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999 STATE OF COLOMDO <br /> DIVISION OF MINERALS AND GEOLOGY <br /> of <br /> Department o1 Natural Resources <br /> 1313 Sherman St.,Room 215 <br /> Denver,Colorado 80203 <br /> Phone:(303)8b6-3567 <br /> FAX:(303)832 8106 <br /> DEPARTNIEN T OF <br /> NATURAL <br /> May 6, 1998 RESOURCES <br /> Roy Romer <br /> Governur <br /> TO: Chris Kamnikar <br /> lames 5 Eochheza <br /> E,ecunae Dneclor <br /> FROM: Harry Posey ik n B.E°nR <br /> Dv,vie,on Director <br /> RE: Proposal to BLM to Modify Plan o perations, Joker Mine, Moffat County <br /> The captioned proposal is contained in the April 29, 1998 letter to BLM, Craig, Colorado. <br /> Although the proposal refers to correspondence from DMG, I would not consider the letter to be <br /> a response to DMG regarding any outstanding issue covered in the letter. <br /> The letter presents a table representing concentrations of various constituents of an SPLP <br /> leachate or rinsed tails. These leachate results differ from previous results because the rinsing <br /> procedure was apparently more rigorous than the one previously used. All of the concentrations <br /> appear to be lower than those reported in earlier submittals, except manganese (Mn). <br /> Mn concentration in the new (April 29) leachate test is 0.321 mg/L. I assume this is a <br /> representative sample of the leached, rinsed tailings. This Mn concentration is higher than the <br /> secondary standard for drinking water, which is 0.050 mg/L, and below the health advisory of <br /> 1.6 mg/L (see pamphlet attached). The secondary standard represents the concentration above <br /> which Mn imparts a foal taste to the water; the health advisory represents the level above which <br /> long term consumption is not advised. At issue is whether manganese of this concentration has <br /> the potential to offend the ambient groundwater condition, the drinking water standard, or the <br /> health advisory. <br /> This letter along with the operator's previous submittals (December 19, 1997 and January 28, <br /> 1998) and the Division's letter of January 9, 1998, collectively indicate that the nearest drinking <br /> water well is about 5 miles from the proposed tailings disposal site. I do not know how close the <br /> disposal site is to the water table, but presume from maps and conversations that it is greater than <br /> 50 feet. From the tailings storage area to the groundwater or to the first downgradient use point, <br /> dilution can be anticipated; the amount of dilution cannot be known without further knowledge <br /> of the groundwater level and local hydrology, but considerable dilution or mixing can certainly <br /> be anticipated. Attenuation through precipitation as an oxyhydroxide, either en route to the <br /> groundwater or within the tailings pile itself, might be anticipated for a slow moving fluid, but <br /> should not be anticipated for slug flow from fresh tailings. <br />