The city of Idaho Falls dumped tens of thousands of dollars last fall into a failed road repaving project, which was meant to be one of several improvements to South Boulevard.

Idaho Falls residents probably noticed loose gravel and reappearing traffic lines on South Boulevard this winter.

The reason: a $60,038 seal coat between 17th Street and Northgate Mile, installed sometime in September or October, that didn’t bond properly.

The failed project has put the city in a sticky situation: the contracting company, TMC Contractors, says the city is at fault because it mismanaged the project’s sensitive timeline.

It’s unclear at this point whether the city or the contractor is to blame for the failed seal coat. If the city is found liable, Idaho Falls taxpayers would have to pay for the road project (or part of the road project, if it’s found to be only partially liable), again.

Last year, contractors installed on South Boulevard new storm drainage, pedestrian crossings and a roundabout at the Elm Street intersection.

The cherry on top of the expansive road remodel was a seal coat over the aging pavement.

But the seal coat didn’t stick.

Over the next few months, vehicles uprooted gravel chips, until most of the seal coat was gone. It will have to be replaced this summer.

What is a seal coat?

The city utilizes three road repaving methods: reconstruction, overlay and seal coat. The latter is the cheapest and least extensive improvement.

Seal coating is a kick-the-can strategy, adding years to a road’s lifespan without having to do costlier improvements, such as a full reconstruction. Chip seal, which was done on South Boulevard, is the type of seal coating most commonly used in Idaho Falls.

A chip seal involves spreading a thick oil and about half-an-inch of gravel chips on top of the pavement. The chips are meant to seep into the oil, and when it dries and loose chips are swept away, there should be a smooth new surface.

“(South Boulevard’s) pavement structure was still in reasonably good condition, but we were starting to see a lot of cracking on the surface,” said city engineer Kent Fugal. “It just needed a good seal to extend its life.”

Why didn’t it stick?

Outside temperature, oil application and thorough road sweeping determine whether a chip seal will stick. It needs to be warm outside and the road needs to be clean.

Of the South Boulevard improvement projects last year, the chip seal had to be done last — after the new storm drainage, pedestrian crossings and roundabout were complete. Delays in those projects pushed the chip seal, which is ideally done in July or August, to later in the year.

“We actually had four different contracts going on at once out there,” Fugal said. “We did hold off until it got, frankly, a little late in the season for a chip seal. We recognize that. To what extent that contributed to that chip seal failing is something we’re still trying to figure out.”

Randy Turnage, owner of TMC Contractors, said an outside temperature of 70 degrees is the minimum recommended for a chip seal.

A Sept. 14 city news release announced that the South Boulevard chip seal would begin on Sept. 15. However, Turnage and Fugal said they think the work didn’t actually begin until mid- to late-October.

According to Weather Underground, the high in Idaho Falls on Sept. 15 was 86 degrees. By Oct. 15, the high had dropped to 53 degrees.

Who’s to blame?

Whatever caused the chip seal to fail would likely put the offending party on the hook for financing its replacement. Contractors typically agree to a warranty on their work, meaning if a project isn’t sufficient they will replace it.

The city’s stance is the cause of the chip seal failure is still unknown, that either the city could be at fault for waiting too long to give the go-ahead or the contractor could be at fault for a failure in one of the many steps involved in the chip seal installation.

“We’re still trying to determine what factors (caused the failure) because we think it’s probably more than one,” Fugal said. “There very well could have been a problem with the oil and certainly temperatures could have played a role.”

Turnage, on the other hand, said the blame — and the financial responsibility — rests with the city.

He said environmental conditions caused the failure. And the city is at fault for giving TMC Contractors the go-ahead, despite poor conditions and despite warnings from TMC that the chip seal might not properly bond.

“It was temperature and the amount of work that was going on both sides,” he said.

Turnage said TMC Contractors recommended against doing the chip seal in the fall, due to low temperatures, but the city gave them the notice to proceed, anyway.

“We just mind our p’s and q’s,” he said. “People make bad decisions. We get beat up over it but I try to explain it as best I can to people and they make the decision.”

TMC Contractors told the city, before the project began, it would not warranty the chip seal, Turnage said, and it will stand by that now. He said TMC Contractors will not finance the replacement chip seal.

Fugal said there will likely be a meeting in the coming weeks between city and TMC representatives to reconstruct timelines, consult notes and “see if we can come to some agreement on what we think was the most likely cause of the failure.”

The chip seal is expected to be replaced this summer, when temperatures are warm enough for the seal coat to stick.

Reporter Ryan Suppe can be reached at 208-542-6762. Follow him on Twitter: @salsuppe.

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