A Tire’s Second Act Earns Applause

A worn tire is far from worn out

Tire shops are typically busy in Spring, swapping out winter tires and replacing worn-out tires before the roads become slick with rain. When a customer leaves a worn tire behind at the shop, its usefulness has just begun.

Millions of tires each year get shredded into pieces six to 12 inches long and reused as lightweight fill to fix civil engineering challenges. One company, First State Tire Recycling and TDA Manufacturing in Isanti, Minnesota has provided tire-derived aggregate (TDA) to more than 350 projects in Minnesota since the 1980s.

A few recent projects illustrate the variety of engineering problems TDA can solve.

The City of Woodbury used TDA as a stormwater treatment technique in their public works and parks facility expansion project. Underneath two parking lots, basins were constructed using 210,000 tires—the equivalent of three years of tires from Woodbury residents’ vehicles. The basins were paved over to create the parking areas with porous pavement to allow water to soak through slowly, infiltrating clean water back into the ground. The city saved money with TDA, which cost about $3 per yard versus traditional fill materials costing between $25 and $35 per yard, according to the Woodbury Green Times, reporting on the project in July, 2019.

University of Wisconsin-Madison Professor Jim Park has studied the chunks of rubber for more than 20 years. His research, in collaboration with First State Tire, shows TDA can help the environment.

“Rubber is like a sponge,” Park said. “It can absorb toxic chemicals, including heavy metals. We designed a method to determine the number of tires needed to remove target contaminants for a design period, typically 50 to 100 years.”

His research shows tires can remove 90 percent or more of 37 different pesticides from water. Removing phosphorus is a major water quality concern which can be accomplished with TDA.

Another benefit of TDA can be found when used around building foundations. Lake Jonathan Flats, a new five-story apartment complex in Chaska, required a design that reduced the lateral soil load against the east side of the building’s 20-foot tall pre-cast concrete foundation wall. The underground parking garage is also under extra stress, with Highway 41 only 270 feet away and 45 feet above the building’s grade, putting soil and water pressure on structure walls. TDA was the solution for reducing the lateral load and for helping control drainage and moisture running from the road to the lake.

Other benefits are realized when site soils are weak or have poor drainage, according to Monte Niemi, CEO of First State Tire Recycling and TDA Manufacturing. TDA is a lightweight material that reduces load and provides a stable base, enabling less excavation. TDA is one-third less weight than soil; it interlocks to create a foundation for overlying structures; and it has 50% better drainage than gravel, Niemi said.

TDA is being used to help with differential settlement at the Eden Prairie Southwest Light Rail Transit station, too. Niemi has watched the popularity of TDA grow over 30 years. Townships, cities, counties, state agencies, major corporations, multi-family housing builders, and individual homeowners now use TDA under roads and driveways, in embankments, around foundations and septic systems, and in rain gardens and stormwater management systems, Niemi said.

“Often, a first-time customer is sold on the price savings,” Niemi said. “TDA is a cost-effective alternative to gravel or lightweight fill. What keeps them coming back is the performance and the sustainability of TDA. A used tire is far from tired out.”

Niemi conducts classes for engineers. “Showing engineers projects from across the country helps them understand this is a proven material that can help solve problems,” Niemi said “Also, when engineers and project owners use TDA in green construction for pollution abatement and resource conservation, everyone wins.”

© Scrap Tire News, May 2020