US Bridges

SH 21 over Five Mile Creek

Fair

Boise County, Idaho · 8.0 E. Lowman · Structure no. 000000000012893

Built
2011
14 years old
Condition
Fair
inspected October 2022
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
128 ft
1 main span
Daily traffic
1,200
2023 count
Owner
State
State Highway Agency

About this bridge

SH 21 over Five Mile Creek is a prestressed concrete stringer/multi-beam or girder carrying SH 21 over Five Mile Creek in Boise County, Idaho. It was built in 2011, so it is 14 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 1,200 vehicles a day, roughly 9% of them trucks, projected to reach 1,800 by 2042. The structure is 128 ft (39 m) long and 36 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

Open in Google Maps
CarriesSH 21
CrossesFive Mile Creek
Location8.0 E. Lowman
RouteState Highway 21
CountyBoise County
StateIdaho
Coordinates44.10069, -115.45644
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.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection9 ExcellentNo problems noted.
Last inspectionOctober 2022
Inspection intervalevery 48 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating58.2 US tons
Inventory rating46.7 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans1
Design loadHL 93
Structure length128 ft (39 m)
Longest span125 ft (38.1 m)
Deck width36 ft (10.9 m)
Roadway width32 ft (9.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,200 (2023)
Projected traffic1,800 by 2042
Trucks9%
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 proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was SH 21 over Five Mile Creek built?

It was built in 2011, making it 14 years old in 2025.

What condition is SH 21 over Five Mile Creek 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 2022.

How much traffic does SH 21 over Five Mile Creek carry?

About 1,200 vehicles per day (2023 count), of which roughly 9% are trucks.

How long is SH 21 over Five Mile Creek?

The structure is 128 ft (39 m) long with a longest span of 125 ft (38.1 m) and a deck 36 ft wide.

Who owns SH 21 over Five Mile Creek?

It is owned by the State Highway Agency.