Umetco Former Mine Site Wetlands
Hot Springs, Arkansas, United States
Creating a thriving aquatic habitat from an open-pit mine. From 1967 to 1985, Umetco conducted mining activities across 150 hectares of this 200-hectare property in the Ouachita Mountain ecoregion, resulting in low pH and mobilized zinc in the surface water. Acid rock drainage further degraded the water quality, and mine spoil areas and unimproved roads increased sedimentation in headwater streams. From 2015 to 2019, Umetco installed permanent, natural treatment systems to restore water quality and improved existing stormwater drainage to promote overland flow into lined, limestone riprap channels. This change limited water infiltrating into buried mine spoils and promoted conveyance of clean water to nearby streams, one such restored by adding cobble substrate and strategically placing downed trees to stabilize the banks and to create riffles and pools. The project team also engineered a unique, three-layer sediment cover in a 52-meter deep former mine pit lake, encapsulating sludge containing metal hydroxides and neutralizing pH in sediments and overlying water. Upland habitats restored with native wildflowers and grasses now provide food for a variety of pollinators and support ground-nesting songbirds. This project emphasized passive engineer ing solutions to improve water and habitat quality and to minimize maintenance. In response, terrestrial and aquatic biological communities are thriving.
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