US Bridges

RD 320 over Cedar CR

Poor

Mineral County, Montana · Cedar CR · Structure no. 011607000000041

Built
1959
66 years old
Condition
Poor
inspected September 2024
Type
Stringer/Multi-beam or Girder
Wood or Timber
Length
31 ft
1 main span
Daily traffic
50
Owner
Federal
U.S. Forest Service

About this bridge

RD 320 over Cedar CR is a wood or timber stringer/multi-beam or girder carrying RD 320 over Cedar CR in Mineral County, Montana. It was built in 1959, so it is 66 years old, older than the Montana average of 47 years.

The most recent inspection reported to the Federal Highway Administration rates it in poor condition with a lowest component rating of 2 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

It carries about 50 vehicles a day, projected to reach 75 by 2045. The structure is 31 ft (9.3 m) long and 17 ft wide.

Location

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CarriesRD 320
CrossesCedar CR
LocationCedar CR
RouteFederal Lands Road 320
CountyMineral County
StateMontana
Coordinates47.07929, -115.00851
Functional classRural Local

Condition and inspection

Poor

The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

ComponentRatingMeaning
Deck4 PoorAdvanced section loss, deterioration, spalling or scour.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure2 CriticalAdvanced deterioration of primary structural elements. Bridge may be closed until corrective action is taken.
Channel and channel protection4 PoorAdvanced section loss, deterioration, spalling or scour.
Last inspectionSeptember 2024
Inspection intervalevery 12 months
Operating statusOpen, no restriction
ScourScour critical; extensive scour has occurred
Structural evaluation2: Basically intolerable, requiring high priority of replacement
Deck geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating35.4 US tons
Inventory rating27.1 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialWood or Timber
DeckWood or timber
Main spans1
Design loadUnknown
Structure length31 ft (9.3 m)
Longest span29 ft (8.8 m)
Deck width17 ft (5.3 m)
Roadway width16 ft (5 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 closed—
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 320 over Cedar CR built?

It was built in 1959, making it 66 years old in 2025.

What condition is RD 320 over Cedar CR in?

The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in September 2024.

How much traffic does RD 320 over Cedar CR carry?

About 50 vehicles per day (latest count).

How long is RD 320 over Cedar CR?

The structure is 31 ft (9.3 m) long with a longest span of 29 ft (8.8 m) and a deck 17 ft wide.

Who owns RD 320 over Cedar CR?

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