US Bridges

SH 55 over N.Fk.Payette River

Fair

Boise County, Idaho · 3.1 N. Banks · Structure no. 000000000014800

Built
1984
41 years old
Condition
Fair
inspected May 2024
Type
Stringer/Multi-beam or Girder
Concrete Continuous
Length
287 ft
3 main spans
Daily traffic
4,700
2023 count
Owner
State
State Highway Agency

About this bridge

SH 55 over N.Fk.Payette River is a concrete continuous stringer/multi-beam or girder carrying SH 55 over N.Fk.Payette River in Boise County, Idaho. It was built in 1984, so it is 41 years old, younger 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 4,700 vehicles a day, roughly 15% of them trucks, projected to reach 7,050 by 2042. The structure is 287 ft (87.5 m) long and 40 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

Open in Google Maps
CarriesSH 55
CrossesN.Fk.Payette River
Location3.1 N. Banks
RouteState Highway 55
CountyBoise County
StateIdaho
Coordinates44.1146, -116.10598
Functional classRural Principal Arterial - Other

Condition and inspection

Fair

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

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionMay 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating75.9 US tons
Inventory rating38 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 25 or greater
Structure length287 ft (87.5 m)
Longest span101 ft (30.8 m)
Deck width40 ft (12.2 m)
Roadway width37 ft (11.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,700 (2023)
Projected traffic7,050 by 2042
Trucks15%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed98.8 mi (159 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$3.9 million (2020 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SH 55 over N.Fk.Payette River built?

It was built in 1984, making it 41 years old in 2025.

What condition is SH 55 over N.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 May 2024.

How much traffic does SH 55 over N.Fk.Payette River carry?

About 4,700 vehicles per day (2023 count), of which roughly 15% are trucks.

How long is SH 55 over N.Fk.Payette River?

The structure is 287 ft (87.5 m) long with a longest span of 101 ft (30.8 m) and a deck 40 ft wide.

Who owns SH 55 over N.Fk.Payette River?

It is owned by the State Highway Agency.