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<br />Letter to Alan D. Cox - 2 - September 16 1997 <br />If the tailings were to drain, the reaction of sulphide minerals with oxygen could be accelerated <br />and may result in pore water and seepage degradation beyond that measured and reported by <br />Shepherd Miller. Depending on the level of seepage degradation that may occur if the tailings <br />drain, it is possible that ground water resources may be adversely impacted. It should be noted, <br />however, that the tailings could only drain in response to the infiltration rate being less than the 6 <br />inches per yeaz estimated in the Shepazd Miller report, and a lower infiltration rate would result <br />in a lower seepage rate from the tailings impoundments. <br />Although the Division has reservations about the finding in the Shepherd Miller report that the <br />tailings will remain saturated or neazly saturated, it would be unreasonable to require monitoring <br />over the several decades it may take to determine the ultimate moisture content of the tailings. <br />The magnitude of seepage impacts to ground water is dependent first on the amount and rate of <br />seepage movement, and second on the chemical reactions and physical dilution processes that <br />take place as the seepage moves. The preponderance of technical information presented in the <br />Shepherd Miller report leads to the conclusion that the magnitude of seepage impacts to ground <br />water that may be caused by the Bulldog tailings impoundments will be minimal. Since this is <br />the determination required by the Mined Land Reclamation Act at section 34-32-116(7)(g), the <br />Division can release Homestake Mining Company from further responsibility under the ground <br />water protection regulations of the Colorado Mined Land Reclamation Boazd. This release of <br />responsibility will be finalized once the minor questions posed in Dr. Posey's memo aze <br />adequately addressed. <br />If you have any questions, please contact me. <br />Sincerely, <br />~'7 - ~ <br />Allen C. Sorenson <br />Reclamation Specialist <br />enclosure(s) <br />cc: Harry Posey, DMG <br />Steve Shuey, DMG (w/enclosure) <br />Bruce Humphries, DMG <br />c:\._~bulldog.wpd <br />