US Bridges

I 90 over Clark Fork River

Fair

Mineral County, Montana · 9.3M W Alberton · Structure no. I00090066+02791

Built
1981
44 years old
Condition
Fair
inspected May 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
867 ft
5 main spans
Daily traffic
4,088
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 Mineral County, Montana. It was built in 1981, so it is 44 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 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 4,088 vehicles a day, roughly 23% of them trucks, projected to reach 4,292 by 2043. The structure is 867 ft (264.2 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
Location9.3M W Alberton
RouteInterstate 90
CountyMineral County
StateMontana
Coordinates47.01905, -114.65838
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.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionMay 2023
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 geometry7: Better than present minimum criteria
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating42.1 US tons
Inventory rating32.5 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans5
Design loadHS 20
Structure length867 ft (264.2 m)
Longest span190 ft (57.9 m)
Deck width44 ft (13.4 m)
Roadway width41 ft (12.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,088 (2023)
Projected traffic4,292 by 2043
Trucks23%
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 1981, making it 44 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 4,088 vehicles per day (2023 count), of which roughly 23% are trucks.

How long is I 90 over Clark Fork River?

The structure is 867 ft (264.2 m) long with a longest span of 190 ft (57.9 m) and a deck 44 ft wide.

Who owns I 90 over Clark Fork River?

It is owned by the State Highway Agency.