US Bridges

I 15 Nbl over SH 40;DOWNEY Ic

Fair

Bannock County, Idaho · 10.3 S. Arimo · Structure no. 000000000011075

Built
1971
54 years old, rebuilt 1987
Condition
Fair
inspected July 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
162 ft
3 main spans
Daily traffic
6,000
2023 count
Owner
State
State Highway Agency

About this bridge

I 15 Nbl over SH 40;DOWNEY Ic is a prestressed concrete stringer/multi-beam or girder carrying I 15 Nbl over SH 40;DOWNEY Ic in Bannock County, Idaho. It was built in 1971 and reconstructed in 1987, so it is 54 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 6,000 vehicles a day, roughly 23% of them trucks, projected to reach 9,000 by 2042. The structure is 162 ft (49.4 m) long and 44 ft wide.

Location

Open in Google Maps
CarriesI 15 Nbl
CrossesSH 40;DOWNEY Ic
Location10.3 S. Arimo
RouteInterstate 15
CountyBannock County
StateIdaho
Coordinates42.43044, -112.18219
Functional classRural Principal Arterial - Interstate

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating65 US tons
Inventory rating38 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length162 ft (49.4 m)
Longest span53 ft (16.2 m)
Deck width44 ft (13.3 m)
Roadway width41 ft (12.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic6,000 (2023)
Projected traffic9,000 by 2042
Trucks23%
Lanes on structure2
Traffic directionOne-way traffic
CarriesOverpass structure at an interchange
CrossesHighway
Detour if closed—
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkInterstate STRAHNET route

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedNone recorded
Estimated improvement cost—
NavigationNot applicable (no waterway)

Frequently asked questions

When was I 15 Nbl over SH 40;DOWNEY Ic built?

It was built in 1971, making it 54 years old in 2025. It was reconstructed in 1987.

What condition is I 15 Nbl over SH 40;DOWNEY Ic 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 I 15 Nbl over SH 40;DOWNEY Ic carry?

About 6,000 vehicles per day (2023 count), of which roughly 23% are trucks.

How long is I 15 Nbl over SH 40;DOWNEY Ic?

The structure is 162 ft (49.4 m) long with a longest span of 53 ft (16.2 m) and a deck 44 ft wide.

Who owns I 15 Nbl over SH 40;DOWNEY Ic?

It is owned by the State Highway Agency.