When Inches Count

NOAA’S Air Gap Technology Provides Safe Passage for New Navy Ship

USS New York sailing under Huey Long Bridge.

USS New York sailing under Huey P. Long Bridge.

High resolution (Credit: NOAA)

Northrop Grumman had just finished building the USS New York — a new Navy ship with a bow built with steel salvaged from the World Trade Center towers. After five years of painstaking construction at the shipyard, the large and expensive warship was finished and ready for sea trials in the Gulf of Mexico.

But it first needed to pass safely under the Huey P. Long Bridge in New Orleans on its way out to the Gulf — something the shipbuilders were seriously concerned about. This is when NOAA’s PORTS® air gap technology was put to the test.

NOAA air gap technology accurately measures a bridge’s clearance — the distance between the bottom of the bridge and the surface of the water flowing underneath.

PORTS or NOAA’s Physical Oceanographic Real-Time System is well known among maritime navigators. The system measures and distributes current and predicted water levels, currents, salinity, and weather parameters (e.g., winds, atmospheric pressure, and air and water temperatures) that mariners need to navigate busy ports, and in this case, cross under a busy bridge. 

Tugboat guides USS New York down Mississippi River.

Tugboats guide USS New York down the Mississippi River.

High resolution (Credit: NOAA)

Setting a Course for Safer Navigation

According to PORTS program director Darren Wright, “The air gap sensor is just one in a suite of PORTS sensors. PORTS data, when combined with up-to-date nautical charts and precise positioning information, provides a clearer picture of the potential dangers that may threaten navigation safety. The sensor on the Huey Long Bridge is part of the new Lower Mississippi River PORTS, which will be completed by the end of the summer and fully operational this fall.”

After thoroughly assessing water gauge measurements and water level predictions, NOAA’s National Weather Service River Forecast Office, NOAA's Center for Operational Oceanographic Products and Services, the U.S. Coast Guard, Northrop Grumman, the Navy, and local port authorities determined that Saturday morning, June 27, would be the best time to attempt the passage.

By a margin of 2.1 feet, the USS New York clears the Huey P. Long Bridge.

By a margin of 2.1 feet, the USS New York clears the Huey P. Long Bridge.

High resolution (Credit: NOAA)

Precision Sensors Ensure Smooth Sailing

Initial calculations suggested that the ship could clear the bottom of the bridge by about 18 inches. Given roughly 140 feet of potential clearance under the bridge, this would mean the ship would occupy about 99.2% of the available space under the Huey Long Bridge as it passed through.

At 3:00 a.m. on Saturday, a final check was performed from the bridge deck. After confirming the calculations, NOAA signaled the ship would clear. At 6:00 a.m., the USS New York set sail under tugboat guidance for the middle of the channel. CO-OPS Director Mike Szabados and PORTS Program Director Darren Wright were on the bridge when, at 6:51 a.m., the ship’s two mast towers slipped smoothly under the bridge by a slim margin of only 2.1 feet.

“It was a great experience for NOAA to collaborate with Northrop Grumman and the Navy,” said Wright. “Using NOAA’s innovative PORTS technology to help protect our nation’s ships and waterways makes for a great day at work and brings home the importance of what we do.”

Watch a video of the USS New York’s passage under the Huey Long Bridge. To learn more about NOAA’s PORTS technology, visit the PORTS Web site. NOAA logo.