Unlike a rainstorm, a hurricane–or superstorm, which Sandy was demoted to–scoops up salt from oceans and estuaries the way a kid scoops up sand at a beach. The “brackish” water (salty but not extremely salty) and the saltwater (about 35 parts per million salt) get mixed up with freshwater and carried inland by the storm surge.

When that water is pushed to shore, it can be more damaging than the salt-free version, especially if comes into contact with electronic equipment (as was the case with Sandy).

Why? Because salt can react badly with, well, just about everything, says Steven Apfelbaum, founder of the environmental consulting firm Applied Ecological Services, Inc. and author of Restoring Ecological Health to Your Land.

Salt has chemical properties that make it react with, and alter the composition of, iron, steel, zinc, concrete, wire insulation, and more–nearly all the building blocks of the manmade environment. It not only corrodes wires that can transmit electricity, it also conducts a charge itself, which means that it can both wear away our safety insulations, causing outages, and increase the chance of an accidental shock. When coated with salt, metal can transfer a jolt, too.

Hurricane Water Damage

In the short term, that means big safety problems. We’ve already seen power outages and extensive clean-up efforts–which were triggered, at least in part, by salt.

In the long term–maybe not even that long term; “weeks or months or years,” Apfelbaum says–it can mean serious, corrosive damage to infrastructure. “It basically breaks, starts decomposing, the molecular bonds,” Apfelbaum says. “Therefore streets and buildings and sidewalks and roads can be weakened.”

Salt can be better than a jackhammer for taking out concrete: the chemical bonding in the usually tough concrete can be disrupted over time by sodium ions. That’s trouble for the enclosed subway, but also all over the city. Apfelbaum recalls an ecological study he did where a storm surge blasted saltwater from the coast to a quarter mile away.

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