US Bridges

Fs Route No. 312 over Upper W. Branch

Poor

Bonner County, Idaho · Upper West Branch · Structure no. 010408000000185

Built
1954
71 years old
Condition
Poor
inspected July 2024
Type
Stringer/Multi-beam or Girder
Wood or Timber
Length
33 ft
1 main span
Daily traffic
50
Owner
Federal
U.S. Forest Service

About this bridge

Fs Route No. 312 over Upper W. Branch is a wood or timber stringer/multi-beam or girder carrying Fs Route No. 312 over Upper W. Branch in Bonner County, Idaho. It was built in 1954, so it is 71 years old, older than the Idaho average of 45.3 years.

The most recent inspection reported to the Federal Highway Administration rates it in poor condition with a lowest component rating of 4 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 33 ft (10 m) long and 15 ft wide. If it were closed, the detour would be 620.7 mi (999 km).

Location

Open in Google Maps
CarriesFs Route No. 312
CrossesUpper W. Branch
LocationUpper West Branch
RouteFederal Lands Road 312
CountyBonner County
StateIdaho
Coordinates48.45702, -116.99272
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure7 GoodSome minor problems.
Substructure4 PoorAdvanced section loss, deterioration, spalling or scour.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJuly 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; action required to protect exposed foundations
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry6: Equal to present minimum criteria
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating34.3 US tons
Inventory rating26.5 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialWood or Timber
DeckWood or timber
Main spans1
Design loadOther
Structure length33 ft (10 m)
Longest span31 ft (9.4 m)
Deck width15 ft (4.7 m)
Roadway width14 ft (4.3 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 closed620.7 mi (999 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 Fs Route No. 312 over Upper W. Branch built?

It was built in 1954, making it 71 years old in 2025.

What condition is Fs Route No. 312 over Upper W. Branch 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 July 2024.

How much traffic does Fs Route No. 312 over Upper W. Branch carry?

About 50 vehicles per day (latest count).

How long is Fs Route No. 312 over Upper W. Branch?

The structure is 33 ft (10 m) long with a longest span of 31 ft (9.4 m) and a deck 15 ft wide.

Who owns Fs Route No. 312 over Upper W. Branch?

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