This just in from EWEB:

Low water forces shutdown of Trail Bridge turbine

With the McKenzie River at or below historic low flows for early July, the Eugene Water & Electric Board on Friday will shut down its Trail Bridge hydroelectric generation turbine, and anticipates it may have to further curtail generation at its Walterville and Leaburg facilities later this summer.

The generation turbines at EWEB’s McKenzie River projects require a minimum flow of water to operate properly. When water volume decreases below a minimum threshold, running the power generation equipment risks damaging the turbine units.

“While it is unusual to take the units offline, it isn’t unprecedented,” said Generation Manager Mike McCann.

“We have had to do this before at each of the projects, just never this early,” McCann said. “We are not alone as there are other utilities in the Northwest experiencing the same conditions.”

The Trail Bridge turbine is part of EWEB’s Carmen-Smith Hydroelectric Project, located about 70 miles east of Eugene. The Trail Bridge powerhouse, located below Trail Bridge dam and reservoir, can generate up to 5 megawatts of electricity, or roughly equal to about 2 percent of Eugene’s average daily consumption of electricity.

McCann said he expects the utility will shut down the Walterville turbine later this month due to the low water levels. The Leaburg facility will continue running one of its two turbines until late July or early August, depending on river flows. EWEB will be able to run its largest hydroelectric generation facility, the Carmen plant, in a “peaking” mode to produce power during the typical daily high-demand hours.

Despite the curtailment of McKenzie generation, EWEB will have adequate supplies of power through the summer. The Bonneville Power Administration, which markets power from a network of 29 hydroelectric dams on the Columbia and Snake rivers, supplies EWEB with the majority of the energy consumed by Eugene residents.

As a result of the low river flow conditions, the public may notice that reservoir and canal levels are lower than normal. This is a temporary condition and operating levels will rise again when river flows increase. The utility will use the downtime to accelerate its preventative maintenance.

EWEB will keep a minimum amount of water in its Leaburg and Walterville power canals to mitigate drying of the canal embankment soils due to warm weather. Excessive drying could damage the embankment soils and increase dam safety risks when the canals resume operation at normal flow levels.

“Once it starts raining, and it will, EWEB will begin generating again,” McCann said. “We don’t expect any long-term negative effects to our infrastructure due to the low water conditions.”

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