US Bridges

478th Avenue over Six Mile Ck

Fair

Brookings County, South Dakota · 0.5N White · Structure no. 000000006240070

Built
1950
75 years old
Condition
Fair
inspected September 2023
Type
Slab
Concrete Continuous
Length
116 ft
5 main spans
Daily traffic
714
2022 count
Owner
County
County Highway Agency

About this bridge

478th Avenue over Six Mile Ck is a concrete continuous slab carrying 478th Avenue over Six Mile Ck in Brookings County, South Dakota. It was built in 1950, so it is 75 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 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 714 vehicles a day, roughly 3% of them trucks, projected to reach 714 by 2034. The structure is 116 ft (35.4 m) long and 28 ft wide. If it were closed, the detour would be 11.2 mi (18 km).

Location

Open in Google Maps
Carries478th Avenue
CrossesSix Mile Ck
Location0.5N White
RouteCounty Highway 0
CountyBrookings County
StateSouth Dakota
Coordinates44.44134, -96.64615
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.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection7 GoodSome minor problems.
Last inspectionSeptember 2023
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 geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating33.4 US tons
Inventory rating20.4 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans5
Design loadH 15
Structure length116 ft (35.4 m)
Longest span26 ft (7.9 m)
Deck width28 ft (8.6 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic714 (2022)
Projected traffic714 by 2034
Trucks3%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed11.2 mi (18 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 proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$1.7 million (2023 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was 478th Avenue over Six Mile Ck built?

It was built in 1950, making it 75 years old in 2025.

What condition is 478th Avenue over Six Mile 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 September 2023.

How much traffic does 478th Avenue over Six Mile Ck carry?

About 714 vehicles per day (2022 count), of which roughly 3% are trucks.

How long is 478th Avenue over Six Mile Ck?

The structure is 116 ft (35.4 m) long with a longest span of 26 ft (7.9 m) and a deck 28 ft wide.

Who owns 478th Avenue over Six Mile Ck?

It is owned by the County Highway Agency.