A federal agency said Tuesday that machines designed to inject extra oxygen for fish to breathe in Georgia’s Savannah Harbor passed a second round of tests that were required as part of the $973 million deepening of the shipping channel to the Port of Savannah. The Army Corps of Engineers released a 172-page report that concluded testing last summer found the injection machines successfully offset a small loss of dissolved oxygen in the water after dredging the main channel.
The Army Corps spent $100 million to build a pair of stations on the river equipped with large machines that suck in water, swirl it with oxygen pulled from the air and inject the mixture back into the river that’s home to blue crabs, striped bass and endangered shortnose sturgeon. A 2013 legal settlement with environmental groups who sued over the harbor deepening required the Army Corps to prove that the machines worked. The groups remain skeptical about the government’s commitment to run the injectors long term, estimated to cost $3 million annually—the Army Corps has not listed a source of funding in their report.
Southern Environmental Law Center attorney Chris DeScherer, who represented the groups in the federal lawsuit, said he had not yet reviewed the Army Corps’ entire report. He said he has concerns about the government’s commitment to operate the machines long-term at an estimated cost of $3 million per year.
The Army Corps said its second round of tests found two oxygen-injection stations on the river pumped an average of 40,000 pounds (roughly 18,000 kilograms) of oxygen into the river daily from late July through September. It concluded the oxygen was mixed well throughout the water column. The injectors will run each year during the hottest months of the year from June through September, when oxygen levels in the river tend to be lowest.
This raises questions about the possibility of using these types of injectors to rejuvenate other estuarine environments that suffer from temporary or even permanent dead zones. Dead zones are areas where algae, chemical runoff or other factors have depleted the dissolved oxygen in the water to the point that it can no longer sustain life. They usually occur during the warmest months of the year and are typically found near the bottom in deeper estuarine waters.