Colowyo Mine to conclude coal production in 2025, transitioning to full reclamation
(August 7, 2025, Westminster, Colo.) — As part of its long-standing commitment to responsible power and environmental restoration, Tri-State Generation and Transmission Association will transition to full reclamation of the Colowyo Mine, following the conclusion of coal production by the end of 2025.
To carry out this next phase, Tri-State has contracted with Kiewit Mining Group Inc., a company with extensive experience in mine reclamation and environmental stewardship. Kiewit's reclamation activities are scheduled to begin on or about Jan. 1, 2026.
“Safety and environmental responsibility have always guided operations at Colowyo Mine, and that commitment will continue through reclamation,” said Duane Highley, CEO of Tri-State. “Kiewit Mining Group Inc. brings a strong track record in responsible mine closure, and we’re confident in their ability to lead this important work.”
“We’re proud to bring our proven expertise in mine reclamation and environmental stewardship to the Colowyo Mine reclamation project and appreciate the trust Tri-State has placed in us,” said Jay Johnson, executive vice president of Kiewit Mining Group. “We look forward to leading this effort and recognize the value the current workforce brings. We are committed to executing the work safely and responsibly while supporting Colowyo’s skilled employees as we transition the site into its next phase.”
The Colowyo Mine was developed in 1978 and has been operated by Tri-State subsidiary Elk Ridge Mining and Reclamation, LLC since 2011. The mine currently employs more than 120 workers and will end coal production by the close of 2025. The transition to reclamation is a continuation of Tri-State’s focus on delivering reliable affordable and responsible power across the rural West.
About Tri-State
Tri-State is a power supply cooperative, operating on a not-for-profit basis, owned by and serving our electric distribution cooperatives and public power district member-owners in four states. Together with our members, we deliver reliable, affordable and responsible power to more than a million electricity consumers across nearly 200,000 square miles of the rural West. Visit www.tristate.coop .
About Kiewit
Kiewit is one of North America’s largest and most respected construction, mining and engineering organizations. With our roots dating back to 1884, our employee-owned organization operates through a network of subsidiaries in the United States, Canada, Mexico and Guam. Kiewit offers construction and engineering services in a variety of markets including transportation; oil, gas and chemical; power; building; water; marine; industrial and mining. Visit www.kiewit.com .
Contact
Lee Boughey, VP Strategic Communications, 720-670-6696, lee.boughey@tristategt.org
Teresa Shada, Kiewit Mining Group spokesperson, Teresa.shada@kiewit.com
Certain information contained in this press statement are forward-looking statements including statements concerning Tri-State’s plans, future events, and other information that is not historical information. These forward-looking statements are subject to a number of risks, uncertainties and assumptions, including those described from time to time in Tri-State’s filings with the Securities and Exchange Commission. Tri-State’s expectations and beliefs are expressed in good faith, and Tri-State believes there is a reasonable basis for them. However, Tri-State cannot assure you that management’s expectations and beliefs will be achieved. There are a number of risks, uncertainties and other important factors that could cause actual results to differ materially from the forward-looking statements contained herein.