US Bridges

12th Ave S over I-90

Fair

King County, Washington · 0.2 E JCT I-5 · Structure no. 0008155F0000000

Built
1968
57 years old
Condition
Fair
inspected April 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
366 ft
4 main spans
Daily traffic
18,400
2012 count
Owner
State
State Highway Agency

About this bridge

12th Ave S over I-90 is a steel stringer/multi-beam or girder carrying 12th Ave S over I-90 in King County, Washington. It was built in 1968, so it is 57 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 18,400 vehicles a day, roughly 1% of them trucks, projected to reach 32,656 by 2034. The structure is 366 ft (111.6 m) long and 65 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
Carries12th Ave S
CrossesI-90
Location0.2 E JCT I-5
RouteCity Street 0
CountyKing County
StateWashington
Coordinates47.59443, -122.31682
Functional classUrban Minor Arterial

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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionApril 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry2: Basically intolerable, requiring high priority of replacement
Approach roadway alignment8: Equal to present desirable criteria
Operating rating99 US tons
Inventory rating87 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans4
Design loadUnknown
Structure length366 ft (111.6 m)
Longest span126 ft (38.4 m)
Deck width65 ft (19.8 m)
Roadway width44 ft (13.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic18,400 (2012)
Projected traffic32,656 by 2034
Trucks1%
Lanes on structure4
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesHighway
Detour if closed3.1 mi (5 km)
TollOn a free road
National Highway SystemNo

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$12.2 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was 12th Ave S over I-90 built?

It was built in 1968, making it 57 years old in 2025.

What condition is 12th Ave S over I-90 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 12th Ave S over I-90 carry?

About 18,400 vehicles per day (2012 count), of which roughly 1% are trucks.

How long is 12th Ave S over I-90?

The structure is 366 ft (111.6 m) long with a longest span of 126 ft (38.4 m) and a deck 65 ft wide.

Who owns 12th Ave S over I-90?

It is owned by the State Highway Agency.