320 Avenue over Ck
Sully County, South Dakota · rated Poor in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- 320 Avenue over Ck in Sully County, South Dakota, is rated in poor condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the superstructure, rated 4 (poor condition) on the 0-9 scale.
- It was built in 1961, making it 64 years old at the 2025 inventory.
- It carries about 25 vehicles a day (traffic count year 2022).
- Its listed owner is the county highway agency.
- It is one of 6 of the 31 inventoried bridges in Sully County rated poor (19.4%); 6 (19.4%) are rated poor.
- A poor rating means at least one major component - deck, superstructure, or substructure - is rated 4 or lower on FHWA's 0-9 scale. It does not by itself mean the bridge is unsafe; bridges judged unsafe are closed or load-restricted by their owners.
View this bridge on a map → (44.56013, -99.75735)
Component ratings
| Component | Rating (2025) | FHWA scale meaning |
|---|---|---|
| Deck | 6 | Satisfactory condition |
| Superstructure | 4 | Poor condition |
| Substructure | 5 | Fair condition |
Bridge details
| Structure | Concrete channel beam |
| Length | about 24 ft |
| Location | 16E & 10.2S Onida |
| NBI structure number | 000000060470231 |
| Condition class | Poor |
Source: FHWA National Bridge Inventory, 2025 data as reported by the South Dakota department of transportation.
Busiest bridges in Sully County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| US083 over Okobojo Ck | 1998 | 1,490 | Good |
| 185 St over Ck | 2017 | 760 | Good |
| SD1804 over Cow Ck | 2007 | 632 | Good |
| SD1804 over Okobojo Ck | 1972 | 632 | Fair |
| SD1804 over Ck | 1995 | 261 | Good |
| 291 Avenue over Okobojo Ck | 1936 | 250 | Fair |
All bridges nearby: Sully County, SD bridge conditions · every bridge in Sully County · South Dakota bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.