Posted on June 11, 2019
Results are preliminary, final report due in August
Required testing of a system to mitigate oxygen loss from the Savannah Harbor Expansion Project (SHEP) is complete, the U.S. Army Corps of Engineers said Wednesday.
SHEP will deepen the Savannah River from 42 to 47 feet to accommodate larger, fully loaded ships and allow for fewer tidal restrictions.
Before dredging on the 22-mile stretch of the inner harbor can begin, the dissolved oxygen (DO) system must be shown to work as expected. The inner harbor deepening starts from near Jones Island to the Garden City port. Jones Island is between Fort Pulaski and Tybee Island.
With a deeper harbor, more salt water will enter the river and estuary, decreasing oxygen levels needed by fish and the whole ecosystem.
Preliminary assessments of the testing data are positive, Corps officials said.
“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,” said Bryan Robinson, an engineer with the Corps who oversaw the tests. “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.”
Robinson said preliminary tests have shown the system can deliver more than the required amount of dissolved oxygen to the river, a “good amount” of dissolved oxygen distribution in the water, it mixes well in the water and remains detectable for days farther up and down stream than expected. Preliminary analysis shows dissolved oxygen at depth is retained on average better than expected.
Oxygen deficiencies show at the bottom of the water, Wicke said.
“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,” said Russell Wicke, corporate communications officer for the Corps.
The testing of the Hutchinson Island plant was conducted over 59 consecutive days from March to May, Wicke said.
Testing was done by LG2 Environmental Solutions of Jacksonville over two complete lunar cycles to see the effects different tidal levels would have on distribution of the super-oxygenated water. Multiple tests were conducted using red dye to show distribution of oxygen 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,” said Beth Williams, chief of the hydrology section at the Corps. “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.”
A second plant is under construction upriver at Plant McIntosh in Effingham County.
Williams stressed that the observations remain preliminary and data will be further analyzed before a final report is due in August.
Wicke said while the preliminary results appear positive, much work remains before the system is declared a success.
“Now we are in the analysis stage,” Wicke said. “We will go through the data meticulously.”
SHEP deepening is being done in two phases, with the first phase of the 19-mile long entrance channel, or the outer harbor, completed in March 2018.
The DO system uses steel cones, called Speece cones, which take river water and mix it at high pressure to dissolve pure oxygen from the air into the water. The machines return the oxygenated water to the river. Corps officials said the plant is automated and requires little human involvement.
The system will be used mostly during the hot summer months when oxygen levels are naturally lower.
Wicke said dredging on the inner harbor could begin in September.
The Effingham County plant will be tested along with the Hutchinson Island plant during hot months. If those tests go well, dredging can continue, Wicke said.
Wicke said he wanted to stress these early results are “not a milestone.” “It looks pretty good, but we have to have it in writing.”
The harbor deepening has faced legal challenges from environmental groups and South Carolina government agencies, some of it focused on the unprecedented setting for Speece cones. The technology isn’t new, but it’s usually used in much smaller projects, such as wastewater treatment ponds, rather than a 47-foot deep harbor with huge tidal swings.
A settlement reached in 2013 requires the Corps to prove the oxygen system works as it should before inner harbor dredging can start. The agreement allows the conservation groups and state agencies to restart their litigation if they are not satisfied with the test results.
Source: blufftontoday.com
