US Bridges

HWY 100 over Viaduct

PoorPosted for load

Multnomah County, Oregon · 0.2 MI W Multnomah Falls · Structure no. 00840 125 01950

Built
1914
111 years old
Condition
Poor
inspected September 2024
Type
Slab
Concrete Continuous
Length
402 ft
20 main spans
Daily traffic
901
2022 count
Owner
State
State Highway Agency

About this bridge

HWY 100 over Viaduct is a concrete continuous slab carrying HWY 100 over Viaduct in Multnomah County, Oregon. It was built in 1914, so it is 111 years old, older than the Oregon average of 49.9 years.

The most recent inspection reported to the Federal Highway Administration rates it in poor condition with a lowest component rating of 4 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. Its operating status is: posted for load restriction.

It carries about 901 vehicles a day, roughly 4% of them trucks, projected to reach 1,200 by 2042. The structure is 402 ft (122.5 m) long and 20 ft wide. If it were closed, the detour would be 14.9 mi (24 km).

Location

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CarriesHWY 100
CrossesViaduct
Location0.2 MI W Multnomah Falls
RouteState Highway 30
CountyMultnomah County
StateOregon
Coordinates45.5771, -122.121
Functional classRural Major Collector

Condition and inspection

Poor

The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure4 PoorAdvanced section loss, deterioration, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionSeptember 2024
Inspection intervalevery 12 months
Operating statusPosted for load restriction
ScourBridge not over waterway
Structural evaluation2: Basically intolerable, requiring high priority of replacement
Deck geometry2: Basically intolerable, requiring high priority of replacement
Approach roadway alignment8: Equal to present desirable criteria
Operating rating6.4 US tons
Inventory rating5 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans20
Design loadH 15
Structure length402 ft (122.5 m)
Longest span20 ft (6.1 m)
Deck width20 ft (6.1 m)
Roadway width17 ft (5.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic901 (2022)
Projected traffic1,200 by 2042
Trucks4%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesOther
Detour if closed14.9 mi (24 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusListed on the National Register of Historic Places
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$2.3 million
NavigationNot applicable (no waterway)

Frequently asked questions

When was HWY 100 over Viaduct built?

It was built in 1914, making it 111 years old in 2025.

What condition is HWY 100 over Viaduct in?

The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in September 2024.

How much traffic does HWY 100 over Viaduct carry?

About 901 vehicles per day (2022 count), of which roughly 4% are trucks.

How long is HWY 100 over Viaduct?

The structure is 402 ft (122.5 m) long with a longest span of 20 ft (6.1 m) and a deck 20 ft wide.

Who owns HWY 100 over Viaduct?

It is owned by the State Highway Agency.