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~ • iii iuiiiiiuiuiii • <br />STATE OF <br />MINED LAND RECLAMATION DIVISION =o <br />~ oF <br /> <br />Department of NaWral Resources ~ <br />; <br />e 'fi <br /> g <br />N <br />1313 Sherman St.. Room 215 y . <br />~ <br />Denver, CO 80203 ~ <br />~ <br />~ <br />303 866-3567 ~,g ~6 • <br />FA%:303 832-8106 <br /> Roy Romer, <br /> Governor <br /> Michael B. Long. <br /> Division Drtector <br />TO: Jim Pendleton <br />//y/ <br />FROM; Allen Sorenson <br />I <br /> ~ <br />RE: Time Required to Detoxify Existing Tailings, Battle Mounta~n Gold, San <br />Luigi Project, File No. M-88-112 <br />DATE: August 14, 1992 <br />In a memorandum to you dated August 10, 1992, attached calculatio~e indicated <br />that it would take 6.8 years to cycle one pore volume of water th ough the <br />existing tails at San Luigi. Those calculations were based on a m ximum <br />tailings thickneee of 60 feet, which was a number taken from the <br />pre-operational tailings deposition sequence estimate in the perm t <br />application. Since that time, Battle Mountain personnel on site t San Luigi <br />have provided me with information that allows an accurate determi ation of <br />maximum tailings thickneee at 68.5 feet. Hy utilizing this thick see, and a <br />hydraulic conductivity of 6E-06 CM/SEC for the tails, a cycle tim of 7.8 years <br />results (see attached calculations). <br />I have also done a calculation for pore volume cycle time utilizi q a hydraulic <br />conductivity for the tails of 1E-06 CM/SEC. This ie the permeabi ity that <br />desiccated tails will eventually attain. This calculation result in a cycle <br />time of 31.1 years. It ie my opinion that 7.8 years is a more re resentative <br />number, since obviously there will be no flow in desiccated tails <br />The effect of hydrodynamic dispersion, adsorption and other react one altering <br />solute concentrations, and heterogeneity of the tails, could affe t the amount <br />of time it would take to cycle water through the tails, and would in general, <br />tend to slow the process. <br />cc: Humphries <br />Oehler <br />Posey <br />Stevens <br />ACS <br />