US Bridges

RD 352 over Twelvemile Creek

Fair

Mineral County, Montana · Henderson-Thompson · Structure no. 011607000000070

Built
1955
70 years old
Condition
Fair
inspected July 2023
Type
Stringer/Multi-beam or Girder
Wood or Timber
Length
24 ft
1 main span
Daily traffic
50
Owner
Federal
U.S. Forest Service

About this bridge

RD 352 over Twelvemile Creek is a wood or timber stringer/multi-beam or girder carrying RD 352 over Twelvemile Creek in Mineral County, Montana. It was built in 1955, so it is 70 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 50 vehicles a day, projected to reach 75 by 2045. The structure is 24 ft (7.2 m) long and 15 ft wide. If it were closed, the detour would be 98.2 mi (158 km).

Location

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CarriesRD 352
CrossesTwelvemile Creek
LocationHenderson-Thompson
RouteFederal Lands Road 352
CountyMineral County
StateMontana
Coordinates47.44683, -115.2419
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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; action required to protect exposed foundations
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating39.7 US tons
Inventory rating30.8 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialWood or Timber
DeckWood or timber
Main spans1
Design loadHS 20
Structure length24 ft (7.2 m)
Longest span22 ft (6.7 m)
Deck width15 ft (4.6 m)
Roadway width14 ft (4.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic50 (—)
Projected traffic75 by 2045
Trucks—
Lanes on structure1
Traffic directionOne-lane bridge for two-way traffic
CarriesHighway
CrossesWaterway
Detour if closed98.2 mi (158 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerU.S. Forest Service
Maintained byU.S. Forest Service
Historic statusHistorical significance not determinable at this time
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was RD 352 over Twelvemile Creek built?

It was built in 1955, making it 70 years old in 2025.

What condition is RD 352 over Twelvemile 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 July 2023.

How much traffic does RD 352 over Twelvemile Creek carry?

About 50 vehicles per day (latest count).

How long is RD 352 over Twelvemile Creek?

The structure is 24 ft (7.2 m) long with a longest span of 22 ft (6.7 m) and a deck 15 ft wide.

Who owns RD 352 over Twelvemile Creek?

It is owned by the U.S. Forest Service.