US Bridges

State Route 1 over Lagunitas Creek

Poor

Marin County, California · 04-MRN-001-28.51 · Structure no. 27 0023

Built
1929
96 years old
Condition
Poor
inspected May 2024
Type
Truss - Thru
Steel
Length
152 ft
1 main span
Daily traffic
3,500
2020 count
Owner
State
State Highway Agency

About this bridge

State Route 1 over Lagunitas Creek is a steel truss - thru carrying State Route 1 over Lagunitas Creek in Marin County, California. It was built in 1929, so it is 96 years old, older than the California average of 54.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in poor condition with a lowest component rating of 4 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

It carries about 3,500 vehicles a day, roughly 2% of them trucks, projected to reach 4,699 by 2042. The structure is 152 ft (46.2 m) long and 29 ft wide. If it were closed, the detour would be 6.2 mi (10 km).

Location

Open in Google Maps
CarriesState Route 1
CrossesLagunitas Creek
Location04-MRN-001-28.51
RouteState Highway 1
CountyMarin County
StateCalifornia
Coordinates38.06457, -122.80511
Functional classRural Minor Arterial

Condition and inspection

Poor

The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure4 PoorAdvanced section loss, deterioration, spalling or scour.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionMay 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourUnknown foundation; not evaluated for scour
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating37.1 US tons
Inventory rating22.5 US tons

Structure

Structure typeTruss - Thru
MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+2 approach)
Design loadHS 15
Structure length152 ft (46.2 m)
Longest span102 ft (31 m)
Deck width29 ft (8.8 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,500 (2020)
Projected traffic4,699 by 2042
Trucks2%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed6.2 mi (10 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 proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$1.6 million (2017 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was State Route 1 over Lagunitas Creek built?

It was built in 1929, making it 96 years old in 2025.

What condition is State Route 1 over Lagunitas Creek in?

The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in May 2024.

How much traffic does State Route 1 over Lagunitas Creek carry?

About 3,500 vehicles per day (2020 count), of which roughly 2% are trucks.

How long is State Route 1 over Lagunitas Creek?

The structure is 152 ft (46.2 m) long with a longest span of 102 ft (31 m) and a deck 29 ft wide.

Who owns State Route 1 over Lagunitas Creek?

It is owned by the State Highway Agency.