New MnDOT specs add to cost of Cottage Grove street repairs
New Minnesota Department of Transportation pavement specifications have increased the cost of street repairs in Cottage Grove in 2014 but will address premature road failures in several areas.
The city’s F1 district (east of Islay Avenue, north of Jareau Avenue and west of Jewel Avenue) and F4 district (east of and including Jergen Avenue, west of and including Jareau Avenue, and south of 91st and 93rd streets) are in disrepair, City Engineer Jennifer Levitt said earlier this year.
Pavement that was installed in 1993, 1994 or 1997, she said, is prematurely failing.
Updated MnDOT specifications are expected to add roughly $150,000 to the proposed $3.6 million pavement replacement and mill and overlay project.
Levitt explained the new specifications during a recent workshop and said while the city adopted the current specification in 2011, a recent MnDOT study showed problems with air voids in the pavement.
The study reported that stripping and road failure is a result of air voids being too great, which allows moisture to get in between cracks in the pavement. But the problem, MnDOT said, was not with the pavement mixture but the compaction process.
To address the premature failing and prevent it from occurring in the future, Levitt said the project should follow the new recommendation of using a half-inch of aggregate instead of the three-fourths-inch of aggregate currently being used. The change will create a tighter pavement, Levitt said, with fewer air voids.
The added asphalt in the aggregate mix will be an increased cost of between $1 to $2 per ton.
Along with the MnDOT updates to pavement specifications, the city is talking about implementing two of its own for the upcoming pavement management project.
The first change is to not allow reclaimed, or recycled, asphalt pavement to be used.
Levitt said she hopes the new standard will give the pavement a greater life expectancy. The additional cost could be as much as $10 per ton.
The final change to the project will also include the use of a nuclear density testing gauge to help create a rolling pattern that achieves the necessary density requirements. The process also eliminates the need to take core samples in the new pavement.
“We can say confidently that the stripping issue will not be a problem moving forward,” Levitt said. “The roadway will look tighter, much like a driveway.”
The City Council has yet to formally sign off on the changes but that is expected to at an upcoming meeting.
Bid awards are also expected by April and a spring start date for construction will follow.
The pavement management project will be paid for with a combination of assessments on benefitting properties, money from the city’s general levy and from various utility funds.