Port restores island habitat under Clean Water Act

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Two years ago, the island lying beneath Charleston’s Arthur Ravenel Jr. Bridge would have looked almost unrecognizable to today’s visitors.

A slurry of sediment and water oozed across the island’s southern tip as millions of cubic tons of silt from the latest ports project rushed in from a pipeline, held in by dikes near the water’s edge. A tangle of invasive plants and trees grappled with indigenous marsh grasses, choking the natives as they reached skyward.

That was Drum Island before Mark Messersmith, S.C. Ports Authority’s permitting manager, and $3.5 million united to launch the port’s lesser-known construction project of the decade — this one built to foster a natural ecosystem instead of just an economic one.

“The south side of the island had been used historically for dredging material disposal but had not been used for a couple of decades,” he said. “So, when we were going through the design for the Hugh Leatherman Terminal, there were some inadvertent impacts to saltwater wetlands as a result of that project at the old Navy base. And so, to counter those impacts, we proposed a mitigation plan to create a 22-acre, brand-new salt marsh out of the portion of Drum Island that is south of Ravenel bridge.”

Now, almost 80% of the island is covered in vegetation after the team planted more than 106,000 native marsh plants, Messersmith said. Fiddler crabs swarm channels re-excavated by Messersmith’s team, and the spot has since become a haven for estuary bird species and the Audubon Society as herons of all hues, clapper rails and snowy egrets fish for prey in the spartina grasses.

“We actually excavated about 110,000 cubic yards of dirt from that island, and in doing that, we created these creek and channels running through there,” he said, laying the groundwork for what he calls a thriving salt marsh.

A hard day on the job involved redesigning a creek mouth “on the fly,” skirting the bones of previous bridges with the aid of Cayce subcontractors L-J Inc. Still, he added that this snarl was rather benign, and the construction crew finished on time and under budget.

The Drum Island restoration project was fueled by a condition of the 1972 federal Clean Water Act that requires companies that impact national waters and wetland properties to mitigate that damage by recreating or preserving new wetland habitats.

The law is long-standing but contentious for some, especially developers. Still, Messersmith said that he’s thankful the law enables the port system to give back — both economically and ecologically — to the extensive harbor property it requires to remain functional and keep expanding.

“There’s always controversy around that kind of thing,” he said. “The way the port sees it is that we’re always going to make an impact in the work that we do, it’s just the nature of where we work. We work on the interface between the water environment and the land environment. No matter what we do, there are going to be some impacts and construction, but we also recognize that we’re users of the harbor, and we’re a part of the community here. We have impacts too on the resources in our community, in our watershed; we should compensate for those impacts in a quantifiable way.”

The success of the Drum Island project may also set a precedent for future environmental restoration initiatives in the area. 

The S.C. Ports Authority continues to use acres of marsh as silt dumping areas for ongoing projects, including the north of Drum Island, Morris Island, the Clouder Creek area and Daniel Island for Hugh Leatherman dredge materials. Additional dredge materials are pumped out to an offshore Environmental Protection Agency dumping site, which undergoes the most stringent vetting after removal from local sites.

Every year, billions of cubic yards must be dredged to maintain Charleston harbor as a viable shipping channel. This occurs even when the deepening project isn’t in full swing. The solid materials drift to the bottom, and the clear water cycles back into the sea.

The Drum Island project remains unusual from some Clean Water Act sites since the S.C. Ports Authority restored the natural habitat of the property previously used as a dumping site instead of conserving additional property. Also, the size of the restored property, 22 acres, is double that of the Leatherman dumping site.

“Sometimes you get a better value for the habitat over all by going away from the project site,” he said. “Certainly, if we had built a 22-acre marsh just adjacent to the new terminal there, it wouldn’t be as valuable as having it where it is, a little bit further away, but still it’s right there. You can see the terminal from the island.”