US Bridges

Olson RD/36 Ave NW over Norman Slough

Fair

Snohomish County, Washington · 0.1 S JCT SR 530 · Structure no. 084574000000000

Built
1979
46 years old
Condition
Fair
inspected July 2024
Type
Stringer/Multi-beam or Girder
Wood or Timber
Length
163 ft
10 main spans
Daily traffic
50
2020 count
Owner
County
County Highway Agency

About this bridge

Olson RD/36 Ave NW over Norman Slough is a wood or timber stringer/multi-beam or girder carrying Olson RD/36 Ave NW over Norman Slough in Snohomish County, Washington. It was built in 1979, so it is 46 years old, younger 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 5 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 50 vehicles a day, roughly 13% of them trucks, projected to reach 100 by 2044. The structure is 163 ft (49.6 m) long and 20 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesOlson RD/36 Ave NW
CrossesNorman Slough
Location0.1 S JCT SR 530
RouteCounty Highway 70690
CountySnohomish County
StateWashington
Coordinates48.22282, -122.28082
Functional classRural Local

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.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJuly 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being 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 rating37 US tons
Inventory rating27 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialWood or Timber
DeckWood or timber
Main spans10
Design loadHS 15
Structure length163 ft (49.6 m)
Longest span17 ft (5.3 m)
Deck width20 ft (6.1 m)
Roadway width19 ft (5.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic50 (2020)
Projected traffic100 by 2044
Trucks13%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.2 mi (2 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$6.2 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was Olson RD/36 Ave NW over Norman Slough built?

It was built in 1979, making it 46 years old in 2025.

What condition is Olson RD/36 Ave NW over Norman 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 July 2024.

How much traffic does Olson RD/36 Ave NW over Norman Slough carry?

About 50 vehicles per day (2020 count), of which roughly 13% are trucks.

How long is Olson RD/36 Ave NW over Norman Slough?

The structure is 163 ft (49.6 m) long with a longest span of 17 ft (5.3 m) and a deck 20 ft wide.

Who owns Olson RD/36 Ave NW over Norman Slough?

It is owned by the County Highway Agency.