US Bridges

Trancas ST over Milliken Creek

Fair

Napa County, California · Just West of SR 121 · Structure no. 21C0051

Built
1908
117 years old
Condition
Fair
inspected May 2024
Type
Arch - Deck
Masonry
Length
169 ft
5 main spans
Daily traffic
3,000
2002 count
Owner
County
County Highway Agency

About this bridge

Trancas ST over Milliken Creek is a masonry arch - deck carrying Trancas ST over Milliken Creek in Napa County, California. It was built in 1908, so it is 117 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 3,000 vehicles a day, roughly 10% of them trucks, projected to reach 12,283 by 2044. The structure is 169 ft (51.5 m) long and 24 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
CarriesTrancas ST
CrossesMilliken Creek
LocationJust West of SR 121
RouteCounty Highway 0
CountyNapa County
StateCalifornia
Coordinates38.32512, -122.27496
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 protection5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
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 adequacy7: Better than present minimum criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating27.4 US tons
Inventory rating16.4 US tons

Structure

Structure typeArch - Deck
MaterialMasonry
DeckNot applicable
Main spans5
Design loadUnknown
Structure length169 ft (51.5 m)
Longest span40 ft (12.2 m)
Deck width24 ft (7.3 m)
Roadway width20 ft (6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,000 (2002)
Projected traffic12,283 by 2044
Trucks10%
Lanes on structure1
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
Detour if closed3.1 mi (5 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusListed on the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was Trancas ST over Milliken Creek built?

It was built in 1908, making it 117 years old in 2025.

What condition is Trancas ST over Milliken 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 2024.

How much traffic does Trancas ST over Milliken Creek carry?

About 3,000 vehicles per day (2002 count), of which roughly 10% are trucks.

How long is Trancas ST over Milliken Creek?

The structure is 169 ft (51.5 m) long with a longest span of 40 ft (12.2 m) and a deck 24 ft wide.

Who owns Trancas ST over Milliken Creek?

It is owned by the County Highway Agency.