With PORTS^®, Ship Clears Bridge with Two Feet to Spare

Tim Osborn, NOAA’s Office of Coast Survey
Sasha Pryborowski, NOAA Ocean Service

July, 21 2009 — When a new Navy ship, the USS New York, required safe passage from the Avondale Shipyard on the west bank of the Mississippi River to the Gulf of Mexico for a month of sea trials at the end of June, it relied on new NOAA technology at one critical juncture.

Luckily, NOAA’s PORTS^® (Physical Oceanographic Real-Time System) — which collects and disseminates data regarding water levels, currents, salinity, and meteorological parameters critical to safe navigation in the nation’s busiest ports and waterways — was in place on the Huey Long Bridge, in the Lower Mississippi River, at just the right time.

And, I was there to see it happen.

The Lower Mississippi River PORTS^®, to be fully functional by this fall, consists of two water current meters, a water level gauge and air-gap sensors on both the Huey Long and Crescent Connection bridges. Specialized air-gap technology measures the bridge’s clearance — the distance between the bottom of the bridge and the surface of the water flowing underneath. 

Northrop Grumman, the ship’s manufacturer, needed the sensor data to make sure the ship could clear the bridge on its way out to the Gulf.

PORTS^® Director Darren Wright and I had briefed Northrop Grumman about the air-gap technology in early June. Soon after, NOAA’s Center for Operational Oceanographic Products and Services (CO-OPS) Director Mike Szabados and the Lower Mississippi River PORTS team started providing preliminary information on air-gap readings for the bridge, which continued up to the day of the ship’s passage.
 
The USS New York would also have the benefit of NOAA’s electronic navigation charts (ENC) for the Mississippi River, recently updated, which river pilots use to steer ships up and down the river.

After integrating and analyzing all the necessary water and current data, the National Weather Service River Forecast Office, CO-OPS, the U.S. Coast Guard, Northrop Grumman, the Navy and local port authorities determined that Saturday morning, June 27, would be the best time for the ship to attempt passage under the bridge.

Initial calculations suggested the ship would clear the Huey Long bridge by about 18 inches. Given roughly 140 feet of clearance under the bridge, this meant the ship would occupy about 99.2 percent of the available space as it passed underneath.

At 3 a.m. Saturday, after a final round of sensor checks, NOAA signaled that the USS New York would clear. At 6 a.m., it set sail under tugboat guidance for the middle of the channel.

Szabados and Wright were standing on the bridge of the ship when, at 6:51 a.m., its two mast towers slipped under the Huey Long by a slim margin of only 2.1 feet. Only then did we all breathe a collective sigh of relief.

“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.”

You can watch a video of the USS New York’s PORTS-assisted passage and learn more about air-gap technology by visiting the NOS Web site.