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John Schroeter • - 3 - 14 November 2006 b. The water balance indicates the maximum storage requirement is 0.38 ac-ft but the proposed pond will provide .1.41 ac-ft of storage. Review of the average powerhouse effluent flow rates indicates higher flow rates occurred in April 2004 through July 2004. If higher flow rates are anticipated to occur in the future, please change theassumptions in the water balance and resubmit it. 9. With regard to the use of the percolation pond to dispose of the wastewater, please address the following: a. Please provide all test results of the soil used to determine the cation exchange capacity described in the RWD. The information should include the sample collection techniques, test method, and analytical results b. Provide an estimate of how long the percolation pond can be operated before waste constituents reach a concentration that results in groundwater degradation. How will the pond be managed to prevent groundwater degradation. For example, will soil be excavated and hauled to a landfill for disposal? c. Section 7.3 of the RWD discusses the ability of the soil to adsorb copper. The RWD states, "The results show that the maximum amount of dissolved copper that can be taken up by the soil is approximately 130 grams per kilogram." Converting the units g/kg to mg/kg indicates a soil concentration of 130,000 mg/kg is possible. The following paragraph in the RWD states appropriate objectives for the soil beneath the proposed pond is the EPA industrial soil Preliminary Remediation Goal (PRG) (41,000 mg/kg). The calculated maximum soil concentration of copper (130,000 mg/kg) is more than three times the EPA PRG for industrial soil. The RWD also describes the surrounding area as undeveloped rural land so it is unclear why a PRG for industrial soil is considered appropriate.. For land discharge, the water quality limit for copper in groundwater is 170 ug/L. That would be considered the least stringent water quality limit. The most stringent water.quality limit would be the background concentration of copper in groundwater. d. The RWD does not present an antidegradation analysis and the PRG levels may not be protective of groundwater quality. Please address the potential for groundwater degradation; the analysis should address all waste constituents and the possibility that evapoconcentration of pond water will degrade groundwater quality. 10. The analysis should include a determination of the possibility wastewater could be classified as designated waste as defined by California Water Code Section 13173. If the discharge could result in groundwater quality degradation, the Discharger must provide documentation that any water quality degradation is consistent with the State W:\S,rtMObdenTSan allovMd-