Capitol Avenue over Swauger Slough
Custer County, Idaho · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- Capitol Avenue over Swauger Slough in Custer County, Idaho, is rated in fair condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the substructure, rated 6 (satisfactory condition) on the 0-9 scale.
- It was built in 1940 and reconstructed in 1999, making it 85 years old at the 2025 inventory.
- It carries about 1,220 vehicles a day (traffic count year 2023).
- Its listed owner is a city or municipal highway agency.
- It is one of 72 of the 126 inventoried bridges in Custer County rated fair (57.1%); 14 (11.1%) 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 July 2023, 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 → (43.91136, -113.61878)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 7 | 7 | Good condition |
| Superstructure | 7 | 7 | Good condition |
| Substructure | 6 | 6 | Satisfactory condition |
Bridge details
| Structure | Steel stringer or multi-beam girder |
| Length | about 22 ft |
| Location | In Mackay |
| NBI structure number | 000000000031815 |
| Condition class | Fair |
| Traffic status (item 41) | Posted for load |
| Last inspection (item 90) | July 2023 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | U: unknown foundation, not evaluated for scour |
Source: FHWA National Bridge Inventory, 2025 data as reported by the Idaho department of transportation.
Busiest bridges in Custer County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| US 93 over Garden Creek | 1941 | 2,300 | Fair |
| SH 21 over Crooked Creek | 1968 | 2,200 | Fair |
| US 93 over Big Lost River | 1987 | 1,500 | Fair |
| US 93 over Challis Creek | 1991 | 1,400 | Good |
| US 93 over Salmon River;challis Br. | 1995 | 1,400 | Good |
| SH 75 over Redfish Lake Creek | 1960 | 1,100 | Fair |
All bridges nearby: Custer County, ID bridge conditions · every bridge in Custer County · Idaho bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.