US Bridges

I 90 over Int Tarkio County Road

Fair

Mineral County, Montana · 13.7M W Alberton · Structure no. I00090061+07931

Built
1959
66 years old, rebuilt 2011
Condition
Fair
inspected April 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
130 ft
3 main spans
Daily traffic
4,088
2023 count
Owner
State
State Highway Agency

About this bridge

I 90 over Int Tarkio County Road is a prestressed concrete stringer/multi-beam or girder carrying I 90 over Int Tarkio County Road in Mineral County, Montana. It was built in 1959 and reconstructed in 2011, so it is 66 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 4,088 vehicles a day, roughly 23% of them trucks, projected to reach 4,292 by 2043. The structure is 130 ft (39.6 m) long and 40 ft wide.

Location

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CarriesI 90
CrossesInt Tarkio County Road
Location13.7M W Alberton
RouteInterstate 90
CountyMineral County
StateMontana
Coordinates47.02587, -114.73935
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.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionApril 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating59 US tons
Inventory rating42 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length130 ft (39.6 m)
Longest span46 ft (14 m)
Deck width40 ft (12.2 m)
Roadway width37 ft (11.4 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
CarriesOverpass structure at an interchange
CrossesHighway
Detour if closed—
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—
NavigationNot applicable (no waterway)

Frequently asked questions

When was I 90 over Int Tarkio County Road built?

It was built in 1959, making it 66 years old in 2025. It was reconstructed in 2011.

What condition is I 90 over Int Tarkio County Road 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 2023.

How much traffic does I 90 over Int Tarkio County Road carry?

About 4,088 vehicles per day (2023 count), of which roughly 23% are trucks.

How long is I 90 over Int Tarkio County Road?

The structure is 130 ft (39.6 m) long with a longest span of 46 ft (14 m) and a deck 40 ft wide.

Who owns I 90 over Int Tarkio County Road?

It is owned by the State Highway Agency.