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• <br /> Treated Water Disposal Evaluation -3- 7 January 1992 <br /> Marley Cooling Tower Company <br /> a. The Table indicates that injection, either into the intermediate or <br /> deep zones, may require additional treatment to meet Drinking Water <br /> Standards (DWS) . If the effluent is injected, additional treatment may <br /> be needed to prevent scaling, but should not be needed to meet the DWS. <br /> Currently, Marley is treating the ground and storm waters to <br /> concentrations which are equivalent to or less than the Primary and <br /> Secondary DWS. These concentrations are established as the effluent <br /> limits in the WDRs No. 88-124. For example, the Primary DWS for <br /> arsenic is 50 micrograms per liter (µg/1 ) whereas the effluent limit <br /> in the WDRs is 10 µg/l (to protect aquatic life) . The installation of <br /> an additional treatment unit to meet the DWS should not be needed for <br /> this reason. <br /> b. The Table indicates that compliance with Proposition 65 (Prop 65) may <br /> be required for surface water discharges and for both the intermediate <br /> and deep zones injection disposal options. Prop 65 may only be <br /> applicable if the contaminant concentration exceeds the Prop 65 Water <br /> Quality Criteria for that particular contaminant and if the injected <br /> water is into a unit which has been established to have background <br /> concentrations below the respective Prop 65 Regulatory Level . <br /> The only contaminant of concern currently monitored under the WDRs, <br /> which has an established Prop 65 concentration, is arsenic. The Prop <br /> 65 regulatory level is currently 5 µg/l (although 0.3 µg/1 is <br /> proposed) . The effluent limit in the WDRs is 10 µg/l and the Primary <br /> DWS is 50 µg/l . In addition, arsenic has been reported to be naturally <br /> occurring in some of the different water bearing zones in the Central <br /> Valley. Therefore, Prop 65 compliance may not be applicable for <br /> injection as a disposal option if the background concentrations exceed <br /> the Prop 65 levels. However, as with any disposal alternative, there <br /> should be no degradation of the water quality. <br /> c. The Table states that there may be a slight chance of public exposure <br /> to residual contaminants in drinking water extracted from public supply <br /> wells if the treated water is injected into the deep zone. It is <br /> unclear how residual contaminants may impact public supply wells when <br /> the water is treated to concentration equal to or below the Primary <br /> DWS. <br /> d. The Table states that normal risks would be anticipated with the <br /> construction of the force main for the intermediate and deep zone <br /> injection options. However, on Page 3-2 of the Evaluation Report, it <br /> states that the existing force main is capable of handling up to 1000 <br /> gpm. The Evaluation Report also indicates on Pages 3-2 to 3-3 that the <br /> injection rate for both intermediate and deep zone injection would be <br /> based on 500 gpm. This discrepancy needs to be resolved. <br /> e. The Table indicates that even with injection, the NPDES permit would <br /> need to be revised. This implies that discharge of the treated water <br /> to the Canal would be needed for those periods when both wells may need <br /> to be shut down for maintenance. However, Marley should consider other <br /> backup disposal options, such as to land or other reuse disposal <br />