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Dr. Dana Humphrey, Professor of Civil Engineering at the University of Maine, recently presented data on the effect of tire shreds in water at a meeting of policy makers and specialists in the fields of transportation and the environment. The meeting was held at the MN Office of Environmental Assistance in St. Paul, MN.

Minnesota has used tires shreds as lightweight fill in road projects above the water table for the past several years. First State Tire Recycling, one of the sponsors of Dr. Humphrey's visit, has supplied waste tires for more than 70 road projects in the state. Monte Niemi, First State Tire Recycling C.E.O., estimates there are 100 more proposed road projects that would benefit by using tire shreds if they could be placed in wet areas.

"We invited Dr. Humphrey to Minnesota to share the scientific information from his most recent paper and to talk about the positive experience of other states," Niemi said.

Dr. Humphrey, whose work includes nine full-scale field trials using tire shreds as lightweight fill said that tire shreds, when used in the water table as lightweight fill in road projects, do release trace amounts of the materials found in tires.

"It's not a big issue, however, because the evidence shows that the compounds that were elevated in our testing, primarily iron and manganese, are naturally present in ground water and are not a health based concern," he said. A few organic compounds were released at low concentrations, but they generally did not migrate. For the most part, the tests showed all detectable compounds to be below the drinking water standards, Dr. Humphrey said.

The Maine Department of Transportation, working with Dr. Humphrey, spent half a million dollars studying the effects of tire shreds on the environment and their engineering properties. Based on the results, the department plans to take full advantage of the engineering properties of tires - above and below the water table, Dr. Humphrey said.

"Maine Department of Transportation and Maine Turnpike Authority have already saved more money by using tire shreds than they spent on the entire nine years of study," Dr. Humphrey said. "Tire shred's properties help us build better engineered projects that are cheaper.

And, we use lots of waste tires, about 75 tires per cubic yard, which is a major contribution to managing the flow of waste."

Across the country, people are capitalizing on the engineering benefits of tire shreds, Dr. Humphrey said. For example, tire shreds can be found in septic fields, fish hatcheries and road beds. In Winnipeg, tire shreds were successfully used to build a road across a bog, Niemi added.

Current Minnesota Policies
In Minnesota, current policies and practices allow tire shreds above the water table when they are deemed to be a beneficial use, as established by the MN Pollution Control Agency (MPCA).

The MN Department of Transportation (MnDOT), the MN Department of Natural Resources (DNR), several local governments, and private citizens have used tire shreds in road projects during the past ten years.

If the state revises its policies to allow tire shreds in the water table, taxpayers will enjoy even greater environmental and financial benefits, Niemi said.

"Tire shreds solve geotechnical problems without destroying sensitive wetland systems," Niemi said. "There are several other benefits, too. They're lightweight -- less than half the weight of earth. They offer good thermal insulation -- eight times better than gravel. They have good drainage. And they're cost effective," Niemi said.

First State Tire Recycling is not alone in wanting to maximize the use of tire shreds. At the meeting with Dr. Humphrey, Blake Nelson, Geotechnologies Engineer, MnDOT, said he sees projects every week that need lightweight fill in wet areas. Rick Dahlman, Best Management Practices Program Coordinator, DNR agreed noting with miles of trails and roads to maintain tire chips offer the agency a cost-effective and environmentally safe material.

To help advance the use of tire chips in Minnesota, Dale Thompson, Supervisor of Policy and Planning, MPCA is heading up a new subgroup at the MPCA to look at the available data, Thompson said. "The main barrier is that waste products get more scrutiny than virgin materials," Thompson said.

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