BIG STONE
OperatingCoal power plant
- Capacity
- 457 MW
- Primary fuel
- Coal
- County
- Grant County
- Operator
- OTTER TAIL POWER CO
- Status
- Operating
- Commissioned
- 1975
- EIA plant ID
- 6098
- Coordinates
- 45.3036, -96.5101
BIG STONE, a 457 MW Coal power plant in Grant County, South Dakota. Operated by OTTER TAIL POWER CO, commissioned 1975.
Weather peril exposure
BIG STONE is a 457 MW coal power plant in Grant County, SD, operated by OTTER TAIL POWER CO, commissioned in 1975. Grant County carries moderate modeled catastrophe exposure in the FEMA National Risk Index, scoring 2.5 of 5 at the 38th national percentile. Heat wave is the leading peril, rated Very Low by FEMA at the 87th percentile.
The Bywatts loss layer is calibrated to solar PV hardware, so it is not applied to a coal plant. The ratings below are the FEMA National Risk Index county hazard ratings for this location.
Grant County hazard ratings
| Peril | FEMA rating | National percentile | Peril score | Events per year |
|---|---|---|---|---|
| Heat wave | Very Low | 87th | 4.5 of 5 | 2.7 |
| Ice storm | Relatively Moderate | 79th | 4.2 of 5 | 0.57 |
| Tornado | Relatively Low | 77th | 4.1 of 5 | 0.43 |
| Strong wind | Relatively Low | 72nd | 3.9 of 5 | 2.7 |
| Wildfire | Very Low | 71st | 3.9 of 5 | <0.01 |
| Winter weather | Relatively Low | 70th | 3.8 of 5 | 23.2 |
| Riverine flooding | Very Low | 65th | 3.6 of 5 | 1.0 |
| Hail | Relatively Low | 45th | 2.8 of 5 | 3.9 |
| Lightning | Very Low | 26th | 2.1 of 5 | 33.5 |
| Earthquake | Very Low | 11th | 1.4 of 5 | <0.01 |
Perils not assessed in Grant County
These perils carry no usable National Risk Index figure for this county, so they are excluded from the scoring rather than scored zero. A zero would claim the peril was assessed and found benign.
| Peril | Why it is not scored |
|---|---|
| Hurricane | FEMA rating is "Not Applicable" for this county |
| Coastal flooding | FEMA rating is "Not Applicable" for this county |
Model hail, wind and flood exposure for Grant County in the weather risk calculator
Ratings are the FEMA National Risk Index county hazard ratings; the peril score is a Bywatts transform of the FEMA national percentile. Full data sources and the solar vulnerability methodology are in the weather risk calculator.
Modeled estimate for screening and negotiation. Built from FEMA National Risk Index county hazard data and a solar vulnerability layer documented above. Not a quote, a binder, or actuarial advice, and not a substitute for a carrier's own model. Hazard data: FEMA National Risk Index December 2025, synced 2026-07-24. Resolution is county level, not site level.