US Bridges

S 43 FH 20 over Big Hole River

Fair

Beaverhead County, Montana · Wisdom · Structure no. P00046025+08221

Built
1962
63 years old
Condition
Fair
inspected April 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
215 ft
4 main spans
Daily traffic
631
2023 count
Owner
State
State Highway Agency

About this bridge

S 43 FH 20 over Big Hole River is a prestressed concrete stringer/multi-beam or girder carrying S 43 FH 20 over Big Hole River 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 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 631 vehicles a day, roughly 8% of them trucks, projected to reach 663 by 2043. The structure is 215 ft (65.4 m) long and 30 ft wide. If it were closed, the detour would be 123.7 mi (199 km).

Location

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CarriesS 43 FH 20
CrossesBig Hole River
LocationWisdom
RouteState Highway 43
CountyBeaverhead County
StateMontana
Coordinates45.61852, -113.45692
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionApril 2024
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 geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating52 US tons
Inventory rating36 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20
Structure length215 ft (65.4 m)
Longest span56 ft (17.2 m)
Deck width30 ft (9.1 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic631 (2023)
Projected traffic663 by 2043
Trucks8%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed123.7 mi (199 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 43 FH 20 over Big Hole River built?

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

What condition is S 43 FH 20 over Big Hole 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 April 2024.

How much traffic does S 43 FH 20 over Big Hole River carry?

About 631 vehicles per day (2023 count), of which roughly 8% are trucks.

How long is S 43 FH 20 over Big Hole River?

The structure is 215 ft (65.4 m) long with a longest span of 56 ft (17.2 m) and a deck 30 ft wide.

Who owns S 43 FH 20 over Big Hole River?

It is owned by the State Highway Agency.