SR 20 over Thunder Arm Bay
Fair Condition65 years old1,322 vehicles/day
Location
| State | Washington |
| County | Whatcom |
| Location | 13.8 E Skagit Co |
| Carries | SR 20 |
| Crosses | Thunder Arm Bay |
| Coordinates | 48.69094, -121.09592 |
Condition Ratings
| Overall Condition | Fair |
| Deck | 7 (Good) |
| Superstructure | 6 (Satisfactory) |
| Substructure | 7 (Good) |
| Channel/Waterway | 6 (Satisfactory) |
| Scour Critical | 8 — Stable, low risk |
Physical Characteristics
| Material | Concrete |
| Design | Stringer/Multi-beam |
| Total Length | 210.0 ft (64 m) |
| Max Span | 29.9 ft (9.1 m) |
| Deck Width | 30.5 ft (9.3 m) |
| Deck Area | 595.2 sq m |
| Main Spans | 7 |
| Year Built | 1961 |
Traffic
| Avg Daily Traffic | 1,322 (2023) |
| Truck Traffic | 8% |
| Lanes On Bridge | 2 |
Inspection & Ownership
| Last Inspection | 624 |
| Inspection Frequency | Every 24 months |
| Owner | State Highway Agency |
| Historical Significance | Bridge is not eligible for the National Register |
| Structure Number | 0006585B0000000 |