US Bridges

Gilbert Cr. Rd. over Rock CR

FairPosted for load

Missoula County, Montana · Valley of the Moon · Structure no. 011603000000007

Built
1975
50 years old
Condition
Fair
inspected August 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
80 ft
1 main span
Daily traffic
50
Owner
Federal
U.S. Forest Service

About this bridge

Gilbert Cr. Rd. over Rock CR is a prestressed concrete stringer/multi-beam or girder carrying Gilbert Cr. Rd. over Rock CR in Missoula County, Montana. It was built in 1975, so it is 50 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. Its operating status is: posted for load restriction.

It carries about 50 vehicles a day, projected to reach 75 by 2045. The structure is 80 ft (24.4 m) long and 12 ft wide. If it were closed, the detour would be 98.2 mi (158 km).

Location

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CarriesGilbert Cr. Rd.
CrossesRock CR
LocationValley of the Moon
RouteFederal Lands Road 34
CountyMissoula County
StateMontana
Coordinates46.69928, -113.66691
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.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionAugust 2024
Inspection intervalevery 24 months
Operating statusPosted for load restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment3: Basically intolerable, requiring high priority of corrective action
Operating rating19 US tons
Inventory rating14.7 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckOther
Main spans1 (+2 approach)
Design loadHS 20
Structure length80 ft (24.4 m)
Longest span79 ft (24.2 m)
Deck width12 ft (3.7 m)
Roadway width11 ft (3.4 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 Gilbert Cr. Rd. over Rock CR built?

It was built in 1975, making it 50 years old in 2025.

What condition is Gilbert Cr. Rd. over Rock CR 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 August 2024.

How much traffic does Gilbert Cr. Rd. over Rock CR carry?

About 50 vehicles per day (latest count).

How long is Gilbert Cr. Rd. over Rock CR?

The structure is 80 ft (24.4 m) long with a longest span of 79 ft (24.2 m) and a deck 12 ft wide.

Who owns Gilbert Cr. Rd. over Rock CR?

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