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Dredging Enough Sediment to Fill 12,230 Olympic-Size Swimming Pools



By: Claudie Benjamin, Guest Writer

Twelve years may not seem quick, but in the world of projects undertaken by the U.S. Army Corps of Engineers, Charleston District, this amount of time from planning to expected completion is extraordinary, fast even, according to Jeremy Johnson (pictured below), Project Manager for the Charleston Harbor Post 45 Harbor Deepening Project.

From the start, development of the project was impressive in terms of how efficiently plans were drawn up and funding approved by Congress in less than two years. Recently, Johnson went up on a Coast Guard helicopter to take a look and capture some images of the broad water span he manages. Eight to ten dredges are currently in operation.  It is nothing short of awesome. This is a historic moment for the District with the unusual amount of dredge activity occurring. Normally, two to three dredges being in one harbor is impressive. This excitement comes as the District is celebrating 150 years of serving South Carolina and the nation, making it even more special.

After graduating from North Carolina State University, Johnson went to work for the U.S. Army Corps of Engineers in 2009. Working near the coast had great appeal. He says, I thought I would be helping out with some technical details.” But, his aptitude and skills were acknowledged and he was soon the leader of the biggest project the Charleston District  has ever undertaken in South Carolina.

Johnson is in charge of coordinating all aspects of the complex implementation of dredging the harbor. This involves working with a team made up of engineers and other professionals from his own district as well as other subject matter experts who work for the other Corps districts. There are multiple contractors from various dredge companies involved as well, in all about 250 contractors on the job 24/7 support this work. He sees himself as the hub of communications. Because of the way the Corps is organized, Johnson has access to expertise among the other 45 Corps of Engineers districts spread throughout the US.  representing a broad range of engineering specialties. Pre-Covid, they would often fly in to consult.  During the Covid period these exchanges have been virtual.

Dredging the harbor to a depth of 52′ is done underwater and therefore is not seen typically  by observers. The amount of soil and sediment removed to deepen the harbor is equivalent to about 12,230 olympic size swimming pools. Some of the material is removed and placed 15 miles offshore. The rest is relocated into large unremarkable parcels of land and built up as dikes, like the one visible from the Ravenel Bridge. These are called upland placement sites.

How monumental is this project?  The huge cost of the deepening is the same $600 million that was required for building the Ravenel Bridge. Johnson says that the Corps counts projects as valuable and justified if they bring in two dollars of benefit for every one dollar spent. In this instance, the economic impact or cost benefit ratio is six dollars for every one dollar spent.

Like the bridge, deepening the harbor has a direct impact on improving the quality of life for the community. More specifically, making the harbor navigable for larger cargo ships and removing the dependence on tides, allows operations of these commercial vessels to proceed in and out of the harbor without delays. The outcome makes it possible for customers to purchase items from Costco, Walmart and Target at lower cost than would otherwise be possible. The project’s purpose is to address transportation inefficiencies.

Weather is always a variable in dredging, but this past year of the pandemic crisis has also brought challenges in keeping staff healthy and on the job.

The harbor deepening is reaching completion soon, in the winter of 2022, but the record dredge activity makes it part of this year’s 150th Anniversary celebration. Harbor deepening was also a priority at that time back then playing a critical role in the growth and prosperity of South Carolina.  “In 1871 the Corps established permanent roots here opening its first District office. Twenty years prior, in 1851 we performed the first harbor deepening to  21′,” says Johnson, noting that “construction of the jetties in 1882 allowed for tide flow and safe navigation. They were built so well that they did not require repair until last year.”

As for the deepened harbor Johnson says it’s anticipated routine maintenance will continue, but this major dredging will expedite shipping in Charleston Harbor for a long time to come. The Corps is proud to deliver solutions that help create a better tomorrow.

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