US Bridges

81st So./Cotton RD over Butte Arm Canal

Fair

Bonneville County, Idaho · 4.6 S. 1.6 W. Idaho Falls · Structure no. 000000000031165

Built
1950
75 years old
Condition
Fair
inspected April 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
30 ft
1 main span
Daily traffic
360
2023 count
Owner
County
County Highway Agency

About this bridge

81st So./Cotton RD over Butte Arm Canal is a steel stringer/multi-beam or girder carrying 81st So./Cotton RD over Butte Arm Canal in Bonneville County, Idaho. It was built in 1950, so it is 75 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 360 vehicles a day, roughly 6% of them trucks, projected to reach 540 by 2042. The structure is 30 ft (9.2 m) long and 28 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
Carries81st So./Cotton RD
CrossesButte Arm Canal
Location4.6 S. 1.6 W. Idaho Falls
RouteCounty Highway 0
CountyBonneville County
StateIdaho
Coordinates43.42478, -112.06994
Functional classRural Local

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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
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 inspectionApril 2024
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 geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating53.6 US tons
Inventory rating31.7 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadH 20
Structure length30 ft (9.2 m)
Longest span29 ft (8.8 m)
Deck width28 ft (8.5 m)
Roadway width23 ft (7.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic360 (2023)
Projected traffic540 by 2042
Trucks6%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.9 mi (3 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$327,000 (2018 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was 81st So./Cotton RD over Butte Arm Canal built?

It was built in 1950, making it 75 years old in 2025.

What condition is 81st So./Cotton RD over Butte Arm Canal 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 April 2024.

How much traffic does 81st So./Cotton RD over Butte Arm Canal carry?

About 360 vehicles per day (2023 count), of which roughly 6% are trucks.

How long is 81st So./Cotton RD over Butte Arm Canal?

The structure is 30 ft (9.2 m) long with a longest span of 29 ft (8.8 m) and a deck 28 ft wide.

Who owns 81st So./Cotton RD over Butte Arm Canal?

It is owned by the County Highway Agency.