US Bridges

US 12 over Imnamatnoon Creek

Fair

Idaho County, Idaho · 15 W. Ida-Mont Line · Structure no. 000000000010510

Built
1957
68 years old, rebuilt 1999
Condition
Fair
inspected July 2023
Type
Stringer/Multi-beam or Girder
Concrete
Length
94 ft
3 main spans
Daily traffic
550
2023 count
Owner
State
State Highway Agency

About this bridge

US 12 over Imnamatnoon Creek is a concrete stringer/multi-beam or girder carrying US 12 over Imnamatnoon Creek in Idaho County, Idaho. It was built in 1957 and reconstructed in 1999, so it is 68 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 550 vehicles a day, roughly 31% of them trucks, projected to reach 825 by 2042. The structure is 94 ft (28.7 m) long and 31 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

Open in Google Maps
CarriesUS 12
CrossesImnamatnoon Creek
Location15 W. Ida-Mont Line
RouteU.S. Route 12
CountyIdaho County
StateIdaho
Coordinates46.51153, -114.76192
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
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 protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourUnknown foundation; not evaluated for scour
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
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 rating89.9 US tons
Inventory rating54 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialConcrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length94 ft (28.7 m)
Longest span31 ft (9.4 m)
Deck width31 ft (9.3 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic550 (2023)
Projected traffic825 by 2042
Trucks31%
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$1.3 million (2023 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was US 12 over Imnamatnoon Creek built?

It was built in 1957, making it 68 years old in 2025. It was reconstructed in 1999.

What condition is US 12 over Imnamatnoon 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 July 2023.

How much traffic does US 12 over Imnamatnoon Creek carry?

About 550 vehicles per day (2023 count), of which roughly 31% are trucks.

How long is US 12 over Imnamatnoon Creek?

The structure is 94 ft (28.7 m) long with a longest span of 31 ft (9.4 m) and a deck 31 ft wide.

Who owns US 12 over Imnamatnoon Creek?

It is owned by the State Highway Agency.