Irr Bia Rte 91 over Rotten Grass Creek
Big Horn County, Montana · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- Irr Bia Rte 91 over Rotten Grass Creek in Big Horn County, Montana, is rated in fair condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the deck, rated 6 (satisfactory condition) on the 0-9 scale.
- It was built in 1970, making it 55 years old at the 2025 inventory.
- It carries about 350 vehicles a day (traffic count year 2024).
- It is one of 90 of the 133 inventoried bridges in Big Horn County rated fair (67.7%); 5 (3.8%) 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 June 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 → (45.46122, -107.72853)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 6 | 6 | Satisfactory condition |
| Superstructure | 7 | 7 | Good condition |
| Substructure | 6 | 6 | Satisfactory condition |
Bridge details
| Structure | Prestressed concrete stringer or multi-beam girder |
| Length | about 67 ft |
| Location | 0.8 Km SW of St. Xavier |
| NBI structure number | 00000000000C207 |
| Condition class | Fair |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | June 2024 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | 5: foundations stable, scour within the limits of the footing or piles |
Source: FHWA National Bridge Inventory, 2025 data as reported by the Montana department of transportation.
Busiest bridges in Big Horn County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I 90 over Irrigation Canal | 1971 | 8,516 | Fair |
| Irr-s 47 over Int W Hardin I 90 | 1970 | 5,396 | Fair |
| Irr - I 90 over Int Dunmore | 1959 | 4,473 | Fair |
| Irr - I 90 over Int Dunmore | 1959 | 4,473 | Fair |
| Irr - I 90 over Bighorn River | 1971 | 4,258 | Good |
| Irr - I 90 over Bighorn River | 1971 | 4,258 | Fair |
All bridges nearby: Big Horn County, MT bridge conditions · every bridge in Big Horn County · Montana bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.