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Whetsto"e <br />Associates Technical Memorandum <br />Detailed engineering design and feasibility studies will be performed for the PRB, if this alternative <br />is selected for long-term sustainable treatment of groundwater at the Schwartzwalder site. The <br />studies will include predicted concentrations of iron in solution and likely locations and mineralogy <br />of precipitates downgradient of the PRB. <br />24) The EPP still contains no provision for management of the mine pool. Under Hard Rock <br />Rule 6.4.20(6)(a), the Operator must specifically describe measures to be taken to prevent any <br />unauthorized release of pollutants to the environment, including adequate reclamation and closure <br />practices for toxic or acid-forming materials. The mine pool has been designated as an <br />Environmental Protection Facility for containment of toxic forming materials under the provisions <br />of Hard Rock Rule 1.1(15). The Division is very concerned about the possibility of mine pool water <br />migrating downgradient along ground water conduits and discharging to Ralston Creek. The <br />Division rejects the Operator's assertion that, since no chemical anomalies are measurable in the <br />creek at present there is no communication with the mine pool. The cone of depression that has been <br />in existence around the underground mine workings needs sufficient time to recover before a <br />hydraulic communication can be established. Operator must include long term plans in the EPP to <br />respond to the possibility of mine pool contaminant migration. This requirement is in addition to the <br />short term directive indicated at item number 2 under the section labeled "Corrective Action - <br />Technical Revision". <br />The technical justification for not pumping the mine pool to 500 feet below the Steve Level was <br />provided in a June 25, 2010 memorandum prepared by Whetstone Associates. The reasons for not <br />pumping down the mine pool are as follows: <br />• If minor amounts of water from the mine pool are exiting the mine, the water would <br />reach the alluvium and fill where it will be collected at Sump 1 and treated in the new <br />water treatment system. <br />The Operator and its contractors installed a new water treatment system to capture and treat <br />groundwater in the alluvium and fill. Groundwater in the alluvium reports to Sump 1, and if <br />not intercepted at the sump, the water reports to the creek. The Operator began actively <br />treating groundwater in the alluvium in a 50-gpm ion exchange system on July 2, 2010. <br />Beginning July 30, 2010, groundwater from Sump 1 is being pumped to a 100-gpm ion <br />exchange system located in the water treatment plant. The treatment system is sized for a <br />nominal flow rate of 100 gpm, with a maximum design flow rate of 200 gpm, and will be <br />capable of treating water collected from the alluvium and fill at Sump 1 and other locations. <br />• Studies have shown that the mine pool is not affecting Ralston Creek via the Schwartz <br />Trend. <br />Studies have shown that the mine pool is not currently affecting Ralston Creek via the <br />Schwartz Trend. <br />• Pumping down the mine pool would result in increased oxidation and mobilization of <br />contaminants within the mine pool, reversing the current trend of declining uranium <br />concentrations. <br />Concentrations have decreased 45% over the last 7 1/2 years. There is no reason to believe <br />this trend will not continue, and if it does continue, water quality in the mine could reach <br />4109C.100731 11