US Bridges

Humboldt Hill Road over US Highway 101

Poor

Humboldt County, California · 01-HUM-101-73.72 · Structure no. 04 0071

Built
1963
62 years old
Condition
Poor
inspected September 2023
Type
Tee Beam
Concrete Continuous
Length
228 ft
4 main spans
Daily traffic
3,100
2010 count
Owner
State
State Highway Agency

About this bridge

Humboldt Hill Road over US Highway 101 is a concrete continuous tee beam carrying Humboldt Hill Road over US Highway 101 in Humboldt County, California. It was built in 1963, so it is 62 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 3,100 vehicles a day, roughly 10% of them trucks, projected to reach 1,636 by 2041. The structure is 228 ft (69.6 m) long and 34 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

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CarriesHumboldt Hill Road
CrossesUS Highway 101
Location01-HUM-101-73.72
RouteCounty Highway 0
CountyHumboldt County
StateCalifornia
Coordinates40.74535, -124.19989
Functional classRural Minor Collector

Condition and inspection

Poor

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.

ComponentRatingMeaning
Deck4 PoorAdvanced section loss, deterioration, spalling or scour.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Last inspectionSeptember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation7: Better than present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating44.3 US tons
Inventory rating31.7 US tons

Structure

Structure typeTee Beam
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20
Structure length228 ft (69.6 m)
Longest span81 ft (24.8 m)
Deck width34 ft (10.4 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,100 (2010)
Projected traffic1,636 by 2041
Trucks10%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesHighway
Detour if closed3.1 mi (5 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$1.2 million (2024 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was Humboldt Hill Road over US Highway 101 built?

It was built in 1963, making it 62 years old in 2025.

What condition is Humboldt Hill Road over US Highway 101 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 September 2023.

How much traffic does Humboldt Hill Road over US Highway 101 carry?

About 3,100 vehicles per day (2010 count), of which roughly 10% are trucks.

How long is Humboldt Hill Road over US Highway 101?

The structure is 228 ft (69.6 m) long with a longest span of 81 ft (24.8 m) and a deck 34 ft wide.

Who owns Humboldt Hill Road over US Highway 101?

It is owned by the State Highway Agency.