US Bridges

SH 55 over Phyllis Canal

Good

Canyon County, Idaho · 3 W. Nampa · Structure no. 000000000014710

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

About this bridge

SH 55 over Phyllis Canal is a concrete frame carrying SH 55 over Phyllis Canal in Canyon County, Idaho. It was built in 1973, 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 good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 19,500 vehicles a day, roughly 7% of them trucks, projected to reach 29,250 by 2042. The structure is 22 ft (6.7 m) long and 52 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
CarriesSH 55
CrossesPhyllis Canal
Location3 W. Nampa
RouteState Highway 55
CountyCanyon County
StateIdaho
Coordinates43.6045, -116.66369
Functional classUrban Other Principal Arterial

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionFebruary 2023
Inspection intervalevery 48 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than 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 rating54 US tons
Inventory rating32 US tons

Structure

Structure typeFrame
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length22 ft (6.7 m)
Longest span22 ft (6.7 m)
Deck width52 ft (15.8 m)
Roadway width50 ft (15.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic19,500 (2023)
Projected traffic29,250 by 2042
Trucks7%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed3.1 mi (5 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 Phyllis Canal built?

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

What condition is SH 55 over Phyllis Canal in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in February 2023.

How much traffic does SH 55 over Phyllis Canal carry?

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

How long is SH 55 over Phyllis Canal?

The structure is 22 ft (6.7 m) long with a longest span of 22 ft (6.7 m) and a deck 52 ft wide.

Who owns SH 55 over Phyllis Canal?

It is owned by the State Highway Agency.