Feds investigate Martis dam integrity | SierraSun.com

Feds investigate Martis dam integrity

Emma Garrard/Sierra SunSoil samples lay next to a drill used by U.S. Army Corps of Engineers for geological testing t Martis Valley Dam Tuesday afternoon. Access to the dam will be closed to the public for 10 weeks.

The U.S. Corps of Engineers has begun an initial investigations to determine what shape the 35-year-old Martis Creek Dam is in ” and what risk it poses to downstream residents.

Located three miles east of Truckee in the Martis Valley, the earthen-fill dam, originally designed for water storage, has largely served to prevent flooding in the Reno-Sparks area.

Issues that brought the dam’s integrity into question surfaced between 2005 and 2006, according to federal officials, leading the Corps of Engineers to place the dam in the “extremely high risk” category.

In a previous news release, the Corps said it had concerns with seepage.

“Recent information indicates that the dam may not be able to store large amounts of water,” the Corps announced.

Despite its ominous status, Corps of Engineers spokesperson David Killam said the dam only poses a risk under conditions well beyond any expected by the historical record.

“The dam could fail, but that’s under very extreme conditions ” we are just taking the extreme to ensure safety,” Killam said.

Conditions are nowhere near record levels, said Project Manager Veronica Petrovsky of the Corps, with 800 acre-feet of water currently behind the dam, compared to the 9,700 acre-feet level considered safe and the dam’s 20,400 acre-feet total capacity.

“Right now we are analyzing the situation with different studies, samples of the dam and soil conditions,” Petrovsky said.

The Corps will investigate three issues, Petrovsky said: seepage, spillway capacity and seismic conditions.

“If the water level is raised, water comes bubbling out at very high levels,” Petrovsky said. “That could potentially undermine the integrity of the dam.”

Investigators will also determine if the spillway has enough capacity, she said.

Additional study of faults in the area ” once thought to be inactive but now believed to be potentially active ” will also help determine the extent of work needed, Petrovsky said.

The $3.5 million federally funded study will take between two and three years, Petrovsky said. The Corps closed the dam to the public Monday, and will keep it off limits for about 10 weeks, and then intermittently until all work is completed.

“The dam will be closed while we are doing drilling; we’ll close it anytime we are doing work with heavy equipment and safety is a concern,” Petrovsky said. “It should be closed off and on for the next few years.”

The closures will not affect access to the reservoir or nearby campground, according to a Corps news release.

Away from the dam, another high priority will be mapping the flood plain in the Reno area to determine the potential extent of damage in a flood event, she said.

“This is urgent in that there is an issue with the dam; but, in order to do this right it’s going to take this long,” Petrovsky said.

Killam said public meetings will be scheduled for interested parties, but dates have not yet been set.

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