ABSTRACT
Hard-rock mining and associated ore processing since the mid-1800s near Leadville, Colorado have contaminated the Arkansas River with lead and other trace elements. Miners worked the watershed extensively for gold, silver, copper, zinc, manganese, and lead causing extensive contamination. Deposits from placer mines and underground mines have disposed large volumes of mining wastes into the Arkansas River. For instance, the 3.4-mile-long Yak tunnel, built between 1895 and 1909, drained numerous underground mines and discharged approximately 210 tons of metals per year into the Arkansas River basin (Environmental Protection Agency [EPA] California Gulch Superfund Web site). Additionally, mercury was used to extract gold from the ore by amalgamation.
