Timothy Stark, aprofessor of civil and environmental engineering at the University ofIllinois at Urbana-Champaign, and Krishna Reddy, a professor of civilengineering at the University of Illinois at Chicago, recentlyevaluated the use of shredded tires as a drainage material inwaste-containment systems. Shredding tires into chips roughly 4 inchesby 6 inches, they report, offers a simple and cost-effective way ofproviding drainage for modern landfills, remediating older landfills,and disposing of mountains of scrap tires.
Nearly 280 milliontires are discarded annually in the United States. Piles of worn-outtires can become eyesores and breeding grounds for mosquitoes. Inlandfills, intact tires can collect methane (produced by decomposingwaste) and create potential fire hazards. Over time, these tires canwork their way to the surface, where they can damage liner covers andcause increased leachate production that could contaminate groundwater.
“Asa result, many states now require that scrap tires be shredded intochips prior to disposal,” Reddy said. “Instead of simply burying thosechips with all the other waste, we suggest using them as a drainagelayer in both modern and abandoned landfills.”
The drainage layerprevents water from percolating through the waste and polluting theground water, Reddy said. Typically, the drainage layer is composed ofsand or gravel, which must be purchased and transported to the landfill.
Toinvestigate the feasibility of using shredded tires as a surrogatedrainage material, scrap tires were shredded and distributed asdrainage layers at two landfills: one in southern Illinois and theother near Chicago.
Stark and Reddy monitored the two sites forsuch characteristics as settlement, erosion, flow rates and waterquality, and compared them with conventional sites that used sand orgravel. The researchers also measured the permeability of tire chips inthe laboratory.
“Our research shows that replacing the sand orgravel with a layer of tire chips works just as well and costs less,”Stark said. “The tires must be shredded for disposal anyway, so thereis fairly little expense compared to buying and hauling sand or gravel.”
Theremediation of old landfills could consume huge quantities of scraptires. “A drainage layer one-foot-thick covering one acre requiresabout 70,000 tires,” Stark said. “A typical landfill covers 10 to 20acres, and there are about 150 abandoned landfills in Illinois, alone,that are in need of some degree of remediation.”
Shredded tiresalso could be used as backfill behind retaining walls and in otherlocations where sand or gravel is commonly used, the researchers report.
The work was funded by the Illinois Department of Commerce and Economic Opportunity.
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