US Bridges

US101 (hwy 9) over Neilson Slough

Fair

Tillamook County, Oregon · 027 MI N Tillamook · Structure no. 07456 009 06284

Built
1952
73 years old
Condition
Fair
inspected March 2023
Type
Stringer/Multi-beam or Girder
Concrete
Length
100 ft
4 main spans
Daily traffic
13,357
2022 count
Owner
State
State Highway Agency

About this bridge

US101 (hwy 9) over Neilson Slough is a concrete stringer/multi-beam or girder carrying US101 (hwy 9) over Neilson Slough in Tillamook County, Oregon. It was built in 1952, so it is 73 years old, older than the Oregon average of 49.9 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.

It carries about 13,357 vehicles a day, roughly 4% of them trucks, projected to reach 13,500 by 2042. The structure is 100 ft (30.5 m) long and 35 ft wide. If it were closed, the detour would be 75.2 mi (121 km).

Location

Open in Google Maps
CarriesUS101 (hwy 9)
CrossesNeilson Slough
Location027 MI N Tillamook
RouteU.S. Route 101
CountyTillamook County
StateOregon
Coordinates45.49729, -123.85165
Functional classRural Principal Arterial - Other

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.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionMarch 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourUnknown foundation; not evaluated for scour
Structural evaluation6: Equal to present minimum criteria
Deck geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating52.1 US tons
Inventory rating40.3 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialConcrete
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20
Structure length100 ft (30.5 m)
Longest span25 ft (7.6 m)
Deck width35 ft (10.6 m)
Roadway width30 ft (9.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic13,357 (2022)
Projected traffic13,500 by 2042
Trucks4%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed75.2 mi (121 km)
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkNon-Interstate STRAHNET route

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedWidening of existing bridge without deck rehabilitation
Estimated improvement cost$512,000
NavigationNo navigation control on waterway

Frequently asked questions

When was US101 (hwy 9) over Neilson Slough built?

It was built in 1952, making it 73 years old in 2025.

What condition is US101 (hwy 9) over Neilson 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 March 2023.

How much traffic does US101 (hwy 9) over Neilson Slough carry?

About 13,357 vehicles per day (2022 count), of which roughly 4% are trucks.

How long is US101 (hwy 9) over Neilson Slough?

The structure is 100 ft (30.5 m) long with a longest span of 25 ft (7.6 m) and a deck 35 ft wide.

Who owns US101 (hwy 9) over Neilson Slough?

It is owned by the State Highway Agency.