US Bridges

Mattole RD over Mattole River

FairPosted for load

Humboldt County, California · E of JCT Wilder Ridge RD · Structure no. 04C0055

Built
1920
105 years old
Condition
Fair
inspected March 2024
Type
Truss - Thru
Steel
Length
384 ft
2 main spans
Daily traffic
514
2009 count
Owner
County
County Highway Agency

About this bridge

Mattole RD over Mattole River is a steel truss - thru carrying Mattole RD over Mattole River in Humboldt County, California. It was built in 1920, so it is 105 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. Its operating status is: posted for load restriction.

It carries about 514 vehicles a day, roughly 5% of them trucks, projected to reach 612 by 2041. The structure is 384 ft (117 m) long and 16 ft wide. If it were closed, the detour would be 60.9 mi (98 km).

Location

Open in Google Maps
CarriesMattole RD
CrossesMattole River
LocationE of JCT Wilder Ridge RD
RouteCounty Highway 0
CountyHumboldt County
StateCalifornia
Coordinates40.24354, -124.12298
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
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection9 ExcellentNo problems noted.
Last inspectionMarch 2024
Inspection intervalevery 12 months
Operating statusPosted for load restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation3: Basically intolerable, requiring high priority of corrective action
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating22.8 US tons
Inventory rating13.6 US tons

Structure

Structure typeTruss - Thru
MaterialSteel
DeckWood or timber
Main spans2
Design loadUnknown
Structure length384 ft (117 m)
Longest span187 ft (57 m)
Deck width16 ft (4.8 m)
Roadway width14 ft (4.3 m)
Vertical clearance over deck14 ft (4.2 m)

Traffic and service

Average daily traffic514 (2009)
Projected traffic612 by 2041
Trucks5%
Lanes on structure1
Traffic directionOne-lane bridge for two-way traffic
CarriesHighway
CrossesWaterway
Detour if closed60.9 mi (98 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 RD over Mattole River built?

It was built in 1920, making it 105 years old in 2025.

What condition is Mattole RD 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 RD over Mattole River carry?

About 514 vehicles per day (2009 count), of which roughly 5% are trucks.

How long is Mattole RD over Mattole River?

The structure is 384 ft (117 m) long with a longest span of 187 ft (57 m) and a deck 16 ft wide.

Who owns Mattole RD over Mattole River?

It is owned by the County Highway Agency.