US Bridges

State Route 121 over Tolay Creek

Good

Sonoma County, California · 04-SON-121-1.53 · Structure no. 20 0020

Built
1996
29 years old
Condition
Good
inspected October 2022
Type
Slab
Concrete Continuous
Length
71 ft
2 main spans
Daily traffic
16,150
2009 count
Owner
State
State Highway Agency

About this bridge

State Route 121 over Tolay Creek is a concrete continuous slab carrying State Route 121 over Tolay Creek in Sonoma County, California. It was built in 1996, so it is 29 years old, younger than the California average of 54.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 16,150 vehicles a day, roughly 8% of them trucks, projected to reach 22,978 by 2039. The structure is 71 ft (21.7 m) long and 44 ft wide. If it were closed, the detour would be 34.8 mi (56 km).

Location

Open in Google Maps
CarriesState Route 121
CrossesTolay Creek
Location04-SON-121-1.53
RouteState Highway 121
CountySonoma County
StateCalifornia
Coordinates38.16996, -122.45736
Functional classRural Minor Arterial

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection9 ExcellentNo problems noted.
Last inspectionOctober 2022
Inspection intervalevery 48 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation7: Better than present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating59.6 US tons
Inventory rating35.7 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20 + Mod
Structure length71 ft (21.7 m)
Longest span35 ft (10.8 m)
Deck width44 ft (13.3 m)
Roadway width40 ft (12.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic16,150 (2009)
Projected traffic22,978 by 2039
Trucks8%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed34.8 mi (56 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 121 over Tolay Creek built?

It was built in 1996, making it 29 years old in 2025.

What condition is State Route 121 over Tolay Creek in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in October 2022.

How much traffic does State Route 121 over Tolay Creek carry?

About 16,150 vehicles per day (2009 count), of which roughly 8% are trucks.

How long is State Route 121 over Tolay Creek?

The structure is 71 ft (21.7 m) long with a longest span of 35 ft (10.8 m) and a deck 44 ft wide.

Who owns State Route 121 over Tolay Creek?

It is owned by the State Highway Agency.