Fault confirmed near risky Truckee dam | SierraSun.com

Fault confirmed near risky Truckee dam

TRUCKEE “-A previously unknown earthquake fault has been confirmed near Martis Creek Dam.

Martis Creek Dam, ranked among the riskiest dams in the country by the Army Corps of Engineers, can now add a fault running between the dam and the spillway to a list of problems making it more likely to fail, sending water down the Truckee River Canyon and into Reno.

“We uncovered a previously unknown fault by digging two trenches,” said Ronn Rose of the Dam Safety Assurance Program, U.S. Army Corps of Engineers. “It looks to be a pretty big structure.”

This summer the Corps will continue studying the faults and the dam itself, which is built on loose glacial till that allows seepage.

That means that at some point this summer the road across the dam will be closed to the public, likely for about a month, said Adam Riley, project manager with the Corps.

“We’re still working out the schedule,” Riley said. “We will post information when it becomes available.”

Rose said the Corps have been leaving the flood gates wide open to minimize the risk of water building up behind the dam ” and the potential for catastrophic failure.

The Corps also have equipment on site to repair the dam if there is any evidence of failure, Rose said.

A panel of national experts will help assess the Corps’ work so far and plans going forward, Rose said.

“We will determine all the risks, and figure out which ones are the highest,” Rose said.

Moving forward, Rose said the Corps will narrow down a couple options starting next year, study the environmental and economic implications of each alternative, and likely be ready for construction in 2014 or 2015.

While the U.S. Bureau of Reclamation is also planing work for Boca Dam on the other side of the Truckee River as a precaution for earthquakes, Rose said the Corps work won’t be affected.

“They were not aware of the fault we discovered so we’ve contacted them on that,” Rose said.

Officials say though failure of Boca Dam west of Reno is remote, recent safety evaluations reveal significant improvements are necessary.

The studies and a cost analysis for Boca will take about two years.

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