US Bridges

15th Ave W over Shilshole Ave NW

Fair

King County, Washington · 4300 15th Ave W · Structure no. 085177000000000

Built
1940
85 years old
Condition
Fair
inspected April 2024
Type
Tee Beam
Concrete Continuous
Length
589 ft
9 main spans
Daily traffic
52,000
2022 count
Owner
City
City or Municipal Highway Agency

About this bridge

15th Ave W over Shilshole Ave NW is a concrete continuous tee beam carrying 15th Ave W over Shilshole Ave NW in King County, Washington. It was built in 1940, so it is 85 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 52,000 vehicles a day, roughly 10% of them trucks, projected to reach 75,000 by 2040. The structure is 589 ft (179.5 m) long and 53 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
Carries15th Ave W
CrossesShilshole Ave NW
Location4300 15th Ave W
RouteCity Street 1140
CountyKing County
StateWashington
Coordinates47.65983, -122.37612
Functional classUrban Other Principal 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.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionApril 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Approach roadway alignment8: Equal to present desirable criteria
Operating rating46 US tons
Inventory rating27 US tons

Structure

Structure typeTee Beam
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans9 (+1 approach)
Design loadH 20
Structure length589 ft (179.5 m)
Longest span72 ft (21.9 m)
Deck width53 ft (16.1 m)
Roadway width42 ft (12.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic52,000 (2022)
Projected traffic75,000 by 2040
Trucks10%
Lanes on structure4
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesHighway
Detour if closed3.1 mi (5 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerCity or Municipal Highway Agency
Maintained byCity or Municipal 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$12.3 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was 15th Ave W over Shilshole Ave NW built?

It was built in 1940, making it 85 years old in 2025.

What condition is 15th Ave W over Shilshole Ave NW 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 15th Ave W over Shilshole Ave NW carry?

About 52,000 vehicles per day (2022 count), of which roughly 10% are trucks.

How long is 15th Ave W over Shilshole Ave NW?

The structure is 589 ft (179.5 m) long with a longest span of 72 ft (21.9 m) and a deck 53 ft wide.

Who owns 15th Ave W over Shilshole Ave NW?

It is owned by the City or Municipal Highway Agency.