Durnam Road over Gallatin River
Gallatin County, Montana · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- Durnam Road over Gallatin River in Gallatin County, Montana, is rated in fair condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the superstructure, rated 5 (fair condition) on the 0-9 scale.
- It was built in 1970 and reconstructed in 1995, making it 55 years old at the 2025 inventory.
- It carries about 99 vehicles a day.
- It is one of 157 of the 212 inventoried bridges in Gallatin County rated fair (74.1%); 12 (5.7%) are rated poor.
- Its traffic status in the 2025 inventory is posted for load (NBI item 41).
- Its class is unchanged from 2024 (fair), but component ratings moved: deck 8 to 7, superstructure 6 to 5.
- Its most recent inspection on record is dated July 2024, on a 24-month routine inspection cycle.
- It has fracture-critical members (NBI item 92A): steel tension members without a redundant load path, which get their own scheduled inspections.
- 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 → (45.32366, -111.17511)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 8 | 7 | Good condition |
| Superstructure | 6 | 5 | Fair condition |
| Substructure | 7 | 7 | Good condition |
Bridge details
| Structure | Steel through truss |
| Length | about 76 ft |
| Location | Durnam Bridge |
| NBI structure number | 011106000000077 |
| Condition class | Fair |
| Traffic status (item 41) | Posted for load |
| Last inspection (item 90) | July 2024 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | 4: foundations stable, field review says exposed foundations need protection |
| Fracture critical (item 92A) | Yes |
Source: FHWA National Bridge Inventory, 2025 data as reported by the Montana department of transportation.
Busiest bridges in Gallatin County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| N Seventh Ave over Int N 7TH Ave-i 90 | 2014 | 26,020 | Fair |
| US 191-huffine Ln over Hyalite Creek | 1956 | 25,670 | Fair |
| N 19TH Ave over Int N 19TH Ave | 1994 | 23,992 | Fair |
| I 90 over Walking Path | 2011 | 21,232 | Fair |
| I 90 over Int Airway Blvd | 2014 | 15,554 | Fair |
| I 90 over Int Airway Blvd | 2014 | 15,554 | Fair |
All bridges nearby: Gallatin County, MT bridge conditions · every bridge in Gallatin County · Montana bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.