US Highway 101 NB over Willow Brook
FairSonoma County, California · 04-SON-101-8.05-PET · Structure no. 20 0161
- Built
- 1956
- 69 years old, rebuilt 2012
- Condition
- Fair
- inspected September 2024
- Type
- Slab
- Concrete Continuous
- Length
- 70 ft
- 3 main spans
- Daily traffic
- 94,000
- 2016 count
- Owner
- State
- State Highway Agency
About this bridge
US Highway 101 NB over Willow Brook is a concrete continuous slab carrying US Highway 101 NB over Willow Brook in Sonoma County, California. It was built in 1956 and reconstructed in 2012, so it is 69 years old, older than the California average of 54.8 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 94,000 vehicles a day, roughly 6% of them trucks, projected to reach 148,144 by 2046. The structure is 70 ft (21.3 m) long and 110 ft wide. If it were closed, the detour would be 1.2 mi (2 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 | 7 Good | Some minor problems. |
| Superstructure | 7 Good | Some minor problems. |
| Substructure | 6 Satisfactory | Structural elements show some minor deterioration. |
| Channel and channel protection | 8 Very Good | No problems noted. |
Structure
Traffic and service
Ownership and planned work
Frequently asked questions
When was US Highway 101 NB over Willow Brook built?
It was built in 1956, making it 69 years old in 2025. It was reconstructed in 2012.
What condition is US Highway 101 NB over Willow Brook 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 September 2024.
How much traffic does US Highway 101 NB over Willow Brook carry?
About 94,000 vehicles per day (2016 count), of which roughly 6% are trucks.
How long is US Highway 101 NB over Willow Brook?
The structure is 70 ft (21.3 m) long with a longest span of 27 ft (8.2 m) and a deck 110 ft wide.
Who owns US Highway 101 NB over Willow Brook?
It is owned by the State Highway Agency.