Today work on Columbus' whitewater course starts at the very beginning.
The Chattahoochee RiverWalk will be closed from the North Highlands Dam 2,300 feet south to South Gordon Boulevard as construction crews gear up to go down in the riverbed and build a "weir" or smaller dam just below North Highlands.
That smaller dam will keep enough water pooled below North Highlands' downstream face for its turbines to function efficiently after the City Mills Dam below it is breached, draining the backwater now extending to North Highlands.
Work in the riverbed won't start until January, but the preparations begin today.
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As Georgia Power works on the weir to keep its generators running smoothly, whitewater construction crews will breach and remove sections of the City Mills Dam downstream, and begin building a "put-in" just south of North Highlands for people using the 3.5-mile whitewater course that's expected to open next summer.
The staging area for this work will be the RiverWalk parking area and pavilion just south of the North Highlands Dam.
"They're going to have to remove the pavilion down there and install a road to get down to the water level, so that area will be in disrepair during the construction," said Deputy City Manager David Arrington.
That work will not extend all the way down to South Gordon Avenue, but that's where a spur of road curves winds up to First Avenue from the RiverWalk, and to let users proceed farther north on the RiverWalk from there would be routing them to a dead end, Arrington said.
So the construction detour will take users from South Gordon on First Avenue to Bibb City, where they can get back on the RiverWalk north of the dam.
The weir construction is necessary because the turbines within the North Highlands Dam are designed to work at the downstream pool's current elevation.
Were that pool drained, the turbines would be subjected to increased "cavitation" that causes pits in their blades, and increased vibration resulting in accelerated degradation of the machinery.
"All indications are that is the problem you would have," said Arnold Lindsay of Georgia Power. "You either build this weir and know you're not going to have an issue, or you could not build the weir and possibly have issues and have to build it later."
So Georgia Power's going to do the work while the water's down, after the City Mills Dam is breached.
During construction the turbines will be shut down and the river will flow through the North Highland Dam's spillway.
Uptown Columbus President Richard Bishop said the City Mills Dam will be breached in January, after which crews will install the put-in or launch for whitewater rafts just south of the pavilion area at the North Highlands Dam.
No riverbed whitewater work is anticipated that far north, unless something unexpected turns up, he said