US Bridges

Santa Rosa Avenue over Colgan Creek

Fair

Sonoma County, California · South of Colgan Avenue · Structure no. 20C0569

Built
1963
62 years old, rebuilt 1969
Condition
Fair
inspected June 2024
Type
Stringer/Multi-beam or Girder
Concrete
Length
20 ft
1 main span
Daily traffic
29,487
2019 count
Owner
City
City or Municipal Highway Agency

About this bridge

Santa Rosa Avenue over Colgan Creek is a concrete stringer/multi-beam or girder carrying Santa Rosa Avenue over Colgan Creek in Sonoma County, California. It was built in 1963 and reconstructed in 1969, so it is 62 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 29,487 vehicles a day, roughly 3% of them trucks, projected to reach 40,807 by 2044. The structure is 20 ft (6.1 m) long and 81 ft wide. If it were closed, the detour would be 0.6 mi (1 km).

Location

Open in Google Maps
CarriesSanta Rosa Avenue
CrossesColgan Creek
LocationSouth of Colgan Avenue
RouteCity Street 0
CountySonoma County
StateCalifornia
Coordinates38.42093, -122.71336
Functional classUrban 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.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJune 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
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 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 typeStringer/Multi-beam or Girder
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadUnknown
Structure length20 ft (6.1 m)
Longest span20 ft (6.1 m)
Deck width81 ft (24.7 m)
Roadway width72 ft (22 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic29,487 (2019)
Projected traffic40,807 by 2044
Trucks3%
Lanes on structure7
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed0.6 mi (1 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCity or Municipal Highway Agency
Maintained byCity or Municipal Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNot applicable (no waterway)

Frequently asked questions

When was Santa Rosa Avenue over Colgan Creek built?

It was built in 1963, making it 62 years old in 2025. It was reconstructed in 1969.

What condition is Santa Rosa Avenue over Colgan 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 June 2024.

How much traffic does Santa Rosa Avenue over Colgan Creek carry?

About 29,487 vehicles per day (2019 count), of which roughly 3% are trucks.

How long is Santa Rosa Avenue over Colgan Creek?

The structure is 20 ft (6.1 m) long with a longest span of 20 ft (6.1 m) and a deck 81 ft wide.

Who owns Santa Rosa Avenue over Colgan Creek?

It is owned by the City or Municipal Highway Agency.