Rubber sidewalks are all grown up. Once perceived mainly as a safe surface for playgrounds, rubber sidewalks have developed into a means of preserving urban trees, reducing stormwater runoff, recycling tires, and curbing greenhouse gas emissions. A company called Rubbersidewalks (what else?) began installing the modular units in 2002, and its rubber sidewalk products now appear in almost 100 cities across the country. Even the U.S. military is getting into the act. Plans are in the works to install rubber sidewalks at Coast Guard Island in Alameda, California, and they’re being promoted by the Pollution Prevention Program at Aberdeen Proving Ground in Maryland.
The Benefits of Rubber Sidewalks for Urban Trees
Rubbersidewalks (the company, that is) attributes its core concept to Richard Valeriano, a senior public works inspector for the City of Santa Monica. The original idea behind a rubber sidewalk was to achieve a flexible surface that would reduce cracking around tree roots. In turn, that would reduce the need to cut or drastically trim trees with overgrown roots. Over the course of several years, city workers noticed that the rubber surface seemed to slow the growth of roots while providing the tree with sufficient water and oxygen, helping to mitigate the problem of root overgrowth at the source. The modular installation system also enables workers to remove sections of sidewalk to inspect tree roots, without the need for pavement-breaking equipment that could damage a tree.
The Other Benefits of Rubber Sidewalks
Aside from the potential savings in reduced personal injury lawsuits, the modular rubber surface makes it easier to open and close sections of sidewalk for maintenance or utility work. Seams in the modules enable stormwater to infiltrate into the soil instead of running into gutters. They’re handy to use for temporary sidewalks, and they’re suitable for surfacing urban tree wells. On the sustainability side, Rubbersidewalks’s first-generation product was made from 100% recycled tires. It now offers a second incarnation called Terrewalks, which uses a mix of tires and waste plastic from farm irrigation equipment. As a means of finding a use for the millions of tires disposed every year, rubber sidewalks promise a scale similar to that of recycled tire roof shingles — a big leap over smaller projects like tire shoes and toys.
Rubber Sidewalks and Greenhouse Gas Emissions
Walking and biking instead of driving are often cited as effective ways to lower one’s personal greenhouse emissions, but the equation skews when you factor in the greenhouse emissions involved in constructing more sidewalks and bike paths. A good chunk of those emissions have to do with concrete surfaces. Concrete is made from cement, which is a significant source of greenhouse gasses. Worldwide, cement is estimated to account for about 5% of all carbon dioxide emissions from human activity, with concrete accounting for about 8% overall. Though rubber surfaces do involve some greenhouse gas in the manufacturing process, there would seem to be a savings in emissions related to transportation, installation, maintenance, and urban street tree health. If there is any way to have your cake and eat it too, a rubber sidewalk could be it.
Image: Derek Diamond on flickr.com