US Bridges

US 20 over Porter Canal

Fair

Bonneville County, Idaho · In Idaho Falls · Structure no. 000000000012330

Built
1966
59 years old, rebuilt 1990
Condition
Fair
inspected November 2023
Type
Frame
Concrete
Length
35 ft
1 main span
Daily traffic
38,000
2023 count
Owner
State
State Highway Agency

About this bridge

US 20 over Porter Canal is a concrete frame carrying US 20 over Porter Canal in Bonneville County, Idaho. It was built in 1966 and reconstructed in 1990, so it is 59 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 38,000 vehicles a day, roughly 18% of them trucks, projected to reach 57,000 by 2042. The structure is 35 ft (10.7 m) long and 134 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

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CarriesUS 20
CrossesPorter Canal
LocationIn Idaho Falls
RouteU.S. Route 20
CountyBonneville County
StateIdaho
Coordinates43.50583, -112.05158
Functional classUrban Other Principal Arterial

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 protection7 GoodSome minor problems.
Last inspectionNovember 2023
Inspection intervalevery 48 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry9: Superior to present desirable criteria
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating69 US tons
Inventory rating41 US tons

Structure

Structure typeFrame
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length35 ft (10.7 m)
Longest span35 ft (10.7 m)
Deck width134 ft (40.8 m)
Roadway width93 ft (28.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic38,000 (2023)
Projected traffic57,000 by 2042
Trucks18%
Lanes on structure6
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed1.9 mi (3 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 proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was US 20 over Porter Canal built?

It was built in 1966, making it 59 years old in 2025. It was reconstructed in 1990.

What condition is US 20 over Porter 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 November 2023.

How much traffic does US 20 over Porter Canal carry?

About 38,000 vehicles per day (2023 count), of which roughly 18% are trucks.

How long is US 20 over Porter Canal?

The structure is 35 ft (10.7 m) long with a longest span of 35 ft (10.7 m) and a deck 134 ft wide.

Who owns US 20 over Porter Canal?

It is owned by the State Highway Agency.