US Bridges

Firth Road over Blackfoot Canal

Good

Bingham County, Idaho · 0.3 N. 0.3 E. Firth · Structure no. 000000000022360

Built
1970
55 years old
Condition
Good
inspected April 2024
Type
Tee Beam
Prestressed Concrete
Length
34 ft
1 main span
Daily traffic
220
2023 count
Owner
County
County Highway Agency

About this bridge

Firth Road over Blackfoot Canal is a prestressed concrete tee beam carrying Firth Road over Blackfoot Canal in Bingham County, Idaho. It was built in 1970, so it is 55 years old, older than the Idaho average of 45.3 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 220 vehicles a day, roughly 50% of them trucks, projected to reach 330 by 2042. The structure is 34 ft (10.4 m) long and 30 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesFirth Road
CrossesBlackfoot Canal
Location0.3 N. 0.3 E. Firth
RouteCounty Highway 0
CountyBingham County
StateIdaho
Coordinates43.30828, -112.17844
Functional classRural Minor Collector

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionApril 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than present minimum criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment4: Meets minimum tolerable limits to be left in place as is
Operating rating52 US tons
Inventory rating31 US tons

Structure

Structure typeTee Beam
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans1
Design loadH 20
Structure length34 ft (10.4 m)
Longest span33 ft (10.1 m)
Deck width30 ft (9.1 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic220 (2023)
Projected traffic330 by 2042
Trucks50%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.2 mi (2 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 Firth Road over Blackfoot Canal built?

It was built in 1970, making it 55 years old in 2025.

What condition is Firth Road over Blackfoot Canal in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in April 2024.

How much traffic does Firth Road over Blackfoot Canal carry?

About 220 vehicles per day (2023 count), of which roughly 50% are trucks.

How long is Firth Road over Blackfoot Canal?

The structure is 34 ft (10.4 m) long with a longest span of 33 ft (10.1 m) and a deck 30 ft wide.

Who owns Firth Road over Blackfoot Canal?

It is owned by the County Highway Agency.