September 9th, 2010 9:52 AM

To shore up Dauphin Island, scientists bring out high-tech tools

Published: Thursday, September 09, 2010, 8:30 AM     Updated: Thursday, September 09, 2010, 9:41 AM

DAUPHIN ISLAND, Ala. — Scientists are deploying high-tech research tools in the hunt for sand to shore up this barrier island’s precarious west end.
               
Like fussy shoppers at a food mart, they’ve examined sand at locations all around the island, both for quality and for possible oil contamination.
               
The sand samples are obtained by a process called “vibracore” in which a tube plunges 20 feet into the sea floor, driven forward by high-speed vibration. Crews then pull out a core 3 inches in diameter, which shows them layer by layer what’s beneath them.
               
The layers examined Wednesday — taken from a shoal not far from Sand Island Lighthouse — showed no evidence of oil, which pleased the researchers aboard the 85-foot Thunderforce. The vessel is operated by American Vibracore Services.
               
“We need sand. Lots of sand,” said Scott Douglass, a professor at the University of South Alabama and a noted coastal engineer who is guiding the work.
               
The project calls for moving 5 million cubic feet of white sand that matches what’s currently on Dauphin Island beaches in terms of grain size and color.
               
The sand hunters also must take care to find what they want in areas not cluttered with shipwrecks from the last three centuries and the extensive infrastructure of pipelines related to oil and gas rigs.
               
Douglass said the shoal near the Sand Island Lighthouse is the most promising spot. The only catch is its distance from Dauphin Island’s west end.
               
“The typical hauling cost is fifteen dollars a cubic yard, so the project may have to be scaled down,” he said.
               

Enlarge John David Mercer Richard McKenzie, a University of Florida geologist and intern for CPE Inc. (Coastal Planning Engineering) out on American Vibracore Services big vessel "Thunderforce" Wednesday Sept. 8, 2010 doing vibracores for rebuilding the Dauphin Island beach. They are searching for good sand just off Dauphin Island. This location was roughly one mile south of the Sand Island Lighthouse. (Press-Register/John David Mercer) Dauphin Island Vibracore gallery (14 photos)

Even if it is pricey, geologist Richard MacKenzie couldn’t hide his enthusiasm as he checked the cores pulled up Wednesday.
               
“This isn’t good sand. This is great sand,” he said. “You have to target the grain size, which shifts as you go deeper. It’s drying lighter and lighter, which is what you want to see.”
               
The work is being done with $1.5 million in federal funding given to Dauphin Island in December.
               
Beach nourishment has worked well for Gulf Shores and Orange Beach, Douglass has said. The 2001 beach nourishment project in central Gulf Shores “has probably paid for itself a dozen times over in reduced storm-induced damages to public and private property.”
               
The Dauphin Island effort is still months away from dredging, and the costs may be covered in part with National Oceanic and Atmospheric Administration money, Douglass said.
               
Much of the erosion that necessitates the beach nourishment work is blamed on Hurricane Opal, which hit in 1995, but in the past 15 years Dauphin Island has been damaged by 16 tropical storms or hurricanes.
               
Dauphin Island’s westernmost mile has moved 350 feet north since 1995, he said.

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