State Route 1 over Blue Slide Gulch
Mendocino County, California · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- State Route 1 over Blue Slide Gulch in Mendocino County, California, 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 1946 and reconstructed in 1989, making it 79 years old at the 2025 inventory.
- It carries about 830 vehicles a day (traffic count year 2009).
- Its listed owner is the state highway agency.
- It is one of 205 of the 356 inventoried bridges in Mendocino County rated fair (57.6%); 27 (7.6%) are rated poor.
- Its traffic status in the 2025 inventory is open, no restriction (NBI item 41).
- It was rated good in the 2024 inventory and is now fair (substructure 7 to 5).
- Its most recent inspection on record is dated September 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 → (39.61158, -123.78222)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 7 | 7 | Good condition |
| Superstructure | 7 | 7 | Good condition |
| Substructure | 7 | 5 | Fair condition |
Bridge details
| Structure | Continuous concrete slab |
| Length | about 143 ft |
| Location | 01-men-001-75.00 |
| NBI structure number | 10 0166 |
| Condition class | Fair |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | September 2023 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | N: not over a waterway |
Source: FHWA National Bridge Inventory, 2025 data as reported by the California department of transportation.
Busiest bridges in Mendocino County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| State Route 1 over Pudding Creek | 1959 | 23,950 | Good |
| State Route 001 over Noyo River & Harbor Dr | 2005 | 23,950 | Good |
| U.S. Highway 101 over Austin Creek | 1964 | 20,900 | Good |
| North State St over Forsythe Creek | 1949 | 20,200 | Fair |
| U.S. Highway 101 over Ncrra/nwp RR | 1957 | 19,000 | Fair |
| U.S. Highway 101 over Baker Creek | 1971 | 19,000 | Good |
All bridges nearby: Mendocino County, CA bridge conditions · every bridge in Mendocino County · California bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.