Recent quakes haven’t shaken at-risk dam near Truckee

Officials study seismology at Martis Creek Dam

By Greyson Howard
Sierra Sun, ghoward@sierrasun.com
May 7, 2008

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Stream affects

Lisa Wallace, executive director of the Truckee River Watershed Council, said she doesn’t expect the Army Corps of Engineer’s work on Martis Creek Dam to affect the creek, but said she is expecting a dry year. The dam’s presence has necessitated work downstream over the last few years however, and the watershed council has replaced gravel for fish spawning below the dam, she said. “We’ve been really happy — the gravel has stayed in place more or less, and we’re seeing a somewhat increased level of spawning,” Wallace said. Martis Creek upstream of the dam will also be targeted this year at the annual Truckee River Day for stream and meadow restoration, Wallace said.

Seismic study is high priority at the Martis Creek Dam, but recent earthquakes in the area haven’t affected the safety of structure.

Located three miles east of Truckee in the Martis Valley, the earthen-fill dam has been categorized as an “extremely high risk” by the Army Corps of Engineers for seepage issues. Geologists blame the coarse glacial soil for the seepage that could destabilize the dam, making it one of the six riskiest dams in the nation.

Because of that risk, officials are keeping water levels low.

Meanwhile, the potential of nearby active faults also compound the risk the dam poses to downstream residents through the Truckee River Canyon, in Reno and in Sparks.

“Our accelerated efforts are due to the potential faults in the area of the dam,” said Veronica Petrovsky, project manager with the Army Corps of Engineers. “We’re seeking an additional $1 million to continue on the fast track for seismic issues.”

An initial study released in March indicated a recently-active fault may lie underneath the dam itself. According to a May 2 situation report from the Corps, investigation of that fault will occur this summer.

Archeological study of cultural resources may be deferred until after seismological work can be completed, Petrovsky said.

Also in the works is an inundation map, she said.

“That will provide the depth of inundation [flooding] along the Truckee River all the way to Pyramid Lake if the dam failed with a full pool behind it,” Petrovsky said.

But the Corps isn’t taking any risks, keeping the reservoir less than 20 percent full, she said.

Potential solutions include removing, repairing, or replacing the dam, she said, but a decision is still years away.

In a best-case scenario, the study is scheduled to continue until 2011, followed by design work in 2012-13, and construction or other work around 2014-15, Petrovsky said.