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American Engineering Testing (St. Paul, MN)

Saving limited valuable real estate space

Year Completed: 2018

Stearns Bank N.A. Equipment Finance Division in Albany needed to add parking lot space for employees and visitors. The new space, however, is more than just a place to park vehicles. Underneath the layers of asphalt and Class 5 gravel, around 95,000 shredded and compacted scrap car tires, or tire-derived aggregate (TDA), serve as a filter and drainage system for storm water runoff.

“When you add more parking, you add more flat surfaces and you have more water to deal with,” said Shawn Robinson, superintendent with Miller Architects & Builders. Storm water ponds are constructed to mitigate and filter excess water runoff. Holding ponds, however, often require space that could be used by business and home owners for other purposes. “Open water ponds are a mosquito breeding ground,” said Curt Hoffman, TDA specialist with TDA Manufacturing. “They can also be dangerous to kids. Kids like to climb fences.”

Miller Architects & Builders out of St. Cloud designed and oversaw the project, while TDA Manufacturing, a division of First State Tire based in Isanti, provided the TDA. Craig Bardson Excavating Inc. of Albany supplied the gravel and did the compacting, while Knife River did the paving.

All the water will come off the parking lot and flow into the drainage system underneath. “Not only does the TDA slow water down and deal with the capacity, it treats it, as well,” Robinson said.

Hoffman agreed. “The carbon in the rubber and the steel banding in the tires attracts phosphorus, nitrates and other contaminants,” he said. Also, TDA is less expensive than traditional aggregate and it lasts longer. “The TDA provides a capillary break,” he said. “It can withstand freeze-thaw cycles and you don’t have to worry about fissures or cracking.”

First State Tire shreds about 2.5 million tires a year, creating 65,000-75,000 cubic yards of aggregate that is applied to various projects, including storm water management, roadway bedding, embankment support, trails, parking lots and other purposes. “TDA has been around for a long time, we’ve been producing it for 30 years,” Hoffman said. “It’s starting to gain popularity through education and workshops. If it’s done right, tires can be environmentally friendly.”

As millions of tires are produced and discarded each year, a portion of them will be reused for other purposes, such as aggregate, which in turn preserves resources. It is one step closer to a greener future.

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