US Bridges

SH 55 over Deer Flat Canal

Fair

Canyon County, Idaho · 3.5 W. Nampa · Structure no. 000000000014705

Built
1973
52 years old, rebuilt 2017
Condition
Fair
inspected February 2023
Type
Frame
Concrete
Length
23 ft
1 main span
Daily traffic
19,500
2023 count
Owner
State
State Highway Agency

About this bridge

SH 55 over Deer Flat Canal is a concrete frame carrying SH 55 over Deer Flat Canal in Canyon County, Idaho. It was built in 1973 and reconstructed in 2017, so it is 52 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 19,500 vehicles a day, roughly 7% of them trucks, projected to reach 29,250 by 2042. The structure is 23 ft (7 m) long and 95 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
CarriesSH 55
CrossesDeer Flat Canal
Location3.5 W. Nampa
RouteState Highway 55
CountyCanyon County
StateIdaho
Coordinates43.60442, -116.67419
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionFebruary 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 rating51 US tons
Inventory rating30 US tons

Structure

Structure typeFrame
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length23 ft (7 m)
Longest span23 ft (7 m)
Deck width95 ft (29 m)
Roadway width93 ft (28.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic19,500 (2023)
Projected traffic29,250 by 2042
Trucks7%
Lanes on structure5
Traffic directionTwo-way traffic
CarriesHighway
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 proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$356,000 (2023 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SH 55 over Deer Flat Canal built?

It was built in 1973, making it 52 years old in 2025. It was reconstructed in 2017.

What condition is SH 55 over Deer Flat 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 February 2023.

How much traffic does SH 55 over Deer Flat Canal carry?

About 19,500 vehicles per day (2023 count), of which roughly 7% are trucks.

How long is SH 55 over Deer Flat Canal?

The structure is 23 ft (7 m) long with a longest span of 23 ft (7 m) and a deck 95 ft wide.

Who owns SH 55 over Deer Flat Canal?

It is owned by the State Highway Agency.