SR 99 over Duwamish River
Fair Condition70 years old48,204 vehicles/day
Location
| State | Washington |
| County | King |
| Location | 0.1 N Jct SR 509 |
| Carries | SR 99 |
| Crosses | Duwamish River |
| Coordinates | 47.53758, -122.33469 |
Condition Ratings
| Overall Condition | Fair |
| Deck | 5 (Fair) |
| Superstructure | 5 (Fair) |
| Substructure | 6 (Satisfactory) |
| Channel/Waterway | 8 (Very Good) |
| Scour Critical | 8 — Stable, low risk |
Physical Characteristics
| Material | Steel |
| Design | Movable - Bascule |
| Total Length | 3009.8 ft (917.4 m) |
| Max Span | 276.9 ft (84.4 m) |
| Deck Width | 58.1 ft (17.7 m) |
| Deck Area | 16238.0 sq m |
| Main Spans | 1 |
| Year Built | 1956 (reconstructed 1998) |
Traffic
| Avg Daily Traffic | 48,204 (2023) |
| Truck Traffic | 6% |
| Lanes On Bridge | 3 |
| Lanes Under Bridge | 14 |
Inspection & Ownership
| Last Inspection | 924 |
| Inspection Frequency | Every 24 months |
| Owner | State Highway Agency |
| Historical Significance | Bridge is on the National Register of Historic Places |
| Structure Number | 0004872A0000000 |