US Bridges

State Route 1 over Tomasini Canyon

Fair

Marin County, California · 04-MRN-001-29.85 · Structure no. 27 0056

Built
1925
100 years old, rebuilt 1978
Condition
Fair
inspected May 2024
Type
Arch - Deck
Concrete
Length
25 ft
1 main span
Daily traffic
2,300
2020 count
Owner
State
State Highway Agency

About this bridge

State Route 1 over Tomasini Canyon is a concrete arch - deck carrying State Route 1 over Tomasini Canyon in Marin County, California. It was built in 1925 and reconstructed in 1978, so it is 100 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 2,300 vehicles a day, roughly 3% of them trucks, projected to reach 8,981 by 2045. The structure is 25 ft (7.6 m) long and 33 ft wide. If it were closed, the detour would be 29.8 mi (48 km).

Location

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CarriesState Route 1
CrossesTomasini Canyon
Location04-MRN-001-29.85
RouteState Highway 1
CountyMarin County
StateCalifornia
Coordinates38.07983, -122.80598
Functional classRural Minor Arterial

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
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 inspectionMay 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment3: Basically intolerable, requiring high priority of corrective action
Operating rating30 US tons
Inventory rating17.9 US tons

Structure

Structure typeArch - Deck
MaterialConcrete
DeckNot applicable
Main spans1
Design loadHS 15
Structure length25 ft (7.6 m)
Longest span16 ft (4.9 m)
Deck width33 ft (10 m)
Roadway width29 ft (8.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,300 (2020)
Projected traffic8,981 by 2045
Trucks3%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed29.8 mi (48 km)
TollOn a free road
National Highway SystemNo

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—
NavigationNo navigation control on waterway

Frequently asked questions

When was State Route 1 over Tomasini Canyon built?

It was built in 1925, making it 100 years old in 2025. It was reconstructed in 1978.

What condition is State Route 1 over Tomasini Canyon 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 1 over Tomasini Canyon carry?

About 2,300 vehicles per day (2020 count), of which roughly 3% are trucks.

How long is State Route 1 over Tomasini Canyon?

The structure is 25 ft (7.6 m) long with a longest span of 16 ft (4.9 m) and a deck 33 ft wide.

Who owns State Route 1 over Tomasini Canyon?

It is owned by the State Highway Agency.