EPA Air · stack tests by state and year
Air-emissions stack tests in Montana, 2025
- 174Stack tests
A stack test measures what a source actually emits, at the stack, against the limit in its permit. Every stack test below was recorded against a source in Montana during 2025; one facility can appear more than once, because this is a record of what happened rather than a list of places.
Counties in Montana, 2025
- Yellowstone County 52
- Glacier County 22
- Rosebud County 20
- Fallon County 13
- Silver Bow County 9
- Blaine County 9
- Richland County 8
- Roosevelt County 6
- Flathead County 6
- Lewis and Clark County 6
- Valley County 5
- Cascade County 4
- Big Horn County 3
- Stillwater County 3
Montana, other years
Air-emissions stack tests recorded in Montana, 2025
| Date | Facility | Where | Kind | Agency |
|---|---|---|---|---|
| 2025-12-30 | WILLISTON BASIN - MONARCH STATION | BAKER, Fallon, MT | Pass | State |
| 2025-12-30 | WILLISTON BASIN - MONARCH STATION | BAKER, Fallon, MT | Pass | State |
| 2025-12-24 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
| 2025-12-24 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
| 2025-12-17 | WEYERHAEUSER-EVERGREEN — high-priority violation on file | KALISPELL, Flathead, MT | Pass | State |
| 2025-12-16 | BAKKEN GATHERING PLANT | SIDNEY, Richland, MT | Pass | State |
| 2025-12-16 | BAKKEN GATHERING PLANT | SIDNEY, Richland, MT | Pass | State |
| 2025-12-16 | BAKKEN GATHERING PLANT | SIDNEY, Richland, MT | Pass | State |
| 2025-12-12 | FLATHEAD ELECTRIC LFGE FACILITY | KALISPELL, Flathead, MT | Pass | State |
| 2025-12-12 | WESTERN SUGAR COOPERATIVE — high-priority violation on file | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-12-12 | WESTERN SUGAR COOPERATIVE — high-priority violation on file | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-12-04 | BILLINGS REFINERY | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-12-04 | BILLINGS REFINERY | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-12-04 | BILLINGS REFINERY | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-12-04 | BILLINGS REFINERY | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-12-04 | BILLINGS REFINERY | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-12-04 | BILLINGS REFINERY | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-12-04 | BILLINGS REFINERY | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-11-26 | MDU - GLENDIVE | GLENDIVE, Dawson, MT | Pass | State |
| 2025-11-25 | WILLISTON BASIN - FORT PECK STATION | NASHUA, Valley, MT | Pass | State |
| 2025-11-25 | WILLISTON BASIN - FORT PECK STATION | NASHUA, Valley, MT | Pass | State |
| 2025-11-19 | WEYERHAEUSER-EVERGREEN — high-priority violation on file | KALISPELL, Flathead, MT | Fail | State |
| 2025-11-18 | YELLOWSTONE COUNTY GENERATING STATION | LAUREL, Yellowstone, MT | Pass | State |
| 2025-11-13 | BILLINGS REFINERY | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-10-28 | BILLINGS REFINERY | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-10-28 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-10-28 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-10-28 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-10-24 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
| 2025-10-16 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
| 2025-10-16 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
| 2025-10-10 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-10-09 | GRAYMONT WESTERN US INC | TOWNSEND, Broadwater, MT | Pass | State |
| 2025-10-09 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-10-09 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-10-09 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-10-09 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-10-09 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-10-06 | NORTHWESTERN ENERGY MAINLINE #1 | CUT BANK, Glacier, MT | Pass | State |
| 2025-10-06 | NORTHWESTERN ENERGY MAINLINE #1 | CUT BANK, Glacier, MT | Pass | State |
| 2025-10-06 | NORTHWESTERN ENERGY MAINLINE #1 | CUT BANK, Glacier, MT | Pass | State |
| 2025-10-06 | NORTHWESTERN ENERGY MAINLINE #1 | CUT BANK, Glacier, MT | Pass | State |
| 2025-10-06 | NORTHWESTERN ENERGY MAINLINE #1 | CUT BANK, Glacier, MT | Pass | State |
| 2025-10-06 | NORTHWESTERN ENERGY MAINLINE #1 | CUT BANK, Glacier, MT | Pass | State |
| 2025-09-12 | BLAINE COUNTY #1 | CHINOOK, Blaine, MT | Pass | State |
| 2025-09-12 | BLAINE COUNTY #1 | CHINOOK, Blaine, MT | Pass | State |
| 2025-09-12 | BLAINE COUNTY #1 | CHINOOK, Blaine, MT | Pass | State |
| 2025-09-12 | BLAINE COUNTY #1 | CHINOOK, Blaine, MT | Pass | State |
| 2025-09-12 | BLAINE COUNTY #1 | CHINOOK, Blaine, MT | Pass | State |
| 2025-09-12 | BLAINE COUNTY #1 | CHINOOK, Blaine, MT | Pass | State |
| 2025-09-12 | BLAINE COUNTY #1 | CHINOOK, Blaine, MT | Pass | State |
| 2025-09-12 | BLAINE COUNTY #1 | CHINOOK, Blaine, MT | Pass | State |
| 2025-09-12 | BLAINE COUNTY #1 | CHINOOK, Blaine, MT | Pass | State |
| 2025-09-12 | BAKKEN GATHERING PLANT | SIDNEY, Richland, MT | Pass | State |
| 2025-09-12 | BAKKEN GATHERING PLANT | SIDNEY, Richland, MT | Pass | State |
| 2025-09-02 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-09-02 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-08-27 | BAKKEN GATHERING PLANT | SIDNEY, Richland, MT | Pass | State |
| 2025-08-27 | BAKKEN GATHERING PLANT | SIDNEY, Richland, MT | Pass | State |
| 2025-08-26 | AUGUSTA MAIN LINE #3 (STA 051) | AUGUSTA, Lewis and Clark, MT | Pass | State |
| 2025-08-26 | AUGUSTA MAIN LINE #3 (STA 051) | AUGUSTA, Lewis and Clark, MT | Pass | State |
| 2025-08-25 | WEYERHAEUSER-CFALLS — high-priority violation on file | COLUMBIA FALLS, Flathead, MT | Pass | State |
| 2025-08-22 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-08-20 | N. BORDER PIPELINE CO STA. 3 | CULBERTSON, Roosevelt, MT | Pass | State |
| 2025-08-20 | N. BORDER PIPELINE CO STA. 3 | CULBERTSON, Roosevelt, MT | Pass | State |
| 2025-08-13 | PAR MONTANA BILLINGS REFINERY | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-08-13 | PAR MONTANA BILLINGS REFINERY | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-08-12 | WEYERHAEUSER-CFALLS — high-priority violation on file | COLUMBIA FALLS, Flathead, MT | Fail | State |
| 2025-08-08 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-08-08 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-08-08 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-08-07 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
| 2025-08-07 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
| 2025-08-06 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-08-06 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-08-06 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-08-06 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-08-06 | PAR MONTANA BILLINGS REFINERY | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-08-06 | PAR MONTANA BILLINGS REFINERY | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-08-06 | PAR MONTANA BILLINGS REFINERY | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-08-06 | PAR MONTANA BILLINGS REFINERY | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-08-06 | PAR MONTANA BILLINGS REFINERY | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-08-04 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-07-31 | CHARLIE CREEK COMPRESSOR STATION | LAMBERT, Richland, MT | Pass | State |
| 2025-07-23 | BASIN ELECTRIC POWER COOPERATIVE | BAINVILLE, Roosevelt, MT | Pass | State |
| 2025-07-23 | BASIN ELECTRIC POWER COOPERATIVE | BAINVILLE, Roosevelt, MT | Pass | State |
| 2025-07-22 | PAR MONTANA BULK TERMINAL | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-07-21 | WILLISTON BASIN - HATHAWAY STATION | HATHAWAY, Rosebud, MT | Pass | State |
| 2025-07-21 | WILLISTON BASIN - CABIN CREEK | BAKER, Fallon, MT | Pass | State |
| 2025-07-21 | WILLISTON BASIN - FORT PECK STATION | NASHUA, Valley, MT | Pass | State |
| 2025-07-14 | ASH GROVE CEMENT | CLANCY, Jefferson, MT | Pass | State |
| 2025-07-14 | ASH GROVE CEMENT | CLANCY, Jefferson, MT | Pass | State |
| 2025-07-02 | YELLOWSTONE POWER PLANT — high-priority violation on file | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-06-25 | ROCKY MOUNTAIN LABORATORIES FACILITY | HAMILTON, Ravalli, MT | Pass | State |
| 2025-06-09 | CALUMET MONTANA REFINING — high-priority violation on file | GREAT FALLS, Cascade, MT | Pass | State |
| 2025-06-02 | STILLWATER MINING CO SMELTER | COLUMBUS, Stillwater, MT | Pass | State |
| 2025-06-02 | STILLWATER MINING CO SMELTER | COLUMBUS, Stillwater, MT | Pass | State |
| 2025-06-02 | STILLWATER MINING CO SMELTER | COLUMBUS, Stillwater, MT | Pass | State |
| 2025-05-30 | YELLOWSTONE POWER PLANT — high-priority violation on file | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-05-20 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
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Dates as filed by the agency that recorded the stack test. Figures from EPA’s ICIS-AIR download.