US Bridges

Nelson Ave over Thermalito Forebay

Fair

Butte County, California · 2.1 MI W/O ST HWY 70 · Structure no. 12C0260

Built
1968
57 years old
Condition
Fair
inspected March 2025
Type
Tee Beam
Concrete Continuous
Length
430 ft
6 main spans
Daily traffic
860
2019 count
Owner
State
Other State Agency

About this bridge

Nelson Ave over Thermalito Forebay is a concrete continuous tee beam carrying Nelson Ave over Thermalito Forebay in Butte County, California. It was built in 1968, so it is 57 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 860 vehicles a day, roughly 2% of them trucks, projected to reach 1,526 by 2047. The structure is 430 ft (131.1 m) long and 37 ft wide. If it were closed, the detour would be 9.9 mi (16 km).

Location

Open in Google Maps
CarriesNelson Ave
CrossesThermalito Forebay
Location2.1 MI W/O ST HWY 70
RouteCounty Highway 0
CountyButte County
StateCalifornia
Coordinates39.52484, -121.61228
Functional classRural Major Collector

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure7 GoodSome minor problems.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection9 ExcellentNo problems noted.
Last inspectionMarch 2025
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
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 adequacy9: Superior to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating45 US tons
Inventory rating31.7 US tons

Structure

Structure typeTee Beam
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans6
Design loadHS 20
Structure length430 ft (131.1 m)
Longest span78 ft (23.8 m)
Deck width37 ft (11.2 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic860 (2019)
Projected traffic1,526 by 2047
Trucks2%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed9.9 mi (16 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerOther State 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 Nelson Ave over Thermalito Forebay built?

It was built in 1968, making it 57 years old in 2025.

What condition is Nelson Ave over Thermalito Forebay 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 March 2025.

How much traffic does Nelson Ave over Thermalito Forebay carry?

About 860 vehicles per day (2019 count), of which roughly 2% are trucks.

How long is Nelson Ave over Thermalito Forebay?

The structure is 430 ft (131.1 m) long with a longest span of 78 ft (23.8 m) and a deck 37 ft wide.

Who owns Nelson Ave over Thermalito Forebay?

It is owned by the Other State Agency and maintained by the County Highway Agency.