US Bridges

Island Mountain RD over Chamise Creek

Fair

Humboldt County, California · 5.7 MI E/O Bellsprings RD · Structure no. 04C0113

Built
1973
52 years old
Condition
Fair
inspected February 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
83 ft
1 main span
Daily traffic
100
2015 count
Owner
County
County Highway Agency

About this bridge

Island Mountain RD over Chamise Creek is a steel stringer/multi-beam or girder carrying Island Mountain RD over Chamise Creek in Humboldt County, California. It was built in 1973, so it is 52 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 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 100 vehicles a day, roughly 1% of them trucks, projected to reach 111 by 2046. The structure is 83 ft (25.4 m) long and 18 ft wide. If it were closed, the detour would be 19.9 mi (32 km).

Location

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CarriesIsland Mountain RD
CrossesChamise Creek
Location5.7 MI E/O Bellsprings RD
RouteCounty Highway 0
CountyHumboldt County
StateCalifornia
Coordinates40.03704, -123.55423
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.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionFebruary 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
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 adequacy7: Better than present minimum criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating59.3 US tons
Inventory rating35.4 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckWood or timber
Main spans1
Design loadUnknown
Structure length83 ft (25.4 m)
Longest span78 ft (23.9 m)
Deck width18 ft (5.5 m)
Roadway width16 ft (4.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic100 (2015)
Projected traffic111 by 2046
Trucks1%
Lanes on structure1
Traffic directionOne-lane bridge for two-way traffic
CarriesHighway
CrossesWaterway
Detour if closed19.9 mi (32 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 Island Mountain RD over Chamise Creek built?

It was built in 1973, making it 52 years old in 2025.

What condition is Island Mountain RD over Chamise 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 February 2024.

How much traffic does Island Mountain RD over Chamise Creek carry?

About 100 vehicles per day (2015 count), of which roughly 1% are trucks.

How long is Island Mountain RD over Chamise Creek?

The structure is 83 ft (25.4 m) long with a longest span of 78 ft (23.9 m) and a deck 18 ft wide.

Who owns Island Mountain RD over Chamise Creek?

It is owned by the County Highway Agency.