I 15 over Sep Old US 91
GoodCascade County, Montana · 3M S Cascade · Structure no. I00015251+06842
- Built
- 1978
- 47 years old
- Condition
- Good
- inspected June 2024
- Type
- Stringer/Multi-beam or Girder
- Prestressed Concrete
- Length
- 99 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 prestressed concrete stringer/multi-beam or girder carrying I 15 over Sep Old US 91 in Cascade County, Montana. It was built in 1978, so it is 47 years old, younger 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 2,218 vehicles a day, roughly 16% of them trucks, projected to reach 2,361 by 2043. The structure is 99 ft (30.2 m) long and 44 ft wide. If it were closed, the detour would be 1.2 mi (2 km).
Location
Open in Google MapsCondition and inspection
All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.
| Component | Rating | Meaning |
|---|---|---|
| Deck | 7 Good | Some minor problems. |
| Superstructure | 8 Very Good | No problems noted. |
| Substructure | 7 Good | Some minor problems. |
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 1978, making it 47 years old in 2025.
What condition is I 15 over Sep Old US 91 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 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 99 ft (30.2 m) long with a longest span of 41 ft (12.6 m) and a deck 44 ft wide.
Who owns I 15 over Sep Old US 91?
It is owned by the State Highway Agency.