Clearwater Dam is operating as intended, officials said Thursday, viewing an overflow spillway that still has approximately 2,000 cubic feet per second of water crossing it.
The amount is equal to nearly 900,000 gallons of water per minute, and is about one-third of the maximum volume seen during this flooding event, said deputy operations project manager Fred Esser.
"The concrete structure is holding the lake back at this stage," Esser explained. "It's doing its job."
The lake had fallen to approximately 568.54 feet as of this morning. That's about 1.5 feet higher than the top of the secondary spillway.
The concrete overflow structure extends 20 feet into the ground and is anchored into bedrock. It stretches the width of the valley that lies between Clearwater Lake and Highway HH.
This is the first time in the lake's nearly 70-year history water has flowed through the valley.
"It's working the way it's supposed to. The erosion is here," Esser said, standing on the south side of the of the secondary spillway, with the lake on the north side.
The power of the water has carved away sections of land estimated to be between 40-50 feet deep across the width of what was a flat valley.
It forced its way through a large section of Highway HH and then continued southeast, to destroy a compound with about five U.S. Army Corps of Engineers work buildings. Water now flows below a 20-foot drop from the remainder of the work road that led to the compound.
The compound area was marked before the flood by only a small creek that only flowed during rain, Esser said.
The overflow continues southeast to re-enter the Black River below the primary lake outlet channel.
"This is cutting into places it probably hasn't been in a long time," Esser said. "It's cut down to bedrock."
Flow from the primary outlet channel was approximately 2,600 cfs Wednesday.
Water will have to stop flowing before the project can get a good look at the damage that has been done, he said.
With a little more than an inch of rain expected overnight, it is not known how long that will take. The lake fell less than half a foot in the past 24 hours.
It will take even longer for the beaches and boat ramps to come out of the flood water, but Clearwater is opening unaffected areas.
River Road and Piedmont Park have camp spaces available, although some portions may still be closed, Esser said.
"Piedmont Park has one loop fully open and the other two partially open," he said.
Portions of Highway K, Webb Creek and Bluff View will open May 15, the scheduled time for those camping areas to start the summer recreation season.
All reservations for campsites have been cancelled because of the limited amount facilities, Esser said.
"We want people to be aware of what they're getting," he said.
Bluff View has no shower house, and no beaches will be open, he said. Playgrounds may be underwater in other areas, as well as all of the boat ramps.
The lake has to fall to approximately 535 feet before any boat ramps will start to come out of the water, Esser said.
Repairs to Highway HH will be under the direction of the Missouri Department of Transportation, which maintains the road.
Meetings are scheduled this week to begin those discussions, but the extent of the damage cannot be determined until water stops flowing, officials say.