State Highway 47 over Big Bend Dam Spillway
Buffalo County, South Dakota · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- State Highway 47 over Big Bend Dam Spillway in Buffalo County, South Dakota, is rated in fair condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the deck, rated 6 (satisfactory condition) on the 0-9 scale.
- It was built in 1963, making it 62 years old at the 2025 inventory.
- It carries about 676 vehicles a day (traffic count year 2022).
- It is one of 16 of the 25 inventoried bridges in Buffalo County rated fair (64.0%); 1 (4.0%) are rated poor.
- Its traffic status in the 2025 inventory is open, no restriction (NBI item 41).
- Its condition class and component ratings are unchanged from the 2024 inventory.
- Its most recent inspection on record is dated September 2023, on a 24-month routine inspection cycle.
- It has fracture-critical members (NBI item 92A): steel tension members without a redundant load path, which get their own scheduled inspections.
- A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.
View this bridge on a map → (44.0608, -99.45388)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 6 | 6 | Satisfactory condition |
| Superstructure | 6 | 6 | Satisfactory condition |
| Substructure | 7 | 7 | Good condition |
Bridge details
| Structure | Steel girder and floorbeam |
| Length | about 134 ft |
| Location | 1 Mi. So. of Ft. Thompson |
| NBI structure number | CEPMROSD0000008 |
| Condition class | Fair |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | September 2023 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | 8: foundations stable, scour above the top of the footing |
| Fracture critical (item 92A) | Yes |
Source: FHWA National Bridge Inventory, 2025 data as reported by the South Dakota department of transportation.
Busiest bridges in Buffalo County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| Bia Rte 4 over Campbell Creek | 2013 | 1,720 | Good |
| SD045 over Crow Ck | 1960 | 949 | Fair |
| Irr SD050 over Wolf Ck | 1954 | 928 | Fair |
| Irr SD050 over Crow Ck | 1999 | 928 | Good |
| Irr SD034 over East Fork Soldier Ck | 1962 | 918 | Fair |
| Irr SD047 over Soldier Ck | 1963 | 917 | Fair |
All bridges nearby: Buffalo County, SD bridge conditions · every bridge in Buffalo County · South Dakota bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.