US Bridges

ST Helena Road over Mark West Creek

Fair

Sonoma County, California · 1.1 MI E Calistoga RD · Structure no. 20C0268

Built
1976
49 years old
Condition
Fair
inspected October 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
103 ft
1 main span
Daily traffic
2,100
2015 count
Owner
County
County Highway Agency

About this bridge

ST Helena Road over Mark West Creek is a steel stringer/multi-beam or girder carrying ST Helena Road over Mark West Creek in Sonoma County, California. It was built in 1976, so it is 49 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 2,100 vehicles a day, roughly 1% of them trucks, projected to reach 2,406 by 2046. The structure is 103 ft (31.4 m) long and 26 ft wide. If it were closed, the detour would be 37.3 mi (60 km).

Location

Open in Google Maps
CarriesST Helena Road
CrossesMark West Creek
Location1.1 MI E Calistoga RD
RouteCounty Highway 0
CountySonoma County
StateCalifornia
Coordinates38.51379, -122.63637
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionOctober 2024
Inspection intervalevery 48 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation6: Equal to present minimum criteria
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 rating62.2 US tons
Inventory rating37.1 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+2 approach)
Design loadUnknown
Structure length103 ft (31.4 m)
Longest span60 ft (18.3 m)
Deck width26 ft (8 m)
Roadway width26 ft (7.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,100 (2015)
Projected traffic2,406 by 2046
Trucks1%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed37.3 mi (60 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 ST Helena Road over Mark West Creek built?

It was built in 1976, making it 49 years old in 2025.

What condition is ST Helena Road over Mark West 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 October 2024.

How much traffic does ST Helena Road over Mark West Creek carry?

About 2,100 vehicles per day (2015 count), of which roughly 1% are trucks.

How long is ST Helena Road over Mark West Creek?

The structure is 103 ft (31.4 m) long with a longest span of 60 ft (18.3 m) and a deck 26 ft wide.

Who owns ST Helena Road over Mark West Creek?

It is owned by the County Highway Agency.