Laserfiche WebLink
Mr. Tom Kaldenbach <br />March 8. 2013 <br />Page 2 <br />and if that upper end point of the confidence interval is less than 3 mg dissolved U(natural) <br />per Liter, then the pumping of the mine pool will cease. In the equation X is the mean of <br />the samples taken, a is the standard deviation of the samples taken, and n is the number of <br />samples collected. For example, if over a period of time the average concentration of six <br />mine pool samples is 2.0 mg /L, and the standard deviation of the samples is 0.5, then the <br />upper confidence limit would be 2.0 + 1.96 (0.5)/sqrt(6) or 2.4 mg /L. <br />The above assumes a random, well -mixed mine pool. If there is a systemic variation then an <br />amended proposal will be developed based on further observations. <br />27. (This comment is intended to address comment 3 from DRMS's August 29 letter.) <br />Returning reverse osmosis (RO) concentrate to the water in the underground workings of a <br />uranium mine, while performing in -situ biologic treatment on the water, is a unique <br />approach to mine water treatment. The outcome of this approach may be unpredictable. <br />Please provide a description of <br />a. Previous barrel testing of in -situ biologic treatment (see Section 10.2.2 of <br />Schwart_walder Mine Hydrologic Evaluation of Mine Closure and Reclamation, <br />2007), <br />Attachment 1 to this letter is the draft February 2002 Shepherd Miller report. This <br />draft report was prepared as part of a program to explore remedial treatment options <br />to address the possibility of mine pool water rising to an elevation where discharge <br />from the Steve Portal was possible. Cotter evaluated the risk associated with mine <br />pool water leaking from the Steve Portal and connecting to Ralston Creek through the <br />waste rock in the valley between the mine and the creek, and concluded construction <br />of bulkheads in the Steve and Pierce adits, to prevent such an occurrence, was the <br />preferred long term solution. It should be noted that this is a draft report that was <br />never finalized. <br />In addition to the practical technical description of the tested remediation process, the <br />following two specific conclusions can be derived from the draft report: <br />I . In the presence of adequate quantities of nutrients and native micro- <br />organisms in the mine pool. uranium and other heavy metal concentrations <br />significantly decrease in a relatively short time frame (see Figures 7 and 10 <br />in the report); and <br />2. The interaction of added nutrients and native micro- organisms created no <br />adverse effects in the mine pool water. <br />b. A plan for conducting pilot -scale testing of disposing RO concentrate and in -situ <br />biologic treatment inside the pumped down mine pool prior to full -scale disposal <br />and treatment inside the pumped down mine pool, <br />