I 15 over Sep Old US 91
FairCascade County, Montana · 3M S Cascade · Structure no. I00015251+06841
- Built
- 1961
- 64 years old
- Condition
- Fair
- inspected June 2024
- Type
- Tee Beam
- Concrete
- Length
- 84 ft
- 3 main spans
- Daily traffic
- 2,218
- 2023 count
- Owner
- State
- State Highway Agency
About this bridge
I 15 over Sep Old US 91 is a concrete tee beam carrying I 15 over Sep Old US 91 in Cascade County, Montana. It was built in 1961, so it is 64 years old, older 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 2,218 vehicles a day, roughly 16% of them trucks, projected to reach 2,361 by 2043. The structure is 84 ft (25.6 m) long and 48 ft wide. If it were closed, the detour would be 1.2 mi (2 km).
Location
Open in Google MapsCondition and inspection
The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.
| Component | Rating | Meaning |
|---|---|---|
| Deck | 7 Good | Some minor problems. |
| Superstructure | 7 Good | Some minor problems. |
| Substructure | 6 Satisfactory | Structural elements show some minor deterioration. |
Structure
Traffic and service
Ownership and planned work
Frequently asked questions
When was I 15 over Sep Old US 91 built?
It was built in 1961, making it 64 years old in 2025.
What condition is I 15 over Sep Old US 91 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 June 2024.
How much traffic does I 15 over Sep Old US 91 carry?
About 2,218 vehicles per day (2023 count), of which roughly 16% are trucks.
How long is I 15 over Sep Old US 91?
The structure is 84 ft (25.6 m) long with a longest span of 30 ft (9.1 m) and a deck 48 ft wide.
Who owns I 15 over Sep Old US 91?
It is owned by the State Highway Agency.