I-5 over Union Slough
FairSnohomish County, Washington · 3.3 N JCT US 2 · Structure no. 0008226B0000000
- Built
- 1968
- 57 years old
- Condition
- Fair
- inspected June 2023
- Type
- Stringer/Multi-beam or Girder
- Prestressed Concrete
- Length
- 396 ft
- 4 main spans
- Daily traffic
- 64,989
- 2023 count
- Owner
- State
- State Highway Agency
About this bridge
I-5 over Union Slough is a prestressed concrete stringer/multi-beam or girder carrying I-5 over Union Slough in Snohomish County, Washington. It was built in 1968, so it is 57 years old, older than the Washington average of 49.8 years.
The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 6 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.
It carries about 64,989 vehicles a day, roughly 6% of them trucks, projected to reach 95,649 by 2039. The structure is 396 ft (120.7 m) long and 52 ft wide. If it were closed, the detour would be 1.2 mi (2 km).
Location
Open in Google MapsCondition and inspection
The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.
| Component | Rating | Meaning |
|---|---|---|
| Deck | 6 Satisfactory | Structural elements show some minor deterioration. |
| Superstructure | 7 Good | Some minor problems. |
| Substructure | 6 Satisfactory | Structural elements show some minor deterioration. |
| Channel and channel protection | 6 Satisfactory | Structural elements show some minor deterioration. |
Structure
Traffic and service
Ownership and planned work
Frequently asked questions
When was I-5 over Union Slough built?
It was built in 1968, making it 57 years old in 2025.
What condition is I-5 over Union Slough in?
The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in June 2023.
How much traffic does I-5 over Union Slough carry?
About 64,989 vehicles per day (2023 count), of which roughly 6% are trucks.
How long is I-5 over Union Slough?
The structure is 396 ft (120.7 m) long with a longest span of 85 ft (25.9 m) and a deck 52 ft wide.
Who owns I-5 over Union Slough?
It is owned by the State Highway Agency.