WATERLOO, Iowa --- City leaders are trying to determine whether asphalt or concrete provides the most bang for their street paving bucks.
Mayor Buck Clark has organized a series of City Council work sessions this month to gather information on both options and determine which material should be used for the roughly $4 million in street reconstruction projects the city awards annually with local option sales tax revenue.
"I was trying to get this done when I was (a councilman) because I never quite understood why we never get bids from concrete contractors," Clark said. "I want to confirm that what we are doing in Waterloo in reconstructing our streets was the right thing."
Representatives of the Iowa Concrete Paving Association made their pitch Monday, while their counterparts from the Asphalt Paving Association of Iowa are on deck this week. Finally, representatives from Tekippe Engineering are scheduled to meet with council members on Feb. 28 to provide a third-party, independent perspective.
At stake is how the city bids a reconstruction project, which involves completely tearing up existing failed streets and replacing the sewers, curbs and gutters and surface.
Waterloo is one of few Iowa cities that accepts both asphalt and concrete options for the same project. But asphalt paver Aspro Inc., of Waterloo, has been the lowest bidder since 1994, while concrete contractors stopped bidding altogether several years ago.
City Engineer Eric Thorson contends the city accounts for differences between asphalt and concrete in the design process to ensure comparable bids. The specifications call for a 6-inch concrete thickness on a residential street while asphalt must be 7.5 inches thick.
But John Cunningham, of the Iowa Concrete Paving Association, said his organization is concerned that cities don't conduct a life cycle cost analysis when determining which bid is better in the long run.
"Our industry believes we're providing a benefit with durability," he said.
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While the city may design a street to last for 30 years, a concrete street will need little maintenance during that period while an asphalt street will need a major overlay in 15 years, he said. The Iowa Department of Transportation often factors in a 20-year resurfacing for asphalt on a 40-year street project.
"That mid-life resurfacing is significant," Cunningham said. "It does matter."
IDOT spokesperson Dena Gray-Fisher confirmed the agency uses a life cycle cost analysis that shows "asphalt pavement is projected to require major rehabilitation in approximately half the time as the concrete pavement."
But she said that's just one factor in the overall decisions on pavement types for state projects. Others include engineering evaluations of traffic, soil, weather and past performance, while issues related to the conservation of aggregates, availability of local materials and a desire to keep both industries viable in the state's economy are also considered.
While less costly to maintain, concrete is typically 10 percent higher in initial construction costs, and asphalt can be installed more quickly with less traffic disruption.
Thorson noted there may be other factors that are keeping local concrete contractors from bidding on the annual reconstruction contract. For example, the work involves a lot of subcontractors which must be coordinated by the winning bidder.
"Some contractors don't particularly want to deal with that," he said.
Along with the annual street reconstruction program, the city typically spends a similar amount each year on an asphalt overlay program. That involves attempting to wring more life out of a decaying street by putting a couple inches of asphalt over the top.
Some of the roads currently showing the washboard effect due to frost heaves were actually concrete streets that had a layer of asphalt placed on top. The bumps are created by underground moisture freezing and pushing up the concrete at its seams.House passes billions in cuts