Charting the perilous channel

By on December 19, 2011

The dredge Merritt works on the main channel. (Rob Morris)

We headed out of Wanchese using the same route the big trawlers would take — if they could squeeze through the channel under the main span of the Bonner Bridge.

Derek Heinrich guided the 25-foot Parker while Steve Shriver, chief of the U.S. Army Corps of Engineers survey team, wrestled with a balky computer network of laptops and sonar devices.

Past the long dredge-spoil islands with the Bodie Island Lighthouse to our east, we motored south toward the big hairpin in the channel called Hell’s Gate. Before the channel under the Bonner Bridge became the source of trouble, this area often lived up to its name.

The Sharon G II, a commercial fishing vessel out of New York, lumbered past our port side heading toward the harbor. It might have been small enough to get past the bridge, but it could have come up from Hatteras, too.

In 2003, the White House Council on Environmental Quality shelved the idea of jetties on the south and north sides of the entrance to Oregon Inlet. Studies suggested that besides environmental problems, the jetties would not eliminate the need for dredging.

Instead, the CEQ decided annual federal funding for an on-site survey team to map the channel and regular maintenance dredging was the best course of action.

A year later, the Corps survey team set shop in temporary quarters at the Wanchese Seafood Industrial Park, built on the promise that maintaining safe passage at the inlet would lead to a sustainable commercial fishing industry.

Eventually the three-person team moved into new offices at the park. The team covers a broad area from Carova to Ocracoke, and west to the Intracoastal Waterway.

Depending on how changeable a waterway is, surveying can take place once every couple of years, annually, semi-annually, monthly or weekly. Oregon Inlet, the team’s most important task right now, is surveyed every week, with the results posted online for mariners to get the latest soundings, or depths.

The shallowest parts of the channel are under and east of the high span of the Bonner Bridge. (Rob Morris)

Making the left turn at Hells Gate, Heinrich pointed the Parker to the high span of the Bonner bridge, still a few miles away.

The computer system was working now, and figures on Shriver’s computer screen showed new calculations second-by-second.

West of the bridge, the channel looked like smooth sailing. Depths were reading 18, 19, 21, 22 feet. But that was inside the channel.

“There’s nothing but shoals on the starboard side,” Shriver said. “It’s all real shallow water.”

A tide differential is figured into the depth measurements. About three hours after high tide, the difference was still 1.6 to 2.6 feet more than the mean depth.

A gyro system in the hull calculates pitch, roll and heave to account for depth differences as the boat bobs up, down and sideways in the swell. It will be working overtime this time out.

As we approached the bridge, the readings dipped, 13 feet, then 9.

Steve Shriver heads to Corps survey team in Wanchese.

Shriver’s computer screen showed parallel lines as we passed under the Bonner Bridge, where the depths were reading 5 to 8 feet. The lines represented paths along the water 100 feet apart and 2,000 feet out.

Henrich, checking his computer screen, lined the boat up on the first line and headed toward the breakers in the distance. The computer will show his progress along the line in real time.

The crew will spend the next couple of hours motoring out short of the bar, heading back along a parallel line toward the main span, then out again, repeating the process more than a dozen times at 7 to 8 knots. The bar channel has been stable at about 13 feet. It is too rough this time to go out that far anyway.

“This is the most important part now,” Shriver said.

As the survey boat motored in and out, west to east, east to west, the side-caster dredge Merrittt worked near the bridge, shooting slurry through a long pipe extending over the water. The pipe runs from a turret that looks like it might belong on a battleship.

The Merritt has been working long hours trying to get the channel to a depth where the big hopper dredge Currituck can do its work deepening the channel enough for the winter trawlers, which draw 9 to 11 feet.

Sidecasters pull slurry from the bottom and shoot it away from the channel. A hopper dredge scoops the sand up and stows it in its hull, hauling it away from the channel. The Currituck needs five feet or more because its draft increases as it fills up with sand.

The Sharon G II heads toward harbor.

The trawlers would never make it through the channel now. Even Heinrich was wary, avoiding areas near the Bodie Island spit on the northern side of the inlet and a big shallow area near the high span where small breakers form over depths of 3 feet and possibly less.

The promise of funding lasted only a few years before a souring economy, budget cutting in Washington and maybe the perception that Oregon Inlet was just a perk for pleasure boaters meant fewer and fewer dollars.

Funding averaged between $4 million and $7 million in recent years, not nearly enough to thoroughly maintain the channel. The current federal budget allows $1 million, barely covering the survey work, much less maintenance dredging.

The Corps has squeezed out a little more money from other projects, and the state has promised up to $1.5 million a year for five years to keep things safe during construction of a new span parallel to the obsolete Bonner Bridge.

Passage under the new bridge looks more promising. High spans are expected to be wider and farther south, where the water can be up to 40 feet deep.

Bodie Island Lighthouse seen from the inner channel.

As far as dredging goes, all bets are off. Already, other areas with so-called shallow draft harbors like Oregon Inlet are being forced to dredge up local and private funding to contract with the Corps to keep them open.

These memorandums of agreement between local entities and the Corps represent the future of smaller inlets on the North Carolina Coast. But if the the deeper south end of Oregon inlet remains stable, Dare County may able to avoid having to look for money to keep it open once the new bridge is built.

If dredging must continue, the cost will have be weighed agains a study in 2006 estimating the economic impact of the inlet at around $460 million.

It was getting past lunch time and the survey team had covered a wide swath of the inlet. Near the center span and the troublesome shallows, Heinrich made a few diagonal loops to plug some extra data into the grid.

Click on the image for the Dec. 12 survey.

Then it was back to port at Wanchese along a quicker route parallel to the bridge, the one many of the charter skippers take.

By this week, the Currituck is expected to arrive for a few days of work before Christmas, returning after the holidays to finish a 14-day tour of duty.

With any luck, the handful of trawlers that have not given up and headed to other ports will be using the Oregon Inlet passage in search of winter catches.

For a few weeks, at least.


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