Nfsr 347 over Grayback Gulch
Boise County, Idaho · rated Good in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- Nfsr 347 over Grayback Gulch in Boise County, Idaho, is rated in good condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the substructure, rated 7 (good condition) on the 0-9 scale.
- It was built in 2018, making it 7 years old at the 2025 inventory.
- It carries about 50 vehicles a day.
- It is one of 45 of the 89 inventoried bridges in Boise County rated good (50.6%); 5 (5.6%) are rated poor.
- A good rating means every major component - deck, superstructure, substructure, or culvert - is rated 7 or higher on FHWA's 0-9 scale: no more than minor problems.
View this bridge on a map → (48.80728, -115.86854)
Component ratings
| Component | Rating (2025) | FHWA scale meaning |
|---|---|---|
| Deck | 8 | Very good condition |
| Superstructure | 8 | Very good condition |
| Substructure | 7 | Good condition |
Bridge details
| Structure | Steel stringer or multi-beam girder |
| Length | about 89 ft |
| Location | 2.5 Mi SW of Idaho City |
| NBI structure number | 040203000032691 |
| Condition class | Good |
Source: FHWA National Bridge Inventory, 2025 data as reported by the Idaho department of transportation.
Busiest bridges in Boise County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| SH 55 over McLEOD WAY | 2024 | 10,500 | Good |
| SH 55 over Payette River | 2021 | 8,800 | Good |
| SH 55 over Power Canal | 1994 | 8,800 | Good |
| SH 55 over Uprr;horseshoe Bend Op | 1971 | 7,800 | Fair |
| SH 55 over Payette River | 1971 | 7,800 | Fair |
| SH 55 over S.fk.payette River | 1955 | 7,300 | Fair |
All bridges nearby: Boise County, ID bridge conditions · every bridge in Boise County · Idaho bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.