US Bridges

S 80 over Chimney Rock

Fair

Chouteau County, Montana · 2M SE Geraldine · Structure no. P00080031+05141

Built
1949
76 years old, rebuilt 1964
Condition
Fair
inspected August 2023
Type
Stringer/Multi-beam or Girder
Wood or Timber
Length
57 ft
3 main spans
Daily traffic
235
2023 count
Owner
State
State Highway Agency

About this bridge

S 80 over Chimney Rock is a wood or timber stringer/multi-beam or girder carrying S 80 over Chimney Rock in Chouteau County, Montana. It was built in 1949 and reconstructed in 1964, so it is 76 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 235 vehicles a day, roughly 12% of them trucks, projected to reach 247 by 2043. The structure is 57 ft (17.4 m) long and 30 ft wide. If it were closed, the detour would be 123.7 mi (199 km).

Location

Open in Google Maps
CarriesS 80
CrossesChimney Rock
Location2M SE Geraldine
RouteState Highway 80
CountyChouteau County
StateMontana
Coordinates47.57099, -110.22627
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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionAugust 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 alignment8: Equal to present desirable criteria
Operating rating43 US tons
Inventory rating31 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialWood or Timber
DeckWood or timber
Main spans3
Design loadH 15
Structure length57 ft (17.4 m)
Longest span19 ft (5.8 m)
Deck width30 ft (9.1 m)
Roadway width29 ft (8.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic235 (2023)
Projected traffic247 by 2043
Trucks12%
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 Chimney Rock built?

It was built in 1949, making it 76 years old in 2025. It was reconstructed in 1964.

What condition is S 80 over Chimney Rock 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 Chimney Rock carry?

About 235 vehicles per day (2023 count), of which roughly 12% are trucks.

How long is S 80 over Chimney Rock?

The structure is 57 ft (17.4 m) long with a longest span of 19 ft (5.8 m) and a deck 30 ft wide.

Who owns S 80 over Chimney Rock?

It is owned by the State Highway Agency.