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The Shoreline
March, 2002
Beach Nourishment Update 31 January 2002
What a difference a couple of months can make. In October, we were wondering whether we would get
permits for the nourishment project. By Christmas, the first mile of new beach was nearly complete.
After the regulatory gauntlet, we thought construction would be easy by comparison. However, true to
form for projects of this nature, we were soon reminded of the engineer’s credo to “expect the
unexpected.”
Before discussing some things that have slowed construction, let’s first review what has been
accomplished.
Great Lakes Dredge & Dock Company, one of the world’s premier dredgers, mobilized to Pine Knoll
Shores in November. With two self-propelled hopper dredges, barges, tugs, cranes, bulldozers, pipe,
and about 100 people, GLD&D established a presence in the community. Part of the $1.4 million
mobilization cost for all this equipment and personnel is being returned to our community in the form of
housing rental, grocery purchases, restaurant meals, and some pretty sizable fuel bills. GLD&D has also
set up an office on the causeway. John Auernhamer is GLD&D’s on-site project manager. ^
Sand pumping began on November 26**^ as the Sugar Island lowered its “drag arms” to the bottom in
borrow area B1 and began making the first shallow cut about 3000 feet offshore. As the dredge moves
slowly, the eight-foot-wide dragheads rake the bottom and suck sediment into the ship’s hold. Once filled
with about 2500 cubic yards (nearly 200 large dump trucks full of sand), the dredge travels to a “booster”
barge anchored close to shore. Thirty-inch hoses are hooked to pipes, and the pumps of the booster
crank up. This draws sand out of the hopper and pushes it thousands of feet to shore. At that point, the
shore crew, working with dozers and pipe loaders, spreads the sand into its final beach shape.
The dredging procedure that we are using on this project is less efficient than traditional pipeline dredging
methods because of the “double handling” of material. However, it is considered more favorable for
environmental reasons. During excavations, we are finding most of the mud and finest sands are
washing out of the hopper back into the borrow area. This material would not be stable on the beach,
so eliminating most of it before pump-out is good.
So far, the sediment that is reaching the beach is more stable than expected. Without getting too
technical, we are finding the sediment quality in the completed sections to be about 10-15 percent better
than design (quantities around which the project was formulated). In simple terms, we expect this to
result in 10-15 percent slower erosion over the long run. |
The first mile of completed beach at the eastern end of Pine Knoll Shores is as much as 200 ft wide. This
is wider than it was planned to be this past summer for two reasons. First, it takes some time for waves