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• iii iiiiiiiniii iii • 5 ~t~i'E OF COLORADO DIVISION OF MINERALS AND GEOLOGY Deparlmenl of Nalu ra Resources 1313 Sherman SI . Ruum ?15 Denver, Colorado ri0'03 Phone: 130}) ri55-3557 FA% f:fU31 83"' 8105 REVISED MEMO DATE: July 29, 1997 (REVISED September 9, 1997) TO: Allen Sorenson f ~,-~" ~~~~~ DEPARTMENT OF NATURAL RESOUFZCES Roy Romer Governor lames 5. Lochhead Executive Dvenor Michael B. Long Division Direcmr FROM: Harry Posey RE: Review: Evaluation of the pper and Lower Tailings Ponds at the Bulldog Mine, Shepherd Miller, Inc. Report prepared for Homestake Mining Company; Permit M-77-215 From the captioned report I examined all of the geochemical characterization and attenuation tests pertaining to the potential for tailings in the upper and lower ponds to form acid rock drainage or release it to groundwater. I considered but did not evaluate the discussions of geotechnical controls on such releases. ARD, as discussed herein, addresses both acidic and metalliferous waters. The general conclusion of the report is that "there is very low potential for pore water from the tailings in the Upper and Lower Tailings Ponds to impact groundwater down gradient from these sites." This conclusion is based on both geochemical and geotechnical testing and considerations. Provided the hydrologic stipulations of this conclusion are supportable, I would concur with the general conclusion that there is very low potential impact to groundwater, and 1 would extend that conclusion to include surface water as well. However, I do not agree completely with the means by which this conclusion was reached, and would not want to see such tests applied generally at other sites in the future. For the record, this memo discuss those reservations. EVALUATION Mineralogy, ABA and XRD. The combined acid-base accounting tests, XRD, and petrographic analyses indicate that there is as much as 2% pyrite in the tailings and nil amounts of carbonate