US Bridges

A-6 Lane over Belt Creek

Fair

Cascade County, Montana · 4.8 KM SE of Monarch · Structure no. AFMTNZBX85160

Built
1960
65 years old
Condition
Fair
inspected September 2024
Type
Stringer/Multi-beam or Girder
Wood or Timber
Length
149 ft
7 main spans
Daily traffic
20
2016 count
Owner
Federal
Air Force

About this bridge

A-6 Lane over Belt Creek is a wood or timber stringer/multi-beam or girder carrying A-6 Lane over Belt Creek in Cascade County, Montana. It was built in 1960, so it is 65 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 20 vehicles a day, projected to reach 24 by 2036. The structure is 149 ft (45.5 m) long and 14 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

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CarriesA-6 Lane
CrossesBelt Creek
Location4.8 KM SE of Monarch
CountyCascade County
StateMontana
Coordinates47.06314, -110.80838
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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionSeptember 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 geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating47 US tons
Inventory rating34 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialWood or Timber
DeckWood or timber
Main spans7
Design loadH 15
Structure length149 ft (45.5 m)
Longest span21 ft (6.5 m)
Deck width14 ft (4.2 m)
Roadway width12 ft (3.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic20 (2016)
Projected traffic24 by 2036
Trucks—
Lanes on structure1
Traffic directionOne-lane bridge for two-way traffic
CarriesHighway
CrossesWaterway
Detour if closed98.8 mi (159 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerAir Force
Maintained byAir Force
Historic statusPossibly eligible for the National Register; requires further investigation
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was A-6 Lane over Belt Creek built?

It was built in 1960, making it 65 years old in 2025.

What condition is A-6 Lane over Belt 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 September 2024.

How much traffic does A-6 Lane over Belt Creek carry?

About 20 vehicles per day (2016 count).

How long is A-6 Lane over Belt Creek?

The structure is 149 ft (45.5 m) long with a longest span of 21 ft (6.5 m) and a deck 14 ft wide.

Who owns A-6 Lane over Belt Creek?

It is owned by the Air Force.