US Bridges

King Ridge RD over Big Austin Creek

Fair

Sonoma County, California · 2.3 MI N Fort Ross RD · Structure no. 20C0433

Built
1965
60 years old
Condition
Fair
inspected June 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
124 ft
3 main spans
Daily traffic
200
2015 count
Owner
County
County Highway Agency

About this bridge

King Ridge RD over Big Austin Creek is a steel stringer/multi-beam or girder carrying King Ridge RD over Big Austin Creek in Sonoma County, California. It was built in 1965, so it is 60 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 200 vehicles a day, roughly 4% of them trucks, projected to reach 298 by 2046. The structure is 124 ft (37.8 m) long and 17 ft wide. If it were closed, the detour would be 29.8 mi (48 km).

Location

Open in Google Maps
CarriesKing Ridge RD
CrossesBig Austin Creek
Location2.3 MI N Fort Ross RD
RouteCounty Highway 0
CountySonoma County
StateCalifornia
Coordinates38.56104, -123.10214
Functional classRural Local

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.
Substructure7 GoodSome minor problems.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJune 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
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 adequacy7: Better than present minimum criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating72.1 US tons
Inventory rating43.2 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans3
Design loadUnknown
Structure length124 ft (37.8 m)
Longest span50 ft (15.2 m)
Deck width17 ft (5.1 m)
Roadway width16 ft (4.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic200 (2015)
Projected traffic298 by 2046
Trucks4%
Lanes on structure1
Traffic directionOne-lane bridge for two-way traffic
CarriesHighway
CrossesWaterway
Detour if closed29.8 mi (48 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty 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 King Ridge RD over Big Austin Creek built?

It was built in 1965, making it 60 years old in 2025.

What condition is King Ridge RD over Big Austin 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 King Ridge RD over Big Austin Creek carry?

About 200 vehicles per day (2015 count), of which roughly 4% are trucks.

How long is King Ridge RD over Big Austin Creek?

The structure is 124 ft (37.8 m) long with a longest span of 50 ft (15.2 m) and a deck 17 ft wide.

Who owns King Ridge RD over Big Austin Creek?

It is owned by the County Highway Agency.