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<br />Mr. Andre J. Douchane -2- April 9, 1993 <br />Battle Mountain Gold Company <br />contamination of ground water from leaks or discharges from <br />mine facilities has been detected during this period by monitor- <br />ing or other means, BMR will be responsible for instituting and <br />completing the remediation procedures approved in the permit. <br />While the plots of the plumes indicate that detectable amounts of a contaminant originating <br />from the toe of the failings facility, northeast and up hydraulic gradient from the collection <br />pond, could register in the existing monitoring well network in even less than nine years <br />when higher dispersivity values are employed in the modeling, a leak at this ex8ct point <br />would not necessarily be the only one to consider. Leaks from more remote locations under <br />the facility might not evidence themselves at this point for many years. In such cases, total <br />time required for the plume to move from the point of the leak untii detected by the <br />monitoring wells might easily exceed 15 years. As a result, the Division is currently inclined <br />to agree with Mr. Scott Mefford's suggestion (copy of Mefford's 1/29/93 letter attached) <br />that practical monitoring of leaks from the tailings facility •r,;ould ba better conducted <br />through installation of another monitoring well located between the collection pond and <br />tailings dam, and proposes the following condition to approval of TR-08: <br />2) BMR will, within 60 days of the approval of TR-08, instaii an <br />additional ground water monitoring well at a location acceptable <br />to the Division between the collection pond and the toe of the <br />tailings dam. This well will be drilled, logged, and completed in <br />a manner acceptable to the Division, and comparable to that <br />employed for wells ^.4-9 and M-12. Evidence demonstrs*.ing the <br />installation will be provided to the Division within 30 days of the <br />completion of the well. This well will be maintained and em- <br />ployed for ground water monitoring as approved in the permit <br />for wells M-9, M-12, and M-13. <br />Even by establishing a monitoring well at the toe of the tailings facility, its operation for the <br />estimated 9- to 15-year life-of-mine time span will apparently not be adequate to insure <br />detection of all potentially significant leaks from the facility. For example, if a IBak occurred <br />at the northeast end of the upper tailings pond immediately after use of the facility began <br />and continued for the life of the mine, evidence of such a leak might not reach a monitoring <br />well located at the toe of the tailings dam fcr over 50 years. A leak from areas ~vithin the <br />lower tailings pond might not register at such a monitoring well for over 20 years. Mainte- <br />nance of the ground water monitoring network for such periods of time does rat seem to be <br />a practical consideration hut, if such monitoring is not conducted, a significant release of <br />fluid from the tailings facility could conceivably go undetected until well after reclamation of <br />the site has been completed and the operator released from his responsibility. As a result <br />the Division proposes the following condition to the approval of TR-08: <br />3) BMR will submit, within 60 days following approval of TR-08, a <br />technical revision to the permit which, when approved, will <br />outline the manner in which BMR will demonstrate to the <br />Division's satisfaction the quality of ground water beneath the <br />