US Bridges

SR 20 over Higgins Slough

Good

Skagit County, Washington · 0.7 E JCT SR 536 · Structure no. 0008044B0000000

Built
1966
59 years old
Condition
Good
inspected March 2023
Type
Slab
Concrete Continuous
Length
62 ft
3 main spans
Daily traffic
13,561
2023 count
Owner
State
State Highway Agency

About this bridge

SR 20 over Higgins Slough is a concrete continuous slab carrying SR 20 over Higgins Slough in Skagit 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 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 13,561 vehicles a day, roughly 8% of them trucks, projected to reach 19,077 by 2039. The structure is 62 ft (18.9 m) long and 37 ft wide. If it were closed, the detour would be 6.2 mi (10 km).

CarriesSR 20
CrossesHiggins Slough
Location0.7 E JCT SR 536
RouteState Highway 20
Coordinates48.44906, -122.4199
Functional classRural Principal Arterial - Other

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 protection7 GoodSome minor problems.
Last inspectionMarch 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation7: Better than 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 rating55 US tons
Inventory rating31 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20 + Mod
Structure length62 ft (18.9 m)
Longest span24 ft (7.3 m)
Deck width37 ft (11.4 m)
Roadway width34 ft (10.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic13,561 (2023)
Projected traffic19,077 by 2039
Trucks8%
Lanes on structure2
Traffic directionTwo-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 statusNot eligible for the National Register of Historic Places
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$1.1 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SR 20 over Higgins Slough built?

It was built in 1966, making it 59 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 13,561 vehicles per day (2023 count), of which roughly 8% are trucks.

How long is SR 20 over Higgins Slough?

The structure is 62 ft (18.9 m) long with a longest span of 24 ft (7.3 m) and a deck 37 ft wide.

Who owns SR 20 over Higgins Slough?

It is owned by the State Highway Agency.