Tires Used as Lightweight Fill in California Interchange Project
Milipitas, CA - Commuters on Interstate 880 will soon have a newly reconstructed interchange on-ramp whose rubbery "chewy center" demonstrates an innovative way to put old tires back to work. Hundreds of thousands of scrap tires that could have littered the state's highways or gone to landfills are, instead, being shredded and used as lightweight fill in the reconstruction of an interchange at one of the Bay Area's busiest freeways. The 700-foot long tire fill on-ramp project, where I-880 crosses the Alameda-Santa Clara county line at Dixon Landing Road, is the first of its kind in the state, but officials hope to see more projects like it in the future.
The unique public works project centers around a brokered agreement between the California Department of Transportation (Caltrans) and California Integrated Waste Management Board to use 860,000 scrap tires as foundation fill for the new Dixon Landing Road interchange on-ramp to southbound I-880. Tire shred placement will cut construction time and divert waste tires from disposal to beneficial public reuse. The Waste Board approved approximately $400,000 for the work.
"This innovative project will provide solutions to some of California's most pressing problems," said Caltrans Director Jeff Morales. "It will help to improve congestion relief on our highways and test a unique method of disposing of troublesome used rubber tires that otherwise could end up in California landfills."
"California's love affair with the automobile results in a glut of 33 million waste tires every year," said Waste Board Chair Linda Moulton-Patterson. "We recycle about 70 percent of that number and public projects like this one will help raise that level even higher."
Caltrans is improving and widening the Dixon Landing Road interchange to improve local access and accommodate an extension of the I-880 carpool lane to Hwy. 237 to alleviate congestion through the corridor. The $30 million project is scheduled to be completed by mid-2004.
University of Maine professor Dana Humphrey, the nation's leading authority on civil engineering applications for used tires and on contract with the Waste Board for the project, will help oversee Caltrans' placement of the tire shreds and other construction aspects at the site. In Maine, civil engineering applications of tire shreds are already making a major contribution to managing scrap tires with four active projects using more than 2 million tires.
The tire shred portion of the project officially got underway in mid-June and is expected to finish in about two months, after which 8,598 tons of scrap tires, shredded down to 2-to-12-inch chips and wrapped in a liner of geotextile fabric and soil, will anchor the on-ramp. The advantage to using tire shred fill, instead of just soil, stems from the lightweight rubber chips-50 pounds per cubic foot (pcf) versus 125 pcf for soil.
Caltrans chose the Dixon Landing Road interchange on-ramp because the site's weak foundation soil makes the use of conventional soil as fill a "sinking" proposition. Tire chips cause less settlement than soil, allowing paving and construction to start much sooner. In addition, the size and location of the fill provides a significant site for this method of construction.
Trucks will deliver 300 tons of rubber chips daily to be laid in a wrap of geotextile fabric and compacted before being covered with soil. The tire shreds are being supplied from Waste Recovery West, the Chicago Grade Landfill, and Laken Tires and are stockpiled by Browning Ferris Industry at nearby Newby Island Landfill and by Republic Services at the Vasco Road Landfill in Livermore. The close proximity of the landfills is instrumental in helping the State agencies deliver the materials in a timely manner despite the area's congested traffic.
Another beneficial reuse for old tires is in rubberized asphalt concrete (RAC) paving. When properly applied, RAC lasts longer than regular asphalt, provides a quieter surface with excellent contrast for striping and marking, resists cracking, and offers superior traction in the rain. A 25-mile stretch of I-880 Oakland to Fremont currently being repaved with RAC by CalTrans will use approximately 400,000 tires when completed.