The Tulsa District, U.S. Army Corps of Engineers completed a dewatering and inspection at Elk City Lake Dam, Oct. 3.

The 2019 flood delayed two prior attempts to complete the project but the third attempt proved to be the charm as engineers and lake office staff completed the effort despite a rainfall the final day.

"We started planning the dewater 10 months in advance," said Chris Hammerschmidt, who oversees four Corps lakes in the state of Kansas. "We were supposed to do it in March of 2019 but the rain kept coming, so we kicked it down the road a little bit."

The team made its second attempt at the dewatering the last week of September but rain again interrupted their plans.

Hammerschmidt's staff at Pearson-Skubitz Big Hill manages Elk City, Toronto and Fall River. The lake office team worked out the logistical aspects of the plan with the Kansas Area field maintenance engineer by reviewing previous dewatering projects.

Accomplishing the task involved closing the service gates and building a small cofferdam between the stilling basin and a creek just downstream. Pumps ensured the conduit was clear of any remaining water and air quality measuring tools kept track of carbon monoxide and other gases.

Nathan Whitcomb, the field maintenance engineer for the Kansas Area, is responsible for overseeing maintenance and engineering at eight Corps lakes in Kansas. He said that dewatering and evaluations are proactive steps to identify problems and plan maintenance.

"It's about dam safety, flood risk management and keeping our structures intact and maintained well so that they can perform when needed, especially for an extreme event which could test our structures."

Dewaterings allow engineers to get an eyes-on view of the physical and mechanical parts of the dam. While water is off of parts of the structure engineers can look at the structural integrity of the conduit, stilling basin and outlet channel.

The team documents erosion, cavitation and wear on mechanical and physical components of the structure said Whitcomb.

Cavitation can occur when water passes through the conduit at high speeds. The turbulence forms bubbles that puts pressure on components or structures and causes pitting.

"We document the rate of erosion or cavitation. So if we see an increased rate we know we need to keep an eye on it or start budgeting out for a repair."

Elk City Lake is located on the Elk River, a tributary of the Verdigris River. The dam's 16 foot-diameter conduit is capable of releasing 10,100 cubic feet per second when the lake is water is at the top of the conservation pool, an elevation of 796.

The Dam was completed in 1966 and includes an earth filled embankment that is 4,840 feet long. The structure rises to 107 feet above the streambed.