Puget Sound Energy (PSE), along with Avista Corp., Portland General Electric Co., NorthWestern Corp., PacifiCorp and plant operator Talen Montana, also said July 12 that the plant will limit pollution levels until that point.

Colstrip, located in eastern Montana, currently has a total capacity of 2,100 MW. Units 1 and 2 are about 40 years old, the oldest of the group. PSE owns 50% of the two units, and Talen owns the other 50%.

The settlement was the result of a lawsuit first filed in 2013 by the Sierra Club and the Montana Environmental Information Center, with the plaintiffs claiming in part that upgrades were performed without proper permits. A proposed consent decree for the agreement has already been entered in to the United States District Court for the District of Montana for review and approval.

In addition to a commitment by the owners to idle the units, the deal includes liability releases for the owners of all four units, without requiring monetary payments to the plaintiffs. All claims against Units 3 and 4, which are not only newer but more efficient, were dismissed and they are not part of the closure plan.

Talen Montana noted there is no formal plan or timeline at this time for the retirements of Units 1 and 2 aside from the final deadline date.

“Our customers expect PSE to be good stewards of the environment and to keep energy costs reasonable,” PSE President and CEO Kimberly Harris said. “The eventual closure of Units 1 and 2 at Colstrip without the risk of further legal proceedings or additional significant investments in the units to meet regulatory requirements enables us to accomplish both of these goals.

“We know this will be a time of transition in Colstrip. We have been a part of the community for four decades, and we will continue to be there for many years to come.”