US Bridges

SH 28 over Lemhi River

Good

Lemhi County, Idaho · 5.5 S. Salmon · Structure no. 000000000013446

Built
2001
24 years old
Condition
Good
inspected August 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
88 ft
1 main span
Daily traffic
1,700
2023 count
Owner
State
State Highway Agency

About this bridge

SH 28 over Lemhi River is a prestressed concrete stringer/multi-beam or girder carrying SH 28 over Lemhi River in Lemhi County, Idaho. It was built in 2001, so it is 24 years old, younger than the Idaho average of 45.3 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 8 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 1,700 vehicles a day, roughly 10% of them trucks, projected to reach 2,550 by 2042. The structure is 88 ft (26.8 m) long and 41 ft wide. If it were closed, the detour would be 78.3 mi (126 km).

CarriesSH 28
CrossesLemhi River
Location5.5 S. Salmon
RouteState Highway 28
StateIdaho
Coordinates45.12972, -113.79722
Functional classRural Minor Arterial

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck8 Very GoodNo problems noted.
Superstructure9 ExcellentNo problems noted.
Substructure9 ExcellentNo problems noted.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionAugust 2024
Inspection intervalevery 48 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation9: Superior to present desirable criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating102 US tons
Inventory rating57 US tons

Structure

MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 25 or greater
Structure length88 ft (26.8 m)
Longest span85 ft (25.9 m)
Deck width41 ft (12.6 m)
Roadway width39 ft (11.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,700 (2023)
Projected traffic2,550 by 2042
Trucks10%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed78.3 mi (126 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 proposedWidening of existing bridge without deck rehabilitation
Estimated improvement cost$1.1 million (2018 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SH 28 over Lemhi River built?

It was built in 2001, making it 24 years old in 2025.

What condition is SH 28 over Lemhi River in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in August 2024.

How much traffic does SH 28 over Lemhi River carry?

About 1,700 vehicles per day (2023 count), of which roughly 10% are trucks.

How long is SH 28 over Lemhi River?

The structure is 88 ft (26.8 m) long with a longest span of 85 ft (25.9 m) and a deck 41 ft wide.

Who owns SH 28 over Lemhi River?

It is owned by the State Highway Agency.