US Bridges

I 15 over Missouri River-Local

Fair

Cascade County, Montana · 7M N Craig · Structure no. I00015241+08671

Built
1971
54 years old
Condition
Fair
inspected June 2024
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
792 ft
5 main spans
Daily traffic
2,201
2023 count
Owner
State
State Highway Agency

About this bridge

I 15 over Missouri River-Local is a steel continuous stringer/multi-beam or girder carrying I 15 over Missouri River-Local in Cascade County, Montana. It was built in 1971, so it is 54 years old, older 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 2,201 vehicles a day, roughly 16% of them trucks, projected to reach 2,343 by 2043. The structure is 792 ft (241.3 m) long and 40 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesI 15
CrossesMissouri River-Local
Location7M N Craig
RouteInterstate 15
CountyCascade County
StateMontana
Coordinates47.1387, -111.86131
Functional classRural Principal Arterial - Interstate

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionJune 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry6: Equal to present minimum criteria
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating32 US tons
Inventory rating24 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans5 (+2 approach)
Design loadHS 20
Structure length792 ft (241.3 m)
Longest span143 ft (43.6 m)
Deck width40 ft (12.1 m)
Roadway width39 ft (11.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,201 (2023)
Projected traffic2,343 by 2043
Trucks16%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway, waterway and railroad
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkInterstate STRAHNET route

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was I 15 over Missouri River-Local built?

It was built in 1971, making it 54 years old in 2025.

What condition is I 15 over Missouri River-Local 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 June 2024.

How much traffic does I 15 over Missouri River-Local carry?

About 2,201 vehicles per day (2023 count), of which roughly 16% are trucks.

How long is I 15 over Missouri River-Local?

The structure is 792 ft (241.3 m) long with a longest span of 143 ft (43.6 m) and a deck 40 ft wide.

Who owns I 15 over Missouri River-Local?

It is owned by the State Highway Agency.