Due to conditions from heavy November and December rainfall we must delay the pool simulation of the recommended fixed crest weir at the New Savannah Bluff Lock and Dam site, originally scheduled to begin Jan. 5.
U.S. Army Corps of Engineers officials in the Savannah District now expect to conduct the simulation in early February if runoff rates return to acceptable levels by the end of January.
During a November public meeting in North Augusta, South Carolina, Corps leadership offered to conduct the simulation for local observation. The simulation, which deviates from normal operations, is part of the district’s effort to maintain transparency with the local community throughout the Fish Passage analysis process.
Congress directed the Fish Passage process through passage of the Water Infrastructure Improvements for the Nation (WIIN) Act in 2016. The simulation will demonstrate how the Savannah River in the Augusta area will appear with the recommended fixed crest weir during the low end of average flows.
The low-end of average flow is approximately 5,000 cubic feet per second (cfs). Just for context, and based on historical flow data, river levels in Augusta are higher than 5,000 cfs 77 percent of the time.
We cannot simulate a low-average flow condition in January because November and December rainfall is approximately 150 percent of normal above Thurmond Dam.
As a result of soil saturation, high water table and winter conditions, Hartwell runoff is at 200 percent of normal and Thurmond runoff is 300 percent of normal. Water levels in both reservoirs have risen into flood storage, requiring discharge rates at Thurmond as high as 28,000 cfs.
This discharge rate is much higher than the necessary low-average flow of 5,000 cfs for the simulation.
Furthermore, Thurmond discharge has remained high for all of December. As a result pool levels in Augusta, Georgia, have likewise been higher than what we typically observe throughout the year, which is roughly between 6,000 and 7,000 cfs.
The plan to conduct the simulation in early February remains tentative depending on January rainfall, runoff conditions and reservoir levels at Hartwell and Thurmond.
The recommended fixed weir with fish passage, which will replace the New Savannah Bluff Lock and Dam, is an environmental mitigation feature of the Savannah Harbor Expansion Project. It is required mitigation in accordance with the Endangered Species Act and is among the final seven proposed alternatives and refinements that the Corps studied under the direction of the WIIN Act.
The intent of the legislation is to provide a means for certain endangered fish to move upstream of the lock and dam to traditional spawning grounds.
~Russell Wicke, Corporate Communications Office