Washoe Lake Dam update: Flood watch canceled following mitigation efforts

Benjamin Spillman | Reno Gazette-Journal

Tuesday 10:15 a.m. update:

The National Weather Service has canceled the flood watch for Steamboat Creek after mitigation efforts at the Washoe Lake Dam that began Monday afternoon.

*Update: FLOOD WATCH CANCELLED



Mitigation efforts have reduced the hazard of a potential breach in the dam at Little Washoe Lake. As such, the Flood Watch has been cancelled for areas near & downstream of the dam which included Pleasant Valley & the Steamboat area south of Reno. — NWS Reno (@NWSReno) June 19, 2018

Original story:

Quick work on Monday afternoon by crews using earth moving equipment plugged a leak in the Washoe Lake Dam that threatened to undermine the structure, which could have caused extensive flooding downstream.

The leak prompted dam operators and officials to enact an emergency action plan on file with the Nevada Division of Water Resources which inspects dams in the state.

Crews work at Washoe Dam trouble spot Crews move earth and inspect the possible breach area at the Washoe Dam site.

“When you have seepage going through an earthen embankment … all of a sudden you can have a failure,” said Jason King, the state engineer.

Louis G. Damonte Jr., director of the company that owns and operates the dam, said he and others rallied workers to the site Monday as soon as they learned of the problem.

The workers used trucks to haul dirt and rocks to the edge of the dam and an excavator to place the material and slow the leak. They planned to use cement to cover the rocks, Damonte said.

"We don't know what caused this," Damonte said. "What is important to note on our part is the protocol and how fast we were able to move equipment in here."

The emergency action plan outlines steps to take in event of a problem that threatens the structure. It includes a map of potential inundation areas, which in the case of Washoe Lake Dam included downstream homes in Pleasant Valley.

About 100 homes could have been affected by a potential dam breach from Pleasant Valley to Toll Road, according to Washoe County officials. They said the downstream Pagni Dam would likely captured some of the flow and mitigated damage.

"It could have been a lot worse," Damonte said.

Damonte said the company that owns the dam, which the Nevada Secretary of State lists as Washoe Lake Reservoir and Galena Creek Ditch Company, has an estimated 50 to 75 users. The users pay assessments to maintain the dam which is in place to store about 5,000 acre-feet of water. Damonte said the users don't always pay an assessment or use their water rights.

"A lot of them are small users," he said.

The apparent leak was discovered Monday following a report from the public, according to the Nevada Division of Water Resources.

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CITY OF RENO SPOKESMAN TWEETED OUT MAP OF POSSIBLE FLOOD AREA, WHICH INCLUDES PORTION OF PLEASANT VALLEY NEIGHBORHOOD:

NEW: Here's Washoe County's emergency map of areas that could be hit by flooding near the old 395: pic.twitter.com/D8YNu6nbQk — Jon Humbert (@jonhumbert) June 18, 2018

The dam holds in Little Washoe Lake upstream from Steamboat Creek.

“Instead of water coming through the spillway … there was also noticed a significant amount of water coming through the embankment,” King said.

King said officials are enacting the emergency action plan for the dam and have notified the Washoe County Sheriff’s Department and Nevada’s Division of Emergency Services.

He said there are no evacuations underway, but that could change.

Potential Washoe Lake Dam breach could affect Steamboat Creek area. Residents advised to prepare for flooding similar to Feb 2017 if dam were to breach. WC Community Services Division is currently setting up sandbag locations and will be announced shortly. — Washoe County (@washoecounty) June 18, 2018

“We have concerns about the seepage and the potential for a release of more water than they would normally see,” King said about communities near Steamboat Creek. “At some point if it gets worse that turns into an evacuation.”

Washoe County issued the following warning: "Should the Washoe Lake Dam breach, Steamboat Creek and Steamboat Ditch areas would be flooded. The dam is showing signs of potential compromise, and residents are asked in these and surrounding areas, to please be prepared to evacuate when notified.

Washoe Lake Dam is categorized as a “high hazard” dam, meaning, “failure carries probability of causing loss of human life and excessive damage to downstream properties,” King said.

King said the dam is holding back the entirety of Little Washoe Lake and a portion of Washoe Lake.

The dam itself is constructed from granite blocks. Damonte said he didn't know what year the structure was built but noted the blocks are similar to those used in the construction of the Comstock-era Virginia and Truckee Railroad.

It was last inspected in August of 2017, said Eddie Quagliere, dam safety manager for the state of Nevada.

Raw video: Crews work to repair Washoe Lake Dam Crews work to repair Washoe Lake Dam on Monday, June 18, 2018.

Here is the flood area of a potential Washoe Lake Dam breech, according to its emergency action plan filed with the Nevada Division of Water Resources: