Savannah Harbor Deepening: Two Changes to Biological Opinion
Two changes to the biological opinion associated with the Savannah Harbor Expansion Project give the Army Corps of Engineers more flexibility in contracting and scheduling construction activities as workers continue with the massive deepening project, USACE said in their latest release.
“After careful study, officials with the National Marine Fisheries Service changed the limit of encounters with certain protected species as the Corps dredges to deepen Savannah harbor and extend its shipping channel by 7 miles. The revisions include both non-lethal encounters where the species captured are simply moved to another nearby location and lethal encounters,” USACE said.
The biological opinion also revised the link between construction of a fish passage around the New Savannah Bluff Lock & Dam and dredging the inner harbor in Savannah. Previously, work on the fish passage had to begin before or concurrent with the start of inner harbor dredging. Now the inner harbor dredging can begin before construction of a fish passage around the 1930s-era structure near Augusta, Georgia.
The amended biological opinion states the fish passage must begin by January 2021.
This revised link enables more time for design changes in order to meet the requirement of the Water Infrastructure Improvements for the Nation (WIIN) Act, a new law enacted December 2016, according to Erik Blechinger, Deputy District Engineer for Planning, Programs and Project Management in the Savannah District. “The revision also allows more time for public involvement on a project that is complex and affects multiple stakeholder groups. The intent is an optimal solution that balances the needs of people and endangered species.”
Because the New Savannah Bluff Lock & Dam sits 182 miles above the harbor, the passage around it is an out-of-kind mitigation and not connected to the harbor deepening in Savannah from a biological standpoint, according to Blechinger.
The amended biological opinion placed particular focus on dredging impacts to the green sea turtle and the Atlantic sturgeon, both considered threatened species. The new limits for green sea turtles increased from three lethal and three non-lethal to 16 lethal and five non-lethal. The limits for Atlantic sturgeon changed from four lethal and 23 non-lethal takes to 20 lethal and 195 non-lethal takes, according to the amended biological opinion dated Oct. 13.
Observations from lethal and non-lethal encounters indicate the populations of these species are much more robust than originally estimated. This led to an increase in the limits, said USACE.
Contractors conducting the dredging of the outer channel use a combination of hopper dredges and slower cutter head dredges. During hopper dredging operations, they employ a relocation trawler to collect turtles and fish that may be in the path of the dredges and move them outside the work area. The relocation trawlers have already moved four green turtles and 95 Atlantic sturgeon to safer areas.
The fish passage will allow shortnose and Atlantic sturgeon and other species access to traditional spawning grounds near the Augusta Shoals and beyond to the Thurmond Dam. Opening these areas for spawning will mitigate for some predicted loss of fresh water habitat in the Savannah River estuary due to the deepening.