Raising lake level could cost $280,000April 4, 2014
By CANDY NEAL
Herald Staff Writer
JASPER — A solution was discussed Thursday for raising Beaver Lake’s water level to match the way things were before a new spillway was installed two years ago.
Reconstruction of the lake’s spillway barrier would elevate the barrier and raise the lake’s water level by at least 10 inches, Brian McKenna of Indianapolis-based Christopher Burke Engineering, told the Jasper Utility Service Board’s water committee Thursday during a special meeting.
McKenna estimated the reconstruction cost at $280,000. The fees would be paid from the water utility’s budget.
A weir barrier is used to slow, but not stop, water flow. The reconstruction would involve making the weir taller, which would slightly reduce the spillway capacity. The concrete reconstruction would have to seal with the current concrete already in place. That can be accomplished by adding a water stop strip to the construction, McKenna said.
Another option would be to add a steel weir plate to the top of the spillway. But McKenna said that’s not the best option.
“The current spillway top has a rounded crest on it. If you put the plate on one side, you will create a pocket of water on one side, which is not ideal,” McKenna said. “That would be a bigger concern than the bonding.”
A new spillway was installed at the lake in June 2012 to fulfill a mandate by the Indiana Department of Natural Resources. Should the area get what the state agency considers the area’s maximum possible precipitation — 26 inches of rain in eight hours — the excess water must pass over the spillway and not the dam. The $3.3 million in improvements made by Columbus-based Force Construction included enlarging the spillway and removing the channel.
It took the rest of 2012 for the lake to refill. Once that finished, residents of the lake community told city officials and workers the water level had dropped about a foot from its elevation with the old spillway. The change was evident by water marks around the lake and on dock beams. Some residents weren’t able to use their docks.
Utility officials became concerned the lower level could be a problem should the city face another drought like 2012 and need a supplemental water supply.
Federal and state regulators may see the weir reconstruction as altering the lake’s level, McKenna said, because wetlands and channels feed into the lake.
But this situation is a little different.
“I think we can make the argument that the lake was at (a certain) elevation before, based on the water level marks,” McKenna said. “We can make the argument that this is restoring the lake to the original lake level, not increasing (the level).”
Water Commissioner Dave Hurst said the $280,000 cost was reasonable.
“I don’t have a problem with the cost, so long as (the weir) is high enough.”
The dozen Beaver Lake residents at Thursday’s meeting agreed that increasing the lake level 10 to 12 inches would bring the level back to the point that it was before the new spillway was installed and to their satisfaction.
Raising the weir could affect the spillway, McKenna said Thursday.
“If we raise the weir, it will reduce the spillway capacity slightly,” meaning more water was being held in the dam,” McKenna said.
McKenna wasn’t sure if the change would concern the DNR, who regulates dams and spillways. But the dam’s embankment would be raised to help compensate if needed, he said.
A scale model of the lake’s spillway is being studied at the University of Evansville and should be finished in the next month. The study, independent of the city’s examination, will determine a capacity rating based on the spillway.
“When we estimated the rating curve, we based it on previous studies of varying sizes,” said McKenna, a graduate of the UE civil engineering program. “Having a physical model would give better numbers.”
The committee decided to wait until McKenna examines the reconstruction cost — and until the UE study is complete — before it decides which route it takes to raise the lake’s water level.
Contact Candy Neal at firstname.lastname@example.org.
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