SAVANNAH, Ga. – The Savannah District, U.S. Army Corps of Engineers, has completed tests on its Hutchinson Island dissolved oxygen injection system, as an environmental mitigation aspect of the Savannah Harbor Expansion Project. Preliminary assessments of the testing data indicate the plant operates as designed and produces results as anticipated or better.
“We've completed the testing and data-collecting phase and we are still making progress in the analysis of the data, and plan to release a final report in August,” Bryan Robinson an engineer with the Corps who oversaw the tests, said. “Our general impression right now is that the tests indicate the system is performing better than expected in the three primary aspects of the tests.”
- Tests demonstrated the system can deliver more than the required amount of DO to the river.
- Analysis of the test data so far indicates a good amount of dissolved oxygen distribution within the river. The dissolved oxygen mixes well in the water and it remains detectable for days further up- and down-stream beyond what was expected.
- Preliminary analysis shows the river retains dissolved oxygen in the water column on average better than anticipated.
Specialists with LG2 Environmental Solutions of Jacksonville, Florida, conducted the tests on 59 consecutive days. This schedule covered two complete lunar cycles to determine the effects the different tidal levels would have on the distribution of super-oxygenated water in the river. In addition, they conducted multiple tests using red dye to show the distribution in the water.
“Even after the dye became too faint to see with the human eye, our instruments could detect it in many parts of the front river and the back river days after the tests,” Beth Williams, Chief of the Hydrology Section at the Corps, said. “We could also detect the dissolved oxygen and red dye at depth in the river, which indicates it reaches the lower parts of the harbor.” Williams emphasized the observations remain preliminary and data will be further analyzed before a final report due out in August 2019.
Injecting super-oxygenated water into the Savannah River helps mitigate for the loss of oxygen as the harbor is deepened from its current 42 feet to 47 feet. The Savannah Harbor Expansion Project, also known as SHEP, will provide greater opportunity for modern container ships to enter and leave the port with greater loads and with fewer tidal restrictions. The extra oxygen added to the river will benefit fish, particularly the endangered shortnose sturgeon and the Atlantic sturgeon as they pass through the area to upstream areas and back to the Atlantic Ocean.
The SHEP will benefit the American economy by a ratio of 7.3 to 1. That means for each $1 spent on deepening the harbor, the U.S. economy will see a net benefit of $7.30, or a net benefit of $282 million per year.
The Corps of Engineers uses Speece cones, giant steel cones which use river water, mixing at high pressure to dissolve pure oxygen into the water. The machinery then returns the super-oxygenated water to the river where tides and currents distribute it naturally. Pure oxygen is extracted from the air at the Hutchinson Island location. As an automated plant, it requires little human involvement.
The system will be used mostly during the hot, summer months when oxygen levels in the river are naturally lower.
The successful demonstration of the dissolved oxygen injection system is a requirement before dredging of the inner harbor can begin. The outer harbor, from approximately Fort Pulaski to 19 miles into the Atlantic, was completed in March 2018.
The construction of a second dissolved oxygen injection system in Effingham County, Georgia, nears completion.