US Bridges

SH 46 over Knowlton Creek

Fair

Camas County, Idaho · 29.9 N. Gooding · Structure no. 000000000014405

Built
1955
70 years old
Condition
Fair
inspected August 2024
Type
Stringer/Multi-beam or Girder
Concrete
Length
40 ft
1 main span
Daily traffic
630
2023 count
Owner
State
State Highway Agency

About this bridge

SH 46 over Knowlton Creek is a concrete stringer/multi-beam or girder carrying SH 46 over Knowlton Creek in Camas County, Idaho. It was built in 1955, so it is 70 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 630 vehicles a day, roughly 15% of them trucks, projected to reach 945 by 2042. The structure is 40 ft (12.2 m) long and 31 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
CarriesSH 46
CrossesKnowlton Creek
Location29.9 N. Gooding
RouteState Highway 46
CountyCamas County
StateIdaho
Coordinates43.33211, -114.71264
Functional classRural Major Collector

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.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionAugust 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating71 US tons
Inventory rating42 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length40 ft (12.2 m)
Longest span39 ft (11.9 m)
Deck width31 ft (9.3 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic630 (2023)
Projected traffic945 by 2042
Trucks15%
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

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$505,000 (2019 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SH 46 over Knowlton Creek built?

It was built in 1955, making it 70 years old in 2025.

What condition is SH 46 over Knowlton Creek 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 August 2024.

How much traffic does SH 46 over Knowlton Creek carry?

About 630 vehicles per day (2023 count), of which roughly 15% are trucks.

How long is SH 46 over Knowlton Creek?

The structure is 40 ft (12.2 m) long with a longest span of 39 ft (11.9 m) and a deck 31 ft wide.

Who owns SH 46 over Knowlton Creek?

It is owned by the State Highway Agency.