US Bridges

I 90 over Clark Fork River

Fair

Mineral County, Montana · 2.5M W Superior · Structure no. I00090045+01802

Built
1960
65 years old, rebuilt 2012
Condition
Fair
inspected June 2023
Type
Girder and Floorbeam System
Steel Continuous
Length
621 ft
3 main spans
Daily traffic
3,719
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 1960 and reconstructed in 2012, so it is 65 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 3,719 vehicles a day, roughly 27% of them trucks, projected to reach 3,904 by 2043. The structure is 621 ft (189.2 m) long and 30 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
Location2.5M W Superior
RouteInterstate 90
CountyMineral County
StateMontana
Coordinates47.20798, -114.93475
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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure7 GoodSome minor problems.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJune 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating54.7 US tons
Inventory rating32.8 US tons

Structure

Structure typeGirder and Floorbeam System
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3 (+2 approach)
Design loadHS 20
Structure length621 ft (189.2 m)
Longest span180 ft (54.9 m)
Deck width30 ft (9.2 m)
Roadway width27 ft (8.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,719 (2023)
Projected traffic3,904 by 2043
Trucks27%
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$1.8 million
NavigationNo navigation control on waterway

Frequently asked questions

When was I 90 over Clark Fork River built?

It was built in 1960, making it 65 years old in 2025. It was reconstructed in 2012.

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 June 2023.

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

About 3,719 vehicles per day (2023 count), of which roughly 27% are trucks.

How long is I 90 over Clark Fork River?

The structure is 621 ft (189.2 m) long with a longest span of 180 ft (54.9 m) and a deck 30 ft wide.

Who owns I 90 over Clark Fork River?

It is owned by the State Highway Agency.