Laserfiche WebLink
'• Page 3 • • <br />• Messrs. Pendleton and Stevens <br />Colorado Division of Minerals and Geology <br />January 10 1996 <br />Likewise, using the maximum hydraulic conductivity (2.1 x 10~ cm/sec), the seepage I <br />velocity is 1.5 or 565 ft/yr. At this seepage velocity, It would take \ <br />approximately 2.5 years to r ach the first downgradient monitoring well. <br />As these data indicate, if there is a high permeability zone beneath the tailings facility <br />(as hypothesized by the Division), and an assumption is made that fluids can escape <br />in sufficient volume to create saturated flow, the travel times would be relatively short <br />(2.5 to 11.8 years). <br />In summary, if the Santa Fe Formation exhibits relatively low permeability, as the data <br />base shows, there would be minimal loss of fluids, and these fluids would not even <br />reach the ground water table. If a higher permeability zone does exist beneath the <br />tailings facility, and sufficient fluids are lost to create saturated flow (as hypothesized <br />by the Division), the time frame for observing these fluids would be well within the <br />monitoring time frame for the project (a fluid head was imposed on the tailings facility <br />in 1991, therefore, almost five years of the travel time frame has already elapsed). <br />We believe that this analysis shows that a 8-year monitoring period after closure is all l I <br />,~ `~ that is warranted, using the existing monitoring well system. I <br />We believe that it would be useful to convene a followup meeting to discuss the <br />issues described herein once you have had a chance to review this letter. We are <br />currently working to address the remaining Phase 2 issues, and that response will be <br />sent to you under separate cover in the near future. <br />In the meantime, if you have any questions regarding this analysis, please feel free to <br />give us a call. <br />Very truly yours, <br />Anne C. Baldrige <br />Director of Environmental and <br />Governmental Affairs <br />ACB/pk <br />enclosures <br />w Sally Hayes <br />Dan Robertson <br />Bruce A. Lytle <br />960110D <br />