US Bridges

I-5 over I-405 NB / SR 518 EB

Good

King County, Washington · 5.2 N JCT SR 516 · Structure no. 0007401E0000000

Built
1966
59 years old
Condition
Good
inspected July 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
217 ft
4 main spans
Daily traffic
106,282
2023 count
Owner
State
State Highway Agency

About this bridge

I-5 over I-405 NB / SR 518 EB is a prestressed concrete stringer/multi-beam or girder carrying I-5 over I-405 NB / SR 518 EB in King County, Washington. It was built in 1966, so it is 59 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 106,282 vehicles a day, roughly 7% of them trucks, projected to reach 173,197 by 2039. The structure is 217 ft (66.1 m) long and 72 ft wide.

Location

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CarriesI-5
CrossesI-405 NB / SR 518 EB
Location5.2 N JCT SR 516
RouteInterstate 5
CountyKing County
StateWashington
Coordinates47.46147, -122.26358
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 inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating37.8 US tons
Inventory rating29.3 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20
Structure length217 ft (66.1 m)
Longest span64 ft (19.5 m)
Deck width72 ft (21.8 m)
Roadway width68 ft (20.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic106,282 (2023)
Projected traffic173,197 by 2039
Trucks7%
Lanes on structure3
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed—
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$7.4 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was I-5 over I-405 NB / SR 518 EB built?

It was built in 1966, making it 59 years old in 2025.

What condition is I-5 over I-405 NB / SR 518 EB 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 July 2023.

How much traffic does I-5 over I-405 NB / SR 518 EB carry?

About 106,282 vehicles per day (2023 count), of which roughly 7% are trucks.

How long is I-5 over I-405 NB / SR 518 EB?

The structure is 217 ft (66.1 m) long with a longest span of 64 ft (19.5 m) and a deck 72 ft wide.

Who owns I-5 over I-405 NB / SR 518 EB?

It is owned by the State Highway Agency.