US Bridges

SH 75 over Big Wood River

Fair

Blaine County, Idaho · 14.6 N. Ketchum · Structure no. 000000000017690

Built
1958
67 years old
Condition
Fair
inspected July 2024
Type
Tee Beam
Concrete
Length
107 ft
3 main spans
Daily traffic
1,400
2023 count
Owner
State
State Highway Agency

About this bridge

SH 75 over Big Wood River is a concrete tee beam carrying SH 75 over Big Wood River in Blaine County, Idaho. It was built in 1958, so it is 67 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 1,400 vehicles a day, roughly 11% of them trucks, projected to reach 2,100 by 2042. The structure is 107 ft (32.6 m) long and 36 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

Open in Google Maps
CarriesSH 75
CrossesBig Wood River
Location14.6 N. Ketchum
RouteState Highway 75
CountyBlaine County
StateIdaho
Coordinates43.78275, -114.54511
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJuly 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
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 rating50 US tons
Inventory rating30 US tons

Structure

Structure typeTee Beam
MaterialConcrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length107 ft (32.6 m)
Longest span67 ft (20.4 m)
Deck width36 ft (11 m)
Roadway width28 ft (8.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,400 (2023)
Projected traffic2,100 by 2042
Trucks11%
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 proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$1.4 million (2020 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SH 75 over Big Wood River built?

It was built in 1958, making it 67 years old in 2025.

What condition is SH 75 over Big Wood 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 Big Wood River carry?

About 1,400 vehicles per day (2023 count), of which roughly 11% are trucks.

How long is SH 75 over Big Wood River?

The structure is 107 ft (32.6 m) long with a longest span of 67 ft (20.4 m) and a deck 36 ft wide.

Who owns SH 75 over Big Wood River?

It is owned by the State Highway Agency.