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Ground Water FS Report -7- 16 September 1991 <br /> DDRW, Sharpe Site <br /> to be seasonal , the reuse for agricultural purposes may have a dual advantage in <br /> that it would alleviate the use of large agricultural supply wells which have been <br /> determined to have detrimental affects on the plume migration. <br /> In addition, other reuses of the treated ground water, such as for cooling water <br /> to nearby industry or for dust suppression for nearby development should also be <br /> considered by Sharpe. Less desirable disposal alternatives may be eliminated as <br /> more desirable disposal alternatives, such as industrial reuse, develop in the <br /> future. <br /> INJECTION WELLS <br /> 16. Section 4.3.3 discusses the Group C technology screening based on effectiveness, <br /> implementability and cost. Included in this group are the disposal options of <br /> spray irrigation, surface water discharge, evaporation pond with connector wells <br /> and water reuse. Injection wells, either shallow or deeper aquifer injection was <br /> not included in this group although injection wells had been retained in Tables <br /> 3.2-2 and 3.2-5 as disposal alternatives for the remediation of VOCs and arsenic- <br /> selenium contaminated ground water. The Report does not discuss why injection <br /> wells were not included in the Group C evaluation. <br /> 17. It is unclear why injection wells were not retained as a viable disposal <br /> alternative when gravity feed connector wells with a direct discharge to the <br /> aquifer were considered as part of a retained disposal alternative. The proposed <br /> connector wells appear to be similar in purpose to injection wells. This apparent <br /> discrepancy needs to be clarified. <br /> 18. It is unclear why injection wells were not considered for further evaluation in <br /> Section 4.3.3 when shallow and deeper aquifer injection are being employed at <br /> nearby facilities. DDRW, Tracy has recently installed an IRM for the cleanup of <br /> the VOC contaminated ground water which uses shallow aquifer injection for <br /> disposal . Oxychemical , in Lathrop, has been discharging of treated pesticide <br /> contaminated ground waters through deeper aquifer injection for several years. <br /> Data from these injection systems should be available to help determine if aquifer <br /> reinjection is feasible at the DDRW, Sharpe Site. Sharpe needs to reconsider <br /> aquifer reinjection as a viable disposal alternative for the treated VOC <br /> contaminated ground water. <br /> 19. Section 5.1.1 lists the federal action specific ARARs. Page 5-3 discusses the <br /> Underground Injection Control (UIC) program in the federal regulations. This <br /> section includes discussion on Class I and IV wells but does not include <br /> discussion on Class V wells. Treated ground water will not be hazardous and <br /> therefore, injection wells used for the purpose of the disposal of treated ground <br /> water are classified as a Class V well . This section needs to be revised to <br /> consider Class V wells. <br /> EVAPORATION POND WITH CONNECTOR WELLS <br /> 20. Evaporation ponds are included in Tables 3.2-2 and 3.2-5 as a potential disposal <br /> alternative for treated ground water. However, in Table 3.2-2, evaporation ponds <br /> are not retained as a disposal option for the remediation of VOC contaminated <br /> ground water but are retained as a disposal option for the remediation of arsenic <br />