DEQ Reaches Settlement Agreement for Cleanup of the Units 1&2 Coal Ash Ponds at Colstrip Power Plant

Department of Environmental Quality
  • Kevin Stone
  • October 19 2021

HELENA—Today, the Montana Department of Environmental Quality (DEQ) and Talen Montana, LLC, the operator of the Colstrip Steam Electric Station, announced a final settlement agreement that completes the dispute resolution process concerning DEQ’s selected remedy for groundwater contamination at the Colstrip Power Plant. The settlement agreement allows DEQ to retain its selected remedy for the Units 1&2 coal ash pond area. 

The Colstrip site is a complex contamination site where groundwater contamination has been caused by leaking coal ash ponds. Enforcement action taken by DEQ in 2012 resulted in an Administrative Order on Consent (AOC) that requires investigations and remediation plans to address the contamination. DEQ’s selected remedy for the Units 1&2 coal ash pond area, Alternative 10, would clean up the contamination though excavation of coal ash from the existing pond area and placement of the ash into a new, lined landfill on Talen Montana’s property, located above the water table and outside the footprint of the current coal ash ponds. The selected remedy includes additional dewatering components and a flushing/capture well network to further address groundwater contamination. 

This settlement agreement requires Talen Montana to complete key aspects of remedial design for Alternative 10 over the next two years. Talen Montana must submit a Remedial Design/Remedial Action Proposal in January 2022, an Amended Closure Plan in April 2022, the Remedial Design/Remedial Action Work Plan in April 2023, and a Landfill Design Package in October 2023.​ 

“This settlement agreement does not change DEQ’s remedy decision and will ensure that design and implementation of Alternative 10 continues to move forward, while allowing Talen Montana the flexibility to concurrently evaluate one additional remedy option,” said Jenny Chambers, DEQ Waste Management and Remediation division administrator. “The agreement also establishes definitive dates for submittal of design documents and stipulated penalties if dates are not met to keep Talen Montana on track to design the remedy for Units 1 & 2” 

Under the settlement agreement, financial assurance will be submitted for Alternative 10 within 60 days of the effective date of the agreement. Discussions on financial assurance during the dispute resolution process resulted in DEQ’s approval in June 2021 of financial assurance for Alternative 10 in the amount of $163,324,679. This amount secures adequate resources for the selected cleanup. The amount will be reviewed annually in accordance with the 2012 AOC and may be adjusted as appropriate to ensure it is sufficient to cover the full cost of the remedy. The first annual review will occur in 2022. 

Concurrent with the Alternative 10 design process, the settlement agreement allows Talen Montana the option to request that DEQ evaluate a single additional remedial alternative. Talen Montana will have the option of submitting a Request to Amend the remedy selection before the end of October 2023. DEQ’s evaluation of a Request to Amend will include a 30-day comment period and public meeting, after which DEQ will issue a written decision. Allowing Talen Montana to evaluate an additional alternative during the next two years will not delay remedy implementation for DEQ’s current selection of Alternative 10.   

This settlement agreement is a final agreement and has legally binding obligations. More information and a copy of the settlement agreement can be found on DEQ’s website at: 

DEQ is holding an informational public meeting on Oct. 26, 2021, to provide updates on remedies, monitoring, and to inform the public of progress made by DEQ and Talen Montana, under the AOC during the past year. DEQ invites attendees to provide input on the implementation of the AOC and will hold time for discussion of the Settlement Agreement. The meeting will be held at 6:00 PM in Colstrip, MT at the Colstrip Parks and Recreation Meeting Room at 110 Park Ave, Colstrip, MT 59323. Participants may join in-person or virtually. For information on accessing the meeting via Zoom or telephone, please visit: