Birch Street over Birch Street Viaduct
Petersburg Borough, Alaska · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- Birch Street over Birch Street Viaduct in Petersburg Borough, Alaska, is rated in fair condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the substructure, rated 5 (fair condition) on the 0-9 scale.
- It was built in 1960 and reconstructed in 1979, making it 65 years old at the 2025 inventory.
- It carries about 200 vehicles a day (traffic count year 2018).
- Its listed owner is the county highway agency.
- It is one of 63 of the 137 inventoried bridges in Petersburg Borough rated fair (46.0%); 11 (8.0%) 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 May 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 → (56.80996, -132.95586)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 6 | 6 | Satisfactory condition |
| Superstructure | 7 | 7 | Good condition |
| Substructure | 5 | 5 | Fair condition |
Bridge details
| Structure | Timber stringer or multi-beam girder |
| Length | about 704 ft |
| Location | Mile Point 0.1 |
| NBI structure number | 1453 |
| Condition class | Fair |
| Traffic status (item 41) | Posted for load |
| Last inspection (item 90) | May 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 Alaska department of transportation.
Busiest bridges in Petersburg Borough
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| Nordic Drive over Hammer Slough | 1974 | 4,210 | Fair |
| Ifa Ferry Route over Petersburg S Mitkof Term | 2006 | 2,659 | Good |
| Irr:ptrsbg/kake Rd over Gunnuk Creek | 1981 | 770 | Fair |
| Mitkof Highway over Twin Creek | 1996 | 760 | Good |
| Irr:keku Rd (kake) over Sitkum Creek | 2011 | 270 | Fair |
| Mitkof Highway over Falls Creek | 1967 | 180 | Fair |
All bridges nearby: Petersburg Borough, AK bridge conditions · every bridge in Petersburg Borough · Alaska bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.