US Bridges

S 324 over Clark Canyon Dam Splwy

Fair

Beaverhead County, Montana · Clark Canyon Dam · Structure no. S00324001+00001

Built
1962
63 years old
Condition
Fair
inspected July 2023
Type
Tee Beam
Concrete
Length
73 ft
2 main spans
Daily traffic
396
2023 count
Owner
State
State Highway Agency

About this bridge

S 324 over Clark Canyon Dam Splwy is a concrete tee beam carrying S 324 over Clark Canyon Dam Splwy in Beaverhead County, Montana. It was built in 1962, so it is 63 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 396 vehicles a day, roughly 1% of them trucks, projected to reach 416 by 2043. The structure is 73 ft (22.1 m) long and 33 ft wide. If it were closed, the detour would be 16.2 mi (26 km).

Location

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CarriesS 324
CrossesClark Canyon Dam Splwy
LocationClark Canyon Dam
RouteState Highway 324
CountyBeaverhead County
StateMontana
Coordinates45.00191, -112.86081
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure7 GoodSome minor problems.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry6: Equal to present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating31 US tons
Inventory rating24 US tons

Structure

Structure typeTee Beam
MaterialConcrete
DeckOther
Main spans2
Design loadHL 93
Structure length73 ft (22.1 m)
Longest span37 ft (11.2 m)
Deck width33 ft (10.2 m)
Roadway width29 ft (8.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic396 (2023)
Projected traffic416 by 2043
Trucks1%
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 Clark Canyon Dam Splwy built?

It was built in 1962, making it 63 years old in 2025.

What condition is S 324 over Clark Canyon Dam Splwy 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 July 2023.

How much traffic does S 324 over Clark Canyon Dam Splwy carry?

About 396 vehicles per day (2023 count), of which roughly 1% are trucks.

How long is S 324 over Clark Canyon Dam Splwy?

The structure is 73 ft (22.1 m) long with a longest span of 37 ft (11.2 m) and a deck 33 ft wide.

Who owns S 324 over Clark Canyon Dam Splwy?

It is owned by the State Highway Agency.