First snow. Then cold. Then a thaw. And now, potholes

The Treasure Valley’s recent cold and wet conditions are perfect for forming potholes, as drivers are finding out on roadways suddenly pockmarked with them.

Potholes are more likely to occur on older or stressed roadways, which is why roads like Broadway Avenue, Franklin Road and Harrison Boulevard in Boise have developed potholes more quickly than newer or recently resurfaced roads.

On Wednesday, the Idaho Transportation Department had to close Interstate 84 between Nampa and Caldwell so it could make emergency pothole repairs.

Potholes form when water seeps into road-surface cracks, saturates the base material below and then freezes. Ice expands in the cracks and base material, loosening the surface, which collapses when the ice melts and traffic drives over it. With each freeze/thaw cycle, the condition worsens.

During a period of high moisture and multiple freeze-thaw cycles, as Southwest Idaho has had lately, potholes and broken pavement proliferate.

“It is about quality of the entire pavement section — asphalt, gravel base and existing ground — moisture, temperatures and traffic loading,” said Tim Morgan, the Ada County Highway District’s deputy director of maintenance. “Resurfacing helps, but the strength of the complete pavement section is crucial.”

Slapping on Band-Aids

ACHD said Wednesday that it is filling potholes as quickly as it can. The district is responsible for all roads in the county except those owned by the state.

“For now we are filling holes we find, or are reported, with ‘cold mix’ asphalt, which is kind of a Band-Aid,” Morgan said.

“Our goal is to fill them within 24 hours of being reported,” he said. “Last year we filled 2,154 potholes, all within 24 hours of notice.”

The Idaho Transportation Department is advising drivers to be on the lookout for potholes and other road damage on state roads. ITD says weather has hampered its ability to keep up.

“There is usually enough time during most winter storms for our road-maintenance crews to complete repairs,” Chief Highway Engineer Kimbol Allen said. “So far this winter season, however, crews have had little time between storms to do much more than prepare for the next storm to hit.”

Crews clear snow and ice first, then aim to fill potholes with temporary patching material, spokeswoman Jennifer Gonzalez said in a news release. “Continued moisture quickly loosens and breaks the patches,” she said.

ITD is responsible for all state and federal highways, including Interstate 84, Idaho 55 (Eagle Road), Idaho 44 (State Street), and U.S. 20/26 (Broadway Avenue and Chinden Boulevard).

Is help on the way for I-84?

Drivers who regularly use I-84 between Nampa and Caldwell are well aware of the rutted, cracked and grooved section stretching eight miles from Franklin Boulevard (Exit 36) in Nampa to Franklin Road (Exit 29) in Caldwell. It has been in poor condition for years.

In September 2014, ITD took a $12.6 million plan to restore the section off its five-year to-do list, saying it had run out of money to pay for the work and that the repair would be more costly than anticipated.

That angered county and city leaders. “The stretch of highway between Caldwell and Nampa is atrocious, “ Caldwell Mayor Garret Nancolas told the Statesman at the time.

ITD conceded as much and put the project back on the list — for 2019. On Wednesday, ITD confirmed that it still plans to rebuild the stretch in 2018 and 2019. But the latest potholes are leading officials to try to speed that up.

“Due to this harsh winter, the department is already working on plans to hopefully begin that project this summer,” Gonzalez said.

When the weather warms and hot-asphalt plants reopen, ACHD will hold its annual “Potholes Days.” This year, from April 12 to 14, an ACHD road brigade will patch a plethora of potholes.

This story was originally published January 11, 2017 at 6:35 PM with the headline "First snow. Then cold. Then a thaw. And now, potholes."