US Bridges

State Route 20 over Chamberlain Creek

Fair

Mendocino County, California · 01-MEN-020-17.29 · Structure no. 10 0101

Built
1948
77 years old
Condition
Fair
inspected May 2023
Type
Tee Beam
Concrete Continuous
Length
82 ft
3 main spans
Daily traffic
2,600
2009 count
Owner
State
State Highway Agency

About this bridge

State Route 20 over Chamberlain Creek is a concrete continuous tee beam carrying State Route 20 over Chamberlain Creek in Mendocino County, California. It was built in 1948, so it is 77 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 6 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 2,600 vehicles a day, roughly 16% of them trucks, projected to reach 4,177 by 2045. The structure is 82 ft (25 m) long and 33 ft wide. If it were closed, the detour would be 72.7 mi (117 km).

Location

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CarriesState Route 20
CrossesChamberlain Creek
Location01-MEN-020-17.29
RouteState Highway 20
CountyMendocino County
StateCalifornia
Coordinates39.35282, -123.55671
Functional classRural Minor Arterial

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.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionMay 2023
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 geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating26.8 US tons
Inventory rating20.7 US tons

Structure

Structure typeTee Beam
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length82 ft (25 m)
Longest span45 ft (13.7 m)
Deck width33 ft (10.2 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,600 (2009)
Projected traffic4,177 by 2045
Trucks16%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed72.7 mi (117 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 proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was State Route 20 over Chamberlain Creek built?

It was built in 1948, making it 77 years old in 2025.

What condition is State Route 20 over Chamberlain 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 May 2023.

How much traffic does State Route 20 over Chamberlain Creek carry?

About 2,600 vehicles per day (2009 count), of which roughly 16% are trucks.

How long is State Route 20 over Chamberlain Creek?

The structure is 82 ft (25 m) long with a longest span of 45 ft (13.7 m) and a deck 33 ft wide.

Who owns State Route 20 over Chamberlain Creek?

It is owned by the State Highway Agency.