US Bridges

State Highway 47 over Big Bend Dam Spillway

Fair

Buffalo County, South Dakota · 1 Mi. So. of Ft. Thompson · Structure no. CEPMROSD0000008

Built
1963
62 years old
Condition
Fair
inspected September 2023
Type
Girder and Floorbeam System
Steel
Length
135 ft
9 main spans
Daily traffic
676
2022 count
Owner
Federal
Corps of Engineers (Civil)

About this bridge

State Highway 47 over Big Bend Dam Spillway is a steel girder and floorbeam system carrying State Highway 47 over Big Bend Dam Spillway in Buffalo County, South Dakota. It was built in 1963, so it is 62 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 676 vehicles a day, roughly 32% of them trucks, projected to reach 350 by 2040. The structure is 135 ft (41.1 m) long and 12 ft wide. If it were closed, the detour would be 96.9 mi (156 km).

Location

Open in Google Maps
CarriesState Highway 47
CrossesBig Bend Dam Spillway
Location1 Mi. So. of Ft. Thompson
RouteState Highway 47
CountyBuffalo County
StateSouth Dakota
Coordinates44.0608, -99.45388
Functional classRural Minor Arterial

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.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionSeptember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating31.7 US tons
Inventory rating24.7 US tons

Structure

Structure typeGirder and Floorbeam System
MaterialSteel
DeckConcrete, cast-in-place
Main spans9
Design loadHS 20
Structure length135 ft (41.1 m)
Longest span16 ft (4.9 m)
Deck width12 ft (3.7 m)
Roadway width8 ft (2.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic676 (2022)
Projected traffic350 by 2040
Trucks32%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed96.9 mi (156 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCorps of Engineers (Civil)
Maintained byCorps of Engineers (Civil)
Historic statusNot eligible for the National Register of Historic Places
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$11,000 (2018 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was State Highway 47 over Big Bend Dam Spillway built?

It was built in 1963, making it 62 years old in 2025.

What condition is State Highway 47 over Big Bend 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 September 2023.

How much traffic does State Highway 47 over Big Bend Dam Spillway carry?

About 676 vehicles per day (2022 count), of which roughly 32% are trucks.

How long is State Highway 47 over Big Bend Dam Spillway?

The structure is 135 ft (41.1 m) long with a longest span of 16 ft (4.9 m) and a deck 12 ft wide.

Who owns State Highway 47 over Big Bend Dam Spillway?

It is owned by the Corps of Engineers (Civil).