US Bridges

I-405 over 115th Ave NE & Trail

Good

King County, Washington · 0.2 N JCT SR 520 · Structure no. 0007742A0000000

Built
1965
60 years old, rebuilt 1993
Condition
Good
inspected August 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete Continuous
Length
296 ft
4 main spans
Daily traffic
67,108
2023 count
Owner
State
State Highway Agency

About this bridge

I-405 over 115th Ave NE & Trail is a prestressed concrete continuous stringer/multi-beam or girder carrying I-405 over 115th Ave NE & Trail in King County, Washington. It was built in 1965 and reconstructed in 1993, so it is 60 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 67,108 vehicles a day, roughly 6% of them trucks, projected to reach 105,460 by 2039. The structure is 296 ft (90.2 m) long and 83 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

CarriesI-405
Crosses115th Ave NE & Trail
Location0.2 N JCT SR 520
RouteInterstate 405
Coordinates47.63442, -122.187
Functional classUrban Principal Arterial - Interstate

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Last inspectionAugust 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation3: Basically intolerable, requiring high priority of corrective action
Deck geometry6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating20.7 US tons
Inventory rating16.1 US tons

Structure

MaterialPrestressed Concrete Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20 + Mod
Structure length296 ft (90.2 m)
Longest span91 ft (27.7 m)
Deck width83 ft (25.3 m)
Roadway width80 ft (24.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic67,108 (2023)
Projected traffic105,460 by 2039
Trucks6%
Lanes on structure5
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkInterstate STRAHNET route

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$10.8 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was I-405 over 115th Ave NE & Trail built?

It was built in 1965, making it 60 years old in 2025. It was reconstructed in 1993.

What condition is I-405 over 115th Ave NE & Trail 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 August 2024.

How much traffic does I-405 over 115th Ave NE & Trail carry?

About 67,108 vehicles per day (2023 count), of which roughly 6% are trucks.

How long is I-405 over 115th Ave NE & Trail?

The structure is 296 ft (90.2 m) long with a longest span of 91 ft (27.7 m) and a deck 83 ft wide.

Who owns I-405 over 115th Ave NE & Trail?

It is owned by the State Highway Agency.