US Bridges

Corby Ave over Colgan Creek

Fair

Sonoma County, California · 0.1 Mile South of Hearn · Structure no. 20C0190

Built
1930
95 years old
Condition
Fair
inspected June 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
32 ft
1 main span
Daily traffic
3,000
2019 count
Owner
City
City or Municipal Highway Agency

About this bridge

Corby Ave over Colgan Creek is a steel stringer/multi-beam or girder carrying Corby Ave over Colgan Creek in Sonoma County, California. It was built in 1930, so it is 95 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 3,000 vehicles a day, roughly 2% of them trucks, projected to reach 5,308 by 2045. The structure is 32 ft (9.8 m) long and 26 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesCorby Ave
CrossesColgan Creek
Location0.1 Mile South of Hearn
RouteCounty Highway 0
CountySonoma County
StateCalifornia
Coordinates38.42033, -122.71732
Functional classUrban Collector

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.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
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 adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating35.4 US tons
Inventory rating21.1 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadUnknown
Structure length32 ft (9.8 m)
Longest span28 ft (8.5 m)
Deck width26 ft (7.9 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,000 (2019)
Projected traffic5,308 by 2045
Trucks2%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.2 mi (2 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—
NavigationNo navigation control on waterway

Frequently asked questions

When was Corby Ave over Colgan Creek built?

It was built in 1930, making it 95 years old in 2025.

What condition is Corby Ave 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 Corby Ave over Colgan Creek carry?

About 3,000 vehicles per day (2019 count), of which roughly 2% are trucks.

How long is Corby Ave over Colgan Creek?

The structure is 32 ft (9.8 m) long with a longest span of 28 ft (8.5 m) and a deck 26 ft wide.

Who owns Corby Ave over Colgan Creek?

It is owned by the City or Municipal Highway Agency.