US Bridges

Oak Knoll Ave over Napa River Overflow

GoodPosted for load

Napa County, California · 0.35 MI SW Slvrdo Trail · Structure no. 21C0068

Built
1930
95 years old
Condition
Good
inspected May 2023
Type
Tee Beam
Concrete Continuous
Length
40 ft
2 main spans
Daily traffic
2,600
2005 count
Owner
County
County Highway Agency

About this bridge

Oak Knoll Ave over Napa River Overflow is a concrete continuous tee beam carrying Oak Knoll Ave over Napa River Overflow in Napa County, California. It was built in 1930, so it is 95 years old, older 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. Its operating status is: posted for load restriction.

It carries about 2,600 vehicles a day, roughly 10% of them trucks, projected to reach 3,965 by 2040. The structure is 40 ft (12.2 m) long and 24 ft wide. If it were closed, the detour would be 6.2 mi (10 km).

CarriesOak Knoll Ave
CrossesNapa River Overflow
Location0.35 MI SW Slvrdo Trail
RouteCounty Highway 0
Coordinates38.36796, -122.30397
Functional classRural Major Collector

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 protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionMay 2023
Inspection intervalevery 24 months
Operating statusPosted for load restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation7: Better than present minimum criteria
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment3: Basically intolerable, requiring high priority of corrective action
Operating rating58.5 US tons
Inventory rating35.1 US tons

Structure

Structure typeTee Beam
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans2
Design loadUnknown
Structure length40 ft (12.2 m)
Longest span19 ft (5.8 m)
Deck width24 ft (7.3 m)
Roadway width21 ft (6.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,600 (2005)
Projected traffic3,965 by 2040
Trucks10%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed6.2 mi (10 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—
NavigationNo navigation control on waterway

Frequently asked questions

When was Oak Knoll Ave over Napa River Overflow built?

It was built in 1930, making it 95 years old in 2025.

What condition is Oak Knoll Ave over Napa River Overflow 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 May 2023.

How much traffic does Oak Knoll Ave over Napa River Overflow carry?

About 2,600 vehicles per day (2005 count), of which roughly 10% are trucks.

How long is Oak Knoll Ave over Napa River Overflow?

The structure is 40 ft (12.2 m) long with a longest span of 19 ft (5.8 m) and a deck 24 ft wide.

Who owns Oak Knoll Ave over Napa River Overflow?

It is owned by the County Highway Agency.