US Bridges

S 80 over Boyle-O`hanlon Coulees

FairPosted for load

Chouteau County, Montana · 6M SE Fort Benton · Structure no. P00080008+07611

Built
1939
86 years old
Condition
Fair
inspected August 2023
Type
Stringer/Multi-beam or Girder
Wood or Timber
Length
75 ft
3 main spans
Daily traffic
479
2023 count
Owner
State
State Highway Agency

About this bridge

S 80 over Boyle-O`hanlon Coulees is a wood or timber stringer/multi-beam or girder carrying S 80 over Boyle-O`hanlon Coulees in Chouteau County, Montana. It was built in 1939, so it is 86 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. Its operating status is: posted for load restriction.

It carries about 479 vehicles a day, roughly 16% of them trucks, projected to reach 503 by 2043. The structure is 75 ft (22.9 m) long and 26 ft wide. If it were closed, the detour would be 123.7 mi (199 km).

Location

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CarriesS 80
CrossesBoyle-O`hanlon Coulees
Location6M SE Fort Benton
RouteState Highway 80
CountyChouteau County
StateMontana
Coordinates47.78676, -110.55303
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
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
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 inspectionAugust 2023
Inspection intervalevery 24 months
Operating statusPosted for load 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 adequacy8: Equal to present desirable criteria
Approach roadway alignment5: Somewhat better than minimum adequacy to tolerate being left in place as is
Operating rating40 US tons
Inventory rating25 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialWood or Timber
DeckWood or timber
Main spans3
Design loadH 15
Structure length75 ft (22.9 m)
Longest span25 ft (7.6 m)
Deck width26 ft (8 m)
Roadway width24 ft (7.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic479 (2023)
Projected traffic503 by 2043
Trucks16%
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 80 over Boyle-O`hanlon Coulees built?

It was built in 1939, making it 86 years old in 2025.

What condition is S 80 over Boyle-O`hanlon Coulees 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 August 2023.

How much traffic does S 80 over Boyle-O`hanlon Coulees carry?

About 479 vehicles per day (2023 count), of which roughly 16% are trucks.

How long is S 80 over Boyle-O`hanlon Coulees?

The structure is 75 ft (22.9 m) long with a longest span of 25 ft (7.6 m) and a deck 26 ft wide.

Who owns S 80 over Boyle-O`hanlon Coulees?

It is owned by the State Highway Agency.