Or 99W(HWY 91)SB over Rock Creek (onion Flat)
FairWashington County, Oregon · 14 Mi. N. of Sherwood · Structure no. 01578 01W 01382
- Built
- 1931
- 94 years old
- Condition
- Fair
- inspected February 2024
- Type
- Tee Beam
- Concrete Continuous
- Length
- 120 ft
- 3 main spans
- Daily traffic
- 14,012
- 2022 count
- Owner
- State
- State Highway Agency
About this bridge
Or 99W(HWY 91)SB over Rock Creek (onion Flat) is a concrete continuous tee beam carrying Or 99W(HWY 91)SB over Rock Creek (onion Flat) in Washington County, Oregon. It was built in 1931, so it is 94 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 14,012 vehicles a day, roughly 3% of them trucks, projected to reach 18,150 by 2042. The structure is 120 ft (36.6 m) long and 42 ft wide. If it were closed, the detour would be 3.1 mi (5 km).
Location
Open in Google MapsCondition and inspection
The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.
| Component | Rating | Meaning |
|---|---|---|
| Deck | 6 Satisfactory | Structural elements show some minor deterioration. |
| Superstructure | 5 Fair | All primary structural elements are sound but may have minor section loss, cracking, spalling or scour. |
| Substructure | 5 Fair | All primary structural elements are sound but may have minor section loss, cracking, spalling or scour. |
| Channel and channel protection | 8 Very Good | No problems noted. |
Structure
Traffic and service
Ownership and planned work
Frequently asked questions
When was Or 99W(HWY 91)SB over Rock Creek (onion Flat) built?
It was built in 1931, making it 94 years old in 2025.
What condition is Or 99W(HWY 91)SB over Rock Creek (onion Flat) 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 Or 99W(HWY 91)SB over Rock Creek (onion Flat) carry?
About 14,012 vehicles per day (2022 count), of which roughly 3% are trucks.
How long is Or 99W(HWY 91)SB over Rock Creek (onion Flat)?
The structure is 120 ft (36.6 m) long with a longest span of 46 ft (14 m) and a deck 42 ft wide.
Who owns Or 99W(HWY 91)SB over Rock Creek (onion Flat)?
It is owned by the State Highway Agency.