Louisiana taps into a buried treasure of sand to rebuild barrier islands

Updated: May. 7, 2018 at 3:37 PM CDT
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(WVUE) - Louisiana is spending hundreds of millions of dollars rebuilding its barrier islands, but it faces a critical challenge in that effort: finding an affordable and plentiful supply of sand to sculpt islands and marsh.

Ten miles off the coast of Terrebonne Parish lies a virtual gold mind of sand, an ancient barrier island buried beneath the sea known as "Ship Shoal."

The state, in a cooperative arrangement with the federal Bureau of Ocean Energy Management (BOEM), has mined sand from the shoal on two barrier island projects, most recently on Whiskey Island south of Cocodrie.

"Ship Shoal is a paradigm shift in Louisiana's approach to coastal restoration," a coastal geologist for BOEM said.

To restore Whiskey Island, a dredge sucked sand from the shoal before it was piped about 10 miles onto the island.

"Where we're standing right now was water a year ago," said Brad Miller, project manager for the Louisiana Coastal Protection and Restoration Authority, as he survey the Whiskey Island project.

Ship Shoal formed roughly 7,000 years ago as the ancient delta sank. First mapped in the 1930s, coastal planners have been eyeing it as a source of building material for decades.

"We're taking a resource that was placed there by the Mississippi (River), and we're basically bringing it back into the active shore zone system and utilizing it," said Darin Lee, a CPRA coastal scientist. "This gives us the opportunity to pump large quantities of sand at one time in one effort."

Just as importantly, scientists say, it represents new material from outside the modern barrier islands system. That addresses one of the root causes of the land loss - the lack of enough sand to replenish islands or build new ones.

"Ship Shoal contains around one-and-a-half-billion cubic yards of sand," Miner said.

Imagine 300 Superdomes worth of high-quality sand.

"It's got a very low percentage of muds," Miner said. "It's almost 99 percent sand."

Coastal planners say the worst place to find sand for rebuilding an island is usually near the island, where they find mostly mud.

The higher quality sand was long ago blown away.

"If you're not bringing sand from outside that system, you're not addressing that deficit," Miner said.

Over the last decade, the state and federal governments have stitched back together 30 miles of islands, creating a first line of hurricane defense. Two recent projects tapped into Ship Shoal, Whiskey Island and the last phase of the Caminada Headland restoration west of Grand Isle.

Scientists say the islands also play a critical role in creating Louisiana's seafood bounty by separating Gulf habitat from the Louisiana estuaries.

"They help to regulate salinities and create that productive wetland that everybody in South Louisiana is familiar with," Lee said.

However, most of Ship Shoal is off limits as a source of rebuilding material.

Active and abandoned oil and gas pipelines dissect the Gulf, making dredging nearby impossible.

"We're working with industry and the state of Louisiana to free up more sand as pipelines are coming out of use," Miner said.

Scientists say they would not want to take it all anyway.

Ship Shoal provides important habitat for marine life, affects how currents move and provides a safe haven for turtles and other creatures during the annual low-oxygen dead zone in the Gulf of Mexico's deeper waters.

"We're only talking about utilizing a portion of it," Lee said, "but that portion is a massive amount of sediment compared to what we have in other locations.

The current estimate suggests only about 10 percent of Ship Shoal could be utilized, enough for about 40-year supply of sand to rebuild islands.

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