The French Gulch/Wellington-Oro Mine Site is located near the town of Breckenridge in Summit County, Colorado. Environmental contamination of surface water, groundwater, soil and sediment at the site resulted from mining activities dating to the 1880s. Site investigations have concluded that the underground workings (tunnels, adits, drifts, stopes and crosscuts) of the site constitute the largest source of metals loading to groundwater and surface water. An on-site seep, FG-6C, is the primary conduit of mine pool water into French Gulch. The surface water and groundwater remedy consists of the water treatment plant (WTP), which treats acid rock drainage (ARD) collected by pumping FG-6C. The WTP removes zinc and cadmium from FG-6C to improve surface water quality in French Gulch and the Blue River.

• Optimization Review: French Gulch/Wellington-Oro Mine Site Water Treatment Plant, Breckenridge, Summit County, Colorado (PDF)(63 pp, 3 MB, 2013, 542-R-13-013)