US Bridges

Mattole Road over Mattole River

Fair

Humboldt County, California · 8.0 MI N/O Honeydew · Structure no. 04C0189

Built
1935
90 years old
Condition
Fair
inspected March 2024
Type
Arch - Deck
Concrete
Length
166 ft
1 main span
Daily traffic
205
2008 count
Owner
County
County Highway Agency

About this bridge

Mattole Road over Mattole River is a concrete arch - deck carrying Mattole Road over Mattole River in Humboldt County, California. It was built in 1935, so it is 90 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 205 vehicles a day, roughly 4% of them trucks, projected to reach 327 by 2042. The structure is 166 ft (50.6 m) long and 18 ft wide. If it were closed, the detour would be 123.7 mi (199 km).

Location

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CarriesMattole Road
CrossesMattole River
Location8.0 MI N/O Honeydew
RouteCounty Highway 0
CountyHumboldt County
StateCalifornia
Coordinates40.27034, -124.22681
Functional classRural Major Collector

Condition and inspection

Fair

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

ComponentRatingMeaning
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 inspectionMarch 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 geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment3: Basically intolerable, requiring high priority of corrective action
Operating rating33.2 US tons
Inventory rating20 US tons

Structure

Structure typeArch - Deck
MaterialConcrete
DeckNot applicable
Main spans1
Design loadUnknown
Structure length166 ft (50.6 m)
Longest span150 ft (45.7 m)
Deck width18 ft (5.5 m)
Roadway width15 ft (4.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic205 (2008)
Projected traffic327 by 2042
Trucks4%
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 statusEligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was Mattole Road over Mattole River built?

It was built in 1935, making it 90 years old in 2025.

What condition is Mattole Road over Mattole River 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 March 2024.

How much traffic does Mattole Road over Mattole River carry?

About 205 vehicles per day (2008 count), of which roughly 4% are trucks.

How long is Mattole Road over Mattole River?

The structure is 166 ft (50.6 m) long with a longest span of 150 ft (45.7 m) and a deck 18 ft wide.

Who owns Mattole Road over Mattole River?

It is owned by the County Highway Agency.