The U.S. Army Corps of Engineers will replace New Savannah Bluff Lock and Dam near Augusta with a rock weir fish passage that results in a lower pool of water in the Savannah River, a move almost certain to be challenged by a lawsuit.

The U.S. Army Corps of Engineers announced Tuesday that it will choose an option that will demolish New Savannah Bluff Lock and Dam in favor of a rock weir fish passage that will lower the pool in the Savannah River significantly.

The decision, which is widely and vehemently opposed by Georgia and South Carolina leaders, will likely end up in a lawsuit perhaps as early as this week, officials said. The Corps left open the door for a higher water level, but it will require local entities to contribute to it.

The Corps said it will hold a "public engagement" on the plan from 6 to 7:30 p.m. Nov. 13 in Augusta at the Boathouse Community Center, 101 Riverfront Drive, where it will discuss details of the plan. But public reaction to the plan from Georgia and South Carolina at all levels of government was swift.

U.S. Rep. Rick Allen, R-Ga., said the move would violate the requirements of the Water Infrastructure Improvements for the Nation Act of 2016, which authorized a fish passage but also required the pool in the Savannah River be maintained "for navigation, water supply, and recreational activities, as in existence on the date of enactment of this Act," which on Dec. 16, 2016, was 114.5 feet above sea level.

The Corps' alternative would maintain an average river pool at least two feet below that, which would not be acceptable under the requirements of the law. The Georgia and South Carolina delegations, including U.S. Sens. Johnny Isakson, David Perdue, Tim Scott and Lindsey Graham, have sent the Corps a letter stating that.

Allen said he expects South Carolina Attorney General Alan Wilson to file suit by the end of the week or next week. Robert Kittle, a spokesman for Wilson's office, said he could not confirm that but noted that the South Carolina Legislature has already appropriated $1.4 million for Savannah River-related litigation.

By not respecting that law, "it's a military takeover of our waterways," Allen said. "We're in the fight of our lives."

In a joint statement with Allen, U.S. Rep. Joe Wilson, R-S.C., said it is a decision to "ignore the will of the American people and the intent of Congress, and move forward in a display of tyranny."

The chosen alternative, known as 2-6d, would be a rock weir that stretches the length of the river just upstream from the current lock and dam and would allow the passage of endangered sturgeon and other migrating fish. The move is necessary to mitigate damage to the habitat those fish currently use in the river near the Savannah Harbor, which is being deepened. The lock and dam would be demolished after the weir is in place.

Augusta Commissioner Brandon Garrett said he was “disappointed,” particularly in light of area leaders’ trip to Washington last week to try to save the aging structure and the findings of an outside expert report, which criticized the Corps' research and analysis.

“What you are going to see now is some litigation,” Garrett said.

The commission and attorneys discussed the potential litigation behind closed doors Tuesday, but the commission took no action afterward.

"It's unfortunate that the Corps didn't take into consideration the concerns our region has with their plan," Commissioner Mary Davis said.

Augusta Mayor Pro Tem Sean Frantom said the community is "disappointed but not surprised" by the Corps' decision.

"The Corps has worked by their own playbook the entire time. It's time we dig our heels in and stay together as a community," he said.

Frantom said he hopes laws can be changed to save the pool, and that Gov. Brian Kemp has plans to assist with the situation.

The Corps has said it is not bound by the literal interpretation of the WIIN Act. While its preferred plan will lead to an average depth about two feet below the current pool at downtown Augusta, none of the alternatives, even the one from 2014 that kept the lock and dam, would result in the river pool staying at the height the Georgia and South Carolina lawmakers are insisting on, the Corps said.

North Augusta Mayor Bob Pettit was among the officials who received a call about the decision from Maj. Gen. Diana Holland, the commanding general of the Corps' South Atlantic Division in Atlanta. While expressing his disappointment to her, "I told Gen. Holland, and if I remember right she agreed with me, this entire thing hinges on the intent of the WIIN Act of 2016 and that's obviously going to have to be decided by the courts," Pettit said.

Allen said the Georgia and South Carolina delegations have documentation showing the legislative intent of the WIIN Act was for the river to remain at its current full pool and that the Corps would be wrong to contest that in litigation.

"There's no way they can win in court," he said.

Savannah Riverkeeper Executive Director Tonya Bonitatibus said rather than a trigger for litigation, the Corps' announcement is the start of a "conversation" about finding a solution agreeable to all.

"They never were going to save the dam," she said. "Hopefully this is enough to allow the communities to come to an understanding that it's time to have real negotiations."

A simulation of the Savannah River pool that the recommended plan would leave in place happened in February during a controlled drawdown, which exposed numerous hazards in the river channel and left some docks and boats sitting on mud, particularly on the North Augusta side. Some damage to riverbanks and a seawall prompted the Corps to end the drawdown early.

However, the Corps determined later that because of repairs to the Stevens Creek Dam upstream of the lock and dam, conditions during the drawdown were of the "lowest possible flows" that could be expected once the weir is in place. But even under those extremes, with virtually no water coming at times from Lake Thurmond into the river, water intakes along the Savannah were still functional.

The Corps acknowledged the desire expressed by Georgia and South Carolina leaders but noted that a higher weir, which would result in a higher river pool, could be negotiated even before construction begins if those leaders can work out a "locally preferred plan" with the Savannah Harbor expansion project's main non-federal sponsor, the Georgia Ports Authority. The authority would have to make the request for the different plan.

Those who ask for a locally preferred plan would also be responsible for paying the difference in costs between that plan and what the Corps recommended. For instance, one of the alternatives the Corps studied, known as 2-6a, had a higher weir and would result in a higher average river pool. The cost of constructing that alternative would be $123 million versus $96 million for the Corps' preferred plan, so local leaders would be on the hook for $27 million, Corps spokesman Russell Wicke confirmed.

That higher weir would also result in more flooding of low-lying areas along the river, so local leaders would also be responsible for getting easements to those properties that would be affected and would also be responsible for those costs, Wicke said.

Perdue said he understands the disappointment in the decision but pledged to continue working with the community, the Corps and the Georgia Ports Authority "to find a financially feasible solution that meets the needs of the community." Isakson said "all stakeholders" should work together "to prevent any negative impacts to either the Augusta riverfront or the Port of Savannah."