Brainerd City Council: Members mull options for deteriorating College Drive
The city of Brainerd may be having something like buyer's remorse with how College Drive has been deteriorating the last two years.
The roadway in downtown Brainerd was reconstructed as recently as 2012 and the city just finished paying it off, City Engineer Paul Sandy said, but a mixture of poor materials and heavy usage have left it in a concerning, and rapidly deteriorating, state of disrepair.
"It gets a little worse and worse every year. We see a few more potholes pop out every year. That surface keeps getting more and distressed," Sandy said. "We need something we need to address sooner rather than later. That stretch sees about 13,000 to 14,000 cars out there everyday, so the more potholes it sees, the faster it's going to degrade."
Sandy pointed to the pavement mixture used at the time for the road— 5 1/2 inches of SP 12.5 bituminous wearing and non-wearing courses, featuring two different types of surface oil—which was a popular pavement across the state in the early 2010s and propagated by the Minnesota Department of Transportation at the time.
However, the large aggregate (or the diameter of the largest rocks in the mixture), coupled with a thin coating of surface oil that quickly wore off with heavy traffic, meant it was susceptible to leakage. Gaps quickly formed and water slipped through, froze and expanded, causing potholes to form. Sandy said, upon consultation with MnDOT officials, that the material has proven ineffective across the state.
So now it's back to the drawing board.
During Monday's council meeting, Sandy presented three options to address College Drive that members could consider:
• Option one was what is called a "chip seal"—essentially, applying some asphalt with a mixture of aggregate in it. Somewhat more of a Band-Aid fix, it would have a life of about 4-5 years before council members could revisit the topic and opt for either another chip seal or more permanent solutions. In his report, Sandy said a chip-seal project would cost approximately $75,000.
However, Sandy advised against a chip-seal treatment.
"With the localized potholing, we're not exactly sure if that is the best way to go about this," Sandy said. "The life of that, with the severity of (traffic on) the surface, I'm not sure if the 4-5 year life is really going to be worth it."
• Option two would be to perform microsurfacing—namely, the application of a tough, thin layer of emulsion (water and oil) asphalt blended with finely crushed stone for traction. While a microsurfacing is a longer-term fix compared to a chip seal, with a projected life span of about 8-12 years, it is not a project that city staff are familiar with and it's difficult to say whether it would be effective for a high volume street like College Drive.
"The only concern is that we've never done one and it's a high-volume street," Sandy said. "If it were to fail, it would be utter disaster."
• Option three entails a thin mill and overlay, which is to remove about ⅜ of existing pavement and replace it with a smaller aggregate and apply oil, this producing a tighter mat finish. Sandy said that this procedure, coupled with standard crack sealing and chip sealing, should extend the life of the pavement beyond its current projections. With anticipated traffic volumes considered, Sandy said it should be 20 years before another mill and overlay project or other treatment is needed. The project would cost about $260,000.
In any case, Sany noted, state aid would be used for whatever option the counsel chose to undertake to address the conditions of College Drive.
Council member Kelly Bevans said that, while he would often lean toward an affordable chip seal and was interested in looking at microsurfacing, the long-term durability of a thin mill and overlay treatment may be the best course, especially in light of how vital College Drive is to southern portions of the city.
"As much as I'd kind of like to try the microsurfacing, we kind of did that once. We tried something. It gets awfully disheartening to fix it five years later," Bevans said. "This is the $9 million mile. If it falls apart after five years—it's really a successful project, at least in terms of usage, I think we would want to this thing functioning as long as possible."
Sandy advised the council to choose the third option. Ultimately, the council voted unanimously to move forward with plans to apply a thin mill and overlay project to College Drive in the future.
Bevans and council member Dave Badeaux expressed their shared position that any repair project should begin as soon as possible to counteract the drive's rapid deterioration.
Sandy said a start date would likely be in 2019, so as to not conflict with the South Sixth Street reconstruction project slated to begin later this month or possibly early May, depending on the weather.