I-405 over Terrain
GoodKing County, Washington · 8.7 N JCT SR 520 · Structure no. 0008382E0000000
- Built
- 1968
- 57 years old
- Condition
- Good
- inspected November 2024
- Type
- Box Beam or Girders - Multiple
- Concrete Continuous
- Length
- 433 ft
- 3 main spans
- Daily traffic
- 10,582
- 2023 count
- Owner
- State
- State Highway Agency
About this bridge
I-405 over Terrain is a concrete continuous box beam or girders - multiple carrying I-405 over Terrain in King 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 good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.
It carries about 10,582 vehicles a day, roughly 5% of them trucks, projected to reach 16,092 by 2039. The structure is 433 ft (132 m) long and 29 ft wide. If it were closed, the detour would be 1.2 mi (2 km).
Location
Open in Google MapsCondition and inspection
All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.
| Component | Rating | Meaning |
|---|---|---|
| Deck | 7 Good | Some minor problems. |
| Superstructure | 7 Good | Some minor problems. |
| Substructure | 7 Good | Some minor problems. |
Structure
Traffic and service
Ownership and planned work
Frequently asked questions
When was I-405 over Terrain built?
It was built in 1968, making it 57 years old in 2025.
What condition is I-405 over Terrain in?
The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in November 2024.
How much traffic does I-405 over Terrain carry?
About 10,582 vehicles per day (2023 count), of which roughly 5% are trucks.
How long is I-405 over Terrain?
The structure is 433 ft (132 m) long with a longest span of 115 ft (35.1 m) and a deck 29 ft wide.
Who owns I-405 over Terrain?
It is owned by the State Highway Agency.