Arizona Public Service (APS) said it would close a coal-fired unit and shut down two others by mid-2020 as part of a compromise with the U.S. Environmental Protection Agency (EPA).

The proposal was made with the understanding that APS would not be required to install emission control equipment on the units in order to comply with EPA’s Regional Haze rule. APS was notified in 2010 that it needed to upgrade its scrubbers and add a baghouse to its 260-MW Unit 2 at the Cholla Power Plant in Arizona to meet EPA’s Mercury and Air Toxics Standards. In 2012, EPA published a federal implementation plan that required units 2 and 3 to install selective catalytic reduction (SCR) technology to reduce nitrogen oxides (NO_x).

APS has proposed shutting down Unit 2 by April 2016, which would reduce mercury emissions by 51 percent, particulates by 34 percent, NO_x by 32 percent and carbon dioxide and sulfur dioxide by 23 percent. The closure would also save more than $350 million in potential costs for the emissions controls. Units 1 and 3 at the plant would stop burning coal by mid-2020.

APS has been closing older units and replacing them with more efficient ones, including three units at the Four Corners Power Plant in New Mexico and two units at the Ocotillo Power Plant in Arizona.

http://www.power-eng.com/articles/2014/09/aps-proposes-closing-three-coal-fired-units-by-2020.html