OLYMPIA - An agreement is expected to be signed next month that will ensure partial restoration of the site of Energy Northwest's two unfinished nuclear power plants north of Richland.

Most of the heaviest work to seal up the plants wouldn't begin for at least 23 years, giving Energy Northwest ample time to consider redevelopment options.

The agreement, long in the works, is essentially a contract that ensures the two cluttered sites will be cleaned up.

"We're very happy it's going to be resolved," said Allen Fiksdal, manager of the state's Energy Facility Site Evaluation Council. "It's always been a money issue. We're anxious to see it go forward."

The two plants, plus the operating Columbia Generating Station nearby and two other unfinished plants in Grays Harbor County, were granted site certificates in the 1970s without any consideration for what would happen to the sites if the plants never produced power.

"Nobody contemplated these projects wouldn't be finished," Fiksdal said.

The two Grays Harbor plants eventually were transferred to a local public development authority, leaving the state and Energy Northwest to figure out plans for the two Hanford plants, known as Plant No. 1 and Plant No. 4.

Various parties involved agreed it would be too expensive to restore the site to sagebrush. Instead, the plants will be cleared of debris and plugged up at a cost estimated to be $45 million.

As part of the agreement, the Bonneville Power Administration has agreed to become financially responsible for both plants, even though it legally is on the hook for Plant No. 1 only. Plant 4 was one of two plants involved in the former Washington Public Power Supply System's infamous $2.25 billion bond default.

It wasn't clear before who would pick up the tab for it.

"That's one of the successes of the agreement," said Jack Baker, an Energy Northwest vice president.

Restoration activities will occur in two phases. The first phase, which already has begun, focuses on eliminating immediate health and safety hazards. Debris and tanks will be removed, underground pipes will be capped, doorways will be secured and new fences will be erected.

Work on the first phase is expected to be complete by the end of July.

The second phase, which wouldn't commence until 2026, would involve removing support buildings, demolishing some walls, pouring new concrete floors and ceilings, grading and seeding the yards around the plants, backfilling water lines and removing roads and rail lines among other activities.

Much of that work would be avoided if other uses for the facilities can be found. Energy Northwest already uses about half the more than 50 office, storage and other support buildings on the site and believes much of the rest also can be put to use.

Bonneville has agreed to put up as much as $4 million for the first phase and will create a trust fund to collect money for the second.