US Bridges

Dam Road over Cascade Dam Spillway

FairPosted for load

Valley County, Idaho · Cascade Dam · Structure no. 15CAS001

Built
1947
78 years old
Condition
Fair
inspected July 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
48 ft
2 main spans
Daily traffic
100
2020 count
Owner
Federal
Bureau of Reclamation

About this bridge

Dam Road over Cascade Dam Spillway is a steel stringer/multi-beam or girder carrying Dam Road over Cascade Dam Spillway in Valley County, Idaho. It was built in 1947, so it is 78 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. Its operating status is: posted for load restriction.

It carries about 100 vehicles a day, projected to reach 150 by 2044. The structure is 48 ft (14.6 m) long and 13 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

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CarriesDam Road
CrossesCascade Dam Spillway
LocationCascade Dam
CountyValley County
StateIdaho
Coordinates44.52463, -116.04958
Functional classRural Local

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.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJuly 2024
Inspection intervalevery 24 months
Operating statusPosted for load restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment4: Meets minimum tolerable limits to be left in place as is
Operating rating44.2 US tons
Inventory rating30.9 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckWood or timber
Main spans2
Design loadH 20
Structure length48 ft (14.6 m)
Longest span22 ft (6.8 m)
Deck width13 ft (4 m)
Roadway width12 ft (3.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic100 (2020)
Projected traffic150 by 2044
Trucks0%
Lanes on structure1
Traffic directionOne-lane bridge for two-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.9 mi (3 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerBureau of Reclamation
Maintained byBureau of Reclamation
Historic statusPossibly eligible for the National Register; requires further investigation
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was Dam Road over Cascade Dam Spillway built?

It was built in 1947, making it 78 years old in 2025.

What condition is Dam Road over Cascade Dam Spillway 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 July 2024.

How much traffic does Dam Road over Cascade Dam Spillway carry?

About 100 vehicles per day (2020 count).

How long is Dam Road over Cascade Dam Spillway?

The structure is 48 ft (14.6 m) long with a longest span of 22 ft (6.8 m) and a deck 13 ft wide.

Who owns Dam Road over Cascade Dam Spillway?

It is owned by the Bureau of Reclamation.