US Bridges

Willis Flat Road over So.Fk.Payette River

Fair

Boise County, Idaho · 14 MI East of Lowman Id · Structure no. 040205000001201

Built
1959
66 years old
Condition
Fair
inspected September 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
128 ft
1 main span
Daily traffic
35
1990 count
Owner
Federal
U.S. Forest Service

About this bridge

Willis Flat Road over So.Fk.Payette River is a steel continuous stringer/multi-beam or girder carrying Willis Flat Road over So.Fk.Payette River in Boise County, Idaho. It was built in 1959, so it is 66 years old, older than the Idaho average of 45.3 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 6 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 35 vehicles a day, projected to reach 52 by 2045. The structure is 128 ft (39 m) long and 16 ft wide. If it were closed, the detour would be 98.2 mi (158 km).

Location

Open in Google Maps
CarriesWillis Flat Road
CrossesSo.Fk.Payette River
Location14 MI East of Lowman Id
RouteFederal Lands Road 25NB
CountyBoise County
StateIdaho
Coordinates44.11732, -115.40769
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure8 Very GoodNo problems noted.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionSeptember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation6: Equal to present minimum criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment3: Basically intolerable, requiring high priority of corrective action
Operating rating31.7 US tons
Inventory rating24.3 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckWood or timber
Main spans1 (+2 approach)
Design loadH 20
Structure length128 ft (39 m)
Longest span76 ft (23.2 m)
Deck width16 ft (4.9 m)
Roadway width15 ft (4.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic35 (1990)
Projected traffic52 by 2045
Trucks—
Lanes on structure1
Traffic directionOne-lane bridge for two-way traffic
CarriesHighway
CrossesWaterway
Detour if closed98.2 mi (158 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerU.S. Forest Service
Maintained byU.S. Forest Service
Historic statusHistorical significance not determinable at this time
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was Willis Flat Road over So.Fk.Payette River built?

It was built in 1959, making it 66 years old in 2025.

What condition is Willis Flat Road over So.Fk.Payette River 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 September 2023.

How much traffic does Willis Flat Road over So.Fk.Payette River carry?

About 35 vehicles per day (1990 count).

How long is Willis Flat Road over So.Fk.Payette River?

The structure is 128 ft (39 m) long with a longest span of 76 ft (23.2 m) and a deck 16 ft wide.

Who owns Willis Flat Road over So.Fk.Payette River?

It is owned by the U.S. Forest Service.