EPA Air · stack tests by county and year
Air-emissions stack tests in Big Horn County, Montana, 2025
- 3Stack tests
A stack test measures what a source actually emits, at the stack, against the limit in its permit. Each row below is one stack test recorded against a source in Big Horn County, Montana during 2025. A facility can appear several times: this is the year’s record of what happened, not a list of places. The sources themselves are on the Big Horn County facility page.
Big Horn County, Montana, 2025
Air-emissions stack tests in Big Horn County, other years
Air-emissions stack tests recorded in Big Horn County, Montana, 2025
| Date | Facility | Kind | Agency |
|---|---|---|---|
| 2025-03-03 | ROCKY MOUNTAIN POWER | Pass | State |
| 2025-01-14 | ROCKY MOUNTAIN POWER | Pass | State |
| 2025-01-13 | ROCKY MOUNTAIN POWER | Pass | State |
Dates as filed by the agency that recorded the stack test. Figures from EPA’s ICIS-AIR download.