US Bridges

State Route 20 over Colusa Trough

Fair

Colusa County, California · 03-COL-020-27.83 · Structure no. 15 0020

Built
1962
63 years old
Condition
Fair
inspected August 2023
Type
Stringer/Multi-beam or Girder
Concrete Continuous
Length
800 ft
20 main spans
Daily traffic
6,400
2015 count
Owner
State
State Highway Agency

About this bridge

State Route 20 over Colusa Trough is a concrete continuous stringer/multi-beam or girder carrying State Route 20 over Colusa Trough in Colusa County, California. It was built in 1962, so it is 63 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 6,400 vehicles a day, projected to reach 8,905 by 2043. The structure is 800 ft (243.8 m) long and 34 ft wide. If it were closed, the detour would be 39.1 mi (63 km).

Location

Open in Google Maps
CarriesState Route 20
CrossesColusa Trough
Location03-COL-020-27.83
RouteState Highway 20
CountyColusa County
StateCalifornia
Coordinates39.19556, -122.06239
Functional classRural Principal Arterial - Other

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.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionAugust 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation7: Better than present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating76.8 US tons
Inventory rating46.1 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans20
Design loadHS 20
Structure length800 ft (243.8 m)
Longest span40 ft (12.2 m)
Deck width34 ft (10.4 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic6,400 (2015)
Projected traffic8,905 by 2043
Trucks0%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed39.1 mi (63 km)
TollOn a free road
National Highway SystemYes

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 Colusa Trough built?

It was built in 1962, making it 63 years old in 2025.

What condition is State Route 20 over Colusa Trough 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 State Route 20 over Colusa Trough carry?

About 6,400 vehicles per day (2015 count).

How long is State Route 20 over Colusa Trough?

The structure is 800 ft (243.8 m) long with a longest span of 40 ft (12.2 m) and a deck 34 ft wide.

Who owns State Route 20 over Colusa Trough?

It is owned by the State Highway Agency.