US Bridges

US 20 over Henrys Fk. Snake River

Fair

Fremont County, Idaho · At Macks Inn · Structure no. 000000000012685

Built
1975
50 years old, rebuilt 2011
Condition
Fair
inspected July 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
180 ft
3 main spans
Daily traffic
6,500
2023 count
Owner
State
State Highway Agency

About this bridge

US 20 over Henrys Fk. Snake River is a prestressed concrete stringer/multi-beam or girder carrying US 20 over Henrys Fk. Snake River in Fremont County, Idaho. It was built in 1975 and reconstructed in 2011, so it is 50 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 6,500 vehicles a day, roughly 10% of them trucks, projected to reach 9,750 by 2042. The structure is 180 ft (54.9 m) long and 60 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

Open in Google Maps
CarriesUS 20
CrossesHenrys Fk. Snake River
LocationAt Macks Inn
RouteU.S. Route 20
CountyFremont County
StateIdaho
Coordinates44.50072, -111.33667
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
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionJuly 2024
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 geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating72 US tons
Inventory rating44 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length180 ft (54.9 m)
Longest span59 ft (18 m)
Deck width60 ft (18.3 m)
Roadway width43 ft (13 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic6,500 (2023)
Projected traffic9,750 by 2042
Trucks10%
Lanes on structure3
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
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$3.3 million (2020 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

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

It was built in 1975, making it 50 years old in 2025. It was reconstructed in 2011.

What condition is US 20 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 2024.

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

About 6,500 vehicles per day (2023 count), of which roughly 10% are trucks.

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

The structure is 180 ft (54.9 m) long with a longest span of 59 ft (18 m) and a deck 60 ft wide.

Who owns US 20 over Henrys Fk. Snake River?

It is owned by the State Highway Agency.