181ST Street over Big Sioux River
Hamlin County, South Dakota · rated Good in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- 181ST Street over Big Sioux River in Hamlin County, South Dakota, is rated in good condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the deck, rated 7 (good condition) on the 0-9 scale.
- It was built in 2016, making it 9 years old at the 2025 inventory.
- It carries about 66 vehicles a day (traffic count year 2022).
- Its listed owner is the county highway agency.
- It is one of 26 of the 61 inventoried bridges in Hamlin County rated good (42.6%); 7 (11.5%) are rated poor.
- Its traffic status in the 2025 inventory is open, no restriction (NBI item 41).
- Its class is unchanged from 2024 (good), but component ratings moved: deck 8 to 7, superstructure 8 to 7.
- Its most recent inspection on record is dated July 2024, on a 24-month routine inspection cycle.
- 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 → (44.76074, -97.05)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 8 | 7 | Good condition |
| Superstructure | 8 | 7 | Good condition |
| Substructure | 8 | 8 | Very good condition |
Bridge details
| Structure | Prestressed concrete stringer or multi-beam girder |
| Length | about 96 ft |
| Location | 2N & 1.2W of Castlewood |
| NBI structure number | 000000029218030 |
| Condition class | Good |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | July 2024 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | 8: foundations stable, scour above the top of the footing |
Source: FHWA National Bridge Inventory, 2025 data as reported by the South Dakota department of transportation.
Busiest bridges in Hamlin County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I029 S over 462 Ave | 1973 | 4,595 | Fair |
| I029 N over 462 Ave | 1973 | 4,595 | Fair |
| I029 S over Stray Horse Ck | 1973 | 4,595 | Fair |
| I029 N over Stray Horse Ck | 1973 | 4,595 | Fair |
| I029 S over SD022 | 1973 | 4,595 | Fair |
| I029 N over SD022 | 1973 | 4,595 | Fair |
All bridges nearby: Hamlin County, SD bridge conditions · every bridge in Hamlin County · South Dakota bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.