A 900-foot stretch of the Chattahoochee's riverbank has dropped significantly and in places completely collapsed into the river, threatening more than 300 feet of the RiverWalk and some Georgia Power transmission towers.
The collapsed section is just north of City Mills Dam, which was recently breached and where work continues in preparation for the May 25 whitewater course opening.
Richard Bishop, president of Uptown Columbus Inc., said the collapse should have no effect on the opening because the put-in is well north of that stretch of river.
The collapsed bank is also directly behind Chase Apartments. The city's public works department has erected a chain link fence to keep the public away from the dangerous area while workers with heavy equipment stabilize the riverbank. The RiverWalk has been closed to the public from City Mills to 23rd Street indefinitely.
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"Without getting on top of this immediately, the problem would continue on down the riverbank and the cost to repair it would have been higher than it would be," Deputy City Manager David Arrington said.
Arrington said because engineers have not finalized a stabilization plan, it's impossible to accurately estimate the final cost or when the work will be finished.
Scott Bridge Co., which is currently working on the 14th Street Bridge project, is performing the stabilization under a time-and-materials contract. Using a company that is already on or near the site will save the city money, Arrington said. The fact that the company will be able to use rocks it had planned to haul away for disposal will save the city more money.
Arrington said Georgia Power Co. is monitoring the conditions around three high voltage transmission towers in case they need to be moved.
During a briefing at Tuesday's Columbus Council meeting, Councilor Judy Thomas pointed out that during whitewater work on the Eagle & Phenix Dam, a section of the RiverWalk in that area collapsed. Now, with work being done on the City Mills Dam, a stretch of riverbank has collapsed near there.
"Are those things connected in any way?" Thomas asked.
Arrington said the damage adjacent to the Eagle & Phenix Dam was a direct result of the whitewater project, and Uptown Columbus Inc. paid to have the repairs made. But there's no apparent connection between the whitewater project and the collapse above City Mills.
"As a matter of fact, there's evidence in the area that there's been prior slippage in this area, where the embankment has fallen and new vegetation has grown," Arrington said. "Apparently, the slippage on the riverbank has been occurring for quite some time."
In addition to the riverbank collapse, a section of the old boat ramp behind the Columbus Convention & Trade Center has also collapsed due to erosion. Scott Bridge will also perform that repair, which is estimated to cost $65,000.