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Henderson Mill 1041 permit approved; company to build treatment plant sized for surplus process water
Summary
Commissioners approved a 1041 permit for Climax (Henderson Mill) to construct a water-treatment plant that will treat surplus process water and discharge to the Williams Fork River under a final CDPHE permit; construction to begin this spring with discharge planned after project completion.
The Grand County Board of County Commissioners on March 4 approved a 1041 permit allowing Climax Molybdenum Company(Henderson Mill) to construct an on-site water-treatment plant at the mill area in Grand County.
Company managers and their consultants told commissioners the project is designed to treat surplus process water that accumulates across the mill/tailings circuit. The proposed facility will treat up to the design flow outlined in the companymaterials (approximately 600 gallons per minute peak processing capability cited in the application) and would discharge treated effluent into the Williams Fork River through an existing pipeline and pump-station outfall. The Colorado Department of Public Health and Environment issued a final discharge permit for the project on the Friday before the hearing; county staff and the independent technical consultants who reviewed the application concluded that the CDPHE permit meets the countycriterion for water-quality review.
Hendersonenvironmental manager Miguel Hamra and mill manager Jeff Nagler explained the treatment process is a high-density-sludge system that raises pH and oxygenates water so metals precipitate and are removed by settling and filtration. Grand CountyPublic Health and the countyconsultant team reviewed sampling, limits and monitoring. Ashley Benbenek of the Northwest Colorado Council of Governments, who assisted county staff, told the commission the permit contains routine monitoring conditions, including weekly sampling for a broad parameter list and continuous flow and temperature monitoring at the outfall.
Commissioners asked about long-term obligations. Company representatives said the plant is the first-phase part of a broader water-management strategy: it is sized to address expected surplus during current operations and transitions (the company estimated initial discharge capability starting after construction completion), but future closure-phase treatment needs would require a larger system. Construction work is expected to begin this month with phased activity through 2027; the company expects to mobilize late March/early April and said operation and initial discharge are expected once construction and commissioning are complete (projected mid-to-late 2027 under current schedule).
Public comment was limited and favorable; no regulatory objections were filed. Commissioners voted to approve the 1041 permit, agreeing with staff that the final CDPHE permit satisfied the countywater-quality criterion and authorizing staff to prepare the formal 1041 resolution for signature.
Why it matters: the Henderson Mill project is intended to reduce operational risk at the mill and tailings facility by giving the operator a route to treat and safely discharge surplus water under state permit standards. Commissioners emphasized public safety and regulatory oversight; the approved permit requires rigorous monitoring and reporting to the state and the county.
Next steps: county staff will prepare the formal resolution and put the final permit on the county file; company representatives said they will continue pre-construction procurement and mobilization and will coordinate any required county inspections and follow-up reporting.
