US Bridges

S 117 over Milk River

Fair

Valley County, Montana · 1M S Nashua · Structure no. P00017011+00781

Built
1957
68 years old
Condition
Fair
inspected May 2023
Type
Girder and Floorbeam System
Steel Continuous
Length
370 ft
3 main spans
Daily traffic
479
2023 count
Owner
State
State Highway Agency

About this bridge

S 117 over Milk River is a steel continuous girder and floorbeam system carrying S 117 over Milk River in Valley County, Montana. It was built in 1957, so it is 68 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 479 vehicles a day, roughly 2% of them trucks, projected to reach 503 by 2043. The structure is 370 ft (112.7 m) long and 27 ft wide. If it were closed, the detour would be 39.8 mi (64 km).

Location

Open in Google Maps
CarriesS 117
CrossesMilk River
Location1M S Nashua
RouteState Highway 117
CountyValley County
StateMontana
Coordinates48.12014, -106.37967
Functional classRural Minor 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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionMay 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating18 US tons
Inventory rating14 US tons

Structure

Structure typeGirder and Floorbeam System
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3 (+2 approach)
Design loadHS 15
Structure length370 ft (112.7 m)
Longest span125 ft (38.1 m)
Deck width27 ft (8.1 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic479 (2023)
Projected traffic503 by 2043
Trucks2%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed39.8 mi (64 km)
TollOn a free road
National Highway SystemNo

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 S 117 over Milk River built?

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

What condition is S 117 over Milk 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 May 2023.

How much traffic does S 117 over Milk River carry?

About 479 vehicles per day (2023 count), of which roughly 2% are trucks.

How long is S 117 over Milk River?

The structure is 370 ft (112.7 m) long with a longest span of 125 ft (38.1 m) and a deck 27 ft wide.

Who owns S 117 over Milk River?

It is owned by the State Highway Agency.