US Bridges

Westside Road over Hillside

Fair

Sonoma County, California · 0.3 MI N/O River RD · Structure no. 20C0548

Built
1987
38 years old
Condition
Fair
inspected October 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
79 ft
4 main spans
Daily traffic
300
2015 count
Owner
County
County Highway Agency

About this bridge

Westside Road over Hillside is a steel continuous stringer/multi-beam or girder carrying Westside Road over Hillside in Sonoma County, California. It was built in 1987, so it is 38 years old, younger 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 6 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 300 vehicles a day, roughly 2% of them trucks, projected to reach 845 by 2040. The structure is 79 ft (24 m) long and 8 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
CarriesWestside Road
CrossesHillside
Location0.3 MI N/O River RD
RouteCounty Highway 0
CountySonoma County
StateCalifornia
Coordinates38.51052, -122.92626
Functional classRural Major 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
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionOctober 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating53.6 US tons
Inventory rating32.2 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckCorrugated steel
Main spans4
Design loadUnknown
Structure length79 ft (24 m)
Longest span20 ft (6 m)
Deck width8 ft (2.5 m)
Roadway width25 ft (7.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic300 (2015)
Projected traffic845 by 2040
Trucks2%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesOther
Detour if closed3.1 mi (5 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 Westside Road over Hillside built?

It was built in 1987, making it 38 years old in 2025.

What condition is Westside Road over Hillside 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 October 2023.

How much traffic does Westside Road over Hillside carry?

About 300 vehicles per day (2015 count), of which roughly 2% are trucks.

How long is Westside Road over Hillside?

The structure is 79 ft (24 m) long with a longest span of 20 ft (6 m) and a deck 8 ft wide.

Who owns Westside Road over Hillside?

It is owned by the County Highway Agency.