US 101 Mcdonnell over Millbrae Slough
FairSan Mateo County, California · 04-SM-101-18.09-MLBR · Structure no. 35 0126
- Built
- 1947
- 78 years old, rebuilt 1961
- Condition
- Fair
- inspected April 2023
- Type
- Culvert
- Concrete Continuous
- Length
- 34 ft
- 3 main spans
- Daily traffic
- 226,000
- 2009 count
- Owner
- State
- State Highway Agency
About this bridge
US 101 Mcdonnell over Millbrae Slough is a concrete continuous culvert carrying US 101 Mcdonnell over Millbrae Slough in San Mateo County, California. It was built in 1947 and reconstructed in 1961, so it is 78 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 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 226,000 vehicles a day, roughly 4% of them trucks, projected to reach 279,030 by 2040. The structure is 34 ft (10.4 m) long. If it were closed, the detour would be 6.2 mi (10 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 |
|---|---|---|
| Channel and channel protection | 7 Good | Some minor problems. |
| Culvert | 5 Fair | All primary structural elements are sound but may have minor section loss, cracking, spalling or scour. |
Structure
Traffic and service
Ownership and planned work
Frequently asked questions
When was US 101 Mcdonnell over Millbrae Slough built?
It was built in 1947, making it 78 years old in 2025. It was reconstructed in 1961.
What condition is US 101 Mcdonnell over Millbrae 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 April 2023.
How much traffic does US 101 Mcdonnell over Millbrae Slough carry?
About 226,000 vehicles per day (2009 count), of which roughly 4% are trucks.
How long is US 101 Mcdonnell over Millbrae Slough?
The structure is 34 ft (10.4 m) long with a longest span of 10 ft (3 m).
Who owns US 101 Mcdonnell over Millbrae Slough?
It is owned by the State Highway Agency.