Posted on February 26, 2018
By Mary Mayle, savannahnow
With an important environmental window narrowing, the U.S. Army Corps of Engineers and its dredging contractor have been working around the clock to make sure a major component of the Savannah Harbor Expansion Project is completed on time.
Dredging of the 20-mile-long entrance channel from 42 to 47 feet must be completed soon, as the quicker and more efficient hopper dredges can only operate during winter months, when impacts to sea turtles and endangered sturgeon are lowest.
Since the window opened in mid-December, the Great Lakes Dredge and Dock Co. has been at times operating up to five hopper dredges 24-hours a day, often employing trawlers to move in front of the dredges to capture, tag and relocate turtles and other endangered sea life.
“The environmental approvals for the SHEP include a hopper dredging window from Dec. 15 to March 31,” said Corps’ spokesman Billy Birdwell. “However, we have received environmental approval to continue hopper dredging if necessary until no later than April 15, dependent on the water temperature.”
That said, Birdwell indicated the Corps expects to be done with the entrance channel, which extends from Fort Pulaski out into the Atlantic, in March.
“This is the first step to allow the larger, neo-Panamax container ships to enter the harbor with fewer tidal restrictions,” said SHEP project manager Spencer Davis.
Later, as the Corps completes more environmental mitigation and testing, they will deepen the inner harbor from Fort Pulaski to the Garden City port to 47 feet.
A delicate dance
Using at times up to four hopper dredges for the deepening and one hopper dredge for routine maintenance in such a busy channel requires close coordination among the vessels, said Jason O’Kane, navigation manager for the Corps’ Savannah District.
“Maintaining crew safety and avoiding shipping disruption remain our highest priorities,” O’Kane said, adding that both Great Lakes Dredge and Dock and maintenance contractor Manson Construction have experience using multiple dredges in one location.
Dredging of the outer harbor alone has been a monumental undertaking, Birdwell said, adding that nearly 11 million cubic yards of material has been removed from the channel to date.”
“That would be approximately 1.1 million truckloads if we were using dump trucks.”
In addition to dredging, SHEP features an unprecedented number of mitigation projects, including a dissolved oxygen injection system that will supply oxygen to the harbor in hotter months, a raw water storage impoundment that will provide an additional freshwater source to the City of Savannah, and a flow re-routing of the Savannah River adjacent to the Savannah National Wildlife Refuge.
Removal and relocation of the Civil War ironclad the CSS Georgia and raising containment dikes wrapped up in the summer of 2017, marking the first portions of the nearly $1 billion SHEP completed.
Removal of tide gates and restoring the width of the Back River between Hutchinson Island and the South Carolina banks of the river finished later last year, while completion of the dissolved oxygen injection system and the raw water storage impoundment will follow in the first half of this year.
Ecology first
Just as hopper dredges can only be used when the water temperature is lower and less likely to attract endangered sea turtles, environmental concerns have been at the forefront of the massive civil works project from the beginning.
When Birdwell was asked if the start of inner harbor dredging would come on the heels of outer harbor completion, he said pointed out that environmental issues would again play a part.
“Before work can begin on the inner harbor dredging, construction of the dissolved oxygen injection system in the river must be completed and testing done,” he said.
Erik Blechinger, the Corps’ deputy district engineer for program and project management, concurred.
“The environmental mitigation program for this project demonstrates the Corps’ emphasis on preserving the ecology of the region, Blechinger said. “We committed to this from the beginning.”
Source: savannahnow
