US Bridges

S 324 over Horse Prairie Creek

Fair

Beaverhead County, Montana · 8M E Grant · Structure no. S00324004+05001

Built
1963
62 years old
Condition
Fair
inspected November 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
92 ft
3 main spans
Daily traffic
241
2023 count
Owner
State
State Highway Agency

About this bridge

S 324 over Horse Prairie Creek is a prestressed concrete stringer/multi-beam or girder carrying S 324 over Horse Prairie Creek in Beaverhead County, Montana. It was built in 1963, so it is 62 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 241 vehicles a day, roughly 2% of them trucks, projected to reach 253 by 2043. The structure is 92 ft (28 m) long and 31 ft wide. If it were closed, the detour would be 16.2 mi (26 km).

Location

Open in Google Maps
CarriesS 324
CrossesHorse Prairie Creek
Location8M E Grant
RouteState Highway 324
CountyBeaverhead County
StateMontana
Coordinates44.97543, -112.92205
Functional classRural Major Collector

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.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionNovember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation6: Equal to present minimum criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating54 US tons
Inventory rating32 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 15
Structure length92 ft (28 m)
Longest span30 ft (9.1 m)
Deck width31 ft (9.5 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic241 (2023)
Projected traffic253 by 2043
Trucks2%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed16.2 mi (26 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 324 over Horse Prairie Creek built?

It was built in 1963, making it 62 years old in 2025.

What condition is S 324 over Horse Prairie 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 November 2023.

How much traffic does S 324 over Horse Prairie Creek carry?

About 241 vehicles per day (2023 count), of which roughly 2% are trucks.

How long is S 324 over Horse Prairie Creek?

The structure is 92 ft (28 m) long with a longest span of 30 ft (9.1 m) and a deck 31 ft wide.

Who owns S 324 over Horse Prairie Creek?

It is owned by the State Highway Agency.