US Bridges

I 90 over Clark Fork River

Fair

Missoula County, Montana · 1.9M W Bonner · Structure no. I00090108+02762

Built
1965
60 years old
Condition
Fair
inspected April 2024
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
455 ft
3 main spans
Daily traffic
10,294
2023 count
Owner
State
State Highway Agency

About this bridge

I 90 over Clark Fork River is a steel continuous stringer/multi-beam or girder carrying I 90 over Clark Fork River in Missoula County, Montana. It was built in 1965, so it is 60 years old, older than the Montana average of 47 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 5 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 10,294 vehicles a day, roughly 11% of them trucks, projected to reach 10,808 by 2043. The structure is 455 ft (138.7 m) long and 32 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesI 90
CrossesClark Fork River
Location1.9M W Bonner
RouteInterstate 90
CountyMissoula County
StateMontana
Coordinates46.87205, -113.93148
Functional classUrban Principal Arterial - Interstate

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionApril 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating46 US tons
Inventory rating36 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3 (+2 approach)
Design loadHS 20
Structure length455 ft (138.7 m)
Longest span136 ft (41.5 m)
Deck width32 ft (9.7 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic10,294 (2023)
Projected traffic10,808 by 2043
Trucks11%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkInterstate STRAHNET route

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$1.3 million
NavigationNo navigation control on waterway

Frequently asked questions

When was I 90 over Clark Fork River built?

It was built in 1965, making it 60 years old in 2025.

What condition is I 90 over Clark Fork River in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in April 2024.

How much traffic does I 90 over Clark Fork River carry?

About 10,294 vehicles per day (2023 count), of which roughly 11% are trucks.

How long is I 90 over Clark Fork River?

The structure is 455 ft (138.7 m) long with a longest span of 136 ft (41.5 m) and a deck 32 ft wide.

Who owns I 90 over Clark Fork River?

It is owned by the State Highway Agency.