US Bridges

SR 20 over Horsetail Creek

Good

Whatcom County, Washington · 16.7 E Skagit CO · Structure no. 0008465A0000000

Built
1968
57 years old
Condition
Good
inspected June 2024
Type
Girder and Floorbeam System
Steel Continuous
Length
363 ft
3 main spans
Daily traffic
1,322
2023 count
Owner
State
State Highway Agency

About this bridge

SR 20 over Horsetail Creek is a steel continuous girder and floorbeam system carrying SR 20 over Horsetail Creek in Whatcom County, Washington. It was built in 1968, so it is 57 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 1,322 vehicles a day, roughly 8% of them trucks, projected to reach 1,927 by 2039. The structure is 363 ft (110.6 m) long and 35 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

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CarriesSR 20
CrossesHorsetail Creek
Location16.7 E Skagit CO
RouteState Highway 20
CountyWhatcom County
StateWashington
Coordinates48.71894, -121.07058
Functional classRural Minor 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 inspectionJune 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations on dry land well above flood water elevations
Structural evaluation7: Better than present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating72 US tons
Inventory rating43 US tons

Structure

Structure typeGirder and Floorbeam System
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length363 ft (110.6 m)
Longest span179 ft (54.6 m)
Deck width35 ft (10.8 m)
Roadway width32 ft (9.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,322 (2023)
Projected traffic1,927 by 2039
Trucks8%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed98.8 mi (159 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$5.9 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SR 20 over Horsetail Creek built?

It was built in 1968, making it 57 years old in 2025.

What condition is SR 20 over Horsetail Creek 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 June 2024.

How much traffic does SR 20 over Horsetail Creek carry?

About 1,322 vehicles per day (2023 count), of which roughly 8% are trucks.

How long is SR 20 over Horsetail Creek?

The structure is 363 ft (110.6 m) long with a longest span of 179 ft (54.6 m) and a deck 35 ft wide.

Who owns SR 20 over Horsetail Creek?

It is owned by the State Highway Agency.