When a massive fire destroyed six blocks of boardwalk in Seaside Park and neighboring Seaside Heights in northern New Jersey last month, blame was placed on an event that had happened 11 months earlier: Superstorm Sandy.
How could last year's storm spark a fire that burned whole blocks of boardwalk and destroyed more than 50 businesses?
The answer lies in the invisible damage that floods can wreak on electrical wiring, experts say.
Even pinhole-size damage to an electrical wire's insulation can lead to the wire heating up over 200 degrees. This can spark a fire that can burn down homes, businesses, or, in this case, a beloved boardwalk that had just gotten back in business.
Using an electrical wire with damaged insulation under a boardwalk or in a home is "like driving a car on bald tires. It doesn't mean the car is going to fail, but it could," said Dave Brender, national program manager of electrical applications for the Copper Development Association, a trade group for the electrical industry. "You're asking for trouble."
Anatomy of a Wire
A typical electrical wire is made up of two components: The first is the metal that carries the electricity, which is commonly copper but can also be copper wound around an aluminum core. The second is the insulation, which is usually made out of polyvinyl chloride, also known as PVC.
PVC is a common insulator, but it's not perfect, said John Destasio, a machinery technician in Seaside Park.
"Because we need wiring to be flexible, we must make it out of a flexible material," he said. But that means it's "vulnerable to breakdown through time, erosion, and heat."
Windblown sand can cut tiny holes in the wiring's insulation, Destasio said. That allows water to seep in and come in contact with the metal of the wire's core.
Freshwater alone can corrode the metal (think about an old car rusting in the rain), but saltwater residue acts as an enhancer and speeds up the process (as does water tainted by gasoline from a flooded gas station, oil from a flooded car, or sewage from a burst sewer main).
That situation can create a dangerous feedback loop, Destasio said. Corrosion of the wire creates resistance to the electricity moving through it, which then generates more heat. Heat quickens corrosion on the wire, which further increases resistance, which generates even more heat.
Eventually, the hot wire reaches a temperature at which it breaks down more of the insulation. At that point, arcs of electricity can pass through the air from one wire to another, like little bolts of lightning.
"If that arc were hot enough, and [if it] comes into contact with something flammable, you get fire," said Destasio.
After a storm like Sandy, it can be hard to tell which wires inside structures were affected by water, and even harder to tell if insulation suffered small-scale damage.
The same problem emerged after the major flooding in Colorado in September and in North Dakota in April.
Even if the lights still work, there could be wire damage that leads to fires months or even years later, Brender said.
Technicians use ohmmeters to measure how much resistance is in a wire, Destasio said. If they find a great deal, it can suggest a wire is compromised, but wires with minimal damage often check out fine but can have problems later.
Much of the wiring used up and down the East Coast is decades old and may not be up to current codes. Some storm-damaged wiring may have had worn or substandard insulation to begin with.
Much of the wire used on boardwalks or in seaside structures was never intended to be flooded by seawater, because large storm events like Sandy have been relatively rare until recently.
The Seaside fire was a big, visible example, but post-Sandy fires have been affecting homes and businesses along the Jersey Shore for months.
In March, the town of Strathmere—which has a year-round population of 158 people and is about 70 miles (113 kilometers) south of Seaside Park—saw two fires within 18 hours of each other. One was in an office and the other was in a home; both were determined to be linked to Sandy's flooding of internal wiring.
The official cause of the Seaside fire was the failure of electrical wiring that ran under the boardwalk. Officials attributed it to both the age of the wiring, some of which dated back to the 1970s, and to exposure to saltwater during Superstorm Sandy.
The danger doesn't stop with boardwalk wiring, though. Anything with a motor that was flooded by saltwater—like a garage refrigerator that started working again when the power came back on—poses a risk, said Brender.
The safest thing to do is replace any wiring that might have been affected by floodwater.
"That light bulb might light, but it's like a ticking time bomb, and you don't know it," Brender said.