Conservation groups say they "remain skeptical" that machines injecting oxygen into the Savannah harbor will offset threats to fish caused by deepening the busy shipping channel.
However, the Southern Environmental Law Center says the groups won't return to court to fight the $973 million expansion of the waterway to the Port of Savannah.
The Army Corps of Engineers said in August a test run of the machines exceeded expectations in boosting dissolved oxygen to help fish breathe in the Savannah River, which Georgia and South Carolina share. The test was required by a 2013 legal settlement.
Law center attorney Chris DeScherer said in a letter Friday to the Corps that while the tests show oxygen increased in the harbor, "we remain skeptical that the System will effectively work in perpetuity."