In 2000, California packed 662,700 shredded waste tires beneath an I-880 on-ramp; they cut...

Engineers working to upgrade a busy highway junction near San Francisco in 2000 faced a serious technical problem. The ground was made up of about 30 feet of unstable bay mud, a soft type of soil that could sink or crack under the weight of normal road-building materials. To solve the problem, project planners used an unusual method: they buried 662,700 shredded waste tires directly beneath the new highway on-ramp. The site, at the intersection of Interstate 880 and Dixon Landing Road in Milpitas, needed a raised embankment about 26 feet high, 700 feet long, and 50 feet wide to support a southbound connecting ramp. Using normal earth or rock fill would have placed a huge amount of weight on the soft ground. This could have caused the road to settle over time and forced engineers to wait up to a year for the soil to become stable.Instead, the California Department of Transportation and local authorities replaced traditional fill with tire-derived aggregate. This lightweight material is made by shredding old vehicle tires into large pieces of rubber. According to records from CalRecycle, the state agency responsible for recycling and waste management programs, the method reduced the ...