US Bridges

I 15 over Beaverhead River

Fair

Beaverhead County, Montana · 5M N Clark Canyon Dam · Structure no. I00015049+07601

Built
1964
61 years old
Condition
Fair
inspected January 2025
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
163 ft
3 main spans
Daily traffic
2,185
2023 count
Owner
State
State Highway Agency

About this bridge

I 15 over Beaverhead River is a prestressed concrete stringer/multi-beam or girder carrying I 15 over Beaverhead River in Beaverhead County, Montana. It was built in 1964, so it is 61 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 2,185 vehicles a day, roughly 25% of them trucks, projected to reach 2,338 by 2043. The structure is 163 ft (49.7 m) long and 47 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesI 15
CrossesBeaverhead River
Location5M N Clark Canyon Dam
RouteInterstate 15
CountyBeaverhead County
StateMontana
Coordinates45.0659, -112.80144
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.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJanuary 2025
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation6: Equal to present minimum criteria
Deck geometry9: Superior to present desirable criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating63.9 US tons
Inventory rating37.5 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length163 ft (49.7 m)
Longest span61 ft (18.7 m)
Deck width47 ft (14.3 m)
Roadway width44 ft (13.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,185 (2023)
Projected traffic2,338 by 2043
Trucks25%
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 15 over Beaverhead River built?

It was built in 1964, making it 61 years old in 2025.

What condition is I 15 over Beaverhead 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 January 2025.

How much traffic does I 15 over Beaverhead River carry?

About 2,185 vehicles per day (2023 count), of which roughly 25% are trucks.

How long is I 15 over Beaverhead River?

The structure is 163 ft (49.7 m) long with a longest span of 61 ft (18.7 m) and a deck 47 ft wide.

Who owns I 15 over Beaverhead River?

It is owned by the State Highway Agency.