US Bridges

County Highway #23 over White Horse Ck

Fair

Mellette County, South Dakota · 4S Mosher · Structure no. 000000048480313

Built
1957
68 years old
Condition
Fair
inspected July 2024
Type
Slab
Concrete Continuous
Length
117 ft
5 main spans
Daily traffic
55
2022 count
Owner
County
County Highway Agency

About this bridge

County Highway #23 over White Horse Ck is a concrete continuous slab carrying County Highway #23 over White Horse Ck in Mellette County, South Dakota. It was built in 1957, so it is 68 years old, older than the South Dakota average of 48.9 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 55 vehicles a day, roughly 3% of them trucks, projected to reach 55 by 2032. The structure is 117 ft (35.7 m) long and 28 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

CarriesCounty Highway #23
CrossesWhite Horse Ck
Location4S Mosher
RouteCounty Highway 0
Coordinates43.41384, -100.29378
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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionJuly 2024
Inspection intervalevery 12 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation6: Equal to present minimum criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating39.1 US tons
Inventory rating23.4 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans5
Design loadH 15
Structure length117 ft (35.7 m)
Longest span25 ft (7.6 m)
Deck width28 ft (8.6 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic55 (2022)
Projected traffic55 by 2032
Trucks3%
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

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$90,000
NavigationNo navigation control on waterway

Frequently asked questions

When was County Highway #23 over White Horse Ck built?

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

What condition is County Highway #23 over White Horse Ck 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 County Highway #23 over White Horse Ck carry?

About 55 vehicles per day (2022 count), of which roughly 3% are trucks.

How long is County Highway #23 over White Horse Ck?

The structure is 117 ft (35.7 m) long with a longest span of 25 ft (7.6 m) and a deck 28 ft wide.

Who owns County Highway #23 over White Horse Ck?

It is owned by the County Highway Agency.