the overall effectiveness of a recent erosion-prevention project at the
Herbert C. Bonner Bridge, scouring has become a concern in one section
south of the channel span.
Baker, division maintenance engineer for the state Department of
Transportation, said that while the safety of the bridge has not been
compromised, measures have to be taken to prevent further erosion.
around bridge pilings of 4-foot concrete structures called A-Jacks was
completed in November. By slowing down the water, the
which look like oversized children’s jacks, are designed to encourage
sand to collect around the piles, providing support.
in a recent inspection, Baker said, divers found scouring at Bent 159,
located under the bridge 1,000 feet south of the high rise.
of the areas are building up sand,” he said. “But there is one area
that may have lost sand.”
bridge, which is monitored regularly, was inspected on Friday and again
on Monday, Baker said. It appears that the scour at the one bent has
gotten a foot or two deeper, he said.
it is not clear why the problem is occurring, Baker said, there is
suspicion that water pressure and currents have been affected by the
breach opened in Pea Island by Hurricane Irene in August.
think the dynamics of the inlet have changed since we got the other
inlet further south,” he said. “In this particular location, there’s
not as much sediment settling out… and no sand has accrued like we
discussion last week with its hydraulics unit, DOT has been working
with the U.S. Army Corps of Engineers to get dredged sand placed in the
scoured area. Baker said the project would use some of the
provided for the A-Jacks project.
Bullock, chief of navigation in the Corps’ Wilmington District, said
that the Corps hopes to be able to “point place” material pumped from
the channel by a small multi-purpose vessel that can be used to dredge.
said that the agency is in the process of coordinating with
environmental agencies. If the Corps gets the go-ahead, he said the
project will likely start soon and take about a week.
Shriver, the Corps’ survey team leader in Wanchese, said that he is
aware of the scouring situation at the bridge, but he hesitated to
attribute its cause to the Pea Island breach.
hard to tell,” he said, adding that the inlet is never the same from
one day to the next.
Inlet is so dynamic,” he said. “There’s always a little change in the
direction of the current . . . It’s always something new, basically."
said that divers will continue to inspect the bridge, especially after
every storm. While emphasizing that the current situation
presents no danger, he said that if DOT believed there was a risk to
the public, the bridge would be shut down until the problem was
aging Bonner Bridge will be replaced by a new bridge, parallel to the
current span. Contractors have already been chosen and work
scheduled to begin on the replacement late this year. The new bridge is
expected to open for traffic in 2015.