‘Unstable’ Fairview Bridge needs to be replaced. ACHD asks the feds for help

The Ada County Highway District is asking for federal help to replace one of the county’s oldest — and busiest — bridges, which is in “alarming” condition after nearly 100 years standing against the Boise River.

District staffers on Monday filed an application for a grant to support the nearly $29 million replacement of the Fairview Avenue Bridge, which spans the Boise River to connect the city’s West End to Garden City.

The highway district has already started preliminary engineering work, according to the application, and has some $5.9 million in local dollars earmarked for the project, plus $2 million in federal money. Now, it hopes the Federal Highway Administration’s Bridge Investment Program can help fill the gap to the tune of $21.1 million — about 73% of the total project cost.

ACHD expects design work to wrap in 2028; if construction money is awarded, the highway district could start work on the new bridge in 2030 and finish in 2031.

By then, the oldest part of the bridge would be 99 years old.

Delaying the construction timeline would “pose increasing risk of failure, operational restrictions, and costly emergency repair for more than 17,000 daily users,” the application states.

In an email to the Idaho Statesman, ACHD spokesperson Rachel Bjornestad said that “there are no immediate safety concerns” with the existing span, which is actually two parallel bridges built side-by-side to form four lanes. Still, replacing the Fairview crossing is the top priority in the district’s “large bridge” portfolio, Bjornestad told the Statesman.

“The purpose of the application is to showcase the need for funding now before replacement becomes critical,” she said.

The condition of the bridges was deemed “fair” overall in 2025 inspections; however, that rating “does not capture the full urgency of the project,” according to the application. While the bridge’s roadway passes federal standards, the survey rated its foundation as “unstable,” deeply scoured by the sand and cobble of the riverbed.

That’s been evident to ACHD since 2017, when high water tore through the base of the bridge and damaged its footings, requiring emergency repairs and riprap. Flooding in late June this year further underscored the threat high water poses to the bridge, the ACHD stated in its application, as well as the accelerating need for short-term “reactive” maintenance to shore up the pilings.

“Without replacement, these conditions will continue,” the application states. “The challenge with substructure issues is that it is not a gradual deterioration. A failure in the substructure is catastrophic; the bridge would collapse.”

Fairview a ‘crucial’ crossing

The two Fairview bridges were built 44 years apart. The second one was developed in 1976, when the city’s population boom demanded expanding the major eastbound crossing to four lanes. Structurally, they’re completely separate, listed individually in federal databases and facing different problems as they age. Despite their tenure, they’re not forecast to totally shut down until 2064, when the younger crossing is almost 90 years old.

But the bridges won’t make it to that date without continual — and costly — interventions, according to the highway district, especially if traffic intensifies. Fairview is already a major alternative to the Boise Connector for cars, trucks and emergency vehicles — namely, from Boise Fire Station No. 5, less than a mile away. In 2021, a National Bridge Inventory Study found an average of 11,000 vehicles crossed the bridge every day. Last year, the number reached around 17,700 vehicles per day, according to Community Planning Association of Southwest Idaho traffic data — about 61% higher. That’s close to 6.5 million cars per year.

“Without proactive improvement, continued deterioration could result in load restrictions, reduced operational capacity, or closure,” ACHD states in the application.

As proposed, ACHD would demolish the existing bridges in favor of a single, four-lane replacement with two multi-use paths, Greenbelt connections, and extended sidewalks onto Fairview Avenue. The new design would be built to state-of-the-art standards, using modern hydrological analysis and construction to minimize scour and stabilize the span. ACHD projects that, once completed, a new bridge would cost 85% less to maintain than the existing set-up.

“It really is a pretty spectacular project,” ACHD director Ryan Head told the highway district’s board on Wednesday. “It’s a big deal — a very apparent project that sits right in the center of our community.”