US Bridges

US 101 over Duckabush Slough

Fair

Jefferson County, Washington · 25.0 S JCT SR 104 · Structure no. 0001764A0000000

Built
1934
91 years old
Condition
Fair
inspected October 2024
Type
Tee Beam
Concrete
Length
121 ft
4 main spans
Daily traffic
2,967
2023 count
Owner
State
State Highway Agency

About this bridge

US 101 over Duckabush Slough is a concrete tee beam carrying US 101 over Duckabush Slough in Jefferson County, Washington. It was built in 1934, so it is 91 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 2,967 vehicles a day, roughly 11% of them trucks, projected to reach 3,769 by 2039. The structure is 121 ft (36.9 m) long and 31 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

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CarriesUS 101
CrossesDuckabush Slough
Location25.0 S JCT SR 104
RouteU.S. Route 101
CountyJefferson County
StateWashington
Coordinates47.65117, -122.933
Functional classRural Principal Arterial - Other

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.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionOctober 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating47 US tons
Inventory rating28 US tons

Structure

Structure typeTee Beam
MaterialConcrete
DeckConcrete, cast-in-place
Main spans4
Design loadH 15
Structure length121 ft (36.9 m)
Longest span30 ft (9.1 m)
Deck width31 ft (9.3 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,967 (2023)
Projected traffic3,769 by 2039
Trucks11%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed98.8 mi (159 km)
TollOn a free road
National Highway SystemYes

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$1.7 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was US 101 over Duckabush Slough built?

It was built in 1934, making it 91 years old in 2025.

What condition is US 101 over Duckabush Slough 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 October 2024.

How much traffic does US 101 over Duckabush Slough carry?

About 2,967 vehicles per day (2023 count), of which roughly 11% are trucks.

How long is US 101 over Duckabush Slough?

The structure is 121 ft (36.9 m) long with a longest span of 30 ft (9.1 m) and a deck 31 ft wide.

Who owns US 101 over Duckabush Slough?

It is owned by the State Highway Agency.