Scuba divers are taking a closer look at the spillway area at Gavins Point Dam, near Yankton, South Dakota.
The dam was a focal point of last year’s historic flooding along the Missouri River that inundated western Iowa and eastern Nebraska.
That dam released more than 160,000 cubic feet of water per second for several weeks last summer as the U.S. Army Corps of Engineers dealt with record rain and runoff.
Dave Becker, operations manager at the dam, says some clean-up is needed before they can finish inspections.
“They got 80 to 90% of the spillway inspected but they determined there’s a lot of debris in the spillway that needs to be removed,” Becker says, “sunken water-logged logs, metal frames to things, old boat docks, things like that.” Becker says the design of the dam makes it more difficult to look at all the wear and tear.
“One of the challenges at our spillway here is, it’s always underwater,” he says. “We can’t do inspections in the dry all the time. There’s in the order of 350 drains on the spillway and we’re determining what level they’ll be inspected at.” Becker says the dam operated as it was designed to during last year’s flooding and he says there are no concerns about the structure being unsound.
“We’ve had some drains that’ve gotten washed away during the flood,” he says. “We’ve had new drains built to replace those. We’ve seen no issues with the concrete. We are concerned somewhat about the gravel, or the frost blanket, down below the concrete so that’s why they want to do the ground-penetrating radar to determine the condition of that.”
Becker says they hope to get much of the work started in the next two weeks. He says a barge and crane will be needed to clean out much of the heavy debris below the dam.