Bridge conditions in Union County, South Dakota
169 inventoried bridges · 41 rated poor · 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
Union County has 41 bridges rated poor out of 169 inventoried, a 24.3% share that puts it well above the national rate of about 7%.
- 41 of the 169 bridges in Union County, South Dakota, are rated in poor condition (24.3%) in the 2025 National Bridge Inventory, as of .
- 51 bridges (30.2%) are rated good and 77 (45.6%) fair.
- The median Union County bridge was built in 1977.
- The busiest poor-rated bridge is I029 N over 302 St (fas 6372) (built 1960), carrying about 8,020 vehicles a day.
Good 30.2% · Fair 45.6% · Poor 24.3% of 169 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 |
|---|---|---|---|
| I029 N over 302 St (fas 6372) | 1960 | 8,020 | Poor |
| 48480 Co Hwy 13 over Green Ck | 1985 | 500 | Poor |
| 47400 302 St. over West Brule Ck | 1960 | 435 | Poor |
| 30330 River Road over Ck | 1972 | 325 | Poor |
| 30999 477TH Ave over Ck | 1989 | 300 | Poor |
| 31490 477TH Ave over Br Brule Ck | 1955 | 300 | Poor |
| 47580 302ND St over East Brule Ck | 1960 | 270 | Poor |
| 48050 311TH St over East Union Ck | 1950 | 110 | Poor |
| 29895 Boyer Ave over Ck | 1992 | 70 | Poor |
| 31490 475TH St over Brule Ck | 1977 | 60 | Poor |
| 48480 298TH St over Ck | 1987 | 55 | Poor |
| 47610 312TH St over Ck | 1992 | 50 | Poor |
| 47230 305 Str. over Ck | 1987 | 45 | Poor |
| 30010 478 Ave. over Ck | 1982 | 45 | Poor |
| 30040 478 Ave. over Drainage Ditch | 1983 | 45 | Poor |
| 47880 306 Str. over Ck | 1950 | 45 | Poor |
| 48020 309 Str. over East Union Ck | 1950 | 45 | Poor |
| 48140 312TH St over Ck | 1940 | 45 | Poor |
| 30320 482ND Ave over Ck | 1983 | 45 | Poor |
| 30310 483RD Ave over Ck | 1983 | 45 | Poor |
| 47320 304 Str over Ck | 1970 | 43 | Poor |
| 47320 305 Str over Brule Ck | 1989 | 40 | Poor |
| 30070 474TH Ave over West Brule Ck | 1982 | 40 | Poor |
| 47460 304 Str. over Brule Ck | 1987 | 40 | Poor |
| 32200 477TH Ave over Lewis Ditch | 1968 | 40 | Poor |
| 32201 478TH Ave. over Lewis Ditch | 1940 | 40 | Poor |
| 47960 312TH St over West Union Ck | 1986 | 40 | Poor |
| 30820 480 Ave. over Ck | 1935 | 40 | Poor |
| 48030 310 Str. over East Union Ck | 1948 | 40 | Poor |
| 47160 310 Str. over Brule Ck | 1970 | 35 | Poor |
| 31128 472ND Ave.rd over Brule Ck | 1985 | 35 | Poor |
| 47230 306 Str. over Brule Ck | 1979 | 35 | Poor |
| 47340 306 Str. over Ck | 1948 | 35 | Poor |
| 31070 476TH Ave over Ck | 1963 | 35 | Poor |
| 47700 300 Str. over Ck | 1982 | 35 | Poor |
| 30330 472 Ave. over Ck | 1973 | 30 | Poor |
| 47570 311 Str. over Ck | 1955 | 30 | Poor |
| 47340 310TH St over Ck | 1935 | 25 | Poor |
| 30600 476 Ave. over Ck | 1965 | 25 | Poor |
| 48040 312TH St over East Union Ck | 1950 | 25 | Poor |
| 29730 484TH Ave over Ck | 1983 | 25 | Poor |
Busiest bridges in the county
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I029 S over Big Sioux Rv | 1990 | 18,090 | Good |
| I029 N over Big Sioux Rv | 1963 | 18,090 | Fair |
| I029 over Ck | 1961 | 11,970 | Good |
| I029 over Ck | 1961 | 11,970 | Good |
| I029 over Ck | 1961 | 11,970 | Good |
| I029 S over River Drive | 1981 | 9,870 | Good |
| I029 N over River Drive | 1981 | 9,870 | Good |
| I029 S over 302 St (fas 6372) | 1960 | 8,020 | Fair |
| I029 N over 302 St (fas 6372) | 1960 | 8,020 | Poor |
| I029 S over Ck | 1961 | 7,770 | 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.