US Bridges

I 90 over Clark Fork River

Fair

Missoula County, Montana · 5M E Alberton · Structure no. I00090080+03411

Built
1979
46 years old
Condition
Fair
inspected December 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
1,020 ft
8 main spans
Daily traffic
4,584
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 1979, so it is 46 years old, younger 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 6 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 4,584 vehicles a day, roughly 20% of them trucks, projected to reach 4,813 by 2043. The structure is 1,020 ft (310.8 m) long and 44 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesI 90
CrossesClark Fork River
Location5M E Alberton
RouteInterstate 90
CountyMissoula County
StateMontana
Coordinates47.01346, -114.4091
Functional classRural 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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionDecember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry7: Better than present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating60.4 US tons
Inventory rating36 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans8
Design loadHS 20
Structure length1,020 ft (310.8 m)
Longest span152 ft (46.3 m)
Deck width44 ft (13.5 m)
Roadway width41 ft (12.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,584 (2023)
Projected traffic4,813 by 2043
Trucks20%
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 proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was I 90 over Clark Fork River built?

It was built in 1979, making it 46 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 December 2023.

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

About 4,584 vehicles per day (2023 count), of which roughly 20% are trucks.

How long is I 90 over Clark Fork River?

The structure is 1,020 ft (310.8 m) long with a longest span of 152 ft (46.3 m) and a deck 44 ft wide.

Who owns I 90 over Clark Fork River?

It is owned by the State Highway Agency.