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SACRAMENTO—A Bay Area commuter rail extension project currently under construction will use 1,300 tons of recycled waste tires to minimize vibration levels from passing trains.
Shredded waste tires, known as tire-derived aggregate, have proven beneficial in many civil engineering applications. In addition to rail vibration mitigation, tire-derived aggregate is commonly used for roadway drainage and insulation, and backfill for retaining walls. Tire-derived aggregate is cost-effective, drains well, and is lighter than conventional processed gravel, making it easier to transport and handle.
Bay Area Rapid Transit’s Warm Springs extension will run 5.4 miles from the current Fremont station and include a new station in South Fremont. The line is expected to open in late 2015 and serve 6,000 additional passengers per day, and eventually will expand into Santa Clara County.
The Department of Resources Recycling and Recovery (CalRecycle), which manages the state’s waste tire programs and promotes the use of products made from recycled tires, is providing technical assistance for the project. BART Project Manager Paul Medved said the transit system has not previously used tire-derived aggregate, but after environmental studies were conducted, BART decided it would be the best material to use for the site.
“The flexibility and vibration-dampening quality of tires makes tire-derived aggregate the optimal material for this project,” CalRecycle Director Caroll Mortensen said. “By choosing tire-derived aggregate, BART will keep 130,000 tires from becoming a nuisance in the waste stream and instead put them to use for the public’s benefit.”
Tri-C Manufacturers of West Sacramento, a tire-shredding company, is supplying the tire-derived aggregate. After workers excavate and prepare the extension line, they will lay a fabric barrier and pour the material on top in a layer about 12 inches thick. Then they will put down another fabric barrier, cover that with stone aggregate, and install the BART tracks on top.
In 2011, Californians generated 40.8 million waste tires, and 88 percent were diverted from disposal and put to beneficial use. Most of the others ended up in landfills, and some were dumped illegally, which can lead to environmental hazards and provide optimal breeding conditions for mosquitos, rodents, and other vermin.
Medved said he is pleased to work with CalRecycle and to promote the use of recycled materials in appropriate applications. “The use of tire-derived aggregate on the Warm Springs extension project offers the triple benefit of reducing the localized effect of vibration in a sensitive area, the reuse of shredded tires, and an opportunity to learn more about its potential for use in heavy rail transit applications,” he said.
For more information on tire-derived aggregate and its use in civil engineering applications, see CalRecycle’s Tire Management and Green Roads webpages.