US Bridges

I-405 over Cedar River

Fair

King County, Washington · 0.9 N JCT SR 515 · Structure no. 0014052A0000000

Built
1993
32 years old
Condition
Fair
inspected November 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
528 ft
4 main spans
Daily traffic
85,117
2023 count
Owner
State
State Highway Agency

About this bridge

I-405 over Cedar River is a steel continuous stringer/multi-beam or girder carrying I-405 over Cedar River in King County, Washington. It was built in 1993, so it is 32 years old, younger 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 85,117 vehicles a day, roughly 6% of them trucks, projected to reach 123,871 by 2039. The structure is 528 ft (160.9 m) long and 82 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesI-405
CrossesCedar River
Location0.9 N JCT SR 515
RouteInterstate 405
CountyKing County
StateWashington
Coordinates47.48017, -122.20031
Functional classUrban Principal Arterial - Interstate

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionNovember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than present minimum criteria
Deck geometry7: Better than present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating62.9 US tons
Inventory rating39 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20 + Mod
Structure length528 ft (160.9 m)
Longest span196 ft (59.7 m)
Deck width82 ft (25 m)
Roadway width70 ft (21.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic85,117 (2023)
Projected traffic123,871 by 2039
Trucks6%
Lanes on structure4
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway and waterway
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 statusHistorical significance not determinable at this time
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$18.1 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was I-405 over Cedar River built?

It was built in 1993, making it 32 years old in 2025.

What condition is I-405 over Cedar River 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 November 2023.

How much traffic does I-405 over Cedar River carry?

About 85,117 vehicles per day (2023 count), of which roughly 6% are trucks.

How long is I-405 over Cedar River?

The structure is 528 ft (160.9 m) long with a longest span of 196 ft (59.7 m) and a deck 82 ft wide.

Who owns I-405 over Cedar River?

It is owned by the State Highway Agency.