US Bridges

Stc 1843; Firth RD over Snake River;firth Bridge

Fair

Bingham County, Idaho · 0.5 N. 0.3 E. Firth · Structure no. 000000000019246

Built
2003
22 years old
Condition
Fair
inspected October 2021
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
419 ft
4 main spans
Daily traffic
510
2023 count
Owner
County
County Highway Agency

About this bridge

Stc 1843; Firth RD over Snake River;firth Bridge is a steel continuous stringer/multi-beam or girder carrying Stc 1843; Firth RD over Snake River;firth Bridge in Bingham County, Idaho. It was built in 2003, so it is 22 years old, younger 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 6 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 510 vehicles a day, roughly 31% of them trucks, projected to reach 765 by 2042. The structure is 419 ft (127.7 m) long and 40 ft wide. If it were closed, the detour would be 14.9 mi (24 km).

Location

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CarriesStc 1843; Firth RD
CrossesSnake River;firth Bridge
Location0.5 N. 0.3 E. Firth
RouteCounty Highway 1843
CountyBingham County
StateIdaho
Coordinates43.31303, -112.18406
Functional classRural Major Collector

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionOctober 2021
Inspection intervalevery 48 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation6: Equal to present minimum criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating78 US tons
Inventory rating47 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadHL 93
Structure length419 ft (127.7 m)
Longest span110 ft (33.5 m)
Deck width40 ft (12.2 m)
Roadway width31 ft (9.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic510 (2023)
Projected traffic765 by 2042
Trucks31%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed14.9 mi (24 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was Stc 1843; Firth RD over Snake River;firth Bridge built?

It was built in 2003, making it 22 years old in 2025.

What condition is Stc 1843; Firth RD over Snake River;firth Bridge 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 October 2021.

How much traffic does Stc 1843; Firth RD over Snake River;firth Bridge carry?

About 510 vehicles per day (2023 count), of which roughly 31% are trucks.

How long is Stc 1843; Firth RD over Snake River;firth Bridge?

The structure is 419 ft (127.7 m) long with a longest span of 110 ft (33.5 m) and a deck 40 ft wide.

Who owns Stc 1843; Firth RD over Snake River;firth Bridge?

It is owned by the County Highway Agency.