Crews in Dakota County are reporting more and bigger holes in streets than last year.

By Liala Helal liala.helal@startribune.com

Heavy steam rose as asphalt mix — heated to 260 degrees — ran down a chute behind a Burnsville dump truck. City maintenance workers shoveled the mix into a pothole on Aston Circle, fighting the heat on an afternoon when temperatures were only in the 30s.

"Too hot!" worker Andrew Wheeler said as the steam turned a thicker white. "This stuff is hot enough to take the skin off your bones." He wiped the sweat from his forehead and kept going.

Pavement-crumbling pothole season is upon Minnesota again, and city crews in Dakota County are trying to stay ahead of the game in a year when the problem is worse than last year — potholes are popping up quickly, and there are more of them. This spring's longer freeze-and-thaw cycle is the culprit — with warm days but freezing nights, water and melting snow expand in pavement cracks and break it up. The situation may get worse in the next few weeks.

"We're just getting into it, and as the frost comes out it's going to get a lot worse," said Lakeville Street Superintendent Troy Grossman. "It's too early to tell how bad it's going to be."

Cam Killmer, in foreground, and co-worker Andrew Wheeler worked with blacktop filler on a street in Burnsville last week.

More and more cities, including Burnsville, Lakeville, Eagan and Apple Valley, are offering online pothole reporting services, then dispatching their crews to trouble spots. Burnsville has already gotten more than half as many requests as it did in all of 2012.

But it's not just the weather — it's also the aging roads.

"Filling a pothole is not a permanent solution," said Eagan transportation operations engineer Tim Plath. Repairing and resurfacing entire streets keeps the roads healthy and cuts down on potholes. "It's kind of a catch-22 — how much work do we do on the potholes to keep the roads safe and keep them from causing damage to vehicles, versus knowing that whatever we do right now is just going to get covered up or taken away when we do some overlay this summer."

Some areas produce the same potholes every year — at times as large as 8 inches deep and 2 feet wide. The never-ending cycle is what many city street leaders cite as the biggest challenge. Lakeville is using a company this week that does "velocity patching" — a more permanent solution to "help get through the pothole season," Grossman said.

"It's overwhelming to know how many are out there and how you're going to get to them all," he said. "Where do you stop and move on to the next one?"

Many Dakota County cities see a pothole pop up right next to one that crews just fixed, sometimes in the same day. Crews use anywhere from four to 20 tons of asphalt mix a day.

Pothole prevention

In Apple Valley, crews maintain about 400 lane-miles of streets. "Geographically, it's a lot of street surface to check, review and fix the troubled areas," said Apple Valley Public Works Director Todd Blomstrom.

The city uses the newest technology for filling potholes — a spray-injection patching that often gives better results than shoveling the mix.

Blomstrom says cities have pavement management programs that try to prevent potholes.

"Looking at the overall condition rating of your whole street system — is it declining, is it projected to decline, or are you sort of holding ground based on the amount of investment you're putting into resurfacing and reconstruction?" he said. "It's a big picture outlook on managing it."

Farmington is in a different boat than most other Dakota County cities. It has less traffic than bigger cities, and the roads in the north half of Farmington are younger because of later developments.

"Not saying we don't have potholes, because we do, but it's nothing that we've even felt the pressure from the public or get enough complaints where we feel like we have to have a pothole [reporting] line," said Farmington City Engineer Kevin Schorzman.

Trying to stay ahead

Farmington also doesn't see much heavy truck traffic, which helps keep weight from cracking pavement.

"We can continue to maintain our roads, doing routine preventative maintenance," Schorzman said. "Hopefully we can stay out of the problems that tend to plague older cities."

In Lakeville, crews are hoping the freeze-and-thaw cycle ends soon.

"It's going to take longer to get them filled," Grossman said. "And they're not all here yet, either."

Liala Helal • 952-746-3286