US Bridges

311 TH Ave SE over Shinglebolt Slough

FairPosted for load

Snohomish County, Washington · 0.2 S Jct. SR 2 · Structure no. 080372000000000

Built
1962
63 years old
Condition
Fair
inspected May 2024
Type
Stringer/Multi-beam or Girder
Wood or Timber
Length
140 ft
1 main span
Daily traffic
1,321
2023 count
Owner
County
County Highway Agency

About this bridge

311 TH Ave SE over Shinglebolt Slough is a wood or timber stringer/multi-beam or girder carrying 311 TH Ave SE over Shinglebolt Slough in Snohomish County, Washington. It was built in 1962, so it is 63 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 1,321 vehicles a day, roughly 12% of them trucks, projected to reach 3,000 by 2042. The structure is 140 ft (42.7 m) long and 31 ft wide. If it were closed, the detour would be 18 mi (29 km).

Location

Open in Google Maps
Carries311 TH Ave SE
CrossesShinglebolt Slough
Location0.2 S Jct. SR 2
RouteCounty Highway 95776
CountySnohomish County
StateWashington
Coordinates47.85836, -121.81499
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionMay 2024
Inspection intervalevery 24 months
Operating statusPosted for load restriction
ScourFoundations stable; scour above top of footing
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
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 rating32 US tons
Inventory rating17 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialWood or Timber
DeckConcrete, cast-in-place
Main spans1 (+2 approach)
Design loadHS 15
Structure length140 ft (42.7 m)
Longest span70 ft (21.3 m)
Deck width31 ft (9.5 m)
Roadway width26 ft (8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,321 (2023)
Projected traffic3,000 by 2042
Trucks12%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed18 mi (29 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$5.4 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was 311 TH Ave SE over Shinglebolt Slough built?

It was built in 1962, making it 63 years old in 2025.

What condition is 311 TH Ave SE over Shinglebolt 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 May 2024.

How much traffic does 311 TH Ave SE over Shinglebolt Slough carry?

About 1,321 vehicles per day (2023 count), of which roughly 12% are trucks.

How long is 311 TH Ave SE over Shinglebolt Slough?

The structure is 140 ft (42.7 m) long with a longest span of 70 ft (21.3 m) and a deck 31 ft wide.

Who owns 311 TH Ave SE over Shinglebolt Slough?

It is owned by the County Highway Agency.