US Bridges

Mill Creek RD over Mill Creek

Fair

Sonoma County, California · 5.5 MI W of Westside RD · Structure no. 20C0345

Built
1961
64 years old
Condition
Fair
inspected May 2023
Type
Slab
Concrete Continuous
Length
63 ft
3 main spans
Daily traffic
210
2015 count
Owner
County
County Highway Agency

About this bridge

Mill Creek RD over Mill Creek is a concrete continuous slab carrying Mill Creek RD over Mill Creek in Sonoma County, California. It was built in 1961, so it is 64 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 210 vehicles a day, roughly 1% of them trucks, projected to reach 274 by 2040. The structure is 63 ft (19.2 m) long and 25 ft wide. If it were closed, the detour would be 123.7 mi (199 km).

CarriesMill Creek RD
CrossesMill Creek
Location5.5 MI W of Westside RD
RouteCounty Highway 0
Coordinates38.596, -122.96532
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
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionMay 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating54.7 US tons
Inventory rating32.8 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadUnknown
Structure length63 ft (19.2 m)
Longest span24 ft (7.3 m)
Deck width25 ft (7.5 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic210 (2015)
Projected traffic274 by 2040
Trucks1%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed123.7 mi (199 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 Mill Creek RD over Mill Creek built?

It was built in 1961, making it 64 years old in 2025.

What condition is Mill Creek RD over Mill 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 May 2023.

How much traffic does Mill Creek RD over Mill Creek carry?

About 210 vehicles per day (2015 count), of which roughly 1% are trucks.

How long is Mill Creek RD over Mill Creek?

The structure is 63 ft (19.2 m) long with a longest span of 24 ft (7.3 m) and a deck 25 ft wide.

Who owns Mill Creek RD over Mill Creek?

It is owned by the County Highway Agency.