US Bridges

HWY 120 over Columbia Slough

FairPosted for load

Multnomah County, Oregon · 5.5 MI NW Portland Cc · Structure no. 01726 120 00038

Built
1933
92 years old
Condition
Fair
inspected January 2025
Type
Stringer/Multi-beam or Girder
Steel
Length
338 ft
1 main span
Daily traffic
11,492
2022 count
Owner
State
State Highway Agency

About this bridge

HWY 120 over Columbia Slough is a steel stringer/multi-beam or girder carrying HWY 120 over Columbia Slough in Multnomah County, Oregon. It was built in 1933, so it is 92 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 5 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 11,492 vehicles a day, roughly 15% of them trucks, projected to reach 19,700 by 2042. The structure is 338 ft (103 m) long and 34 ft wide. If it were closed, the detour would be 6.8 mi (11 km).

Location

Open in Google Maps
CarriesHWY 120
CrossesColumbia Slough
Location5.5 MI NW Portland Cc
RouteState Highway 120
CountyMultnomah County
StateOregon
Coordinates45.60038, -122.71951
Functional classUrban Minor Arterial

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.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionJanuary 2025
Inspection intervalevery 24 months
Operating statusPosted for load restriction
ScourFoundations stable; scour above top of footing
Structural evaluation3: Basically intolerable, requiring high priority of corrective action
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 rating19.6 US tons
Inventory rating15 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+11 approach)
Design loadH 15
Structure length338 ft (103 m)
Longest span85 ft (25.9 m)
Deck width34 ft (10.3 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic11,492 (2022)
Projected traffic19,700 by 2042
Trucks15%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed6.8 mi (11 km)
TollOn a free road
National Highway SystemYes

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$1.7 million
NavigationNo navigation control on waterway

Frequently asked questions

When was HWY 120 over Columbia Slough built?

It was built in 1933, making it 92 years old in 2025.

What condition is HWY 120 over Columbia 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 January 2025.

How much traffic does HWY 120 over Columbia Slough carry?

About 11,492 vehicles per day (2022 count), of which roughly 15% are trucks.

How long is HWY 120 over Columbia Slough?

The structure is 338 ft (103 m) long with a longest span of 85 ft (25.9 m) and a deck 34 ft wide.

Who owns HWY 120 over Columbia Slough?

It is owned by the State Highway Agency.