Irr Bia Rte 121 over Big Spring Creek
Roberts County, South Dakota · rated Good in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- Irr Bia Rte 121 over Big Spring Creek in Roberts County, South Dakota, is rated in good condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the culvert, rated 8 (very good condition) on the 0-9 scale.
- It was built in 2018, making it 7 years old at the 2025 inventory.
- It carries about 75 vehicles a day (traffic count year 2024).
- It is one of 41 of the 158 inventoried bridges in Roberts County rated good (25.9%); 40 (25.3%) are rated poor.
- A good rating means every major component - deck, superstructure, substructure, or culvert - is rated 7 or higher on FHWA's 0-9 scale: no more than minor problems.
View this bridge on a map → (45.49692, -97.04061)
Component ratings
| Component | Rating (2025) | FHWA scale meaning |
|---|---|---|
| Culvert | 8 | Very good condition |
Bridge details
| Structure | Concrete culvert |
| Length | about 20 ft |
| Location | 18.2 Km SW of Sisseton |
| NBI structure number | 0000A09347B0105 |
| Condition class | Good |
Source: FHWA National Bridge Inventory, 2025 data as reported by the South Dakota department of transportation.
Busiest bridges in Roberts County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| Irr SD010 over Ck | 2019 | 7,072 | Good |
| Irr SD010 over Ck | 1979 | 6,275 | Fair |
| 458TH Avenue over Creek | 1941 | 5,850 | Fair |
| 458TH Avenue over Creek | 1941 | 5,850 | Fair |
| 459TH Avenue over Creek | 1941 | 5,850 | Good |
| Irr I029 over Big Spring Ck | 1978 | 5,340 | Fair |
All bridges nearby: Roberts County, SD bridge conditions · every bridge in Roberts County · South Dakota bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.