Irr US018 over Trib to Lake Andes
Charles Mix County, South Dakota · rated Good in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- Irr US018 over Trib to Lake Andes in Charles Mix 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 2005, making it 20 years old at the 2025 inventory.
- It carries about 1,298 vehicles a day (traffic count year 2024).
- Its listed owner is the state highway agency.
- It is one of 39 of the 103 inventoried bridges in Charles Mix County rated good (37.9%); 24 (23.3%) 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 → (43.14922, -98.51886)
Component ratings
| Component | Rating (2025) | FHWA scale meaning |
|---|---|---|
| Culvert | 8 | Very good condition |
Bridge details
| Structure | Continuous concrete culvert |
| Length | about 21 ft |
| Location | 1.0 E Jct Sd 50 W |
| NBI structure number | 000000012394244 |
| Condition class | Good |
Source: FHWA National Bridge Inventory, 2025 data as reported by the South Dakota department of transportation.
Busiest bridges in Charles Mix County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| SD045 over Drainage Channel | 1994 | 3,934 | Good |
| SD044 over Platte Ck | 1964 | 2,420 | Fair |
| SD044 over Castalia Ck | 1963 | 1,538 | Good |
| Irr US018 over Saint Francis Bay | 2023 | 1,494 | Good |
| Irr SD050 over Trib Choteau Ck | 2020 | 1,329 | Good |
| Old Irr SD050 over Ck | 1940 | 1,329 | Fair |
All bridges nearby: Charles Mix County, SD bridge conditions · every bridge in Charles Mix County · South Dakota bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.