Structure 4C0174 · Humboldt County, CA
Carries Etsbrg Hnydew RD over Mattole River, 5.77 Mi N/o Thorne RD.
Set by its lowest-rated component: Deck and Superstructure at 5 of 9.
How ratings work103 ft end to end. Lengths and the car on the deck are drawn to the same scale. Each part is colored by its latest inspection rating. The inventory records lengths but not heights or the layout of the shorter spans, so those are drawn as typical for a deck arch.
| State | California |
| County | Humboldt |
| Location | 5.77 Mi N/o Thorne RD |
| Carries | Etsbrg Hnydew RD |
| Crosses | Mattole River |
| Coordinates | 40.13951, -123.99144 |
| Material | Concrete |
| Design | Arch - Deck |
| Total Length | 103.0 ft (31.4 m) |
| Max Span | 95.1 ft (29 m) |
| Deck Width | 19.7 ft (6 m) |
| Deck Area | 188.4 sq m |
| Main Spans | 1 |
| Year Built | 1928 |
| Avg Daily Traffic | 200 (2009) |
| Truck Traffic | 5% |
| Lanes On Bridge | 1 |
| Last Inspection | July 2023 |
| Inspection Frequency | Every 24 months |
| Owner | County Highway Agency |
| Historical Significance | Bridge is not eligible for the National Register |
| Scour Critical | 8 — Stable, low risk |
| Structure Number | 04C0174 |
Inspectors rate each major part of a bridge (the deck you drive on, the superstructure of beams that holds it up, and the substructure of piers and abutments beneath) on a 0–9 scale. A bridge's overall condition is its lowest of those ratings, so one deteriorated component makes the whole bridge "poor."
A poor rating is not a closure. It means the bridge is flagged for priority repair or replacement; bridges judged unsafe are closed or posted with weight limits. The waterway (channel) rating is reported, but it does not count toward the overall classification.