US Bridges

HWY 91 SB over Tualatin River

Fair

Washington County, Oregon · 0.5 MI S of King City Cc · Structure no. 01417S01W 01220

Built
1929
96 years old
Condition
Fair
inspected February 2024
Type
Truss - Deck
Steel
Length
513 ft
1 main span
Daily traffic
14,983
2022 count
Owner
State
State Highway Agency

About this bridge

HWY 91 SB over Tualatin River is a steel truss - deck carrying HWY 91 SB over Tualatin River in Washington County, Oregon. It was built in 1929, so it is 96 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.

It carries about 14,983 vehicles a day, roughly 3% of them trucks, projected to reach 17,500 by 2042. The structure is 513 ft (156.5 m) long and 39 ft wide.

Location

Open in Google Maps
CarriesHWY 91 SB
CrossesTualatin River
Location0.5 MI S of King City Cc
RouteState Highway 99
CountyWashington County
StateOregon
Coordinates45.39404, -122.79935
Functional classUrban Other Principal 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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionFebruary 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
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 rating23.3 US tons
Inventory rating17.9 US tons

Structure

Structure typeTruss - Deck
MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+9 approach)
Design loadHS 20
Structure length513 ft (156.5 m)
Longest span150 ft (45.7 m)
Deck width39 ft (12 m)
Roadway width27 ft (8.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic14,983 (2022)
Projected traffic17,500 by 2042
Trucks3%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
Detour if closed—
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusPossibly eligible for the National Register; requires further investigation
Work proposedWidening of existing bridge without deck rehabilitation
Estimated improvement cost$2.6 million
NavigationNo navigation control on waterway

Frequently asked questions

When was HWY 91 SB over Tualatin River built?

It was built in 1929, making it 96 years old in 2025.

What condition is HWY 91 SB over Tualatin River 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 February 2024.

How much traffic does HWY 91 SB over Tualatin River carry?

About 14,983 vehicles per day (2022 count), of which roughly 3% are trucks.

How long is HWY 91 SB over Tualatin River?

The structure is 513 ft (156.5 m) long with a longest span of 150 ft (45.7 m) and a deck 39 ft wide.

Who owns HWY 91 SB over Tualatin River?

It is owned by the State Highway Agency.