Nevada Dams Inspected Closely After Storms, Earthquakes - KTVN Channel 2 - Reno Tahoe Sparks News, Weather, Video

Nevada Dams Inspected Closely After Storms, Earthquakes

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There are 850 dams in Nevada.  Officials from the state and federal government are paying close attention to these dams after the Twentyone Mile Dam broke in rural Elko County and after land next to an emergency spillway washed away on the Oroville Dam, in California.  The Bureau of Reclamation is in charge of five dams in northern Nevada, and officials say they do not pose any threat because of recent rain storms.

"We're not even to flood stage in Stampede, for instance," Scott Schoenfeld, Operation and Maintenance Division Manager for the Bureau of Reclamation said. "So, we still have some room there to store before we even get to a point where we have to maintain a Level 4 potential flood."

Federally operated dams are inspected on an annual basis at the local level.  A regional inspection happens every four years, followed by a national inspection every eight years.

"Every eight years, we do a comprehensive review to see what has changed in the sciences that are out there, so we can make our dams as safe as possible," Schoenfeld said.

Major storms and natural incidents require even more inspections, including earthquakes like the magnitude 5.7 temblor that shook Hawthorne, in December.  Officials pay close attention to the integrity of the structures when they happen.

"A lot of it is earthquakes, how our dams will be impacted by an earthquake, how our dams will be impacted by hydrological events," Schoenfeld said.

The Nevada Division of Water Resources oversees 657 of the Silver State's dams, paying close attention to every detail.

"You walk the entire dam, the upstream face, the downstream face," Jason King, State Engineer for Nevada Division of Water Resources said. "You walk the crest. You look for slumping in the material."

The average age of U.S. dams is 52 years, and many of Nevada's dams exceed that number.  King says the aging structures require more attention than newer ones.  The American Society of Civil Engineers gave Nevada's infrastructure a C- in a 2014 report, which included dams.

"A big part of that grade is due to the age of these dams, so it concerns every state dam safety program," King said.

The Twentyone Mile Dam was built in 1929, and King says it likely broke because so much inflow caused the reservoir to overflow.  The investigation could take some time to complete.

"We were actually going to try to get some personnel up to it, yesterday, and we were told that they're probably a week out before we can even get to see it," King said.

Twentyone Mile Dam is a low-hazard dam, which requires an inspection every five years.  It's most recent inspection was in July, 2016.  Nevada's dams are classified as high, significant, or low-hazard.  Their classifications are not determined by which ones are more or less likely to fail, but by the amount of downstream development.

"It means that should they fail, there could be loss of life down below and it raises the bar on how we review those dams, how we inspect those dams and how the dam owner has to maintain those dams," King said.

High-hazard dams are inspected annually, and significant-hazard dams are inspected every three years.  Weather can accelerate the process, and that is why officials keep a close eye on the capacity of reservoirs, and the amount of inflow expected.

"You want to get with the dam owner and you want, then, to start releasing water in anticipation of the inflow, so that it doesn't over-top and you do have this large wall of water that could be released downstream," King said.

While it does not appear that any more of the state's dams are in danger, inspections will continue and officials will keep an eye on the weather forecast.

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