US Bridges

State Route 37 over Petaluma River

Fair

Marin County, California · 04-MRN-037-14.47 · Structure no. 27 0013

Built
1958
67 years old
Condition
Fair
inspected May 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
2,183 ft
1 main span
Daily traffic
34,000
2020 count
Owner
State
State Highway Agency

About this bridge

State Route 37 over Petaluma River is a steel stringer/multi-beam or girder carrying State Route 37 over Petaluma River in Marin County, California. It was built in 1958, so it is 67 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 34,000 vehicles a day, roughly 4% of them trucks, projected to reach 55,074 by 2046. The structure is 2,183 ft (665.4 m) long and 67 ft wide. If it were closed, the detour would be 29.8 mi (48 km).

Location

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CarriesState Route 37
CrossesPetaluma River
Location04-MRN-037-14.47
RouteState Highway 37
CountyMarin County
StateCalifornia
Coordinates38.11418, -122.50721
Functional classUrban Principal Arterial - Other Freeway or Expressway

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.
Superstructure7 GoodSome minor problems.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionMay 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating72.1 US tons
Inventory rating35.7 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+28 approach)
Design loadHS 20
Structure length2,183 ft (665.4 m)
Longest span160 ft (48.8 m)
Deck width67 ft (20.5 m)
Roadway width60 ft (18.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic34,000 (2020)
Projected traffic55,074 by 2046
Trucks4%
Lanes on structure4
Traffic directionTwo-way traffic
CarriesHighway
CrossesHighway and waterway
Detour if closed29.8 mi (48 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was State Route 37 over Petaluma River built?

It was built in 1958, making it 67 years old in 2025.

What condition is State Route 37 over Petaluma River 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 May 2024.

How much traffic does State Route 37 over Petaluma River carry?

About 34,000 vehicles per day (2020 count), of which roughly 4% are trucks.

How long is State Route 37 over Petaluma River?

The structure is 2,183 ft (665.4 m) long with a longest span of 160 ft (48.8 m) and a deck 67 ft wide.

Who owns State Route 37 over Petaluma River?

It is owned by the State Highway Agency.