US Bridges

SH 55 over Low Line Canal

Fair

Canyon County, Idaho · 5.5 N. Marsing · Structure no. 000000000014690

Built
1974
51 years old
Condition
Fair
inspected January 2024
Type
Tee Beam
Prestressed Concrete
Length
74 ft
2 main spans
Daily traffic
10,000
2023 count
Owner
State
State Highway Agency

About this bridge

SH 55 over Low Line Canal is a prestressed concrete tee beam carrying SH 55 over Low Line Canal in Canyon County, Idaho. It was built in 1974, so it is 51 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 10,000 vehicles a day, roughly 7% of them trucks, projected to reach 15,000 by 2042. The structure is 74 ft (22.6 m) long and 52 ft wide. If it were closed, the detour would be 3.7 mi (6 km).

Location

Open in Google Maps
CarriesSH 55
CrossesLow Line Canal
Location5.5 N. Marsing
RouteState Highway 55
CountyCanyon County
StateIdaho
Coordinates43.60311, -116.76308
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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJanuary 2024
Inspection intervalevery 24 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 rating60 US tons
Inventory rating31 US tons

Structure

Structure typeTee Beam
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20
Structure length74 ft (22.6 m)
Longest span35 ft (10.8 m)
Deck width52 ft (16 m)
Roadway width50 ft (15.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic10,000 (2023)
Projected traffic15,000 by 2042
Trucks7%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed3.7 mi (6 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 SH 55 over Low Line Canal built?

It was built in 1974, making it 51 years old in 2025.

What condition is SH 55 over Low Line 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 January 2024.

How much traffic does SH 55 over Low Line Canal carry?

About 10,000 vehicles per day (2023 count), of which roughly 7% are trucks.

How long is SH 55 over Low Line Canal?

The structure is 74 ft (22.6 m) long with a longest span of 35 ft (10.8 m) and a deck 52 ft wide.

Who owns SH 55 over Low Line Canal?

It is owned by the State Highway Agency.