Tide gate removal pushes SHEP closer to completion

The tide gate structure in 2016 (above) and in December 2017 following its removal.

SAVANNAH, Ga. – The removal of a 1970s-era structure from the Savannah River’s Back River marks another major milestone in the deepening of the nation’s fourth busiest container port. It also returns the Back River to its natural width to enhance the area for fish habitat.

Removal of the tide gates on the Back River is the latest mitigation feature to be completed for the massive improvement of the Savannah harbor. The Savannah Harbor Expansion Project (SHEP) will deepen the harbor and entrance channel from 42 feet to 47 feet, allowing larger neo-Panamax container ships to enter the harbor with fewer tidal restrictions.

“By removing the tide gates we restored the Back River to its natural state,” Spencer Davis, project manager for the SHEP, said. “This is the first part of the flow re-routing measures in the SHEP, designed to protect freshwater marshes in the Savannah National Wildlife Refuge from saltwater intrusion.”

While removing the tide gates, workers recycled some of the concrete by placing it in the Back River to enhance fish habitat. The wider channel also slows river flow which also enhances fish habitat, according to Davis.

The tide gates, installed in the early 1970s, closed with each ebb tide forcing more river water through the front river along the Savannah city front. This increased velocity forced sediments away from that area into one more easily dredged, thus saving on expensive channel dredging.

However, through the years of their use, the tide gates began to change upstream freshwater marshes in the refuge to saltwater marshes. The negative environmental impacts outweighed the benefits of lower dredging costs and the gates were taken out of service. The gates’ support structure and the narrowed channel remained until removal in December 2017.

The $21.3 million project, performed by the Miami-based DeMoya / Continental Joint Venture, came in $900,000 under budget and on-schedule, moving the deepening of the harbor another major step forward, according to Davis.

Workers removed more than 3,200 tons of concrete and more than 650,000 cubic yards of soil and placed approximately 130,000 tons of rock along the 3,000 feet of shoreline in both Georgia and South Carolina.

(Video: Tide gate / sediment basin work from March 2017.)

The SHEP involves significant environmental mitigation features, with many nearing completion.

These include a dissolved oxygen injection system that will supply oxygen to the harbor in hotter months, a raw water storage impoundment that will provide additional freshwater storage for the city of Savannah, and the remaining features of work on the 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 area dikes, which wrapped up in the summer of 2017, marked SHEP’s first completed portions. Completion of the dissolved oxygen injection system and the raw water storage impoundment will follow in the first half of this year.

“The tide gate removal again demonstrates the extraordinary dedication the Corps of Engineers has for the environment while striving to enhance America’s economic strength,” said Erik Blechinger, deputy district engineer for Programs and Project Management.

The SHEP is funded jointly between the state of Georgia and the U.S. government. The current schedule estimates the project will be complete in 2022.

~ Billy Birdwell, Corporate Communications Office

About U.S. Army Corps of Engineers Savannah District

The U.S. Army Corps of Engineers Savannah District oversees a multimillion dollar military construction program at 11 Army and Air Force installations in Georgia and North Carolina. We also manage water resources across the Coastal Georgia region, including maintenance dredging of the Savannah and Brunswick harbors; operation of three hydroelectric dams and reservoirs along the upper Savannah River; and administration of an extensive stream and wetland permitting and mitigation program within the state of Georgia. Follow us on Twitter @SavannahCorps and on Facebook.com/SavannahCorps
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