US Bridges

12 Ave S over Dearborn ST

Fair

King County, Washington · 12th Ave S & Dearborn ST · Structure no. 085042000000000

Built
1917
108 years old
Condition
Fair
inspected May 2023
Type
Truss - Deck
Steel Continuous
Length
495 ft
3 main spans
Daily traffic
22,000
2020 count
Owner
City
City or Municipal Highway Agency

About this bridge

12 Ave S over Dearborn ST is a steel continuous truss - deck carrying 12 Ave S over Dearborn ST in King County, Washington. It was built in 1917, so it is 108 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 22,000 vehicles a day, roughly 5% of them trucks, projected to reach 24,000 by 2040. The structure is 495 ft (150.9 m) long and 65 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
Carries12 Ave S
CrossesDearborn ST
Location12th Ave S & Dearborn ST
RouteCity Street 1140
CountyKing County
StateWashington
Coordinates47.59583, -122.31722
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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionMay 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Approach roadway alignment6: Equal to present minimum criteria
Operating rating48 US tons
Inventory rating28 US tons

Structure

Structure typeTruss - Deck
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3 (+3 approach)
Design loadUnknown
Structure length495 ft (150.9 m)
Longest span171 ft (52.1 m)
Deck width65 ft (19.8 m)
Roadway width42 ft (12.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic22,000 (2020)
Projected traffic24,000 by 2040
Trucks5%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesHighway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCity or Municipal Highway Agency
Maintained byCity or Municipal Highway Agency
Historic statusListed on the National Register of Historic Places
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$29.6 million (2019 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was 12 Ave S over Dearborn ST built?

It was built in 1917, making it 108 years old in 2025.

What condition is 12 Ave S over Dearborn 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 2023.

How much traffic does 12 Ave S over Dearborn ST carry?

About 22,000 vehicles per day (2020 count), of which roughly 5% are trucks.

How long is 12 Ave S over Dearborn ST?

The structure is 495 ft (150.9 m) long with a longest span of 171 ft (52.1 m) and a deck 65 ft wide.

Who owns 12 Ave S over Dearborn ST?

It is owned by the City or Municipal Highway Agency.