Rubber sidewalks go where concrete fears to tread

Every fall, Richard Valeriano spends all day, every day, staring at sidewalks that have been busted and broken by tree roots.

But the idea to build sidewalks of rubber didn't come to Mr. Valeriano during the day. It came to him at night – in a dream. "I went home and the image was lodged in my subconscious," says the senior public works inspector for Santa Monica, Calif. "But in my dream, the sidewalks were moving. They were twisting and turning like waves on the ocean."

Although making sidewalks out of rubber seemed "kind of preposterous," Valeriano acted on the idea in 1998. Thanks to some partnerships and public grants, his rubber reveries are now very much a reality. Some 130,000 square feet of rubberized sidewalks grace about 60 North American cities, giving local governments an alternative to concrete and its attendant pitfalls, such as rising prices, exorbitant trip-and-fall lawsuits, and a trail of chopped-down urban trees.

"In the early days, whenever you'd say that to someone, they'd just burst out laughing," says Lindsay Smith of her company, Rubbersidewalks Inc., which she founded in 2001 with inspiration from Valeriano's vision. "There would be disbelief at first, because we think of sidewalks as synonymous with concrete."

Ms. Smith's company, a for-profit firm based out of Gardena, Calif., recycles discarded tires to make premolded sidewalk pavers – which she uses as a big selling point.

Unlike concrete, which is poured and set on location, the prefab rubber squares arrive from its California factory and are cut to fit. Installers usually place Rubbersidewalks pavers over a bed of crushed granite and connect the pavers using interlocking dowels. The result: a sidewalk with a two-inch-deep footprint – far shallower than its concrete cousins. To repair a rubber sidewalk, workers simply unlock the dowels and remove the individual paver.

Each square foot of rubberized sidewalk contains almost one discarded tire. Americans generate about 290 million waste tires a year, according to the Rubber Manufacturers Association in Washington – many of which languish in junk yards or are burned. As Smith sees it, there should be no shortage of rubber solutions.

"Our goal is to have rubber sidewalks in every municipality in the United States, to eliminate the problems that concrete causes," Smith says. "I think in five years, there will be rubber sidewalks everywhere."

Another reason Smith classifies her firm as a "green tech" company is its service to urban foliage. When faced with replacing sidewalks or razing street-side trees, many cities choose the latter, less-expensive option.

That's not to say Rubbersidewalks Inc. – which so far is the only name in the business – sells its rubbery wares on the cheap. Individual panels can be double or triple the cost of concrete, depending on how far the pavers are shipped to their final resting places.

New Rochelle, N.Y., which installed a 400-square-foot tract of rubberized sidewalks two years ago, paid $20 per square foot of Rubbersidewalks pavers imported from California, compared with $8 for traditional, local concrete.

In April, the District of Columbia installed about 4,000 square feet of rubber sidewalk, at a cost of $60,000. The investment, however, may have saved 35 half-century-old trees, which John Deatrick, the district's chief engineer, values at about $40,000 to $50,000 each.

"The advantage is that you can effectively drape the rubber sidewalk over the tree roots. When you do concrete, in order to get a smooth walking area, you tend to trim the roots," says Mr. Deatrick.

"Finding some way to preserve our investment in trees, if you want to look at it in dollars and cents, is the driving financial factor here," he says. "Unfortunately, we've killed a lot of trees doing sidewalk work over the years."

Also in the dollars-and-cents category: The district spent $7 million to repair concrete sidewalks in 2005. Beyond that, it is fighting three trip-and-fall lawsuits related to sidewalks.

Rubbersidewalks plans to open a new factory in Lockport, N.Y., in the fall, a move it hopes will cut costs to customers in the eastern half of the country. Still, the cross-continental cost of transporting the tiles amounts to only about $1.50 per square foot, Smith estimates.

"I haven't determined if it's cost-effective," says Jeffrey Coleman, New Rochelle's commissioner for public works. The city installed a stretch of rubberized walkway to preserve one of its older and more scenic tree-lined streets. "We wouldn't put this in our downtown. In a downtown area, if you have to take a tree down, it's not the end of the world."

So far, Mr. Coleman is impressed that the material hasn't cracked after two New York winters. "It's flexible, pliable. That's one of the nice features," he says. "I figured they would have been beat up by a snow shovel or something."

So, what's it like to tread on a rubber sidewalk? No bounce, it turns out, but the walkway on Summit Manor Road in New Rochelle definitely has more give than your run-of-the-mill sidewalk, especially where tree roots have shifted the ground beneath the rubber. It's akin, perhaps, to the surface beneath a state-of-the-art playground.

As for the street's linden trees, they've turned the concrete walks into something resembling a snowless mogul run. The Rubbersidewalks pavers, however, lie serenely, appearing almost smug in their rubberness.

"They're wonderful. We're the envy of the neighborhood," says Anne Gargan, who lives in front of the city's small experiment. She and her husband plan to petition the city for rubber's expansion. "They're pleasant to walk on. They rise and fall with the trees."