US Bridges

SH 75 over Salmon River

Fair

Custer County, Idaho · 5.6 S. Obsidian · Structure no. 000000000017730

Built
1985
40 years old
Condition
Fair
inspected July 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
103 ft
1 main span
Daily traffic
800
2023 count
Owner
State
State Highway Agency

About this bridge

SH 75 over Salmon River is a prestressed concrete stringer/multi-beam or girder carrying SH 75 over Salmon River in Custer County, Idaho. It was built in 1985, so it is 40 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 800 vehicles a day, roughly 16% of them trucks, projected to reach 1,200 by 2042. The structure is 103 ft (31.4 m) long and 40 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

Open in Google Maps
CarriesSH 75
CrossesSalmon River
Location5.6 S. Obsidian
RouteState Highway 75
CountyCuster County
StateIdaho
Coordinates44.00075, -114.83317
Functional classRural Minor Arterial

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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionJuly 2024
Inspection intervalevery 48 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry7: Better than present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating75 US tons
Inventory rating40 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 25 or greater
Structure length103 ft (31.4 m)
Longest span100 ft (30.5 m)
Deck width40 ft (12.2 m)
Roadway width37 ft (11.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic800 (2023)
Projected traffic1,200 by 2042
Trucks16%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed98.8 mi (159 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState 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 SH 75 over Salmon River built?

It was built in 1985, making it 40 years old in 2025.

What condition is SH 75 over 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 July 2024.

How much traffic does SH 75 over Salmon River carry?

About 800 vehicles per day (2023 count), of which roughly 16% are trucks.

How long is SH 75 over Salmon River?

The structure is 103 ft (31.4 m) long with a longest span of 100 ft (30.5 m) and a deck 40 ft wide.

Who owns SH 75 over Salmon River?

It is owned by the State Highway Agency.