US Bridges

SH 21 over Canyon Creek

Good

Boise County, Idaho · 25 Ne. Lowman · Structure no. 000000000012925

Built
1964
61 years old
Condition
Good
inspected October 2024
Type
Tee Beam
Concrete Continuous
Length
120 ft
3 main spans
Daily traffic
620
2023 count
Owner
State
State Highway Agency

About this bridge

SH 21 over Canyon Creek is a concrete continuous tee beam carrying SH 21 over Canyon Creek in Boise County, Idaho. It was built in 1964, so it is 61 years old, older than the Idaho average of 45.3 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 620 vehicles a day, roughly 22% of them trucks, projected to reach 930 by 2042. The structure is 120 ft (36.6 m) long and 31 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

CarriesSH 21
CrossesCanyon Creek
Location25 Ne. Lowman
RouteState Highway 21
StateIdaho
Coordinates44.20481, -115.24743
Functional classRural Minor Arterial

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.
Superstructure8 Very GoodNo problems noted.
Substructure8 Very GoodNo problems noted.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionOctober 2024
Inspection intervalevery 24 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 adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating50 US tons
Inventory rating29 US tons

Structure

Structure typeTee Beam
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length120 ft (36.6 m)
Longest span75 ft (22.9 m)
Deck width31 ft (9.4 m)
Roadway width28 ft (8.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic620 (2023)
Projected traffic930 by 2042
Trucks22%
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 Canyon Creek built?

It was built in 1964, making it 61 years old in 2025.

What condition is SH 21 over Canyon Creek 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 October 2024.

How much traffic does SH 21 over Canyon Creek carry?

About 620 vehicles per day (2023 count), of which roughly 22% are trucks.

How long is SH 21 over Canyon Creek?

The structure is 120 ft (36.6 m) long with a longest span of 75 ft (22.9 m) and a deck 31 ft wide.

Who owns SH 21 over Canyon Creek?

It is owned by the State Highway Agency.