Q: Has the U.S. Army Corps of Engineers finished work on the emergency spillway gate operating system and outlet “tubes,” both of which had been going on during the past year? Have they been tested recently, given the situation with rising water at Tuttle Creek Lake?
A: While not completely finished, a good portion of the construction projects near Tuttle Creek Dam has done.
Since February 2018, contractors hired by the Corps of Engineers have been working on two major projects: rehabilitating the stilling basin (below the dam in Riley County) and replacing the bridge deck above the spillway structure (southeast of the dam in Pottawatomie County).
The stilling basin project, commonly known as the “tubes,” is at least half done. Brian McNulty, operations project manager for the Corps at Tuttle Creek Lake, said workers were nearly finished replacing the 8 feet of the side walls of the stilling basin in a public meeting Wednesday with other Corps officials.
“The more difficult part of that project is we’re actually drilling down holes vertically (on either side of the basin) and putting anchors in,” he said.
McNulty said implementation of the anchors has stopped for now as the contractor would be unable to work on the project when releases from the basin, or “tubes,” is more than 20,000 cubic feet per second. This is the routine way of releasing water from the reservoir.
When conditions eventually allow Corp officials to release water and begin emptying the lake, which recently reached its second-highest elevation at 1,130.35 feet, McNulty said releases will probably be between 20,000-25,000 cfs over the course of several weeks. McNulty said this would probably begin some time in the next few months.
The maximum releases that can be made from the tubes would be 48,800 cfs.
For now, workers are refilling sides of the stilling basin with dirt to improve its safety for when those elevated releases do occur.
As far as the other project, the bridge (Kansas Highway 13) itself already has been replaced and checked by the Kansas Department of Transportation. However, restoration of the site surrounding the bridge still needs to be finished, which requires dry weather conditions.
Lake officials originally had planned to reopen in early May, but constant bouts of rain in the area have made further work difficult.
They said the high water in the lake is not affecting the project.
Neither of the projects affect the normal operation of the dam or its integrity, but Corps staff have regularly been collecting and verifying data about the lake and dam as the water level rises.
“We have instruments measuring flow that’s going underneath or through the dam,” McNulty said. “Tuttle Creek is designed to leak, believe it not, and we have water that moves its way through the embankment. As the lake rises, those pressures increase so the probability for problems increase with that.
It’s a very safe dam, but our inspection and monitoring of those features of the dam increases as the lake goes higher.
“Right now we’re reading every instrument of the dam with each 5-foot rise of the lake,” he said. “And we’ll read those instruments as the lake comes back down as well. The analysis of info goes through the district office and people verifying that internal pressures of the dam are within safe limits, et cetera.”