US Bridges

Humboldt Road over Colby Creek

Fair

Butte County, California · 10.5 MI E JCT S.R. 32 · Structure no. 12C0185

Built
1979
46 years old
Condition
Fair
inspected July 2024
Type
Stringer/Multi-beam or Girder
Concrete
Length
35 ft
1 main span
Daily traffic
401
2019 count
Owner
County
County Highway Agency

About this bridge

Humboldt Road over Colby Creek is a concrete stringer/multi-beam or girder carrying Humboldt Road over Colby Creek in Butte County, California. It was built in 1979, so it is 46 years old, younger 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 401 vehicles a day, roughly 17% of them trucks, projected to reach 421 by 2046. The structure is 35 ft (10.7 m) long and 29 ft wide. If it were closed, the detour would be 123.7 mi (199 km).

Location

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CarriesHumboldt Road
CrossesColby Creek
Location10.5 MI E JCT S.R. 32
RouteCounty Highway 0
CountyButte County
StateCalifornia
Coordinates40.11123, -121.48567
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.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJuly 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating41.8 US tons
Inventory rating32.2 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length35 ft (10.7 m)
Longest span34 ft (10.4 m)
Deck width29 ft (8.8 m)
Roadway width29 ft (8.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic401 (2019)
Projected traffic421 by 2046
Trucks17%
Lanes on structure2
Traffic directionTwo-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 Humboldt Road over Colby Creek built?

It was built in 1979, making it 46 years old in 2025.

What condition is Humboldt Road over Colby Creek 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 July 2024.

How much traffic does Humboldt Road over Colby Creek carry?

About 401 vehicles per day (2019 count), of which roughly 17% are trucks.

How long is Humboldt Road over Colby Creek?

The structure is 35 ft (10.7 m) long with a longest span of 34 ft (10.4 m) and a deck 29 ft wide.

Who owns Humboldt Road over Colby Creek?

It is owned by the County Highway Agency.