Wright County hadn’t planned on using tire chips (TDA) for a new road, but then, they hadn’t planned on the road failing during construction, either.

A 1,300-foot realignment of County Road 14, which connects two major state highways between Buffalo and Delano, MN, was under construction in order to improve safety at an intersection. The road was being built through a man-made wetland that had been drained. The county originally used soil to build the new road up eight to 12 feet. The weight of the fill caused the underlying soil to slip. The project stopped. Back to square one.

Consultation with geo technical people showed that the problem could be corrected with lightweight fill. A comparison of costs and benefits convinced the county to go with Tire Derived Aggregate (TDA). “Economically and probably functionally, tire chips were the best way to go,” said Virgil Hawkins, assistant county highway engineer. “The value of the tire chips is when they interlock they get compressed and they hold the road together. They’re a third of the weight of other fill material The price made it a good option, too."

Roughly 12,000 loose volume yards of tire chips (equivalent to 360,000 tires) were placed inside a wrap of geotextile fabric during the re-construction of the road. Then, the county slowly loaded three feet of sand on top to compress the chips.

“The chips are settled well,” Hawkins said. Once the settling stopped, the sand was removed. Class five gravel was put down and the road paved and opened for 4,000 cars per day. The sand was recycled into a railroad crossing project adjacent to the new road.

For Pete Forare, senior engineering technician, this was the first time using TDA. “They worked well because they spread the load out and bridged the soft area,” he said.

Before Wright County decided to use TDA, they checked out their options with officials from the Minnesota Dept. of Transportation and others. Engineers, county staff and soil consultants spoke highly of TDA, according to Hawkins. This doesn’t surprise Monte Niemi, CEO, First State Tire Recycling. “The track record for scrap tires keeps growing,” he said. “More and more people are recognizing the economic and engineering benefits of using them.”