Irr Bia Rte 13 over South Fork Milk River
Glacier County, Montana · rated Poor in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- Irr Bia Rte 13 over South Fork Milk River in Glacier County, Montana, is rated in poor condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the substructure, rated 4 (poor condition) on the 0-9 scale.
- It was built in 1979, making it 46 years old at the 2025 inventory.
- It carries about 60 vehicles a day (traffic count year 2023).
- It is one of 3 of the 71 inventoried bridges in Glacier County rated poor (4.2%); 3 (4.2%) are rated poor.
- Its traffic status in the 2025 inventory is posted for load (NBI item 41).
- Its condition class and component ratings are unchanged from the 2024 inventory.
- Its most recent inspection on record is dated September 2023, on a 24-month routine inspection cycle.
- A poor rating means at least one major component - deck, superstructure, or substructure - is rated 4 or lower on FHWA's 0-9 scale. It does not by itself mean the bridge is unsafe; bridges judged unsafe are closed or load-restricted by their owners.
View this bridge on a map → (48.85965, -113.01708)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 5 | 5 | Fair condition |
| Superstructure | 5 | 5 | Fair condition |
| Substructure | 4 | 4 | Poor condition |
Bridge details
| Structure | Timber stringer or multi-beam girder |
| Length | about 102 ft |
| Location | 31KM North Blackfeet Schl |
| NBI structure number | 00000000000C130 |
| Condition class | Poor |
| Traffic status (item 41) | Posted for load |
| Last inspection (item 90) | September 2023 |
| 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 Glacier County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| Irr - US 2 over RR | 1997 | 3,716 | Good |
| Irr - US 2 over Cut Bank Creek | 2007 | 3,523 | Fair |
| Irr - US 2 over RR | 1997 | 2,515 | Good |
| Irr - US 89 over St Marys River | 1956 | 2,355 | Fair |
| Going-to-the-sun R over St. Mary River | 1934 | 2,300 | Fair |
| Going-to-the-sun R over Divide Creek | 1934 | 2,300 | Fair |
All bridges nearby: Glacier County, MT bridge conditions · every bridge in Glacier County · Montana bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.