Image: HARALD FRANZEN/ScientificAmerican.com 1,300 "REDBIRD" SUBWAY CARS may soon find a new home on the ocean floor.

For the past half year, New York City's Metropolitan Transit Authority (MTA) has been shopping around an unusual proposal: the agency wants to find locations nearby to sink 1,300 aging subway cars into the ocean. The cars, they hope, will serve as artificial reefs and attract marine fauna to the barren, sandy, submarine slopes off the Mid-Atlantic coast. Several environmental groups have voiced concerns over the effectiveness and possible dangers of the project, but preparations are nonetheless under way to begin submerging the first cars in mid- to late August.

In fact, the idea is not entirely new. People have built artificial reefs off the Atlantic coast since the 1830s, according to Jeff Tinsman, the reef program manager for the Delaware Department of Natural Resources and Environmental Control. "I guess they recognized that natural or accidental shipwrecks made good fishing grounds, so that was the first attempt to make and submerge wooden structures, which would attract and support reef fish," he says. Mussels, mollusks and other crustaceans attach to the large structures and spur the growth of underwater grasses, worms and other organisms. The structures also offer shelter to small fish and other marine life.

Over the years, people have experimented with a variety of reef materials, ranging from rubble and concrete to old ships, tanks, refrigerators, cars, tires and so-called reef balls¿hollow concrete spheres containing many holes. This kind of starter reef is especially important off the mid-Atlantic shoreline. "New England has its rocky coast; tropical Florida and the Gulf have some coral reef. We have nothing like that," Tinsman says.

Scientists, fishermen and environmentalists all refer to the sandy slopes off the mid-Atlantic as a submarine desert. Most agree that creating artificial reefs is a good idea, but they are divided on how to do it. The Gulf States Marine Fisheries Commission defines four criteria for artificial reef material: function, compatibility, stability and durability. "If money weren't an object, probably granite stone [would be the perfect reef-building material] because it's natural," Bill Muir, regional oceanographer at the Environmental Protection Agency's Philadelphia office, says. But money is an object¿and New York City's old subway cars are free.

Image: HARALD FRANZEN/ScientificAmerican.com STRIPPED OF SEATS, light fixtures, ad banners and lead paint, the submerged subway cars will be difficult to recognize. Windows and doors will also be removed, to prevent divers from getting trapped inside.

The giveaway is part of a larger plan in which the MTA will replace 1,300 of its more than 5,800 subway cars. The agency plans to dump its oldest cars, called Redbirds for their dark red paint color, which were introduced in 1962 for the 1964-65 World's Fair. "The trucks [the wheels of the cars] weigh between 18,000 and 20,000 pounds each, and there are two of those per subway car," says Mike Zacchea, assistant chief operations officer at New York City Transit. "The subway car body itself, after being stripped of certain components, probably weighs between 15,000 and 18,000 pounds." In other words, the agency is left with between 66 and 75 million pounds of scrap metal to dispose of.

If only the car bodies went into the ocean and the trucks were recycled as scrap metal¿which is what the MTA proposes¿19 to 23 million pounds of that metal would find a new home on the ocean floor. In the process, the transit authority would save an estimated $11 million to $13 million in disposal cost, Zacchea says. "Clearly the number of cars raised some eyebrows, particularly because New York was going to save so much money by dumping them into the ocean," says Cindy Zipf, executive director of Clean Ocean Action, an environmental advocacy group based in New Jersey. "That sort of sends up a red flag that there's a little bit of a disposal factor here."

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