US Bridges

Twin Bridges RD over Stillwater River

Fair

Flathead County, Montana · 5M SW Whitefish · Structure no. S00424015+08491

Built
1988
37 years old
Condition
Fair
inspected August 2024
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
353 ft
4 main spans
Daily traffic
2,028
2023 count
Owner
State
State Highway Agency

About this bridge

Twin Bridges RD over Stillwater River is a steel continuous stringer/multi-beam or girder carrying Twin Bridges RD over Stillwater River in Flathead County, Montana. It was built in 1988, so it is 37 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 2,028 vehicles a day, roughly 2% of them trucks, projected to reach 2,150 by 2043. The structure is 353 ft (107.5 m) long and 30 ft wide. If it were closed, the detour would be 39.8 mi (64 km).

Location

Open in Google Maps
CarriesTwin Bridges RD
CrossesStillwater River
Location5M SW Whitefish
RouteState Highway 424
CountyFlathead County
StateMontana
Coordinates48.38649, -114.43251
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.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionAugust 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 geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating28 US tons
Inventory rating25 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20
Structure length353 ft (107.5 m)
Longest span97 ft (29.6 m)
Deck width30 ft (9.2 m)
Roadway width27 ft (8.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,028 (2023)
Projected traffic2,150 by 2043
Trucks2%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed39.8 mi (64 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 proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$948,000
NavigationNo navigation control on waterway

Frequently asked questions

When was Twin Bridges RD over Stillwater River built?

It was built in 1988, making it 37 years old in 2025.

What condition is Twin Bridges RD over Stillwater 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 August 2024.

How much traffic does Twin Bridges RD over Stillwater River carry?

About 2,028 vehicles per day (2023 count), of which roughly 2% are trucks.

How long is Twin Bridges RD over Stillwater River?

The structure is 353 ft (107.5 m) long with a longest span of 97 ft (29.6 m) and a deck 30 ft wide.

Who owns Twin Bridges RD over Stillwater River?

It is owned by the State Highway Agency.