US Bridges

N Fork RD over Big Creek

Fair

Flathead County, Montana · 17M SE Polebridge · Structure no. S00486020+01461

Built
1980
45 years old
Condition
Fair
inspected August 2023
Type
Tee Beam
Concrete Continuous
Length
124 ft
3 main spans
Daily traffic
461
2023 count
Owner
County
County Highway Agency

About this bridge

N Fork RD over Big Creek is a concrete continuous tee beam carrying N Fork RD over Big Creek in Flathead County, Montana. It was built in 1980, so it is 45 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 461 vehicles a day, projected to reach 542 by 2043. The structure is 124 ft (37.8 m) long and 41 ft wide. If it were closed, the detour would be 123.7 mi (199 km).

Location

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CarriesN Fork RD
CrossesBig Creek
Location17M SE Polebridge
RouteCounty Highway 486
CountyFlathead County
StateMontana
Coordinates48.60237, -114.16562
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.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionAugust 2023
Inspection intervalevery 24 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 adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating68 US tons
Inventory rating52 US tons

Structure

Structure typeTee Beam
MaterialConcrete Continuous
DeckNot applicable
Main spans3
Design loadHS 20
Structure length124 ft (37.8 m)
Longest span80 ft (24.4 m)
Deck width41 ft (12.6 m)
Roadway width34 ft (10.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic461 (2023)
Projected traffic542 by 2043
Trucks0%
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

OwnerCounty Highway Agency
Maintained byCounty 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 N Fork RD over Big Creek built?

It was built in 1980, making it 45 years old in 2025.

What condition is N Fork RD over Big Creek 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 N Fork RD over Big Creek carry?

About 461 vehicles per day (2023 count).

How long is N Fork RD over Big Creek?

The structure is 124 ft (37.8 m) long with a longest span of 80 ft (24.4 m) and a deck 41 ft wide.

Who owns N Fork RD over Big Creek?

It is owned by the County Highway Agency.