US Bridges

Old Boulder Road over Boulder River 029

Fair

Sweet Grass County, Montana · East Big Timber · Structure no. 000000202004523

Built
2020
5 years old
Condition
Fair
inspected November 2024
Type
Tee Beam
Prestressed Concrete
Length
138 ft
1 main span
Daily traffic
100
2025 count
Owner
County
County Highway Agency

About this bridge

Old Boulder Road over Boulder River 029 is a prestressed concrete tee beam carrying Old Boulder Road over Boulder River 029 in Sweet Grass County, Montana. It was built in 2020, so it is 5 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 100 vehicles a day, roughly 3% of them trucks, projected to reach 100 by 2040. The structure is 138 ft (42.1 m) long and 26 ft wide. If it were closed, the detour would be 18 mi (29 km).

Location

Open in Google Maps
CarriesOld Boulder Road
CrossesBoulder River 029
LocationEast Big Timber
RouteCounty Highway 49103
CountySweet Grass County
StateMontana
Coordinates45.83408, -109.93839
Functional classRural Minor 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
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionNovember 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 geometry6: Equal to present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating56 US tons
Inventory rating36 US tons

Structure

Structure typeTee Beam
MaterialPrestressed Concrete
DeckConcrete, precast panels
Main spans1
Design loadHL 93
Structure length138 ft (42.1 m)
Longest span135 ft (41.1 m)
Deck width26 ft (8 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic100 (2025)
Projected traffic100 by 2040
Trucks3%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed18 mi (29 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedNone recorded
Estimated improvement cost—
NavigationNot applicable (no waterway)

Frequently asked questions

When was Old Boulder Road over Boulder River 029 built?

It was built in 2020, making it 5 years old in 2025.

What condition is Old Boulder Road over Boulder River 029 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 November 2024.

How much traffic does Old Boulder Road over Boulder River 029 carry?

About 100 vehicles per day (2025 count), of which roughly 3% are trucks.

How long is Old Boulder Road over Boulder River 029?

The structure is 138 ft (42.1 m) long with a longest span of 135 ft (41.1 m) and a deck 26 ft wide.

Who owns Old Boulder Road over Boulder River 029?

It is owned by the County Highway Agency.