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 |
|---|---|---|---|---|
| 2025-05-20 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
| 2025-05-15 | DRY CREEK FIELD STATION 056 | RED LODGE, Carbon, MT | Pass | State |
| 2025-05-14 | WILLISTON BASIN - HATHAWAY STATION | HATHAWAY, Rosebud, MT | Pass | State |
| 2025-05-14 | WILLISTON BASIN - FORT PECK STATION | NASHUA, Valley, MT | Pass | State |
| 2025-05-05 | CHS INC. | GLENDIVE, Dawson, MT | Pass | State |
| 2025-05-02 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
| 2025-05-01 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-05-01 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-05-01 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-05-01 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-05-01 | CHS INC REFINERY LAUREL | LAUREL, Yellowstone, MT | Pass | State |
| 2025-04-29 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
| 2025-04-29 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
| 2025-04-29 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
| 2025-04-29 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
| 2025-04-28 | WILLISTON BASIN - LITTLE BEAVER | BAKER, Fallon, MT | Pass | State |
| 2025-04-28 | WILLISTON BASIN - LITTLE BEAVER | BAKER, Fallon, MT | Pass | State |
| 2025-04-28 | BASIN ELECTRIC POWER COOPERATIVE | BAINVILLE, Roosevelt, MT | Pass | State |
| 2025-04-28 | BASIN ELECTRIC POWER COOPERATIVE | BAINVILLE, Roosevelt, MT | Pass | State |
| 2025-04-25 | YELLOWSTONE POWER PLANT — high-priority violation on file | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-04-25 | YELLOWSTONE POWER PLANT — high-priority violation on file | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-04-23 | NORTHWESTERN ENERGY MAINLINE #1 | CUT BANK, Glacier, MT | Pass | State |
| 2025-04-23 | NORTHWESTERN ENERGY MAINLINE #1 | CUT BANK, Glacier, MT | Pass | State |
| 2025-04-23 | NORTHWESTERN ENERGY MAINLINE #1 | CUT BANK, Glacier, MT | Pass | State |
| 2025-04-23 | NORTHWESTERN ENERGY MAINLINE #1 | CUT BANK, Glacier, MT | Pass | State |
| 2025-04-23 | NORTHWESTERN ENERGY MAINLINE #1 | CUT BANK, Glacier, MT | Pass | State |
| 2025-04-23 | NORTHWESTERN ENERGY MAINLINE #1 | CUT BANK, Glacier, MT | Pass | State |
| 2025-04-10 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
| 2025-04-10 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
| 2025-04-09 | WILLISTON BASIN - CABIN CREEK | BAKER, Fallon, MT | Pass | State |
| 2025-04-09 | WILLISTON BASIN - CABIN CREEK | BAKER, Fallon, MT | Pass | State |
| 2025-04-09 | WILLISTON BASIN - CABIN CREEK | BAKER, Fallon, MT | Pass | State |
| 2025-04-09 | MSU - CENTRAL HEATING PLANT | BOZEMAN, Gallatin, MT | Pass | State |
| 2025-04-07 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
| 2025-04-07 | COLSTRIP STEAM ELECTRIC STATION | COLSTRIP, Rosebud, MT | Pass | State |
| 2025-03-28 | WILLISTON BASIN - MONARCH STATION | BAKER, Fallon, MT | Pass | State |
| 2025-03-21 | FLATHEAD ELECTRIC LFGE FACILITY | KALISPELL, Flathead, MT | Pass | State |
| 2025-03-17 | MALMSTROM AFB | GREAT FALLS, Cascade, MT | Pass | State |
| 2025-03-17 | MALMSTROM AFB | GREAT FALLS, Cascade, MT | Pass | State |
| 2025-03-17 | MALMSTROM AFB | GREAT FALLS, Cascade, MT | Pass | State |
| 2025-03-10 | COBB STORAGE FIELD STATION 017 | CUT BANK, Glacier, MT | Pass | State |
| 2025-03-10 | COBB STORAGE FIELD STATION 017 | CUT BANK, Glacier, MT | Pass | State |
| 2025-03-10 | COBB STORAGE FIELD STATION 017 | CUT BANK, Glacier, MT | Pass | State |
| 2025-03-10 | COBB STORAGE FIELD STATION 017 | CUT BANK, Glacier, MT | Pass | State |
| 2025-03-10 | COBB STORAGE FIELD STATION 017 | CUT BANK, Glacier, MT | Pass | State |
| 2025-03-10 | COBB STORAGE FIELD STATION 017 | CUT BANK, Glacier, MT | Pass | State |
| 2025-03-10 | COBB STORAGE FIELD STATION 017 | CUT BANK, Glacier, MT | Pass | State |
| 2025-03-10 | COBB STORAGE FIELD STATION 017 | CUT BANK, Glacier, MT | Pass | State |
| 2025-03-10 | COBB STORAGE FIELD STATION 017 | CUT BANK, Glacier, MT | Pass | State |
| 2025-03-10 | COBB STORAGE FIELD STATION 017 | CUT BANK, Glacier, MT | Pass | State |
| 2025-03-03 | ROCKY MOUNTAIN POWER | HARDIN, Big Horn, MT | Pass | State |
| 2025-02-25 | AUGUSTA MAIN LINE #3 (STA 051) | AUGUSTA, Lewis and Clark, MT | Pass | State |
| 2025-02-25 | AUGUSTA MAIN LINE #3 (STA 051) | AUGUSTA, Lewis and Clark, MT | Pass | State |
| 2025-02-25 | AUGUSTA MAIN LINE #3 (STA 051) | AUGUSTA, Lewis and Clark, MT | Pass | State |
| 2025-02-25 | AUGUSTA MAIN LINE #3 (STA 051) | AUGUSTA, Lewis and Clark, MT | Pass | State |
| 2025-02-21 | BASIN CREEK POWER SERVICES | BUTTE, Silver Bow, MT | Pass | State |
| 2025-02-21 | BASIN CREEK POWER SERVICES | BUTTE, Silver Bow, MT | Pass | State |
| 2025-02-21 | BASIN CREEK POWER SERVICES | BUTTE, Silver Bow, MT | Pass | State |
| 2025-02-21 | BASIN CREEK POWER SERVICES | BUTTE, Silver Bow, MT | Pass | State |
| 2025-02-21 | BASIN CREEK POWER SERVICES | BUTTE, Silver Bow, MT | Pass | State |
| 2025-02-21 | BASIN CREEK POWER SERVICES | BUTTE, Silver Bow, MT | Pass | State |
| 2025-02-21 | BASIN CREEK POWER SERVICES | BUTTE, Silver Bow, MT | Pass | State |
| 2025-02-21 | BASIN CREEK POWER SERVICES | BUTTE, Silver Bow, MT | Pass | State |
| 2025-02-21 | BASIN CREEK POWER SERVICES | BUTTE, Silver Bow, MT | Pass | State |
| 2025-01-27 | WILLISTON BASIN - FORT PECK STATION | NASHUA, Valley, MT | Pass | State |
| 2025-01-20 | WESTERN SUGAR COOPERATIVE — high-priority violation on file | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-01-20 | WESTERN SUGAR COOPERATIVE — high-priority violation on file | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-01-14 | ROCKY MOUNTAIN POWER | HARDIN, Big Horn, MT | Pass | State |
| 2025-01-14 | WESTERN SUGAR COOPERATIVE — high-priority violation on file | BILLINGS, Yellowstone, MT | Pass | State |
| 2025-01-13 | ROCKY MOUNTAIN POWER | HARDIN, Big Horn, MT | Pass | State |
| 2025-01-07 | WILLISTON BASIN - LITTLE BEAVER | BAKER, Fallon, MT | Pass | State |
| 2025-01-07 | WILLISTON BASIN - LITTLE BEAVER | BAKER, Fallon, MT | Pass | State |
| 2025-01-07 | WILLISTON BASIN - CABIN CREEK | BAKER, Fallon, MT | Pass | State |
| 2025-01-07 | WILLISTON BASIN - CABIN CREEK | BAKER, Fallon, 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.