US Bridges

I-405 over SE 8th ST

Fair

King County, Washington · 1.7 N JCT I-90 · Structure no. 0008812B0000000

Built
1971
54 years old, rebuilt 1995
Condition
Fair
inspected April 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete Continuous
Length
189 ft
3 main spans
Daily traffic
89,237
2023 count
Owner
State
State Highway Agency

About this bridge

I-405 over SE 8th ST is a prestressed concrete continuous stringer/multi-beam or girder carrying I-405 over SE 8th ST in King County, Washington. It was built in 1971 and reconstructed in 1995, so it is 54 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 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 89,237 vehicles a day, roughly 6% of them trucks, projected to reach 132,829 by 2039. The structure is 189 ft (57.6 m) long and 67 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesI-405
CrossesSE 8th ST
Location1.7 N JCT I-90
RouteInterstate 405
CountyKing County
StateWashington
Coordinates47.60297, -122.18364
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.
Last inspectionApril 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation7: Better than present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating74 US tons
Inventory rating44 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20 + Mod
Structure length189 ft (57.6 m)
Longest span90 ft (27.4 m)
Deck width67 ft (20.4 m)
Roadway width64 ft (19.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic89,237 (2023)
Projected traffic132,829 by 2039
Trucks6%
Lanes on structure4
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$5.9 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was I-405 over SE 8th ST built?

It was built in 1971, making it 54 years old in 2025. It was reconstructed in 1995.

What condition is I-405 over SE 8th 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 April 2024.

How much traffic does I-405 over SE 8th ST carry?

About 89,237 vehicles per day (2023 count), of which roughly 6% are trucks.

How long is I-405 over SE 8th ST?

The structure is 189 ft (57.6 m) long with a longest span of 90 ft (27.4 m) and a deck 67 ft wide.

Who owns I-405 over SE 8th ST?

It is owned by the State Highway Agency.