US Bridges

US 310 over Rock Creek

Fair

Carbon County, Montana · Rockvale · Structure no. P00004042+04541

Built
1934
91 years old, rebuilt 1968
Condition
Fair
inspected October 2024
Type
Tee Beam
Concrete
Length
137 ft
3 main spans
Daily traffic
4,561
2023 count
Owner
State
State Highway Agency

About this bridge

US 310 over Rock Creek is a concrete tee beam carrying US 310 over Rock Creek in Carbon County, Montana. It was built in 1934 and reconstructed in 1968, so it is 91 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 4,561 vehicles a day, roughly 7% of them trucks, projected to reach 4,789 by 2043. The structure is 137 ft (41.8 m) long and 42 ft wide. If it were closed, the detour would be 8.1 mi (13 km).

Location

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CarriesUS 310
CrossesRock Creek
LocationRockvale
RouteU.S. Route 310
CountyCarbon County
StateMontana
Coordinates45.51785, -108.86258
Functional classRural Principal Arterial - Other

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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionOctober 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourCountermeasures installed to correct a previously existing problem
Structural evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating36 US tons
Inventory rating27 US tons

Structure

Structure typeTee Beam
MaterialConcrete
DeckConcrete, cast-in-place
Main spans3
Design loadH 15
Structure length137 ft (41.8 m)
Longest span45 ft (13.7 m)
Deck width42 ft (12.9 m)
Roadway width39 ft (11.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,561 (2023)
Projected traffic4,789 by 2043
Trucks7%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed8.1 mi (13 km)
TollOn a free road
National Highway SystemYes

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 US 310 over Rock Creek built?

It was built in 1934, making it 91 years old in 2025. It was reconstructed in 1968.

What condition is US 310 over Rock 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 October 2024.

How much traffic does US 310 over Rock Creek carry?

About 4,561 vehicles per day (2023 count), of which roughly 7% are trucks.

How long is US 310 over Rock Creek?

The structure is 137 ft (41.8 m) long with a longest span of 45 ft (13.7 m) and a deck 42 ft wide.

Who owns US 310 over Rock Creek?

It is owned by the State Highway Agency.