Laserfiche WebLink
<br />MINED LAND RECLAMATION DIVISION <br />Department of Natural Resources <br />1313 Sherman St., Room 275 <br />Denver, CO 60203 <br />303 666-3567 <br />FAX: 303 1332-8 7 06 <br />DATE: May 9, 1990 <br />STA~ OF COLORADO <br />O4. C~[p <br />~W _., y <br />Nom/ ~. \~`~f$ <br />• ~~~)))• <br />~ re 76 ~ <br />Roy Romer, <br />Gwemor <br />Fred R. Banta. <br />Division Direolor <br />T0: Gregg R. Squire <br />FROM: John T. Doerfer <br />RE: Hydrologic and Geochemical Adenuacy Review, Hunter-Bates Mine, <br />Central City Consolidated Mining, File No, M-90-041 <br />Exhibit C - Mining Plan <br />1, Waste rock is proposed to be backstowed in the underground workings and <br />also placed on an existing waste rock dump. The dump is located about <br />lOD feet from Gregory Gulch, The sulfide nature of the ore indicates the <br />waste rock may be acidic. Although the ratio of waste rock to ore is <br />small, what amount of waste rock is expected to be placed on the existing <br />dump? In accordance with Rule 6.1(4), what measures will be taken to <br />insure that all acid-forming ar toxic-producing materials that have been <br />mined will be handled in a manner that will protect the drainage system <br />from pollution? <br />2, The mill as proposed will include a final flotation cleanup circuit to <br />depress pyrite. Please describe the method and reagents to be used in <br />the final cleanup circuit. <br />3, The tailings are described on page C-2 as to be essentially free of all <br />acid-generating sulfide minerals. Is this statement based on test data <br />or a characteristic of the milling process planned to be used? Please <br />provide any testing data which may have been collected to date. If not <br />available, a representative sample of tailings solids and decant solution <br />should be collected and analyzed for acid-base potential, pH, Ph, Zn, Ct3, <br />Cd, As, Ni, Ag, Al and Mn, Dissolved metals should be run on the liquid <br />fraction. Results should be provided within 120 days of the initiation <br />of milling, <br />4, No ground water impacts are projected to occur at the Golden Gilpin <br />mi1'I. This would be the case if water discharged from the mill is of <br />comparable quality to existing ground water or there is nn percolation of <br />water from the tailings disposal area into the local around water table. <br />Please provide any information on existing ground water Duality, expected <br />quality of the tailings leachate prior to treatment, permeability of the <br />tailings disposal area, or other information used to substantiate the <br />conclusion drawn that no impact is expected to occur, <br />