Recycled streets are paving the way to savings in the capital of Silicon Valley.
San Jose, Calif., is in the midst of using an environmentally friendly road paving method that, if successful, will save the city some money and help reduce its carbon footprint.
Called “cold in-place recycling” (CIR), the process involves a machine chewing up existing city streets — in this case, Monterey Road in San Jose — grinding up and recycling the rock, injecting it with binding material, and spitting it out as new pavement. A two-inch rubberized coating is placed on top to protect the road.
The initial results have been positive. By using recycled material, the city avoided using 10,000 tons of new asphalt, and saved 1,500 truck trips to dispose of 10,000 tons of waste. In addition, had the road been redone using traditional paving with new asphalt, it would have cost $3.1 million. But the price tag for using CIR was $2.3 million, saving San Jose $800,000.
Michael Witkovski, with the San Jose Department of Transportation (DOT), said the technology has been around in various forms for 20 years and the California Department of Transportation has used it to redo some stretches of Interstate 80 in the state’s Sierra Nevada mountain area.
He explained that while the city always looks for new technologies to improve pavement, keep costs down and find greener ways of doing things, it has only been recently that San Jose felt the time was right to try CIR.
“We determined that it now has reached a state of maturity that makes sense to use it,” Witkovski said. “We didn’t want to be too far out on the bleeding edge, but we wanted to be using best practices.”
The San Jose DOT reached out to officials with the state of Virginia, the Canadian province of Ontario and some manufacturers over the past year about their use of CIR. The city then developed a specification to use it and ultimately selected Monterey Road as its first testing ground for the technology.
The city doesn’t really consider the use of CIR on Monterey Road a test, however. Witkovski said that the San Jose DOT is confident the use of CIR will work, as its life cycle should be equivalent to new asphalt.
The key is being vigilant on maintenance.
While the city applies two inches of melted tire rubber coating on top of the recycled roadway materials, that seal needs to be redone every decade to ensure that the road underneath remains preserved.
“We’ll come in 10 years and … seal the top of the rubberized asphalt to keep it from deteriorating,” Witkovski said. “Asphalt ages from the top down, so as long as we keep the wear course good, there is no reason the base should fail.”
The final day of paving Monterey Road is Thursday, Nov. 17, with striping, concrete and electrical work to be completed by the end of the year.
The city plans to use CIR to rehabilitate other streets in San Jose in 2012. Witkovski said 11 roads are “in the hopper” for work next year, although he stressed that San Jose could probably only afford to rehab three or four of the streets.
In addition, CIR may not be appropriate for use in all cases. Witkovski explained that in testing, while recycled asphalt is measuring up to be just as strong as new asphalt, the San Jose DOT rates CIR at 80 percent of the strength that new asphalt provides, just to be on the safe side. So depending on the road, using CIR may not be appropriate.
“If a road was never designed for garbage trucks and now garbage trucks are tearing it up, I can’t just go in and rehab the existing asphalt and expect it to last,” Witkovski said. “I may have to go thicker and rehab the road to handle the load.”