US Bridges

I 15 over Sep County Road

Good

Cascade County, Montana · 3M N Ulm · Structure no. I00015274+02692

Built
1969
56 years old
Condition
Good
inspected July 2024
Type
Slab
Concrete Continuous
Length
79 ft
3 main spans
Daily traffic
3,145
2023 count
Owner
State
State Highway Agency

About this bridge

I 15 over Sep County Road is a concrete continuous slab carrying I 15 over Sep County Road in Cascade County, Montana. It was built in 1969, so it is 56 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 3,145 vehicles a day, roughly 12% of them trucks, projected to reach 3,301 by 2043. The structure is 79 ft (24.1 m) long and 44 ft wide.

Location

Open in Google Maps
CarriesI 15
CrossesSep County Road
Location3M N Ulm
RouteInterstate 15
CountyCascade County
StateMontana
Coordinates47.45238, -111.42945
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
Deck8 Very GoodNo problems noted.
Superstructure8 Very GoodNo problems noted.
Substructure7 GoodSome minor problems.
Last inspectionJuly 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation7: Better than present minimum criteria
Deck geometry7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating45 US tons
Inventory rating35.1 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length79 ft (24.1 m)
Longest span30 ft (9.1 m)
Deck width44 ft (13.5 m)
Roadway width42 ft (12.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,145 (2023)
Projected traffic3,301 by 2043
Trucks12%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
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—
NavigationNot applicable (no waterway)

Frequently asked questions

When was I 15 over Sep County Road built?

It was built in 1969, making it 56 years old in 2025.

What condition is I 15 over Sep County Road 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 July 2024.

How much traffic does I 15 over Sep County Road carry?

About 3,145 vehicles per day (2023 count), of which roughly 12% are trucks.

How long is I 15 over Sep County Road?

The structure is 79 ft (24.1 m) long with a longest span of 30 ft (9.1 m) and a deck 44 ft wide.

Who owns I 15 over Sep County Road?

It is owned by the State Highway Agency.