US Bridges

Whitlow Road over Sonoma Creek #1

Fair

Humboldt County, California · 2.2 MI E of Elk Creek RD · Structure no. 04C0139

Built
1966
59 years old, rebuilt 1989
Condition
Fair
inspected February 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
40 ft
1 main span
Daily traffic
53
2011 count
Owner
County
County Highway Agency

About this bridge

Whitlow Road over Sonoma Creek #1 is a steel stringer/multi-beam or girder carrying Whitlow Road over Sonoma Creek #1 in Humboldt County, California. It was built in 1966 and reconstructed in 1989, so it is 59 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 53 vehicles a day, roughly 3% of them trucks, projected to reach 71 by 2042. The structure is 40 ft (12.2 m) long and 12 ft wide. If it were closed, the detour would be 123.7 mi (199 km).

Location

Open in Google Maps
CarriesWhitlow Road
CrossesSonoma Creek #1
Location2.2 MI E of Elk Creek RD
RouteCounty Highway 0
CountyHumboldt County
StateCalifornia
Coordinates40.30029, -123.79767
Functional classRural Local

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection7 GoodSome minor problems.
Last inspectionFebruary 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating34.6 US tons
Inventory rating20.7 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckCorrugated steel
Main spans1
Design loadUnknown
Structure length40 ft (12.2 m)
Longest span39 ft (11.9 m)
Deck width12 ft (3.8 m)
Roadway width11 ft (3.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic53 (2011)
Projected traffic71 by 2042
Trucks3%
Lanes on structure1
Traffic directionOne-lane bridge for two-way traffic
CarriesHighway
CrossesWaterway
Detour if closed123.7 mi (199 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was Whitlow Road over Sonoma Creek #1 built?

It was built in 1966, making it 59 years old in 2025. It was reconstructed in 1989.

What condition is Whitlow Road over Sonoma Creek #1 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 Whitlow Road over Sonoma Creek #1 carry?

About 53 vehicles per day (2011 count), of which roughly 3% are trucks.

How long is Whitlow Road over Sonoma Creek #1?

The structure is 40 ft (12.2 m) long with a longest span of 39 ft (11.9 m) and a deck 12 ft wide.

Who owns Whitlow Road over Sonoma Creek #1?

It is owned by the County Highway Agency.