SAVANNAH, Ga. – The U.S. Army Corps of Engineers today unveiled its recommended plan to allow fish passage around the currently existing New Savannah Bluff Lock and Dam. The new plan will consist of a fixed weir to allow fish access to traditional spawning grounds between the lock and dam and Thurmond Dam.
The plan included demolition of the current lock and dam and the construction of the fixed weir with an in-channel fish passage. It also includes a floodplain bench that enables passing of higher water flows. Instead of having gates that can be lifted out of the water to pass higher flows, the floodplain bench will serve this purpose after the Corps excavates extra channel space adjacent to the weir and fish passage. As the river rises above the crest of the weir, water flows into the floodplain bench which provides additional capacity and ultimately prevents upstream flooding impacts from water backing up behind the weir.
The fixed weir’s set height will maintain the pool in Augusta. This will enable continued water supply, boating and other recreation along the cities’ waterfronts. With this design the water level is estimated to decrease only 1 to 2 feet in the downtown Augusta area under average flow conditions. River flows between 5,000 and 8,000 cubic feet per second are considered average flows. Flows above 5,000 cfs occur approximately 77 percent of the time.
Although the Corps’ recommendation is not the final selected plan, it does indicate the Corps’ direction in accomplishing the goal of opening more of the Savannah River to certain fish species. Several more steps must be completed before a final decision. One of these steps, a formal public comment period will immediately follow the scheduled February 2019 release of the draft report to the public for full review.
The public will then have 30-days to review the Corps’ work, modelling and analysis and provide written comments or concerns. From March through May 2019, the design team will review and address comments received on the draft report and recommended plan. If the Corps makes necessary adjustments based on public comments, those adjustments will occur during this time. The study is scheduled for completion in June 2019 and the final decision is anticipated in August 2019 by the commanding general of the Corps’ South Atlantic Division.
The protocol followed for the lock and dam and the fish passage is a nationally-approved, federal process used for all civil works projects. It is a process required by modifications as outlined in the Water Infrastructure Improvements for the Nation Act.
Out of seven possible alternative plans that were revealed in June, the recommended plan is the “Higher Fixed Weir with Dry Floodplain Bench,” known for short as Alt 2-6d. The construction cost for this plan is estimated at $68.9 million.
When combined with the total lifecycle cost which includes operations and maintenance, the cost of this plan over the life of the project is estimated at $73 million, far less than the original plan which would have cost more than $142 million with operations and maintenance of the life of the project.
The Fish Passage project is an environmental mitigation feature of the Savannah Harbor Expansion Project, and is required mitigation in accordance with the Endangered Species Act and the WIIN Act.
For more on the Fish Passage and the New Savannah Bluff Lock and Dam, see our past blog posts here.
For a history of the lock and dam, check our web page here.
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