The coal-fired Nucla Station, which is owned and operated by Tri-State Generation and Transmission Association, will be retired under an agreement with the Colorado Department of Public Health and Environment, U.S. Environmental Protection Agency, WildEarth Guardians and the National Parks Conservation Association as part of revisions to the Colorado regional haze State Implementation Plan (SIP).
The 100-MW, coal-fired Nucla Station, which is located in Nucla, Colorado, will be retired by Dec. 31, 2022. The power plant will have more stringent limits on NOx emissions beginning in 2020. The nearby New Horizon Mine, which supplies coal to Nucla, will cease coal production with the retirement of the station. Reclamation efforts at the mine will continue for a time after that.
Additionally, an agreement by the owners of Craig Station Unit 1, regulators and the environmental groups will retire the 427-MW Unit 1 at the three-unit, coal-fired Craig facility in Craig, Colorado, by Dec. 31, 2025. The agreement only affects Unit 1 at Craig Station. Craig Station Unit 2 and Unit 3 will continue to operate.
The decision to propose revising the SIP is driven by the significant costs to install additional emissions controls at Nucla Station under the increasingly stringent regional haze rule, the state and federal regulatory environment for coal-based generation and current and forecasted market conditions.
“Tri-State has worked tirelessly to preserve our ability to responsibly use coal to produce reliable and affordable power, which makes the decision to retire a coal-fired generating unit all the more difficult,” said Mike McInnes, CEO of Tri-State, in a Sept. 1 statement. “We are not immune to the challenges that face coal-based electricity across the country.”
Under the federal regional haze regulations, the state of Colorado develops and implements a SIP to address visibility in national parks and wilderness areas. Colorado’s plan requires reductions of NOx emissions from generation sources. Several procedural steps are required to implement the terms of the agreement, including approval by the Colorado Air Quality Control Commission and the EPA.
The retirements of both Nucla Station and Craig Station Unit 1 will result in carbon dioxide emission reductions that the state of Colorado has set a goal to achieve and will help meet other proposed federal requirements.
Tri-State is the sole owner of the Nucla Station, which employs 55 people and is the world's first utility-scale power plant to utilize atmospheric circulating fluidized-bed combustion. Original construction of the power plant was completed in 1959, and the unit was repowered in 1987. The New Horizon Mine, located near Nucla, Colorado, employs 28 people. Tri-State acquired the plant and mine in 1992.
Tri-State Generation and Transmission is the wholesale power supplier, operating on a not-for-profit basis, to 43 electric cooperatives and public power districts that serve more than one million consumers throughout nearly 200,000 square-miles of Colorado, Nebraska, New Mexico and Wyoming.