Stc 1843; Firth Rd over Snake River;firth Bridge
Bingham County, Idaho · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- Stc 1843; Firth Rd over Snake River;firth Bridge in Bingham County, Idaho, 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 2003, making it 22 years old at the 2025 inventory.
- It carries about 510 vehicles a day (traffic count year 2023).
- Its listed owner is the county highway agency.
- It is one of 210 of the 263 inventoried bridges in Bingham County rated fair (79.8%); 9 (3.4%) 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 October 2021, on a 48-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 → (43.31303, -112.18406)
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 | Continuous steel stringer or multi-beam girder |
| Length | about 418 ft |
| Location | 0.5 N. 0.3 E. Firth |
| NBI structure number | 000000000019246 |
| Condition class | Fair |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | October 2021 |
| Inspection interval (item 91) | 48 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 Idaho department of transportation.
Busiest bridges in Bingham County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I 15 Nbl & Sbl over Ross Fork Creek | 2023 | 29,000 | Good |
| I 15 over Riverside Canal | 2019 | 26,000 | Good |
| US 26 Ebl & Wbl over Snake River;w.blackfoot | 1965 | 18,000 | Fair |
| I 15 Nbl over Aberdeen Springfield Cnl | 1962 | 14,250 | Fair |
| I 15 Sbl over Aberdeen Springfield Cnl | 1962 | 14,250 | Fair |
| I 15 Nbl over Peoples Canal | 1962 | 14,250 | Fair |
All bridges nearby: Bingham County, ID bridge conditions · every bridge in Bingham County · Idaho bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.