6TH St SW over Sun River
Cascade County, Montana · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- 6TH St SW over Sun River in Cascade County, Montana, is rated in fair condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the deck, rated 5 (fair condition) on the 0-9 scale.
- It was built in 1980, making it 45 years old at the 2025 inventory.
- It carries about 13,800 vehicles a day (traffic count year 2023).
- Its listed owner is the state highway agency.
- It is one of 97 of the 185 inventoried bridges in Cascade County rated fair (52.4%); 11 (5.9%) are rated poor.
- Its traffic status in the 2025 inventory is open, no restriction (NBI item 41).
- Its condition class and component ratings are unchanged from the 2024 inventory.
- Its most recent inspection on record is dated July 2024, on a 24-month routine inspection cycle.
- A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.
View this bridge on a map → (47.49194, -111.32837)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 5 | 5 | Fair condition |
| Superstructure | 8 | 8 | Very good condition |
| Substructure | 7 | 7 | Good condition |
Bridge details
| Structure | Prestressed concrete stringer or multi-beam girder |
| Length | about 505 ft |
| Location | Great Falls-6th St SW |
| NBI structure number | U05201000+01031 |
| Condition class | Fair |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | July 2024 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | 8: foundations stable, scour above the top of the footing |
Source: FHWA National Bridge Inventory, 2025 data as reported by the Montana department of transportation.
Busiest bridges in Cascade County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| Central Ave over Missouri River-ped Trail | 1980 | 24,549 | Good |
| 15TH St N-us 87 over Missouri R-rivers Trail | 1962 | 14,369 | Fair |
| 9TH St N over Missouri River | 1996 | 14,024 | Fair |
| US 87-mt 3-mt 200 over Missouri River-u5205-rr | 1983 | 13,666 | Fair |
| US 89-mt 3-mt 200 over Missouri River-u5205-rr | 1951 | 13,666 | Fair |
| I 315S over Int I 15 | 1967 | 12,651 | Fair |
All bridges nearby: Cascade County, MT bridge conditions · every bridge in Cascade County · Montana bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.