US Bridges

S 35 over Swan River

Fair

Flathead County, Montana · Big Fork · Structure no. P00052031+00211

Built
1954
71 years old
Condition
Fair
inspected September 2024
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
220 ft
4 main spans
Daily traffic
9,246
2023 count
Owner
State
State Highway Agency

About this bridge

S 35 over Swan River is a steel continuous stringer/multi-beam or girder carrying S 35 over Swan River in Flathead County, Montana. It was built in 1954, so it is 71 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.

It carries about 9,246 vehicles a day, roughly 1% of them trucks, projected to reach 9,708 by 2043. The structure is 220 ft (67 m) long and 33 ft wide. If it were closed, the detour would be 19.9 mi (32 km).

Location

Open in Google Maps
CarriesS 35
CrossesSwan River
LocationBig Fork
RouteState Highway 35
CountyFlathead County
StateMontana
Coordinates48.06077, -114.07991
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.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionSeptember 2024
Inspection intervalevery 24 months
Operating statusOpen, no 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 adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating39 US tons
Inventory rating23 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadHS 15
Structure length220 ft (67 m)
Longest span94 ft (28.7 m)
Deck width33 ft (10.1 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic9,246 (2023)
Projected traffic9,708 by 2043
Trucks1%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed19.9 mi (32 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 35 over Swan River built?

It was built in 1954, making it 71 years old in 2025.

What condition is S 35 over Swan 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 September 2024.

How much traffic does S 35 over Swan River carry?

About 9,246 vehicles per day (2023 count), of which roughly 1% are trucks.

How long is S 35 over Swan River?

The structure is 220 ft (67 m) long with a longest span of 94 ft (28.7 m) and a deck 33 ft wide.

Who owns S 35 over Swan River?

It is owned by the State Highway Agency.