US Bridges

I 90 over Clark Fork River

Fair

Mineral County, Montana · 10.5M E Superior · Structure no. I00090058+05501

Built
1967
58 years old
Condition
Fair
inspected May 2023
Type
Girder and Floorbeam System
Steel Continuous
Length
826 ft
3 main spans
Daily traffic
3,825
2023 count
Owner
State
State Highway Agency

About this bridge

I 90 over Clark Fork River is a steel continuous girder and floorbeam system carrying I 90 over Clark Fork River in Mineral County, Montana. It was built in 1967, so it is 58 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 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 3,825 vehicles a day, roughly 24% of them trucks, projected to reach 4,015 by 2043. The structure is 826 ft (251.7 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
Location10.5M E Superior
RouteInterstate 90
CountyMineral County
StateMontana
Coordinates47.06883, -114.76487
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionMay 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
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 rating51 US tons
Inventory rating30.3 US tons

Structure

Structure typeGirder and Floorbeam System
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3 (+4 approach)
Design loadHS 20
Structure length826 ft (251.7 m)
Longest span195 ft (59.4 m)
Deck width32 ft (9.7 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,825 (2023)
Projected traffic4,015 by 2043
Trucks24%
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$2.3 million
NavigationNo navigation control on waterway

Frequently asked questions

When was I 90 over Clark Fork River built?

It was built in 1967, making it 58 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 May 2023.

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

About 3,825 vehicles per day (2023 count), of which roughly 24% are trucks.

How long is I 90 over Clark Fork River?

The structure is 826 ft (251.7 m) long with a longest span of 195 ft (59.4 m) and a deck 32 ft wide.

Who owns I 90 over Clark Fork River?

It is owned by the State Highway Agency.