US Bridges

US 12 over Little Blackfoot Riv-Rr

Fair

Powell County, Montana · 5M E Garrison · Structure no. P00008006+02301

Built
2009
16 years old
Condition
Fair
inspected December 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
745 ft
6 main spans
Daily traffic
3,217
2023 count
Owner
State
State Highway Agency

About this bridge

US 12 over Little Blackfoot Riv-Rr is a prestressed concrete stringer/multi-beam or girder carrying US 12 over Little Blackfoot Riv-Rr in Powell County, Montana. It was built in 2009, so it is 16 years old, younger than the Montana average of 47 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 3,217 vehicles a day, roughly 8% of them trucks, projected to reach 3,394 by 2043. The structure is 745 ft (227.1 m) long and 41 ft wide. If it were closed, the detour would be 123.7 mi (199 km).

Location

Open in Google Maps
CarriesUS 12
CrossesLittle Blackfoot Riv-Rr
Location5M E Garrison
RouteU.S. Route 12
CountyPowell County
StateMontana
Coordinates46.54852, -112.67818
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.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionDecember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than 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 alignment6: Equal to present minimum criteria
Operating rating75.9 US tons
Inventory rating46 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans6
Design loadHL 93
Structure length745 ft (227.1 m)
Longest span131 ft (40 m)
Deck width41 ft (12.6 m)
Roadway width39 ft (11.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,217 (2023)
Projected traffic3,394 by 2043
Trucks8%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesHighway, waterway and railroad
Detour if closed123.7 mi (199 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$1.2 million
NavigationNo navigation control on waterway

Frequently asked questions

When was US 12 over Little Blackfoot Riv-Rr built?

It was built in 2009, making it 16 years old in 2025.

What condition is US 12 over Little Blackfoot Riv-Rr 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 December 2024.

How much traffic does US 12 over Little Blackfoot Riv-Rr carry?

About 3,217 vehicles per day (2023 count), of which roughly 8% are trucks.

How long is US 12 over Little Blackfoot Riv-Rr?

The structure is 745 ft (227.1 m) long with a longest span of 131 ft (40 m) and a deck 41 ft wide.

Who owns US 12 over Little Blackfoot Riv-Rr?

It is owned by the State Highway Agency.