US Bridges

Madison St-Us 12 over Clark Fork River

Fair

Missoula County, Montana · Missoula-Madison ST · Structure no. P00007095+00581

Built
1958
67 years old, rebuilt 2017
Condition
Fair
inspected June 2024
Type
Girder and Floorbeam System
Steel Continuous
Length
552 ft
3 main spans
Daily traffic
18,393
2023 count
Owner
State
State Highway Agency

About this bridge

Madison St-Us 12 over Clark Fork River is a steel continuous girder and floorbeam system carrying Madison St-Us 12 over Clark Fork River in Missoula County, Montana. It was built in 1958 and reconstructed in 2017, so it is 67 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 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 18,393 vehicles a day, projected to reach 19,313 by 2043. The structure is 552 ft (168.2 m) long and 69 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
CarriesMadison St-Us 12
CrossesClark Fork River
LocationMissoula-Madison ST
RouteU.S. Route 12
CountyMissoula County
StateMontana
Coordinates46.86696, -113.98786
Functional classUrban Other Principal 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
Deck7 GoodSome minor problems.
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 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 geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating42 US tons
Inventory rating25 US tons

Structure

Structure typeGirder and Floorbeam System
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3 (+2 approach)
Design loadHS 20
Structure length552 ft (168.2 m)
Longest span150 ft (45.7 m)
Deck width69 ft (20.9 m)
Roadway width54 ft (16.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic18,393 (2023)
Projected traffic19,313 by 2043
Trucks0%
Lanes on structure4
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed1.9 mi (3 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$4.7 million
NavigationNo navigation control on waterway

Frequently asked questions

When was Madison St-Us 12 over Clark Fork River built?

It was built in 1958, making it 67 years old in 2025. It was reconstructed in 2017.

What condition is Madison St-Us 12 over Clark Fork River 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 Madison St-Us 12 over Clark Fork River carry?

About 18,393 vehicles per day (2023 count).

How long is Madison St-Us 12 over Clark Fork River?

The structure is 552 ft (168.2 m) long with a longest span of 150 ft (45.7 m) and a deck 69 ft wide.

Who owns Madison St-Us 12 over Clark Fork River?

It is owned by the State Highway Agency.