State Route 299 over Mad River
PoorHumboldt County, California · 01-HUM-299-R1.56 · Structure no. 04 0036L
- Built
- 1965
- 60 years old
- Condition
- Poor
- inspected November 2023
- Type
- Stringer/Multi-beam or Girder
- Steel Continuous
- Length
- 518 ft
- 2 main spans
- Daily traffic
- 4,775
- 2010 count
- Owner
- State
- State Highway Agency
About this bridge
State Route 299 over Mad River is a steel continuous stringer/multi-beam or girder carrying State Route 299 over Mad River in Humboldt County, California. It was built in 1965, so it is 60 years old, older than the California average of 54.8 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.
It carries about 4,775 vehicles a day, roughly 14% of them trucks, projected to reach 5,469 by 2041. The structure is 518 ft (157.9 m) long and 38 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 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.
| Component | Rating | Meaning |
|---|---|---|
| Deck | 4 Poor | Advanced section loss, deterioration, spalling or scour. |
| Superstructure | 7 Good | Some minor problems. |
| Substructure | 7 Good | Some minor problems. |
| Channel and channel protection | 6 Satisfactory | Structural elements show some minor deterioration. |
Structure
Traffic and service
Ownership and planned work
Frequently asked questions
When was State Route 299 over Mad River built?
It was built in 1965, making it 60 years old in 2025.
What condition is State Route 299 over Mad River 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 November 2023.
How much traffic does State Route 299 over Mad River carry?
About 4,775 vehicles per day (2010 count), of which roughly 14% are trucks.
How long is State Route 299 over Mad River?
The structure is 518 ft (157.9 m) long with a longest span of 150 ft (45.7 m) and a deck 38 ft wide.
Who owns State Route 299 over Mad River?
It is owned by the State Highway Agency.