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Tailings andMine Waste 98O 1998 Balkema,Rotterdam,ISBN 90 54 10 922X /ze Stability of water treatment sludge,Climax Mine,Colorado Part I: Chemical and mineralogical properties R.Craig Ford Cyprts Climas Metals Company.Tempe.Ariz.,USA John L.Clapper&Bryce R.Romig Clima.r Molybdenran Company Climar Mine,Colo.,USA ABSTRACT: Ponds have been used as reactors for lime neutralisation water treatment at the s..�' Climax Molybdenum Mine since 1977, with sludge disposed of in two of the three tailings t-� impoundments at the site. Proposed changes to the water treatment process resulted in a program to determine the long-letm geochemical stability of sludge in the Mayflower impoundment. Sludge samples were collected from four locations in the Mayflower impoundment to evaluate the spatial variability of water treatment products throughout the water pool. Bulk chemical analyses, static acid generation tests,X-ray diffraction and electron microprobe analyses were perfotmed, and indicate that the samples can be subdivided into those dominated by water treatment sludge and those with a significant tailings component,derived from the underlying impoundment. 1 INTRODUCTION The long-term geochemical stability of sludge products is an important issue for mines that have active water treatment processes, and has recently been the focus of the Canadian Mine Environment Neutral Drainage(MEND)program(Zinck 1997;Zinck et al. 1997). Active water treatment at mine sites is generally accomplished by chemical neutralisation involving lime, sodium hydroxide or ammonia,and produces low-to medium density sludge depending on the specific process. At the Climax Molybdenum Mine,ponds have been used as reactors for lime • neutralisation since 1977,with sludge disposed of in two of the three tailings impoundments at the site. Water treatment is required to reduce the concentrations of specific elements to meet discharge requirements into Tenmile Creek. Proposed modifications to the water treatment process resulted in a project 10 determine the long-term geochemical stability of sludge in the Mayflower impoundment. This paper describes the chemical and mineralogical properties of the sludge samples;a companion paper(Ford et al.1997,this volume)describes their leaching characteristics. 2 DESCRIPTION OF WATER TREATMENT AT THE CLIMAX MINE The Climax Mine,located IJ miles north of Leadville,CO in the hear of the Colorado Rocky Mountains,exploits a world-class molybdenum(Mo)orebody(Figure 1). The Climax property covers an area of approximately 14,300 acres in Summit,fake,Eagle and Park Counties. The site is at the summit of Fremont Pass(11,J 18 feet above sea level),straddling the Continental Divide at the headwaters of the Arkansas River, Eagle River and Tenmile Creek drainages. These drainages are important fisheries and recreational waterways,ss well as sources of domestic water for downstream own. The mine property receives more than 25 inches of precipitation annually, approximately 74%(271 inches)of which occurs as snow. 645