US Bridges

SR 20 over Higgins Slough

Good

Skagit County, Washington · 2.2 E JCT SR 536 · Structure no. 0017484A0000000

Built
2008
17 years old
Condition
Good
inspected March 2023
Type
Slab
Prestressed Concrete
Length
74 ft
1 main span
Daily traffic
14,588
2023 count
Owner
State
State Highway Agency

About this bridge

SR 20 over Higgins Slough is a prestressed concrete slab carrying SR 20 over Higgins Slough in Skagit County, Washington. It was built in 2008, so it is 17 years old, younger than the Washington average of 49.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 14,588 vehicles a day, roughly 8% of them trucks, projected to reach 20,487 by 2039. The structure is 74 ft (22.6 m) long and 40 ft wide. If it were closed, the detour would be 6.2 mi (10 km).

Location

Open in Google Maps
CarriesSR 20
CrossesHiggins Slough
Location2.2 E JCT SR 536
RouteState Highway 20
CountySkagit County
StateWashington
Coordinates48.45506, -122.38864
Functional classUrban Other Principal Arterial

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionMarch 2023
Inspection intervalevery 48 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than present minimum criteria
Deck geometry7: Better than present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating99 US tons
Inventory rating60 US tons

Structure

Structure typeSlab
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans1
Design loadHL 93
Structure length74 ft (22.6 m)
Longest span67 ft (20.4 m)
Deck width40 ft (12.2 m)
Roadway width38 ft (11.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic14,588 (2023)
Projected traffic20,487 by 2039
Trucks8%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
Detour if closed6.2 mi (10 km)
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkSTRAHNET connector

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$1.4 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SR 20 over Higgins Slough built?

It was built in 2008, making it 17 years old in 2025.

What condition is SR 20 over Higgins Slough in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in March 2023.

How much traffic does SR 20 over Higgins Slough carry?

About 14,588 vehicles per day (2023 count), of which roughly 8% are trucks.

How long is SR 20 over Higgins Slough?

The structure is 74 ft (22.6 m) long with a longest span of 67 ft (20.4 m) and a deck 40 ft wide.

Who owns SR 20 over Higgins Slough?

It is owned by the State Highway Agency.