US Bridges

I-5 over Duwamish R RR City ST

Fair

King County, Washington · 0.4 N JCT SR 599 · Structure no. 0007171B0000000

Built
1964
61 years old, rebuilt 1996
Condition
Fair
inspected May 2024
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
812 ft
2 main spans
Daily traffic
95,981
2023 count
Owner
State
State Highway Agency

About this bridge

I-5 over Duwamish R RR City ST is a steel continuous stringer/multi-beam or girder carrying I-5 over Duwamish R RR City ST in King County, Washington. It was built in 1964 and reconstructed in 1996, so it is 61 years old, older 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 5 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 95,981 vehicles a day, roughly 7% of them trucks, projected to reach 143,337 by 2039. The structure is 812 ft (247.5 m) long and 70 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesI-5
CrossesDuwamish R RR City ST
Location0.4 N JCT SR 599
RouteInterstate 5
CountyKing County
StateWashington
Coordinates47.48694, -122.26657
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
Deck7 GoodSome minor problems.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionMay 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating74 US tons
Inventory rating44 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans2 (+2 approach)
Design loadHS 20
Structure length812 ft (247.5 m)
Longest span275 ft (83.8 m)
Deck width70 ft (21.3 m)
Roadway width68 ft (20.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic95,981 (2023)
Projected traffic143,337 by 2039
Trucks7%
Lanes on structure5
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway, waterway and railroad
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$27 million (2022 estimate)
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was I-5 over Duwamish R RR City ST built?

It was built in 1964, making it 61 years old in 2025. It was reconstructed in 1996.

What condition is I-5 over Duwamish R RR City ST 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 May 2024.

How much traffic does I-5 over Duwamish R RR City ST carry?

About 95,981 vehicles per day (2023 count), of which roughly 7% are trucks.

How long is I-5 over Duwamish R RR City ST?

The structure is 812 ft (247.5 m) long with a longest span of 275 ft (83.8 m) and a deck 70 ft wide.

Who owns I-5 over Duwamish R RR City ST?

It is owned by the State Highway Agency.