Army ‘goose' migrates up and down the coast replenishing beaches

Mar 1, 2007 12:00 AM
On a drizzly March day, the hull of Currituck split open in the shallows fronting the Old Coast Guard Station museum in Virginia Beach, Va. The Army Corps of Engineers' split-hulled dredge dumped her hopper of fine sand, adding 250 cubic yards to the popular beach community's main attraction.

Currituck's hull splits open as it deposits a load of fine sand in the surf off Virginia Beach. The dredge's hopper can hold 315 cubic yards of material.
   Image Credit: Brian Gauvin

"It seems to me that it's as important where you put the sand as where you dig it from," said Assistant Capt. Leroy Potter. "Over the last 10 or 15 years, it's been a major consideration to recycle the sand." They used to just "take it out and drop it," he explained. "Every shovelful of beach sand is a valuable thing now. The whole East and Gulf Coast is worried about the erosion."

The word "currituck" is said to be an American Indian name for "land of the wild goose." Currituck the dredge shares some of the characteristics of the goose, besides the ability to float. The vessel spends most of the year migrating north and south along the Atlantic coast from her home base in Wilmington, N.C., contracting channel dredging and beach nourishment programs where erosion threatens local environments and economies.

Image Credit: Brian Gauvin

Currituck has 12 intake pipes that fill the hopper with dredged material.

Like the goose, Currituck follows a pattern dictated by the weather. This year, she began her northward journey in Clearwater on the west coast of Florida, then moved to North Miami, the Carolinas and up to Virginia Beach. Later she carried on up to Cape Cod and Maine before heading back south, revisiting Cape Cod and Virginia Beach again, as well as other stops, before returning to Wilmington.

"Barnegat Light, 30 or 40 miles north of Atlantic City, is one of our big jobs â€" four months," Potter said.

In Virginia Beach's Rudee Inlet, Currituck keeps the narrow channel leading into Virginia Beach Marina passable for the recreational boats and commercial fishing vessels that tuck in against the constant swells and caprice of the Atlantic.

"The sand is moving south, down the beach," Potter said. "When they get a strong nor'easter, the sand moves south. Same with most inlets that we do. It's the weather that causes the sand to fill in the jetties."

There are no accommodations aboard the 150-foot-long dredge, so I met the crew of Currituck in the lobby of the Comfort Inn on Pacific Avenue at 0530. The six-man crew consisted of Potter, Mate and dredge control officer Bud Gaskins, drag tender Bill Stahl, Chief Engineer Pete Gainey, deck hand and relief dredge tender Phil Cline, and oiler Paul Allen.

Currituck has two complete crews based in Wilmington. Each one works 12-hour days on alternating weeks, rendezvousing with the vessel, wherever she might be.

We boarded the crew van and drove to the marina. Within minutes, Currituck's engines were humming, and the aromas of coffee and breakfast were wafting up from the galley, warm comfort from the dark, wet and cold of an unpromising day.

Image Credit: Brian Gauvin

Bill Stall regulates the position of the suction hose along the bottom.

At 0604, dredging began and would continue for the next 12 hours. In the charcoal light, jets of water flashed a bright white as they gushed from the 12 intake pumps, six per side, along the hopper, stretching from the wheelhouse at the stern to the bow. The streams of water turned beige and then a murky brown as the drag head sank deeper into the bottom. "It's every man's dream to make mud," Potter said.

At 0610 we made the first turn. Even though Currituck was churning at a mere half knot, it was a short run in the tight channel, measuring 150 feet wide by 250 feet long.

"We spend all our time turning," said Potter, taking his direction from the fathometer and survey chart of the channel. The track lines, registering on the GPS, looked like bright-red yarn being carded, the voids filling with each pass. By the end of the contract, the screen will show an opaque red mass between the channel markers.

 

 

Image Credit: Brian Gauvin

Currituck dredges sand from the channel in Rudee Inlet that leads to the Virginia Beach Marina. When the dredge arrived, the channel was only 8 feet deep in places. After the dredging, the channel had been brought down to a depth of 12 to 14 feet.

"We hit the channel from where it is 12 feet under the boat to where it is 8 feet under the boat," Potter said. "We dig the channel out to a consistent 12 feet. In five days of dredging, we will take that 8-foot shallow spot to where it is 12 to 14 feet deep."

Currituck began life as a self-propelled, split-hull barge, working in tandem with a side-casting dredge in the Corps' Wilmington district. In 1977, her wheelhouse was widened, and intake pipes, pumps and drag heads were installed to convert Currituck to a self-contained dredge.

Commonly called a hopper dredge or split-hull dredge, Currituck carries the official designation of split-hulled, self-propelled, all-purpose vessel because she serves other functions, such as beach nourishment and oil-spill response. After the conversion, Currituck became the first dredge of her kind operating in the United States, and her life changed dramatically. Soon, other ports outside the district began requesting her service.

"We fit in the cracks that are not handled by the private companies," Potter said. Most private dredges are much bigger, drawing 15 to 18 feet of water and using a 250-foot-long hopper to make them cost-effective. Currituck, on the other hand, at 150 feet by 24.75 feet, draws 4.5 feet, light, and 8.5 feet, loaded, a size and draft particularly suited to shallow waters and tight channels. She is economical to operate, safe and easy to maintain.

Many private companies began using her as a model to incorporate into their own designs. "Now it seems that other ports have caught on to us and use us more than North Carolina," Potter said. "We start as far south as Destin, Fla., and work our way north to Portland, Maine."

"She's a busy little boat," said dredge control officer Gaskins.

Currituck is powered by two 364-hp Detroit Diesel 1271 engines with Caterpillar reduction gears at a 1:1 ratio. The gears are shafted to Holland Rudder outdrive units that are retractable, rotate 360° and have 42-inch propellers in Kort nozzles. The outdrive units are adjusted to the topography of the bottom.

The split hull opens and closes by means of hydraulic ram hinges at each end of the hopper. Inside each side of the hull is a 160-hp Caterpillar 3304 diesel engine powering a Dredge Master centrifugal pump that provides 22 to 24 inches of vacuum to a drag head, port and starboard. The 10-inch-diameter drag heads are raised and lowered by a winch on either side of the hopper, and feed material into 12 discharge pumps, six per side.

The drag heads, drawing 12 inches of vacuum, pull the material from the bottom into the discharge pipes that then dump it into the hopper. Four weirs at each of the hoppers' corners allow water rising above the sand to escape back into the sea. Each weir's door can be adjusted to regulate the water flowing over it to allow trimming of the hull.

As we cleared the channel and prepared for a turn, drag tender Stahl hunched over the dredge-vacuum-control levers waiting for Potter's command to raise the drag heads. "OK, pick them up," said Potter, idling the outdrives to allow two graceful Chesapeake Bay fishing boats to enter the channel and a third to head out into the swells for a day's fishing. Gaskins turned the outdrives to starboard, and we made our turn. "You want the drags off the bottom before you start turning or backing up so you don't snap the dredge pipes off," Gaskins said. "The drag heads last about a year. Up North the cobble (rock) beats them up pretty bad. You have to beat (the rocks) out with a hammer." On the other hand, sand is as abrasive as sandpaper, withering away the pipe's dimensions.

Image Credit: Brian Gauvin

As Currituck approaches the beach, its hull begins to split, allowing the sand to flow out. Drawing 8.5 feet when loaded, the vessel can go right into the surf to drop its load. When light, Currituck draws only 4.5 feet, permitting it to rise up and back out without getting stuck.

Dredging a channel is like "working a cliff edge," Stahl added. "You've got to watch the height of the drag under the boat â€" set one higher than the other."

It takes an hour and a half to fill the hopper. "On some projects where we're pumping, it takes only 20 to 25 minutes to fill to 90 percent capacity," Stahl said. Those projects, where the sand is courser and the dredge runs longer, can net as much as 4,000 to 5,000 cubic yards per day in 11 or 12 loads. At Virginia Beach, with short runs and fine sand, the tally is 1,500 cubic yards in six or seven loads per day.

Although the hopper capacity is 315 cubic yards, the pumps are shut down at 250 cubic yards to allow Currituck to creep closer in to the beach to drop the sand. Currituck runs comfortably in light swells, but "at 5 or 6 feet, it starts getting critical," Potter said. Loaded, the dredge's speed drops from 10.5 to 8 mph, and her displacement increases from 175 to 615 long tons.

Soon the little museum became visible through the drizzle, a modest clapboard relief from the beach-strip architecture crowding the shoreline. Potter maneuvered Currituck head-on to the beach. A less than perpendicular approach can offer a "side to the sea," which renders the dredge vulnerable to the swells, eager to push her aground. The challenge is to bring Currituck in as close as possible to the shore and allow the relentless surf to spread the sand closer to the beach. "You've got to take into account the direction of the sea and the current running up and down the beach," Potter said. "Mother Nature's got a lot more force than these engines have."

"We draw 8 1/2 feet of water (loaded), and when we feel her nudge up on the beach, we open her up," Gaskins said. "As she drops her material, we pop back up like a cork. You know you're in trouble when you go to dump the material and it stays in the hopper," Gaskins added. "You know you're aground. We just drop the drag heads into the water, not to the bottom, and pump clear water and work the dredge out. The propeller wash also helps dig us out."

Later in the day, huddled in the drizzle on the porch of the museum, I watched as Currituck made another beach approach. She looked like a huge shoe, low in the water and edging ashore in the swells. When the hull split open, she rose in the water, regaining her lines. She backed off the pile of sand, turned and headed back for another load. I recalled Potter's comment in the wheelhouse. "It's like mowing the lawn," he said.

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