US Bridges

I 15 over Beaverhead River

Fair

Beaverhead County, Montana · 3.1M S Dillon · Structure no. I00015060+01771

Built
1982
43 years old
Condition
Fair
inspected February 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
142 ft
2 main spans
Daily traffic
2,863
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 1982, so it is 43 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 2,863 vehicles a day, roughly 23% of them trucks, projected to reach 3,120 by 2043. The structure is 142 ft (43.4 m) long and 44 ft wide.

Location

Open in Google Maps
CarriesI 15
CrossesBeaverhead River
Location3.1M S Dillon
RouteInterstate 15
CountyBeaverhead County
StateMontana
Coordinates45.18493, -112.68795
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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionFebruary 2024
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 geometry7: Better than present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating61.9 US tons
Inventory rating48 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20
Structure length142 ft (43.4 m)
Longest span100 ft (30.5 m)
Deck width44 ft (13.5 m)
Roadway width41 ft (12.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,863 (2023)
Projected traffic3,120 by 2043
Trucks23%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
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—
NavigationNo navigation control on waterway

Frequently asked questions

When was I 15 over Beaverhead River built?

It was built in 1982, making it 43 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 February 2024.

How much traffic does I 15 over Beaverhead River carry?

About 2,863 vehicles per day (2023 count), of which roughly 23% are trucks.

How long is I 15 over Beaverhead River?

The structure is 142 ft (43.4 m) long with a longest span of 100 ft (30.5 m) and a deck 44 ft wide.

Who owns I 15 over Beaverhead River?

It is owned by the State Highway Agency.