US Bridges

I 15 over Beaverhead River

Good

Beaverhead County, Montana · 0.6M N Dillon · Structure no. I00015064+00882

Built
1973
52 years old
Condition
Good
inspected November 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
143 ft
2 main spans
Daily traffic
1,958
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 1973, so it is 52 years old, older than the Montana average of 47 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 1,958 vehicles a day, roughly 23% of them trucks, projected to reach 2,114 by 2043. The structure is 143 ft (43.6 m) long and 44 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

CarriesI 15
CrossesBeaverhead River
Location0.6M N Dillon
RouteInterstate 15
StateMontana
Coordinates45.22969, -112.64132
Functional classRural Principal Arterial - Interstate

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionNovember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry7: Better than present minimum criteria
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating45 US tons
Inventory rating19 US tons

Structure

MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20
Structure length143 ft (43.6 m)
Longest span70 ft (21.3 m)
Deck width44 ft (13.4 m)
Roadway width41 ft (12.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,958 (2023)
Projected traffic2,114 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 15 over Beaverhead River built?

It was built in 1973, making it 52 years old in 2025.

What condition is I 15 over Beaverhead River in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in November 2023.

How much traffic does I 15 over Beaverhead River carry?

About 1,958 vehicles per day (2023 count), of which roughly 23% are trucks.

How long is I 15 over Beaverhead River?

The structure is 143 ft (43.6 m) long with a longest span of 70 ft (21.3 m) and a deck 44 ft wide.

Who owns I 15 over Beaverhead River?

It is owned by the State Highway Agency.