US Bridges

HWY 31 over Bowers Slough

Fair

Benton County, Oregon · 062 MI E Corvallis · Structure no. 01036A031 00703

Built
1964
61 years old
Condition
Fair
inspected July 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
150 ft
3 main spans
Daily traffic
15,140
2022 count
Owner
State
State Highway Agency

About this bridge

HWY 31 over Bowers Slough is a prestressed concrete stringer/multi-beam or girder carrying HWY 31 over Bowers Slough in Benton County, Oregon. It was built in 1964, so it is 61 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 15,140 vehicles a day, roughly 10% of them trucks, projected to reach 17,200 by 2042. The structure is 150 ft (45.7 m) long and 35 ft wide. If it were closed, the detour would be 9.9 mi (16 km).

Location

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CarriesHWY 31
CrossesBowers Slough
Location062 MI E Corvallis
RouteU.S. Route 20
CountyBenton County
StateOregon
Coordinates44.63923, -123.17133
Functional classRural 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.
Superstructure8 Very GoodNo problems noted.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
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 rating24.3 US tons
Inventory rating18.5 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length150 ft (45.7 m)
Longest span50 ft (15.2 m)
Deck width35 ft (10.6 m)
Roadway width30 ft (9.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic15,140 (2022)
Projected traffic17,200 by 2042
Trucks10%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed9.9 mi (16 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$769,000
NavigationNo navigation control on waterway

Frequently asked questions

When was HWY 31 over Bowers Slough built?

It was built in 1964, making it 61 years old in 2025.

What condition is HWY 31 over Bowers 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 2023.

How much traffic does HWY 31 over Bowers Slough carry?

About 15,140 vehicles per day (2022 count), of which roughly 10% are trucks.

How long is HWY 31 over Bowers Slough?

The structure is 150 ft (45.7 m) long with a longest span of 50 ft (15.2 m) and a deck 35 ft wide.

Who owns HWY 31 over Bowers Slough?

It is owned by the State Highway Agency.