US Bridges

SR 20 over Powell Slough

Good

Colusa County, California · 03-COL-020-28.54 · Structure no. 15 0019

Built
1915
110 years old, rebuilt 1940
Condition
Good
inspected August 2023
Type
Tee Beam
Concrete
Length
59 ft
1 main span
Daily traffic
6,400
2013 count
Owner
State
State Highway Agency

About this bridge

SR 20 over Powell Slough is a concrete tee beam carrying SR 20 over Powell Slough in Colusa County, California. It was built in 1915 and reconstructed in 1940, so it is 110 years old, older than the California average of 54.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 6,400 vehicles a day, projected to reach 9,084 by 2043. The structure is 59 ft (18 m) long and 41 ft wide. If it were closed, the detour would be 39.1 mi (63 km).

Location

Open in Google Maps
CarriesSR 20
CrossesPowell Slough
Location03-COL-020-28.54
RouteState Highway 20
CountyColusa County
StateCalifornia
Coordinates39.19536, -122.04917
Functional classRural Principal Arterial - Other

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionAugust 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation6: Equal to present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating44.6 US tons
Inventory rating26.8 US tons

Structure

Structure typeTee Beam
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadUnknown
Structure length59 ft (18 m)
Longest span21 ft (6.4 m)
Deck width41 ft (12.5 m)
Roadway width36 ft (11 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic6,400 (2013)
Projected traffic9,084 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 SR 20 over Powell Slough built?

It was built in 1915, making it 110 years old in 2025. It was reconstructed in 1940.

What condition is SR 20 over Powell Slough in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in August 2023.

How much traffic does SR 20 over Powell Slough carry?

About 6,400 vehicles per day (2013 count).

How long is SR 20 over Powell Slough?

The structure is 59 ft (18 m) long with a longest span of 21 ft (6.4 m) and a deck 41 ft wide.

Who owns SR 20 over Powell Slough?

It is owned by the State Highway Agency.