US Bridges

Forest Road 221 over Allison Creek

Fair

Idaho County, Idaho · No Data Entered · Structure no. 011701000000122

Built
1964
61 years old
Condition
Fair
inspected September 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

Forest Road 221 over Allison Creek is a wood or timber stringer/multi-beam or girder carrying Forest Road 221 over Allison Creek in Idaho County, Idaho. It was built in 1964, so it is 61 years old, older than the Idaho average of 45.3 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 (7.3 m) long and 15 ft wide. If it were closed, the detour would be 98.2 mi (158 km).

Location

Open in Google Maps
CarriesForest Road 221
CrossesAllison Creek
LocationNo Data Entered
RouteFederal Lands Road 221
CountyIdaho County
StateIdaho
Coordinates45.49095, -116.16209
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
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection7 GoodSome minor problems.
Last inspectionSeptember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry6: Equal to present minimum criteria
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating73.2 US tons
Inventory rating56.4 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialWood or Timber
DeckWood or timber
Main spans1
Design loadHS 25 or greater
Structure length24 ft (7.3 m)
Longest span24 ft (7.2 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 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 Forest Road 221 over Allison Creek built?

It was built in 1964, making it 61 years old in 2025.

What condition is Forest Road 221 over Allison 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 September 2023.

How much traffic does Forest Road 221 over Allison Creek carry?

About 50 vehicles per day (latest count).

How long is Forest Road 221 over Allison Creek?

The structure is 24 ft (7.3 m) long with a longest span of 24 ft (7.2 m) and a deck 15 ft wide.

Who owns Forest Road 221 over Allison Creek?

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