EA is supporting mine rehabilitation, geochemical investigation, and remediation to decrease acid mine drainage (AMD) from reaching a nearby river at this inactive copper, zinc, and gold mine. Our team is implementing an investigation of the adit and AMD discharge in preparation for rehabilitation work. EA prepared a UFP-QAPP, a HASP for both above- and underground work, a Technical Access Plan, Surface and Subsurface Mapping Plans, and a Soil and Water Chemistry Plan.

On behalf of EPA, EA is providing oversight of the Potentially Responsible Parties’ remedial activities and removal actions including 3 stream diversion projects, removal of 325,000 tons of contaminated sediment and mine waste, slope stabilization, construction of onsite repository for mine wastes, and characterizing sources of contamination from former mine adits.

EA operates and maintains the interim water treatment plant, which was constructed to control ongoing releases of metal-laden water from the Gold King Mine. Tasks include performing site operational monitoring and sampling, sludge management, pond maintenance, and seasonal cleaning of the conveyance systems.

EA is conducting a focused RI and providing community involvement support at this large, high-profile complex former mercury hard rock mining site. The RI is focused on providing an engineering evaluation and cost analysis for a non-time critical removal action to address portions of the Northwest Waste Rock Pile. The community involvement is focused on providing outreach and education regarding the fish consumption advisory for Clear Lake.

To facilitate the cleanup of this historical hard rock gold mine, EA performed a CERCLA RI, prepared engineering evaluation and cost analyses, and is currently completing the engineering design of remedial actions including construction of drainage ditches and waste consolidation/disposal. Continuing our efforts, EA is developing a pilot-scale system, using in situ biofiltration swales, to treat mine tailing seepage.

EA conducted an RI/FS at this 340-acre site and the accompanying abandoned smelter. Tasks included extensive environmental sampling and analysis, human health and ecological risk assessments, characterization of mine tailings and groundwater impacts, and associated contaminant transport. EA developed remedial alternatives, which included stabilization design for the tailings and provided agency coordination and community involvement.