US Bridges

SH 21 over S.Fk.Payette R;lowman Br

Fair

Boise County, Idaho · At Lowman · Structure no. 000000000012885

Built
1948
77 years old
Condition
Fair
inspected October 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
245 ft
6 main spans
Daily traffic
410
2023 count
Owner
State
State Highway Agency

About this bridge

SH 21 over S.Fk.Payette R;lowman Br is a steel stringer/multi-beam or girder carrying SH 21 over S.Fk.Payette R;lowman Br in Boise County, Idaho. It was built in 1948, so it is 77 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 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 410 vehicles a day, roughly 17% of them trucks, projected to reach 615 by 2042. The structure is 245 ft (74.7 m) long and 34 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

Open in Google Maps
CarriesSH 21
CrossesS.Fk.Payette R;lowman Br
LocationAt Lowman
RouteState Highway 21
CountyBoise County
StateIdaho
Coordinates44.08083, -115.61912
Functional classRural Minor Arterial

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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection7 GoodSome minor problems.
Last inspectionOctober 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry6: Equal to present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating40 US tons
Inventory rating24 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans6
Design loadHS 15
Structure length245 ft (74.7 m)
Longest span59 ft (17.9 m)
Deck width34 ft (10.4 m)
Roadway width31 ft (9.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic410 (2023)
Projected traffic615 by 2042
Trucks17%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed98.8 mi (159 km)
TollOn a free road
National Highway SystemNo

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$2.9 million (2020 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SH 21 over S.Fk.Payette R;lowman Br built?

It was built in 1948, making it 77 years old in 2025.

What condition is SH 21 over S.Fk.Payette R;lowman Br 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 October 2024.

How much traffic does SH 21 over S.Fk.Payette R;lowman Br carry?

About 410 vehicles per day (2023 count), of which roughly 17% are trucks.

How long is SH 21 over S.Fk.Payette R;lowman Br?

The structure is 245 ft (74.7 m) long with a longest span of 59 ft (17.9 m) and a deck 34 ft wide.

Who owns SH 21 over S.Fk.Payette R;lowman Br?

It is owned by the State Highway Agency.