US Bridges

I 15 over Sep High Bridge RD

Fair

Beaverhead County, Montana · 3.7M N Clark Canyon Dam · Structure no. I00015048+07471

Built
1986
39 years old
Condition
Fair
inspected December 2023
Type
Slab
Concrete Continuous
Length
80 ft
3 main spans
Daily traffic
2,185
2023 count
Owner
State
State Highway Agency

About this bridge

I 15 over Sep High Bridge RD is a concrete continuous slab carrying I 15 over Sep High Bridge RD in Beaverhead County, Montana. It was built in 1986, so it is 39 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 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 80 ft (24.4 m) long and 40 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesI 15
CrossesSep High Bridge RD
Location3.7M N Clark Canyon Dam
RouteInterstate 15
CountyBeaverhead County
StateMontana
Coordinates45.05289, -112.81061
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 inspectionDecember 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 rating42 US tons
Inventory rating33 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length80 ft (24.4 m)
Longest span30 ft (9.1 m)
Deck width40 ft (12.3 m)
Roadway width37 ft (11.4 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
CrossesHighway
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—
NavigationNot applicable (no waterway)

Frequently asked questions

When was I 15 over Sep High Bridge RD built?

It was built in 1986, making it 39 years old in 2025.

What condition is I 15 over Sep High Bridge RD 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 December 2023.

How much traffic does I 15 over Sep High Bridge RD carry?

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

How long is I 15 over Sep High Bridge RD?

The structure is 80 ft (24.4 m) long with a longest span of 30 ft (9.1 m) and a deck 40 ft wide.

Who owns I 15 over Sep High Bridge RD?

It is owned by the State Highway Agency.