US Bridges

US 93 over N.Fk.Salmon River

Fair

Lemhi County, Idaho · 1.0 N. North Fork · Structure no. 000000000017930

Built
1955
70 years old
Condition
Fair
inspected October 2022
Type
Tee Beam
Concrete
Length
59 ft
1 main span
Daily traffic
670
2023 count
Owner
State
State Highway Agency

About this bridge

US 93 over N.Fk.Salmon River is a concrete tee beam carrying US 93 over N.Fk.Salmon River in Lemhi County, Idaho. It was built in 1955, so it is 70 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 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 670 vehicles a day, roughly 37% of them trucks, projected to reach 1,005 by 2042. The structure is 59 ft (18 m) long and 32 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

Open in Google Maps
CarriesUS 93
CrossesN.Fk.Salmon River
Location1.0 N. North Fork
RouteU.S. Route 93
CountyLemhi County
StateIdaho
Coordinates45.42028, -113.99497
Functional classRural Principal Arterial - Other

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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionOctober 2022
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 geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating61.9 US tons
Inventory rating37 US tons

Structure

Structure typeTee Beam
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length59 ft (18 m)
Longest span53 ft (16.2 m)
Deck width32 ft (9.8 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic670 (2023)
Projected traffic1,005 by 2042
Trucks37%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed98.8 mi (159 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$792,000 (2018 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was US 93 over N.Fk.Salmon River built?

It was built in 1955, making it 70 years old in 2025.

What condition is US 93 over N.Fk.Salmon River 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 2022.

How much traffic does US 93 over N.Fk.Salmon River carry?

About 670 vehicles per day (2023 count), of which roughly 37% are trucks.

How long is US 93 over N.Fk.Salmon River?

The structure is 59 ft (18 m) long with a longest span of 53 ft (16.2 m) and a deck 32 ft wide.

Who owns US 93 over N.Fk.Salmon River?

It is owned by the State Highway Agency.