Come harvest season, farmers will haul heavy crop loads in grain wagons. Come spring, loaded manure applicators will head to those fields. A law passed 14 years ago exempts those vehicles from size, weight and load provisions on all roads except interstates. Farms have grown since 1993, and so have the farm vehicles, according to Polk County Engineer Rich Sanders.
Sanders says he and other county engineers are worried about the damage these vehicles are doing to county roads and bridges.
"The problem with them is is you have all the weight on a few axles. On a grain cart you might only have two axles or you might only have one axle, and it probably weighs one hundred thousand pounds," Sanders says. "When it comes to crossing a bridge, it becomes a problem because bridges weren't designed on a single axle." 100,000 pounds is the loaded weight of some of this farm equipment. It's more than the average semi, which can legally weigh about 80,000 pounds. County roads and bridges are actually designed for less weight, but the real trouble is the design of the vehicles. Instead of carrying 80,000 pounds over five axles, like a semi does, a manure spreader loads it over no more than three axles and sometimes just one.
“Honestly, I would ask these highway engineers how many grain carts have they ever seen on their roads that are full?”Minnesota Farm Bureau President Kevin Paap
All that weight connecting with concrete at a single point creates a tremendous amount of pressure. Minnesota County Engineers Association President Don Theisen says several years ago, a wheel of a grain cart punctured the deck of a timber bridge. And he says because these vehicles are exempt from weight restrictions, the farmers driving them are also exempt from liability.
"Is one pass with one of these pieces of equipment going to cause a bridge to fail? We're not saying that," Theisen says. "But they are definitely consuming more life of the bridge than the public dollars were used for. The real simple issue here is that this is the only piece of equipment going over our bridges that's unregulated."
MnDOT commissioned a study from Iowa State University on farm equipment and its effects on rural bridges. It showed a connection between heavy vehicles with fewer axles and deteriorating pavement and bridges. The study's authors also showed these vehicles could bend and puncture shorter bridges.
The Minnesota County Engineers Association hopes to get legislation passed that would require farm vehicles to abide by tonnage restrictions on bridges. This is the second time the association has pushed such legislation on weight restrictions.
The Minnesota Pork Producers Executive Director Dave Preisler says manure applicators can weigh up to 100,000 pounds. He says five years ago farmers drove the applicators, filled with manure, down county roads to the field. But he says, today farmers do things differently.
"The trend has been to look at loading manure into a semi first and then transporting the manure then out to the field where the tank would be used then to pull through the field," Preisler says.
Unlike farm equipment, semis have to adhere to weight restrictions on county roads. Preisler says his group would prefer that Minnesota improve its bridges with gas tax dollars rather than limit the weight of farm equipment.
Minnesota Farm Bureau President Kevin Paap says he doesn't believe farm vehicles are a problem for greater Minnesota's roads either and he's against weight restrictions. Paap says in his 22 years of farming he's only seen 10 grain carts fully loaded on county roads.
"I know that grain carts, because it's a lot of weight on one axle, typically seem to get a whole bunch of the blame," Papp says. "But honestly, I would ask these highway engineers how many grain carts have they ever seen on their roads that are full?"
But no one has any statistics. And come harvest time there will be more trucks hauling more corn for ethanol over Greater Minnesota's roads and bridges.