Bridge conditions in Day County, South Dakota
34 inventoried bridges · 9 rated poor · 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
About one in 4 bridges in Day County is rated in poor condition: 9 of 34 on the federal inventory, one of the higher shares in South Dakota.
- 9 of the 34 bridges in Day County, South Dakota, are rated in poor condition (26.5%) in the 2025 National Bridge Inventory, as of .
- 15 bridges (44.1%) are rated good and 10 (29.4%) fair.
- The median Day County bridge was built in 1970.
- The busiest poor-rated bridge is 425TH Avenue over Burlington Northern RR (built 1960), carrying about 274 vehicles a day.
Good 44.1% · Fair 29.4% · Poor 26.5% of 34 bridges
Bridges rated poor
Every bridge in the county with a poor rating, busiest first. Poor means a major component is rated 4 or lower on FHWA's 0-9 scale; it is a repair flag, not a closure notice.
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| 425TH Avenue over Burlington Northern RR | 1960 | 274 | Poor |
| 423RD Avenue over Burlington Northern RR | 1938 | 218 | Poor |
| 137TH Street over Creek | 1926 | 115 | Poor |
| 12590-416th Avenue over Ck | 1932 | 70 | Poor |
| 412TH Avenue over Creek | 1920 | 69 | Poor |
| 127TH Street over Creek | 1930 | 15 | Poor |
| 418TH Avenue over Antelope Creek | 1928 | 15 | Poor |
| 133RD Street over Creek | 1935 | 10 | Poor |
| 421ST Avenue over Antelope Creek | 1935 | 10 | Poor |
Busiest bridges in the county
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| 446A Avenue over Blue Dog Lake | 2023 | 852 | Good |
| SD027 over Antelope Ck | 1970 | 428 | Fair |
| SD027 over Ck | 1970 | 428 | Fair |
| 130TH Street over Creek | 1935 | 385 | Fair |
| 130TH Street over Creek | 1930 | 376 | Good |
| 128TH Street over Creek | 2011 | 307 | Good |
| 128TH Street over Creek | 1993 | 307 | Fair |
| 425TH Avenue over Burlington Northern RR | 1960 | 274 | Poor |
| 423RD Avenue over Burlington Northern RR | 1938 | 218 | Poor |
| SD027 over Mud Ck | 1970 | 209 | Fair |
Source: FHWA National Bridge Inventory, 2025. Counts cover inventoried highway bridges over 20 feet; ratings are reported by the state DOT.
All of South Dakota: South Dakota bridge conditions by county · every download on the data page.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.