Wwp Plans Project At Nine Mile Dam Installation Of Bypass Pipe Would Limit Damage To Turbines

With coarse sediment chewing on its turbines, Washington Water Power Co. wants to drill a bypass pipe through Nine Mile Dam.

An environmental coordinator for the project says that already the company has been forced to shut down a turbine installed at the facility just three years ago when the bearings failed.

Rod Pharness, the coordinator, said heavy runoff the last two years has carried coarse sediment that normally settles out of the water upstream right to the dam.

Latah Creek carries 180,000 tons of sediment into the Spokane River above the dam every year, he noted.

The coarser material is swept along the west bank of the river, then into Unit No. 4, the turbine that failed two months ago.

The sediment has since been redirected into Unit No. 3, which remains in operation, said Project Engineer Steve Schultz.

He said the bypass pipe, five feet in diameter, would intercept the sediment before it reaches the turbine intakes.

Installation will cost $2 million, Schultz said.

Still unknown is the extent - and cost - of the damage to the turbines, which replaced two units that dated back to 1908.

That work, done in 1993 and 1994, was part of a $20 million project to boost the dam’s output, add a new switchyard and improve the facility’s links to the rest of WWP’s grid.

“It’s been a very reliable plant,” Pharness said. “At this point, we’re struggling to keep it on line.”

Energy from Nine Mile, he added, is among WWP’s cheapest.

The dam has four generators. Two of the original units are still in place.

Pharness said the project will entail removal of as much as 5,000 cubic yards of sediment. He does not know where the material would be taken, but added that the heavy metal content will not require special handling.

“It’s not considered a toxic or hazardous waste in any way,” he said.

Pharness said the project received a shoreline permit from Spokane County on June 11. The company is awaiting other state and federal permits.

Schultz said WWP hopes to start the pipeline project in August and complete it in October. Turbine repairs may take longer, he said.

, DataTimes