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~ III IIIIIIIIIIIIIIII ~ <br />STATE OF <br />MINED LAND RECLAMATION DIVISION <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver. CO 80203 <br />303 866-3567 <br />Fn x: 303 832-8106 <br />DATE: August 25, 1992 <br />pF' COQ <br />~~ .99 <br />r ^® <br />•~ <br />~ re76 ~ <br />Foy Romer. <br />Governor <br />Michael B. Long, <br />Division Director <br />TO: Jim Pendleton 'nI <br />FROM: Allen Sorenson f'~ <br />RE: Comments on Long-'T`erm Detoxification of the Battle Mountain Gold <br />Tailings <br />There are two items in your memorandum that you may wish to modif}~ for the sake <br />of absolute accuracy. Both items are rather minor. <br />1. The statement that "7.8 years would be required to compl tely purge <br />the pre-July, 1992 liquid from the tailings" is not tots ly accurate. <br />The figure 7.8 years ie based on the average linear velo ity of liquid <br />through the tails. By definition, a portion of the liquid will be <br />travelling at a velocity lower than the average velocity, and will <br />take longer than 7.8 years to migrate through the pile. Also the <br />calculations that yielded the 7.8 year figure ignore the affects of <br />hydrodynamic dispersion, adsorption, and other reactions altering <br />solute concentrations which would tend to retard the pro rese of the <br />contaminant front through the pile. I think that 7.8 ye re ie a good <br />figure to use in the frame-work of your memo, but I woul delete the <br />word "completely" from the sentence. <br />2. The diagram included in your memorandum shows the standi g liquid pool <br />in direct contact with the drainage layer. By design, t e pool should <br />be resting entirely on deposited tailings. This has the beneficial <br />affect of limiting the amount of water that enters the d ainage layer <br />by "short-circuiting" around the edge of the tails, but 'e detrimental <br />for tailings detoxification in that the component of the pile that is <br />not under ponded water does not have a driving force to 'nduce the <br />flow that will purge contaminated interstitial water fro the tails. <br />Enclosed is the recommended modification to the diagram. <br />Also note the typo on page three of the memo where I have croesedlout the word <br />"liquid". <br />