Portland General Electric (PGE) plans to stop burning coal at the Boardman power plant in Oregon in the US by the end of 2020 to comply with Regional Haze rules under the Clean Air Act.
PGE spokesman Steve Corson told Reuters that the firm is yet to decide over closing down the 585MW facility or to convert it to another fuel such as biomass.
The Oregon Public Utility Commission has approved PGE's plan to supply electricity over the next 20 years, including the Boardman proposal, which calls for the initial control retrofits followed by an end to coal burning at the plant by 31 December 2020.
PGE president and CEO Jim Piro said in a statement: "The plan provides a reasonable transition time for moving away from coal to other sources of energy supply."
About $500m would be needed for emission controls upgrades if the plant is to continue through 2040 and beyond, according to PGE.
Instead, PGE plans to invest about $75m to upgrade the plant and keep it running until 2020.