Minnesota road surfaces that were supposed to last for 30 years are beginning to crumble in half that time, raising concerns that cities could have to spend millions of dollars to fix deteriorating streets.
The state made changes in blacktop mix designs in the early 1990s that resulted in more porous pavements, Woodbury city administrator Clint Gridley told the Minneapolis Star Tribune. That allowed water to seep in, causing the streets to deteriorate faster than expected.
The City Council in Woodbury was informed in October that “unprecedented failures” could affect about one-third of the streets and cost more than $20 million to fix. Pavement issues have also been reported in places such as Edina, Rochester and Stillwater.
Kevin Gutknecht, a spokesman for the Minnesota Department of Transportation, said the asphalt mix was only a recommendation, not a mandate.
“Nobody’s required to use it,” he said.
Klayton Eckles, Woodbury’s engineering and public-works director, said most cities follow the state’s recommendation. He said mix designs were produced in a state laboratory and cities adapted them, but problems began about 20 years ago when local governments wanted more cost-effective means of applying blacktop.
“Woodbury made a lot of blacktop roads in the 1990s, and we probably saw (more) failure than any other city,” he said.
A MnDOT report issued in April said most of the problem spots were on urban streets with curbs and gutters. It said the deterioration starts as a small blister and grows to the size of a small pothole.
“Better construction methods are recommended,” the report said.
Jill Thomas, a spokeswoman for the Minnesota Asphalt Pavers Association, was skeptical about whether the pavement problems were a direct result of the state’s design mix.
“I’ve heard of this theory, but it’s not been proven,” said Thomas, whose trade group represents 31 contractors.
She said a deeper study was needed to study factors such as snowplowing in winter and the role of chip sealing.
Woodbury is working with the transportation department to determine the best way to maintain existing streets and slow or eliminate their deterioration, Gridley said.
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