Army Corps looks for feedback on what to do with limestone dug up in Charleston Harbor deepening

A container ship approaches the Arthur Ravenel Jr. Bridge through the Charleston shipping channel.

The problem with digging up 9 million cubic yards of limestone rock is that it weighs a lot. That’s why Army Corps of Engineers staffers are talking with conservation and sports groups in the Lowcountry.

They’re looking for ideas and potentially funding support if there’s more limestone removed during the Charleston Harbor deepening project than can be used to build eight artificial reefs and a huge berm out to sea off the Charleston jetties.

The prospect of handy limestone to set inshore fishing reefs or secure oyster reefs is “incredible. The potential is ‘once in a lifetime,’ ” said Dave Fladd of the Summerville Saltwater Anglers, one of those groups.

The cost and logistics to move the weighty rock, though, could be as daunting as lifting one of those huge chunks.

“We need to find out what the costs are, environmental impacts and other details before we can make any decision (about seeking grants or other funds),” said George McDaniel of the Ashley River Scenic Advisory Committee, another of the groups. But the groups are spreading the word through the sports and conservation communities.

“We need to get the word out so this opportunity can be maximized,” he said.

The $509 million deepening project aims to dig the 45 feet-deep shipping channel to 52 feet from State Ports Authority terminals through the harbor and 3 miles out to sea, or about to the end of the jetties. It would give the state the deepest port on the East Coast, able to handle larger ships sailing the Panama Canal when an expansion of that waterway is completed this year. The harbor deepening is expected to be done by 2020.

The limestone disposal is an unusual challenge of the project: Because of the new depth, the dredges will be digging into different material than before, said Sean McBride, Army Corps Charleston district public affairs specialist. The meetings are preliminary as the Army Corps explores options and analyzes alternatives.

“We use the money we are allotted to complete a project. If the most beneficial design has funding to take the rock to a certain location, that’s what we would have to do, ” he said.

“Taking rock to a site farther away would cost more money and a longer project schedule. The government’s funding is very complicated and we can’t just take money from any particular group. We have to do what is the most economically beneficial and environmentally responsible,” he said.

Samples have suggested 9 million cubic yards of the limestone will be removed. But how much will actually be removed and how it potentially could be used “really will depend on what we would be able to pull up, the type of rock and the size,” said Holly Carpenter, Army Corps district manager for the project.

As part of the project, the limestone would be used to build four artificial, 30 acre-plus fishing reefs outside the jetties on either side of the channel, as well as a 400 acre-plus, U-shaped berm outside the south jetty three miles to sea, where some of the dredged material would be placed. That also would serve as a fishing reef.

Public input so far has suggested uses for the dredged material including:

Bolstering the Crab Bank bird rookery in the harbor.

Renourishing sand lost near the Morris Island Lighthouse.

Protecting the shoreline of Shutes Folly, where Castle Pinckney is located.

The district office is weighing the costs and benefits of those options now.

“There is a possibility that we’d work with local groups on additional uses,” Carpenter said.

But to do something like bring limestone through the harbor to the lower Ashley River for fishing or oyster reefs would mean the groups interested would have to search for grant funding, Fladd said.

The Summerville anglers group has been trying to restore an oyster bed in the lower Ashley for three years, he said. Oysters are not growing well on the shells placed, but they grow well on rebar when it’s set to hold the shells in place. The suspicion is the bottom in that stretch, where deep deposits of pluff mud are found, gets too muddy.

“Imagine what a limestone reef would do for oyster beds there,” Fladd said.

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