The company that operates the Colstrip coal fired power plant is proposing to partially excavate waste ponds that have been contaminating groundwater for decades.
State regulators are now accepting comments on the plan.
Talen Energy’s report explores ways to prevent future groundwater pollution from the Units 1 and 2 coal ash ponds, which are leaking coal ash contaminants like boron and sulfate into groundwater.
The coal ash in the ponds at Units 1 and 2 are in contact with groundwater, which could be a source of continued pollution after closures if not permanently fixed. The ponds leak 33 gallons per minute, according to Sara Edinberg with the Department of Environmental Quality (DEQ).
The DEQ brought enforcement action against Talen Energy in 2012. This is one stage in that cleanup agreement. Units 1 and 2 closed earlier this year.
Edinberg says out of the four ways Talen proposes to prevent future contamination, the company prefers partially removing the ash ponds.
“Talen is basically proposing to excavate all the ash that’s within five feet of the water table,” Edinberg said.
Talen would relocate that ash to impoundments on the property where it would not be in contact with water and then permanently cover the ponds with plastic.
Some environmental groups, like Montana Environmental Information Center and Northern Plains Resource Council, say they prefer full excavation. That option requires Talen to dig up all the ash, relocate it to a new lined landfill above the water table on the property and reclaim the former waste ponds.
Other options entail draining the ponds, replacing soil caps with plastic ones and removing the ash from one of the unlined impoundments.
DEQ is accepting public comment on the proposed cleanup methods through Oct. 26. The agency will select its preferred course of action after the comment period ends.