US Bridges

SR 9 over Harts Slough

Fair

Skagit County, Washington · 4.9 N JCT SR 538 · Structure no. 0006000A0000000

Built
1959
66 years old
Condition
Fair
inspected August 2024
Type
Slab
Concrete Continuous
Length
206 ft
9 main spans
Daily traffic
11,660
2023 count
Owner
State
State Highway Agency

About this bridge

SR 9 over Harts Slough is a concrete continuous slab carrying SR 9 over Harts Slough in Skagit County, Washington. It was built in 1959, so it is 66 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 11,660 vehicles a day, roughly 5% of them trucks, projected to reach 16,125 by 2039. The structure is 206 ft (62.8 m) long and 35 ft wide. If it were closed, the detour would be 21.1 mi (34 km).

Location

Open in Google Maps
CarriesSR 9
CrossesHarts Slough
Location4.9 N JCT SR 538
RouteState Highway 9
CountySkagit County
StateWashington
Coordinates48.48819, -122.24522
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.
Channel and channel protection7 GoodSome minor problems.
Last inspectionAugust 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating40.7 US tons
Inventory rating31.4 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans9
Design loadHS 20
Structure length206 ft (62.8 m)
Longest span24 ft (7.3 m)
Deck width35 ft (10.7 m)
Roadway width32 ft (9.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic11,660 (2023)
Projected traffic16,125 by 2039
Trucks5%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed21.1 mi (34 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$4.3 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SR 9 over Harts Slough built?

It was built in 1959, making it 66 years old in 2025.

What condition is SR 9 over Harts 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 August 2024.

How much traffic does SR 9 over Harts Slough carry?

About 11,660 vehicles per day (2023 count), of which roughly 5% are trucks.

How long is SR 9 over Harts Slough?

The structure is 206 ft (62.8 m) long with a longest span of 24 ft (7.3 m) and a deck 35 ft wide.

Who owns SR 9 over Harts Slough?

It is owned by the State Highway Agency.