US Bridges

SH 75 over Big Wood River

Fair

Lincoln County, Idaho · 17.9 N. Shoshone · Structure no. 000000000017635

Built
1955
70 years old
Condition
Fair
inspected March 2023
Type
Tee Beam
Concrete
Length
100 ft
3 main spans
Daily traffic
4,500
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 Lincoln 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 5 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 4,500 vehicles a day, roughly 13% of them trucks, projected to reach 6,750 by 2042. The structure is 100 ft (30.5 m) long and 36 ft wide. If it were closed, the detour would be 39.8 mi (64 km).

Location

Open in Google Maps
CarriesSH 75
CrossesBig Wood River
Location17.9 N. Shoshone
RouteState Highway 75
CountyLincoln County
StateIdaho
Coordinates43.19014, -114.32256
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.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection7 GoodSome minor problems.
Last inspectionMarch 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
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 rating66 US tons
Inventory rating39 US tons

Structure

Structure typeTee Beam
MaterialConcrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length100 ft (30.5 m)
Longest span40 ft (12.2 m)
Deck width36 ft (11.1 m)
Roadway width34 ft (10.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,500 (2023)
Projected traffic6,750 by 2042
Trucks13%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed39.8 mi (64 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 (2021 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SH 75 over Big Wood River built?

It was built in 1955, making it 70 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 March 2023.

How much traffic does SH 75 over Big Wood River carry?

About 4,500 vehicles per day (2023 count), of which roughly 13% are trucks.

How long is SH 75 over Big Wood River?

The structure is 100 ft (30.5 m) long with a longest span of 40 ft (12.2 m) and a deck 36 ft wide.

Who owns SH 75 over Big Wood River?

It is owned by the State Highway Agency.