US Bridges

SR 530 over N Fk Stillaguamish R

Fair

Snohomish County, Washington · 7.6 E JCT SR 9 · Structure no. 0007733A0000000

Built
1966
59 years old
Condition
Fair
inspected May 2023
Type
Arch - Thru
Steel
Length
377 ft
1 main span
Daily traffic
5,455
2023 count
Owner
State
State Highway Agency

About this bridge

SR 530 over N Fk Stillaguamish R is a steel arch - thru carrying SR 530 over N Fk Stillaguamish R in Snohomish County, Washington. It was built in 1966, so it is 59 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 5,455 vehicles a day, roughly 11% of them trucks, projected to reach 7,748 by 2039. The structure is 377 ft (114.9 m) long and 32 ft wide. If it were closed, the detour would be 18 mi (29 km).

Location

Open in Google Maps
CarriesSR 530
CrossesN Fk Stillaguamish R
Location7.6 E JCT SR 9
RouteState Highway 530
CountySnohomish County
StateWashington
Coordinates48.26717, -122.01353
Functional classRural 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.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure7 GoodSome minor problems.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionMay 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; action required to protect exposed foundations
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating74 US tons
Inventory rating44 US tons

Structure

Structure typeArch - Thru
MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+2 approach)
Design loadHS 20
Structure length377 ft (114.9 m)
Longest span279 ft (85 m)
Deck width32 ft (9.8 m)
Roadway width26 ft (7.9 m)
Vertical clearance over deck18 ft (5.5 m)

Traffic and service

Average daily traffic5,455 (2023)
Projected traffic7,748 by 2039
Trucks11%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed18 mi (29 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusPossibly eligible for the National Register; requires further investigation
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$6.1 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SR 530 over N Fk Stillaguamish R built?

It was built in 1966, making it 59 years old in 2025.

What condition is SR 530 over N Fk Stillaguamish R 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 SR 530 over N Fk Stillaguamish R carry?

About 5,455 vehicles per day (2023 count), of which roughly 11% are trucks.

How long is SR 530 over N Fk Stillaguamish R?

The structure is 377 ft (114.9 m) long with a longest span of 279 ft (85 m) and a deck 32 ft wide.

Who owns SR 530 over N Fk Stillaguamish R?

It is owned by the State Highway Agency.