US Bridges

Road 20N24 over Ponderosa Spillway

Good

Butte County, California · Ponderosa Reservoir · Structure no. 051153000001034

Built
1960
65 years old, rebuilt 2000
Condition
Good
inspected September 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
105 ft
2 main spans
Daily traffic
50
Owner
Federal
U.S. Forest Service

About this bridge

Road 20N24 over Ponderosa Spillway is a steel stringer/multi-beam or girder carrying Road 20N24 over Ponderosa Spillway in Butte County, California. It was built in 1960 and reconstructed in 2000, so it is 65 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.

It carries about 50 vehicles a day, projected to reach 75 by 2045. The structure is 105 ft (31.9 m) long and 20 ft wide. If it were closed, the detour would be 620.7 mi (999 km).

Location

Open in Google Maps
CarriesRoad 20N24
CrossesPonderosa Spillway
LocationPonderosa Reservoir
RouteFederal Lands Road 20N24
CountyButte County
StateCalifornia
Coordinates39.54976, -121.30368
Functional classRural Local

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.
Last inspectionSeptember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation*: *
Deck geometry3: Basically intolerable, requiring high priority of corrective action
Approach roadway alignment5: Somewhat better than minimum adequacy to tolerate being left in place as is
Operating rating—
Inventory rating—

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans2
Design loadUnknown
Structure length105 ft (31.9 m)
Longest span51 ft (15.6 m)
Deck width20 ft (6.1 m)
Roadway width17 ft (5.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic50 (—)
Projected traffic75 by 2045
Trucks—
Lanes on structure1
Traffic directionOne-lane bridge for two-way traffic
CarriesHighway
CrossesWaterway
Detour if closed620.7 mi (999 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerU.S. Forest Service
Maintained byPrivate (other than railroad)
Historic statusHistorical significance not determinable at this time
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was Road 20N24 over Ponderosa Spillway built?

It was built in 1960, making it 65 years old in 2025. It was reconstructed in 2000.

What condition is Road 20N24 over Ponderosa Spillway 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 September 2024.

How much traffic does Road 20N24 over Ponderosa Spillway carry?

About 50 vehicles per day (latest count).

How long is Road 20N24 over Ponderosa Spillway?

The structure is 105 ft (31.9 m) long with a longest span of 51 ft (15.6 m) and a deck 20 ft wide.

Who owns Road 20N24 over Ponderosa Spillway?

It is owned by the U.S. Forest Service and maintained by the Private (other than railroad).