US Bridges

I 15 over Beaverhead River

Good

Beaverhead County, Montana · 5M N Clark Canyon Dam · Structure no. I00015049+07602

Built
1980
45 years old
Condition
Good
inspected December 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
154 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 1980, so it is 45 years old, younger 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 2,185 vehicles a day, roughly 25% of them trucks, projected to reach 2,338 by 2043. The structure is 154 ft (46.9 m) long and 45 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
Coordinates45.06591, -112.80173
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.
Superstructure8 Very GoodNo problems noted.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionDecember 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 geometry7: Better than present minimum criteria
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating46 US tons
Inventory rating25 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length154 ft (46.9 m)
Longest span60 ft (18.3 m)
Deck width45 ft (13.7 m)
Roadway width41 ft (12.6 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 1980, making it 45 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 December 2023.

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 154 ft (46.9 m) long with a longest span of 60 ft (18.3 m) and a deck 45 ft wide.

Who owns I 15 over Beaverhead River?

It is owned by the State Highway Agency.