Idaho Power scaling back plans at Shoshone Falls facility

BOISE – Idaho Power is scaling back its plan to boost hydroelectric capacity at its power-generating facility at Shoshone Falls in south-central Idaho.

The Federal Energy Regulatory Commission in a notice on Tuesday said Idaho Power is seeking to amend its plan and increase the capacity by only 3.2 megawatts instead of 50 megawatts.

The commission in 2010 approved the company’s request to add a 50-megawatt generating unit at its Shoshone Falls Hydroelectric Project on the Snake River that currently has a capacity of about 12 megawatts.

But the company said changes in the energy landscape, lack of high year-round flows at the Shoshone facility and increased solar and wind power makes boosting the hydroelectric project’s capacity less feasible.

“Our analysis and review of the available water and the cost of putting in a 50-megawatt increase just didn’t pan out,” said Lewis Wardle, Idaho Power’s lands and licensing coordinator with the commission.

The facility currently has three units, which each include a turbine and generator. Two of the units are more than a century old, and combined produce about 1 megawatt. The third unit built in 1921 produces about 11 megawatts, said Jerrod Vaughn, an engineering and construction project manager at Idaho Power. When all three operate, they can handle about 1,000 cubic feet per second of water.

Flows during the summer are typically lower than that as the entire Snake River about 30 miles upstream is allocated for irrigation, and whatever makes it to the Shoshone Falls is mostly from springs returning to the river.

Also, from Memorial Day to Labor Day, Idaho Power is required to send 300 cubic feet per second over Shoshone Falls, one of the most spectacular waterfalls in the state.

Wardle said that in some years, there’s not enough water left to run the generators to produce electricity.

However, flows can increase significantly in the spring with snowmelt and in the fall when the farming irrigation season ends. That can boost the river to 5,000 cubic feet per second, enough to run the 11-megawatt and 50-megawatt units.

Yet another consideration, said Idaho Power spokesman Brad Bowlin, is that those high river flows don’t coincide with energy use.

“Typically, when we see the highest flows in the Snake is not when we see our highest demand,” he said.

So the new plan Idaho Power has proposed is to remove the two century-old turbines, retain the 1921 11-megawatt turbine and add a 3.2-megawatt turbine.

The commission is taking public comments on Idaho Power’s request to lower the capacity at the Shoshone facility through mid-January.

Vaughn said, if everything is approved, the company hopes to start work in July and finish by the fall of 2019.

Wardle said several entities have expressed interest in the century-old turbines and generators, and the company has had informal talks with the Twin Falls County Historical Museum and the Danish Hydraulic Institute, an international company specializing in large-scale projects involving water.

The institute didn’t immediately return a call from the Associated Press on Thursday.