I-90 over Mercer Sl
PoorKing County, Washington · 6.6 E JCT I-5 · Structure no. 0008610A0000000
- Built
- 1970
- 55 years old, rebuilt 1993
- Condition
- Poor
- inspected February 2023
- Type
- Box Beam or Girders - Multiple
- Concrete Continuous
- Length
- 2,669 ft
- 4 main spans
- Daily traffic
- 74,410
- 2023 count
- Owner
- State
- State Highway Agency
About this bridge
I-90 over Mercer Sl is a concrete continuous box beam or girders - multiple carrying I-90 over Mercer Sl in King County, Washington. It was built in 1970 and reconstructed in 1993, so it is 55 years old, older than the Washington average of 49.8 years.
The most recent inspection reported to the Federal Highway Administration rates it in poor condition with a lowest component rating of 3 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.
It carries about 74,410 vehicles a day, roughly 3% of them trucks, projected to reach 117,268 by 2039. The structure is 2,669 ft (813.5 m) long and 75 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 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.
| Component | Rating | Meaning |
|---|---|---|
| Deck | 6 Satisfactory | Structural elements show some minor deterioration. |
| Superstructure | 3 Serious | Loss of section, deterioration, spalling or scour have seriously affected primary structural components. |
| Substructure | 7 Good | Some minor problems. |
| Channel and channel protection | 8 Very Good | No problems noted. |
Structure
Traffic and service
Ownership and planned work
Frequently asked questions
When was I-90 over Mercer Sl built?
It was built in 1970, making it 55 years old in 2025. It was reconstructed in 1993.
What condition is I-90 over Mercer Sl in?
The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in February 2023.
How much traffic does I-90 over Mercer Sl carry?
About 74,410 vehicles per day (2023 count), of which roughly 3% are trucks.
How long is I-90 over Mercer Sl?
The structure is 2,669 ft (813.5 m) long with a longest span of 100 ft (30.5 m) and a deck 75 ft wide.
Who owns I-90 over Mercer Sl?
It is owned by the State Highway Agency.