <br /> because it is already treated. <br /> 14. The Draft FS Report did not quantify the amount of ground water to be discharged <br /> from each treatment area and did not estimate the amount of ground water that can <br /> be discharged through each disposal alternative. The Report should provide <br /> estimates of the flows for each disposal alternative to insure that all possible <br /> discharge alternatives are considered. In addition, a cost comparison of all of <br /> the different disposal options may clarify which options may be the most desirable <br /> for the long-term remediation of the site. The Board continues to advocate <br /> reclamation/recharge over surface water disposal . We commend Sharpe on the <br /> existing reuse of the treated ground water effluent. <br /> 15. As part of the FS for the disposal alternatives, Sharpe conducted a survey of <br /> water users in the vicinity of the Sharpe Site (Section 5. 11.1) We commend Sharpe <br /> for conducting this survey. The list of contacted water users is primarily <br /> industrial . However, it is unclear whether Sharpe contacted any agricultural <br /> water users in the area of the Sharpe site. Although agricultural water use tends <br />