US Bridges

RD 231 over Libby CR

Fair

Lincoln County, Montana · Old Town · Structure no. 011405000000225

Built
1984
41 years old
Condition
Fair
inspected August 2021
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
92 ft
1 main span
Daily traffic
99
Owner
Federal
U.S. Forest Service

About this bridge

RD 231 over Libby CR is a prestressed concrete stringer/multi-beam or girder carrying RD 231 over Libby CR in Lincoln County, Montana. It was built in 1984, so it is 41 years old, younger 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 99 vehicles a day, projected to reach 148 by 2045. The structure is 92 ft (28 m) long and 17 ft wide. If it were closed, the detour would be 98.2 mi (158 km).

Location

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CarriesRD 231
CrossesLibby CR
LocationOld Town
RouteFederal Lands Road 231
CountyLincoln County
StateMontana
Coordinates48.14929, -115.52401
Functional classRural Local

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.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionAugust 2021
Inspection intervalevery 48 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation7: Better than present minimum criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating58.5 US tons
Inventory rating45.3 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 25 or greater
Structure length92 ft (28 m)
Longest span90 ft (27.4 m)
Deck width17 ft (5.1 m)
Roadway width14 ft (4.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic99 (—)
Projected traffic148 by 2045
Trucks—
Lanes on structure1
Traffic directionOne-lane bridge for two-way traffic
CarriesHighway
CrossesWaterway
Detour if closed98.2 mi (158 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerU.S. Forest Service
Maintained byU.S. Forest Service
Historic statusHistorical significance not determinable at this time
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was RD 231 over Libby CR built?

It was built in 1984, making it 41 years old in 2025.

What condition is RD 231 over Libby CR 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 2021.

How much traffic does RD 231 over Libby CR carry?

About 99 vehicles per day (latest count).

How long is RD 231 over Libby CR?

The structure is 92 ft (28 m) long with a longest span of 90 ft (27.4 m) and a deck 17 ft wide.

Who owns RD 231 over Libby CR?

It is owned by the U.S. Forest Service.