EVERYONE KNOWS THAT tires are an anathema for landfills, but the Delaware County Department of Public Works (DCDPW), Delhi, N.Y., may have found a way to alleviate its mounting scrap tire problem while extending road life.
During the winter of 2001 and 2002, the DCDPW began repairing a county roadway damaged by ice and winter weather. Primarily, the DCDPW installed a tire chip insulation layer on a two-thirds-mile stretch of road to prevent frost heave and protect the road from wet and cold conditions.
Frost heave is caused by water wicking up from the ground into colder regions of the pavement. The water then turns to ice, expands in the road and causes the asphalt to break apart.
Prior to beginning the project in 2001, Susan McIntyre, the DCDPW's solid waste coordinator, attended an area conference where she heard a speaker discuss potential uses for scrap tires, including as roadway insulation and as lightweight aggregate fill. This led McIntyre to the New York State Department of Environmental Conservation (NYSDEC), Albany, N.Y.
To replicate the insulation project in her community, McIntyre needed the NYSDEC's permission to use tires outside of a solid waste stream capacity. While the NYSDEC worked on the approval, the department's staff also suggested that McIntyre contact the Albany, N.Y.-based New York State Empire State Development (ESD) to secure funding. ESD is the division of the New York State Economic Development office that promotes businesses in the recycling industry and helps to foster markets for waste products.
ESD did provide DCDPW with some funding, although the majority of the project costs were paid for by Delaware County, McIntyre states. Nevertheless, as part of its agreement with the ESD, McIntyre had to ask a third state agency to become involved in the project: Albany-based New York State Department of Transportation (NYSDOT).
NYSDOT then reviewed DCDPW's plan and helped to brainstorm ideas to make the project more successful. NYSDOT suggested that the county install a temperature monitor below the roadway surface. This allowed the tire chips' insulation value to be measured. Meanwhile, DCDPW also decided to install a geotextile layer around the tire chips to separate the tire chip layer from the subgrade and an overlying gravel layer.
Based on the temperature monitor's readings, the project has been a success, according to McIntyre. Data shows that the depth of frost penetration was substantially lower on the roadway, which prevented freezing in the insulated sections whereas uninsulated areas did freeze, she says.
“Because the expansion and contraction [of frozen water]… tears roads apart, you need to get the water out,” McIntyre explains. “Also, you need to deal with the depth of the frost line and … deal with that freezing action. The tire chips have been successful in all three of those areas.”
For DCDPW, acquiring the tire chips was the greatest project challenge. The department obtained chips from three sources — companies that produce tire chips, from whole tires collected as part of the county's solid waste program and from cleanup efforts at local farms and dumps. Of these sources, McIntyre reports tire chips were the most cost-effective.
The costs for tires that were a part of a site cleanup totaled $1.61 per tire. Tire handling costs as part of the county's daily solid waste operations were 69 cents per tire. And to obtain the tire chips alone cost the DCDPW approximately 4 cents per tire, McIntyre says.
In total, incremental costs for the tire chips and geotextile layer were $114,500. However, the project used nearly 400,000 scrap tires, which helped to offset the cost of the layer and prevented the county from “having to purchase either an alternate insulation material or fill gravel for that area,” McIntyre says.
The DCDPW is investigating other uses for used tires and currently has another tire chip project in the works. It is using chips to help reconstruct a hilly county road to prevent the gravel surface from loosening, sliding and causing additional road damage.