Peter Zipf sounds more cardiologist than civil engineer when he talks about subjecting the George Washington Bridge to the equivalent of the classic battery of tests for heart disease and finding the first signs of plaque.
“It really is a little like giving somebody an EKG and checking their cholesterol levels,” said Zipf, the Port Authority’s chief engineer. “There are certain things you know you have to watch for, to catch them before they go too far.”
And chief among those certain things, as a bridge ages, is the corrosion that can sap the strength of its steel.
“Moisture is the big culprit,’” continued Zipf. “You have to constantly monitor the amount of corrosion and the rate of deterioration, and then determine when to intervene.”
The GWB’s test results have spurred the Port to intervene now and undertake the biggest rehabilitation in the 81-year history of the world’s busiest bridge. When the work is completed in 2022 – yes, 10 years from now – the Port will have spent $1.5 billion, a piffle in comparison to the $6-billion-to-$8-billion that it would cost to build the GWB today.
The centerpiece of this your-tolls-at-work program will be the first-ever replacement of the GWB’s suspender ropes, all 592 of them. The ropes, vertical bundles of woven steel wire that attach to the four main cables and support the deck, will be replaced a couple or three at a time to keep the 600,000-ton bridge on an even keel.
To assist, the Port, fittingly, has hired Ammann & Whitney, the consulting engineering firm founded by Othmar Ammann, the man who designed and built the GWB and five other suspension bridges in the city.
The Port will also rehabilitate the upper level’s deck (work already in progress), remove the lower level’s original, and failing, lead paint, rebuild the 177th and 178th Street ramps as well as the multiple ramps to the GWB bus station and repair the Center and Lemoine Avenue bridges.
“The bridge can withstand this extreme work because it’s very robust in terms of strength – remember it was built to handle rail,” explained Zipf. “So that extra strength becomes a safety factor that gives the bridge the tolerance for rehabilitation.”
(Careful readers will recall the Thruway Authority will spend more to build the new Tappan Zee Bridge strong enough to support rail – or serious rehabilitation in the next century, if rail is never added.)
Does any or all of this mean the bridge-and-tunnel crowd is doomed to construction delays at the GWB for 10 years?
“In all of our work, through design, staging of construction and so on, we strive to minimize the impact on traffic,” pledged Zipf. “We’ll only close a lane during off-hours or at night, so if you cross the bridge at rush hour, you aren’t going to be aware that anything’s going on.”
…For 10 years.