NorthWestern Energy Clark Fork River Pipeline Relocation Permit to Minimize Impacts to the Waterway

NorthWestern Energy is proposing to abandon an existing natural gas pipeline under the Clark Fork River and replace it with a new pipeline directly upstream of the Madison Street Bridge. This proposal came before the Missoula County commissioners as part of the County’s responsibility to enforce 310 permits (see below). This project will be executed and paid for by NorthWestern Energy with no direct impacts to taxpayers.

The existing gas pipeline runs under the Double Tree Hotel, and NorthWestern Energy is proposing to relocate it because it is difficult to maintain in its current location. When the existing line is abandoned, NorthWestern will purge it with nitrogen, cut and then cap it. This is a standard process for cleaning out pipelines, and according to the depth survey completed by the applicant, the existing line is not in danger of exposure from river channel scouring. The applicant plans to set up a staging area away from the river in an existing paved parking lot. The site plans identify grassy areas as the only disturbed vegetation, and the applicant plans to restore these areas when the project is finished. Excavated material will be temporarily stored next to bore holes and will be used to backfill when the bore is complete. The applicant will not use equipment directly on the riverbank or in the water.

Project construction is anticipated to start in October and is projected to take four to six weeks for completion. A 310 permit from the County does not directly authorize construction. The applicant also needs, and has requested, a Floodplain Development Permit from the City of Missoula Floodplain Administrator.

County staff recommended approval of the project as proposed. Impacts to the river channel should be small because the excavation and temporary stockpiling of materials will take place outside the riparian area and riverbanks. The proposed project complies with review criteria and construction standards pursuant to the Missoula County 310 Administrative Rules (2004), and staff have no further conditions or modifications to mitigate adverse impacts to natural resources or agricultural water uses than what is already in the proposal.

The Missoula County commissioners heard and approved this proposal at their public meeting on Sept. 14.