US Bridges

US 20B over Henrys Fk. Snake River

Fair

Fremont County, Idaho · In ST Anthony · Structure no. 000000000012730

Built
1965
60 years old
Condition
Fair
inspected July 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
104 ft
1 main span
Daily traffic
11,500
2023 count
Owner
State
State Highway Agency

About this bridge

US 20B over Henrys Fk. Snake River is a steel stringer/multi-beam or girder carrying US 20B over Henrys Fk. Snake River in Fremont County, Idaho. It was built in 1965, so it is 60 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 11,500 vehicles a day, roughly 2% of them trucks, projected to reach 17,250 by 2042. The structure is 104 ft (31.7 m) long and 66 ft wide. If it were closed, the detour would be 3.7 mi (6 km).

Location

Open in Google Maps
CarriesUS 20B
CrossesHenrys Fk. Snake River
LocationIn ST Anthony
RouteU.S. Route 20
CountyFremont County
StateIdaho
Coordinates43.96464, -111.68228
Functional classRural Major Collector

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 inspectionJuly 2023
Inspection intervalevery 24 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 adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating91.1 US tons
Inventory rating54 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length104 ft (31.7 m)
Longest span102 ft (31.1 m)
Deck width66 ft (20.1 m)
Roadway width52 ft (15.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic11,500 (2023)
Projected traffic17,250 by 2042
Trucks2%
Lanes on structure3
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed3.7 mi (6 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$2.3 million (2019 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was US 20B over Henrys Fk. Snake River built?

It was built in 1965, making it 60 years old in 2025.

What condition is US 20B over Henrys Fk. Snake 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 2023.

How much traffic does US 20B over Henrys Fk. Snake River carry?

About 11,500 vehicles per day (2023 count), of which roughly 2% are trucks.

How long is US 20B over Henrys Fk. Snake River?

The structure is 104 ft (31.7 m) long with a longest span of 102 ft (31.1 m) and a deck 66 ft wide.

Who owns US 20B over Henrys Fk. Snake River?

It is owned by the State Highway Agency.