US Bridges

Stc 8317;DUFF Lane over Mill Slough

FairPosted for load

Canyon County, Idaho · 0.3 N. 1.3 E. Middleton · Structure no. 000000000027420

Built
1957
68 years old
Condition
Fair
inspected November 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
27 ft
1 main span
Daily traffic
3,100
2023 count
Owner
Local
Other Local Agency

About this bridge

Stc 8317;DUFF Lane over Mill Slough is a steel stringer/multi-beam or girder carrying Stc 8317;DUFF Lane over Mill Slough in Canyon County, Idaho. It was built in 1957, so it is 68 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 3,100 vehicles a day, roughly 4% of them trucks, projected to reach 4,650 by 2042. The structure is 27 ft (8.2 m) long and 36 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
CarriesStc 8317;DUFF Lane
CrossesMill Slough
Location0.3 N. 1.3 E. Middleton
RouteCounty Highway 8317
CountyCanyon County
StateIdaho
Coordinates43.71044, -116.59281
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionNovember 2023
Inspection intervalevery 24 months
Operating statusPosted for load restriction
ScourFoundations stable; action required to protect exposed foundations
Structural evaluation3: Basically intolerable, requiring high priority of corrective action
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 rating20 US tons
Inventory rating12 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadHS 15
Structure length27 ft (8.2 m)
Longest span25 ft (7.6 m)
Deck width36 ft (11 m)
Roadway width34 ft (10.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,100 (2023)
Projected traffic4,650 by 2042
Trucks4%
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

OwnerOther Local Agency
Maintained byOther Local 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 Stc 8317;DUFF Lane over Mill Slough built?

It was built in 1957, making it 68 years old in 2025.

What condition is Stc 8317;DUFF Lane over Mill Slough 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 November 2023.

How much traffic does Stc 8317;DUFF Lane over Mill Slough carry?

About 3,100 vehicles per day (2023 count), of which roughly 4% are trucks.

How long is Stc 8317;DUFF Lane over Mill Slough?

The structure is 27 ft (8.2 m) long with a longest span of 25 ft (7.6 m) and a deck 36 ft wide.

Who owns Stc 8317;DUFF Lane over Mill Slough?

It is owned by the Other Local Agency.