The Idarado Mine in Colorado's San Juan Mountains includes 11 tailing areas, numerous waste rock dumps, and a large number of underground openings connected by over 100 miles of raises and drifts. The tailings and mine wastes were generated from different mining and milling operations between 1975 and 1978. the Idarado Remedial Action Plan (RAP) was an innovative 5-year program developed for remediating the impacts of historic mining activities in the San Miguel River and Red Mountain Creek drainages. The challenges during implementation included seasonal access limitations due to the high altitude construction areas, high volumes of runoff during snow melt, numerous abandoned underground openings and stopped-out veins, and high profile sites adjacent to busy jeep trails and a major ski resort town. Implementation of the RAP has included pioneering efforts in engineering design and construction of remedial measures. Innovative engineering designs included direct revegetation techniques for the stabilization of tailings piles, concrete cutoff walls and French drains to control subsurface flows, underground water controls that included pipelines, weeplines, and portal collection systems, and various underground structures to collect and divert subsurface flows often exceeding 2,000 gpm. Remote work locations have also required the use of innovative construction techniques suchmore » as heavy lift helicopters to move construction materials to mines above 10,000 feet. This paper describes the 5-year implementation program which has included over 1,000,000 cubic yards of tailing regrading, application of 5,000 tons of manure and 26,000 tons of limestone, and construction of over 10,000 feet of pipeline and approximately 45,000 feet of diversion channel.« less