Mine stope coverage cuts acid mine drainage

In 2005, the Animas River Stakeholders Group (ARSG), through the contracting capacity of the Colorado Division of Minerals & Geology (CDMG), contracted Frontier Environmental Services Inc. (FESI) to build a massive steel cover over the historic Pride of the West Mine stope, near Silverton, CO. FESI conducted the construction project from 27 June through 25 October 2005 in three overlapping phases. Phase I work focused on the installation of safety systems and site preparation to accommodate equipment, supplies and the placement of steel beams across the stope. Phase II consisted of placing 49 W12 × 65 steel beams weighing from 442 to 1,179 kg to span the stope opening. Phase III covered the completion of the steel structure of the beams and cross members by covering it with 6.35 mm steel plate. The completed cover will prevent the infiltration of surface waters, snow and avalanche deposits into the stope that accounts for most of the metals laden discharge from the lower mine adit.