US Bridges

Plumbago Road over Kanaka Creek

FairPosted for load

Sierra County, California · 1.6 MI South of Alleghany · Structure no. 13C0051

Built
1985
40 years old
Condition
Fair
inspected August 2023
Type
Girder and Floorbeam System
Steel
Length
95 ft
1 main span
Daily traffic
20
2005 count
Owner
County
County Highway Agency

About this bridge

Plumbago Road over Kanaka Creek is a steel girder and floorbeam system carrying Plumbago Road over Kanaka Creek in Sierra County, California. It was built in 1985, so it is 40 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. Its operating status is: posted for other load-capacity restriction.

It carries about 20 vehicles a day, roughly 20% of them trucks, projected to reach 33 by 2043. The structure is 95 ft (29 m) long and 9 ft wide. If it were closed, the detour would be 13 mi (21 km).

Location

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CarriesPlumbago Road
CrossesKanaka Creek
Location1.6 MI South of Alleghany
RouteCounty Highway 0
CountySierra County
StateCalifornia
Coordinates39.46441, -120.83881
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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
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 protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionAugust 2023
Inspection intervalevery 24 months
Operating statusPosted for other load-capacity 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 geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating32.8 US tons
Inventory rating19.6 US tons

Structure

Structure typeGirder and Floorbeam System
MaterialSteel
DeckSteel plate
Main spans1
Design loadUnknown
Structure length95 ft (29 m)
Longest span78 ft (23.8 m)
Deck width9 ft (2.7 m)
Roadway width9 ft (2.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic20 (2005)
Projected traffic33 by 2043
Trucks20%
Lanes on structure1
Traffic directionOne-lane bridge for two-way traffic
CarriesHighway
CrossesWaterway
Detour if closed13 mi (21 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 Plumbago Road over Kanaka Creek built?

It was built in 1985, making it 40 years old in 2025.

What condition is Plumbago Road over Kanaka 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 August 2023.

How much traffic does Plumbago Road over Kanaka Creek carry?

About 20 vehicles per day (2005 count), of which roughly 20% are trucks.

How long is Plumbago Road over Kanaka Creek?

The structure is 95 ft (29 m) long with a longest span of 78 ft (23.8 m) and a deck 9 ft wide.

Who owns Plumbago Road over Kanaka Creek?

It is owned by the County Highway Agency.