US Bridges

IRR Pioneer Parkwa over Swinomish Slough

FairPosted for load

Skagit County, Washington · 0.95 JCT Morris on Maple · Structure no. 084845000000000

Built
1957
68 years old
Condition
Fair
inspected April 2024
Type
Arch - Thru
Steel
Length
797 ft
1 main span
Daily traffic
3,101
2020 count
Owner
County
County Highway Agency

About this bridge

IRR Pioneer Parkwa over Swinomish Slough is a steel arch - thru carrying IRR Pioneer Parkwa over Swinomish Slough in Skagit County, Washington. It was built in 1957, so it is 68 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. Its operating status is: posted for load restriction.

It carries about 3,101 vehicles a day, roughly 7% of them trucks, projected to reach 5,600 by 2040. The structure is 797 ft (242.9 m) long and 30 ft wide. If it were closed, the detour would be 14.3 mi (23 km).

Location

Open in Google Maps
CarriesIRR Pioneer Parkwa
CrossesSwinomish Slough
Location0.95 JCT Morris on Maple
RouteCounty Highway 42000
CountySkagit County
StateWashington
Coordinates48.38575, -122.50163
Functional classRural Major Collector

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionApril 2024
Inspection intervalevery 24 months
Operating statusPosted for load restriction
ScourFoundations on dry land well above flood water elevations
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating25.4 US tons
Inventory rating19.6 US tons

Structure

Structure typeArch - Thru
MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+6 approach)
Design loadHS 15
Structure length797 ft (242.9 m)
Longest span580 ft (176.8 m)
Deck width30 ft (9.1 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deck17 ft (5.1 m)

Traffic and service

Average daily traffic3,101 (2020)
Projected traffic5,600 by 2040
Trucks7%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesHighway and waterway
Detour if closed14.3 mi (23 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusListed on the National Register of Historic Places
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$29.1 million (2022 estimate)
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was IRR Pioneer Parkwa over Swinomish Slough built?

It was built in 1957, making it 68 years old in 2025.

What condition is IRR Pioneer Parkwa over Swinomish 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 April 2024.

How much traffic does IRR Pioneer Parkwa over Swinomish Slough carry?

About 3,101 vehicles per day (2020 count), of which roughly 7% are trucks.

How long is IRR Pioneer Parkwa over Swinomish Slough?

The structure is 797 ft (242.9 m) long with a longest span of 580 ft (176.8 m) and a deck 30 ft wide.

Who owns IRR Pioneer Parkwa over Swinomish Slough?

It is owned by the County Highway Agency.