Hebgen Dam Repair Update – Fins and Feathers Bozeman
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Hebgen Dam Repair Update

Update from NW Energy on Hebgen Dam Repairs…specifically vague?


NorthWestern Details Hebgen Dam Rehabilitation Plan

Butte, Mont. – Nov. 16, 2015 – Reconstruction of the intake structure at Hebgen Dam is near completion and the second phase of the multi-year rehabilitation projection got a strong start in 2015.

A third and final phase of the project, the rehabilitation of the wood outlet pipe that takes water from the intake structure through the dam to the Madison River, is tentatively scheduled to begin in May 2017. The details of the outlet pipe rehabilitation, duration and specific schedule are not yet finalized. The project details will be developed in 2016 and the tentative schedule will then be re-evaluated based on final plans, fisheries considerations and the actual water year that will be understood in the first quarter of 2017.

In recent weeks, concern has been expressed about the timing of the project’s final phase. “While the multi-phase plan has not changed, we acknowledge that the 2017 outlet pipe project has needed to be more effectively communicated to the public over the last few years while the work on the intake structure has been in progress,” said John VanDaveer, manager, Hydro Generation for NorthWestern Energy. “We will be working to improve the communication on the remaining Hebgen project as we move forward.”

NorthWestern Energy will also continue to consult with Montana Fish, Wildlife and Parks and other appropriate agencies on issues affecting downstream river and recreation resources.

Along with providing timely updates via news releases and on social media, NorthWestern is planning to host evening public meetings on the Hebgen project in Ennis, West Yellowstone and Bozeman in early 2016. The meetings are intended to keep the public aware of updates to the rehabilitation plan.

The overall Hebgen project stems from the 2008 failure of the dam’s original wood stoplogs that were used to control flow in the original intake structure. After making emergency repairs, an extensive rehabilitation project, that included a significant seismic upgrade, was launched in 2009 as required by the Federal Energy Regulatory Commission, the agency that regulates NorthWestern Energy’s hydroelectric operations.

The dam’s intake tower has been completely rebuilt, with gates and operating mechanisms scheduled to be ready for operation by the end of this year. The intake gates will be fully automated with control established at NorthWestern Energy’s Madison hydroelectric project north of Ennis. The automation is expected to help NorthWestern more efficiently manage operations, including downstream flow requirements.

The second phase of the project involves the removal and reconstruction of the dam’s spillway. During this work, downstream flows will be provided through the dam’s new intake gates from a reservoir depth of approximately 40 feet. The work will replace the spillway gates and deteriorated concrete and increase the spillway capacity. The spillway work is expected to be finished in the fall of 2016.

The final phase of the multi-year project is the rehabilitation of the outlet pipe, with a conversion back to spillway flow from the reservoir surface for the duration of this phase of the project.

While NorthWestern Energy considered alternative schedules for the outlet pipe work, a fully functional intake structure gate system was first necessary to allow the outlet work to be conducted safely. Those gates will be completed this fall. In addition, the outlet pipe is required for reservoir operation and maintaining Madison River flows in winter months.

NorthWestern Energy assumed ownership of Hebgen Dam and the Madison hydroelectric project in November 2014 as part of its purchase of PPL Montana’s hydro facilities. Between the two companies, more than $40 million will be spent on the Hebgen rehabilitation project, which will bring the dam into compliance with the FERC seismic guidelines. NorthWestern planned for these expenditures as it sought regulatory permission to buy the hydroelectric facilities in 2014.

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