Until late November, the subsidiaries of Pennsylvania-based PPL Corp. had planned to retire Green River in April 2015 to comply with the federal Environmental Protection Agency’s new Mercury and Air Toxics Standards (MATS) rule. The rule takes effect next April and Green River’s two vintage units, dating from 1954 and 1959, respectively, are not equipped with pollution controls to sufficiently reduce mercury emissions.

Because of the plant’s age, LG&E and KU opted not to spend the millions of dollars that would be necessary to comply with MATS. They proposed, and later withdrew, plans to construct a new 700-megawatt natural gas-fired plant at the Green River site near the Green River.

But after considering the amount of coal-fired generating capacity planned for retirement by electric utilities in the region over the next few years to meet MATS, more than several thousand megawatts, LG&E and KU had a change of heart and decided to keep Green River open a while longer.

By December 17, they plan to submit a formal application to the Kentucky Division of Air Quality for an additional year of operation for Green River. Typically, these types of extension requests are granted by state regulators.

“With the additional shutdown driven by MATS in that area, we felt like there were some reliability concerns,” said Chris Whelan, an LG&E/KU spokeswoman. If approved by KDAQ, “Green River would operate until April 2016.”

In an integrated resource plan filed with the Kentucky Public Service Commission earlier this year, LG&E and KU indicated they might retire two units at the 739-megawatt E.W. Brown coal plant near Harrodsburg, Kentucky, in 2020.

However, that is not a foregone conclusion, Whelan stressed. “We have no current plans to shut Brown down,” she said.

A new study prepared by the engineering firm of Black and Veatch for LG&E and KU found that Units 1 and 2 at Brown are in good condition and presumably could produce electricity for many more years.

“The Brown Units 1 and 2 boilers are in good general condition,” the study said, “and plant staff has indicated they are satisfied with the performance of both boilers and concerns about slagging associated with burning Illinois Basin coal have not materialized.”

The study concluded: “With the proper operation, maintenance, renewals and replacements, Brown Units 1 and 2 would be expected to be able to continue to operate at or above recent historical performance.”

Units 1 and 2 have a total generating capacity of 272 megawatts. LG&E and KU said Brown Unit 3, rated at 446 megawatts, is not in any danger of closing.

LG&E and KU already have announced plans to close the 645-megawatt Cane Run coal plant in southwestern Louisville in 2015.