Portland’s City Council is poised to water down its tax on big trucks, a step that would bow to industry pressure and buck elected leaders’ promise to voters to ensure truckers pay their share for road upkeep.

As part of a successful campaign to win voter approval of a local gas tax, city leaders including then-mayoral candidate Ted Wheeler pledged to give truck drivers a share of the bill for roads.

They settled on collecting $10 million over four years from operators of heavy trucks who use city streets, with the tax rate to be adjusted each year to ensure the full total was collected.

But Portland Bureau of Transportation officials now say the tax, called the Heavy Vehicle Use Tax, will not meet that target, in part because so many truck drivers got out of paying it. At the current tax rate, the city would collect about $8 million, officials say.

Rather than raise the tax rate for the final two years of the tax’s four year lifespan, transportation staffers want city commissioners to delete the $10 million goal from city law. A City Council vote to do that is scheduled for Wednesday.

The tax works by tacking a 2.5 percent city surcharge onto a state tax truckers pay. Money it generates funds road upgrades in Portland, with a focus on projects that improve safety and benefit truckers. For example, the tax paid to repave parts of North Columbia Boulevard, a road often used by freight trucks.

The city council adopted the tax in 2016 as a way to level the playing field between trucks and cars just before voters approved a 10-cent city gas tax, which truckers generally do not pay because diesel fuel is exempt.

At the time, the mayor, city commissioners and Wheeler signed a voters pamphlet statement promoting the gas tax. They highlighted that a yes vote would require the city to study “how to get heavy trucks to pay their fair share.”

City council members also made clear their intention to raise $10 million via the heavy truck tax. The city law that created it says officials “will adjust” the tax rate every year to meet the $10 million goal. But they have not done that.

Explaining the decision to not exercise that power, city revenue chief Thomas Lannom said the rate would have to be increased 60 percent to meet the target. Revenue collection fell far behind projections, he said, because officials worked with “imperfect information and had to make assumptions.”

Far more truckers than anticipated got out of paying the tax by submitting paperwork to show that, although their business operates in Portland, their trucks rarely use city-owned streets, he said.

The city also had only 682 eligible trucking businesses to tax rather than the more than 2,500 as projected, said Bureau of Transportation spokesman Dylan Rivera. The problem was only discovered this summer, Rivera said, because it took that long to finish collections for the 2016 tax year.

City officials also faced industry pressure not to raise the tax rate to collect all $10 million. In September a city committee of freight industry representatives voted unanimously to do away with the $10 million goal. (Another city panel overseeing spending of the tax said it found the truckers’ arguments “less than convincing” but nevertheless agreed the city should keep the tax rate as is.)

Truckers generally view the city tax as cumbersome and unfair, said Jana Jarvis, president of the Oregon Trucking Associations. She said it’s right for Portland to axe the revenue goal because the city will get additional money for transportation from the state owing to an infrastructure bill passed last year.

“Our perspective has been, ‘Let this thing die its death and move on,’” Jarvis said of the city tax.

The council had scheduled the same vote last month but did not go through with it after Commissioner Amanda Fritz criticized the idea. Fritz raised concerns about paring back the tax after a phone call from Steve Novick, a former Portland commissioner who headed the Bureau of Transportation.

Novick, the architect of the truck tax, had been alerted to the vote by a reporter for The Oregonian/OregonLive who was seeking comment. Fritz’s chief of staff, Tim Crail, said the vote to scale back the tax was “sailing through” prior to Novick’s call alerting Fritz.

“Council members signed a letter saying the trucks would pay their fair share. … That was basically a promise to the voters,” Fritz said during that October meeting. “I think this is something we need to be very careful about.”

Fritz told The Oregonian/OregonLive on Tuesday that the city should uphold its commitment to voters.

“What we should be doing is adjusting the rate” to meet the $10 million goal, Fritz said, “not doing away with the target.”

Commissioner Dan Saltzman, who until September was commissioner-in-charge for the Transportation Bureau, said Monday he believes bureau officials have “solid reasons for doing what they’re doing.”

But he cautioned that gutting the truck tax could backfire when the city asks voters to renew the gas tax in 2020 because voters could perceive it as unfair.

“This could be an action that would come back to haunt us,” he said.

-- Gordon R. Friedman

GFriedman@Oregonian.com

Correction: An earlier version of this article misstated when the Heavy Vehicle Use Tax was adopted. It was adopted before voters approved a 10-cent gas tax.