How Recycled Tires Can Save California Roads at Risk of Landslide
Santa Barbara’s Ortega Ridge Road is no longer in danger of washing away thanks to 80,000 recycled waste tires. Like many paved pathways that curve and bend along with California’s rugged terrain, the ground beneath the road absorbed water in the rainy season - undermining its stability and causing the asphalt to crack, sink, and slide down the hillside. At one point, the road was reduced to just one safe lane.
Now, thanks to an innovative new road repair technique, Ortega Ridge Road is stable, safe, and a model for what’s possible in areas prone to landslides.
A First for California
With grant assistance and technical guidance from the California Department of Resources Recycling and Recovery (CalRecycle), Santa Barbara County rebuilt Ortega Ridge Road in 2019 using more than 80,000 recycled tires that were shredded and processed into Tire-Derived Aggregate (TDA). The highly permeable fill material allows water to drain through it (unlike conventional soil)– avoiding excess weight that often causes these types of roadways to wash away.
The Ortega Ridge Road repair was the first infrastructure project in California to use TDA material in this type of civil engineering application.
CalRecycle Funding Stopped the Cycle of Failure
Santa Barbara County spent decades on this problem. “We were looking for a solution for this continually failing road,” says Chris Doolittle, an engineer geologist with Santa Barbara County. “It had been failing for 20 years at a minimum.” Over and over again, crews tried the more traditional repair technique of laying down new asphalt – one layer after another - only to watch the road degrade again.
“We had a good relationship with CalRecycle and determined this site would be a really good candidate for a pilot project,” Doolittle recalls.
In March of 2018, CalRecycle awarded Santa Barbara County $158,241 in funding from its Tire-Derived Aggregate Grant Program to purchase the recycled tire fill material. Armed with research from the University of California San Diego, which provided engineering data for the project design, CalRecycle worked alongside the county and engineering contractor GHD Services to design and construct a more eco-friendly and long-lasting repair on a 225-foot section of Ortega Ridge Road.
Tire-derived aggregate, made from 810 tons of California waste tires, was used to backfill a retaining wall composed of large, rock-filled welded wire baskets (called gabions) to replace failed soil and provide lateral support to the reconstructed embankment. The repair resulted in a more permanent repair, saved the county permitting time, money for easements, construction costs and expensive road materials.
“CalRecycle provided expert support,” notes CalRecycle senior waste management engineer William Heung. “As a result, public works was able to open a safe, stable roadway to the public more quickly and inexpensively than traditional methods, with the environmental benefit of reducing the number of used tires buried in landfills.”
There’s an Award for That!
The Ortega Ridge Road repair earned the 2020 Outstanding Local Streets and Road Repair Project award from the County Engineers Association of California (CEAC).
“What we want is to see something that is out-of-the-box thinking and innovative,” explained CEAC President Rick Tippett, also the director of transportation for Trinity County. “What this award is intended to do is share success, so other agencies will take those ideas back to their communities.”
Project leaders are hopeful a recognition like this will encourage other local cities and counties to consider the use of TDA and this groundbreaking engineering technique to improve local infrastructure and protect public safety. “We would like to see more of this type of project around the state,” says Heung. “It is a superior alternative material to other products out there and a great use for California’s scrap tires.”
Longer Lasting Roads with Little Environmental Impact
Tire-Derived Aggregate is a smart, cost-effective way to repurpose some of the 51 million waste tires that Californians generate every year. Beneficial uses for this material include:
- Lightweight, permeable backfill that’s lighter than gravel and more permeable than soil
- A low-cost option to reduce train noise. When placed under tracks, TDA reduces the vibration and noise that is often a nuisance to those living nearby.
- Retaining wall backfill, particularly in areas prone to landslides. Because of TDA’s lightweight properties, retaining walls can be designed using less reinforcing steel.
- Landfill gas collection trenches. The high porosity of TDA makes it an excellent material for filling landfill gas collection trenches that transport methane, hydrogen sulfide, and carbon dioxide.
CalRecycle’s Tire-Derived Aggregate Grant Program supports projects that use recycled waste tires in place of conventional construction materials for civil engineering applications such as retaining wall backfill, landslide stabilization, vibration mitigation, and various landfill uses. The unique engineering properties of shredded waste tires allow for free-draining, lightweight, and typically less expensive solutions for these types of projects.
- Since 2011, CalRecycle has awarded $5,582,126 in TDA grants to 28 projects statewide.
- Grants are funded through a portion of the $1.75 fee consumers pay on each new tire purchased in California.
- For more information about CalRecycle’s waste tire management grants, including application criteria and maximum award amounts, see our Tire Recycling, Cleanup, and Enforcement Grants webpage.
- Get direct notifications about funding availability, applicant and project eligibility, and application due dates by joining CalRecycle’s Tire-Derived Aggregate listserv.