PENNSVILLE TOWNSHIP, N.J. — When it gets really humid in your home, envelopes stick together and mold can begin to grow.
When humid air gets to the steel cables which support one of the world's largest suspension bridges it can create a $1 billion problem.
To prevent any future failures of part of the cables which hold up the twin spans, operators of the Delaware Memorial Bridge put a $35 million dehumidification system into operation Tuesday afternoon designed to protect the bridges.
It's only the second bridge in the U.S. to employ this new technology.
“This is an investment in the future and something that will lengthen the life span of this bridge,” said Delaware River and Bay Authority Executive Director Thomas Cook. “It's a small investment which will pay dividends for years.”
The South Jersey Times reports that Cook was one of several authority officials and members of the team which installed the cable preservation system who donned hardhats and safety vests and made their way down the narrow stairs and catwalks inside the New Jersey anchorage on the Delaware-bound span of the bridge.
They made their way into a new, small room which houses the dehumidification plant. Identical ones have been installed in each of the three other anchorages on the twin spans.
With the flick of a switch, DRBA Commissioners Doug VanSant and Michael Ratchford, the chair and vice chair of the authority's Project Committee, actually put the system into operation for the north cable on the span of the bridge.
“The primary goal is to extend the lives of the main cables that form the suspension bridge and carry the load from the suspended spans,” said DRBA Project Engineer Shekhar Scindia. “The main cables are the most critical components of the suspension span.”
American Bridge Company of Coraopolis, Pennsylvania, was awarded the contract to install the system in early 2016. The project is expected to be finished in the spring of 2018.
Part of the project includes installing airtight wraps around the two 4,100-foot-long cables on each of the two two bridges. That process has been the most visible for those who drive across the bridges with the suspended walkways the workers use following the cables from the road surface to the top of the bridge towers.
This painting work on the Delaware Memorial Bridge is perhaps the most important one in years. Multiple coats of paint are coming off for the first time ever.
Inside the bridges’ anchorages the high-tech dehumidification plants were installed and air injection and exhaust ports were positioned along the cables.
The system works by forcing dry air through the entire length of the cable which pushes out the moist air. The cables are made up of about 8,000 single strands of steel wire which air can travel between.
Scindia says officials want the humidity levels in the cables to “go as low as possible.” He said that once humidity levels fall to around 30 percent “corrosion rates drop to nil.”
Inspections done more than five years ago found some signs of corrosion already taking place on the bridge cables so the dehumidification system was seen as a proactive step, officials said.
“If the main cables fail it's better to build a new bridge,” said Vince Meconi, the DRBA's chief operations officer.
Officials said estimates for a single new span like one of the twin bridges could cost anywhere from $800 million to $1.2 billion.
Meconi said the dehumidification system is key to the bridges' future.
“This is what infrastructure maintenance looks like,” he said of the new system.
The first span of the bridge was opened in 1951 and the second in 1968.
The system — paid for through toll receipts — is equipped with remote sensors and advanced monitoring systems to insure it is functioning as intended, officials say.
Carrying about 70 million vehicles each year, the bridges connecting New Jersey and Delaware are a key transportation link along the Northeast Corridor between Washington, D.C. and New York City.
According to the DRBA, there are about 25 suspension bridges in the world equipped with a cable preservation system. In the U.S., the only other system like that being installed in the Delaware Memorial Bridge is on the Bay Bridge linking Annapolis and Maryland's Eastern Shore.