US Bridges

I-405-SR 520 Nbcd over I-405 N-E & N-W Ramps

Good

King County, Washington · 3.1 N JCT I-90 · Structure no. 0017726G0000000

Built
2011
14 years old
Condition
Good
inspected November 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete Continuous
Length
440 ft
4 main spans
Daily traffic
9,875
2023 count
Owner
State
State Highway Agency

About this bridge

I-405-SR 520 Nbcd over I-405 N-E & N-W Ramps is a prestressed concrete continuous stringer/multi-beam or girder carrying I-405-SR 520 Nbcd over I-405 N-E & N-W Ramps in King County, Washington. It was built in 2011, so it is 14 years old, younger 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 8 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 9,875 vehicles a day, roughly 3% of them trucks, projected to reach 14,954 by 2039. The structure is 440 ft (134.1 m) long and 27 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

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CarriesI-405-SR 520 Nbcd
CrossesI-405 N-E & N-W Ramps
Location3.1 N JCT I-90
RouteInterstate 405
CountyKing County
StateWashington
Coordinates47.62333, -122.18821
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
Deck8 Very GoodNo problems noted.
Superstructure8 Very GoodNo problems noted.
Substructure8 Very GoodNo problems noted.
Last inspectionNovember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation8: Equal to present desirable criteria
Deck geometry7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating58.5 US tons
Inventory rating45 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadHL 93
Structure length440 ft (134.1 m)
Longest span138 ft (42.1 m)
Deck width27 ft (8.2 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic9,875 (2023)
Projected traffic14,954 by 2039
Trucks3%
Lanes on structure1
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed3.1 mi (5 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$5.4 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was I-405-SR 520 Nbcd over I-405 N-E & N-W Ramps built?

It was built in 2011, making it 14 years old in 2025.

What condition is I-405-SR 520 Nbcd over I-405 N-E & N-W Ramps 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 2023.

How much traffic does I-405-SR 520 Nbcd over I-405 N-E & N-W Ramps carry?

About 9,875 vehicles per day (2023 count), of which roughly 3% are trucks.

How long is I-405-SR 520 Nbcd over I-405 N-E & N-W Ramps?

The structure is 440 ft (134.1 m) long with a longest span of 138 ft (42.1 m) and a deck 27 ft wide.

Who owns I-405-SR 520 Nbcd over I-405 N-E & N-W Ramps?

It is owned by the State Highway Agency.