As a clammer raked the bottom of Sandy Hook Bay off Atlantic Highlands last week, a U.S. Army Corps of Engineers’ vessel also searched beneath the murky waters.
Both crews were focused on the seafloor, but the latter hunted information — not food.
The impact of Hurricane Sandy on dry land is clearly visible: tattered homes and businesses litter the coast of New Jersey. But the storm also left its imprint offshore, hidden beneath the sea.
So with the use of multibeam sonar technology, the Corps has undertaken a "massive effort" funded through the aid package Congress approved after Sandy struck to survey where — and to what extent — the storm affected federal navigation channels. That’s the first step in determining how much dredging needs to be done because of the storm.
"A storm like Hurricane Sandy is moving sand around and it does start to impede the channels," said Randall Hintz, the chief of the Operations Support Branch for the Corps’ New York district. "If there was a shoal" — or shallow area — "in some of our channels it could have easily got exacerbated by the sand from Hurricane Sandy."
Though the Corps regularly surveys the federal channels this survey effort is beyond the average scope. The number of all surveys conducted by the Corps in the New York district is expected to double this year.
The $60 billion Sandy aid package passed by Congress earlier this year set aside roughly $5.35 billion for the Corps. Of that funding, $600 million is financing what’s called operation and maintenance projects, which will include dredging navigation channels, in the Corps’ North Atlantic division.
John Amici, the manager of the Atlantic Highlands Municipal Harbor, said the Corps needs to conduct such work, "just to make sure there’s no debris and that nothing moved or shifted," since the Oct. 29 megastorm.
The Corps mapped out rough schedules for dredging projects throughout the region because of the storm in an industry briefing. Those projects included channels in the Sandy Hook Bay, Shark River and Shoal Harbor and Compton Creek, among dozens of others.
But before dredging begins the Corps needs to know what happened beneath the water.
"The first step in determining how much dredging is out there is going out there with these boats and doing this massive effort," Hintz said.
As the sun beamed down on the Sandy Hook Bay last week, two survey technicians went to work mapping a channel near the municipal harbor in Atlantic Highlands.
On the front of a 25 foot catamaran Jeremy Abrahamsen lowered a $180,000 multi-beam sonar scanner head into the water, while Mike Appeld cast a probe off the stern.
"The temperature, the salinity" — and other qualities of the water — "actually affects how fast the sonar signal travels through water so it has to be accounted for to arrive at the correct depth," Appeld said as he went over the measurements.
With everything in place — and all variables accounted for — Abrahamsen and Appeld sat in front of six computer screens to monitor the survey as a boat operator steered the vessel through the channel.
As the multibeam sonar relays back information, it paints a picture of the bottom of the sea floor for the technicians.
"It’s pretty much a consistent, flat bottom here," said Appeld as he monitored the screen where a running gray image showed what the sonar picked up. "This is probably just a piece of wood laying there," he said, pointing to a small inconsistency on the screen.
Since Sandy, Appeld, who has worked with the Corps for two years after decades in private industry, said he’s seeing "more debris on the bottom" and "the shoals have changed quite a bit."
Once the operators finish surveying a channel, engineers analyze the data, comparing the actual depth to the federally-authorized depth. From there, the decision is made on how much dredging — if any — needs to done.
Jack Bevins, the vice president of operations for the commuter ferry service Seastreak, which docks in Atlantic Highlands, said the Corps’ work in the area is critical. Bevins said the company’s high-speed ferries are some of the deeper vessels working out of the harbor. Since the storm, he said, "we have to play the tide" to avoid shallow points.
"We’ve had shoaling in multiple areas," he said. "It’s extremely important that they come in and redredge and increase the depth."