US Bridges

I 15 over Sep Galena Gulch Road

Fair

Jefferson County, Montana · 4.3M E Basin · Structure no. I00015161+01511

Built
1981
44 years old
Condition
Fair
inspected November 2024
Type
Slab
Concrete Continuous
Length
78 ft
3 main spans
Daily traffic
3,856
2023 count
Owner
State
State Highway Agency

About this bridge

I 15 over Sep Galena Gulch Road is a concrete continuous slab carrying I 15 over Sep Galena Gulch Road in Jefferson County, Montana. It was built in 1981, so it is 44 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 3,856 vehicles a day, roughly 13% of them trucks, projected to reach 4,164 by 2043. The structure is 78 ft (23.8 m) long and 88 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesI 15
CrossesSep Galena Gulch Road
Location4.3M E Basin
RouteInterstate 15
CountyJefferson County
StateMontana
Coordinates46.25415, -112.181
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 inspectionNovember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry9: Superior to present desirable criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating34 US tons
Inventory rating27 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length78 ft (23.8 m)
Longest span30 ft (9.1 m)
Deck width88 ft (26.9 m)
Roadway width85 ft (26 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,856 (2023)
Projected traffic4,164 by 2043
Trucks13%
Lanes on structure4
Traffic directionTwo-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 Galena Gulch Road built?

It was built in 1981, making it 44 years old in 2025.

What condition is I 15 over Sep Galena Gulch Road 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 November 2024.

How much traffic does I 15 over Sep Galena Gulch Road carry?

About 3,856 vehicles per day (2023 count), of which roughly 13% are trucks.

How long is I 15 over Sep Galena Gulch Road?

The structure is 78 ft (23.8 m) long with a longest span of 30 ft (9.1 m) and a deck 88 ft wide.

Who owns I 15 over Sep Galena Gulch Road?

It is owned by the State Highway Agency.