EPA Air · stack tests by state and year

Air-emissions stack tests in Montana, 2026

91Stack 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 2026; one facility can appear more than once, because this is a record of what happened rather than a list of places.

Counties in Montana, 2026

Montana, other years

Air-emissions stack tests recorded in Montana, 2026

Date	Facility	Where	Kind	Agency
2026-08-17	CHS INC REFINERY LAUREL	LAUREL, Yellowstone, MT	Pass	State
2026-08-13	CHS INC REFINERY LAUREL	LAUREL, Yellowstone, MT	Pass	State
2026-08-13	PAR MONTANA BILLINGS REFINERY	BILLINGS, Yellowstone, MT	Pass	State
2026-08-13	PAR MONTANA BILLINGS REFINERY	BILLINGS, Yellowstone, MT	Pass	State
2026-08-13	PAR MONTANA BILLINGS REFINERY	BILLINGS, Yellowstone, MT	Pass	State
2026-08-11	CHS INC REFINERY LAUREL	LAUREL, Yellowstone, MT	Pass	State
2026-08-05	CHS INC REFINERY LAUREL	LAUREL, Yellowstone, MT	Pass	State
2026-08-05	CHS INC REFINERY LAUREL	LAUREL, Yellowstone, MT	Pass	State
2026-08-05	CHS INC REFINERY LAUREL	LAUREL, Yellowstone, MT	Pass	State
2026-08-04	CHS INC REFINERY LAUREL	LAUREL, Yellowstone, MT	Pass	State
2026-08-04	CHS INC REFINERY LAUREL	LAUREL, Yellowstone, MT	Fail	State
2026-07-20	CALUMET MONTANA REFINING — high-priority violation on file	GREAT FALLS, Cascade, MT	Pass	State
2026-07-20	CALUMET MONTANA REFINING — high-priority violation on file	GREAT FALLS, Cascade, MT	Pass	State
2026-07-20	CALUMET MONTANA REFINING — high-priority violation on file	GREAT FALLS, Cascade, MT	Pass	State
2026-07-09	ASH GROVE CEMENT	CLANCY, Jefferson, MT	Pass	State
2026-07-09	ASH GROVE CEMENT	CLANCY, Jefferson, MT	Pass	State
2026-07-09	ASH GROVE CEMENT	CLANCY, Jefferson, MT	Pass	State
2026-07-09	ASH GROVE CEMENT	CLANCY, Jefferson, MT	Pass	State
2026-06-25	WILLISTON BASIN - FORT PECK STATION	NASHUA, Valley, MT	Pass	State
2026-06-24	PAR MONTANA BULK TERMINAL	BILLINGS, Yellowstone, MT	Pass	State
2026-06-11	DRY CREEK FIELD STATION 056	RED LODGE, Carbon, MT	Pass	State
2026-06-05	WILLISTON BASIN - HATHAWAY STATION	HATHAWAY, Rosebud, MT	Pass	State
2026-06-05	WILLISTON BASIN - HATHAWAY STATION	HATHAWAY, Rosebud, MT	Pass	State
2026-06-05	WILLISTON BASIN - CABIN CREEK	BAKER, Fallon, MT	Pass	State
2026-06-01	ROCKY MOUNTAIN LABORATORIES FACILITY	HAMILTON, Ravalli, MT	Pass	State
2026-05-21	COLSTRIP STEAM ELECTRIC STATION	COLSTRIP, Rosebud, MT	Pass	State
2026-05-21	COLSTRIP STEAM ELECTRIC STATION	COLSTRIP, Rosebud, MT	Pass	State
2026-05-18	YELLOWSTONE POWER PLANT — high-priority violation on file	BILLINGS, Yellowstone, MT	Pass	State
2026-05-08	WILLISTON BASIN - CABIN CREEK	BAKER, Fallon, MT	Pass	State
2026-05-07	YELLOWSTONE POWER PLANT — high-priority violation on file	BILLINGS, Yellowstone, MT	Pass	State
2026-05-07	BILLINGS TRANSPORTATION OPERATIONS	BILLINGS, Yellowstone, MT	Pass	State
2026-04-30	WILLISTON BASIN - CABIN CREEK	BAKER, Fallon, MT	Fail	State
2026-04-27	CHS INC REFINERY LAUREL	LAUREL, Yellowstone, MT	Pass	State
2026-04-27	CHS INC REFINERY LAUREL	LAUREL, Yellowstone, MT	Pass	State
2026-04-27	CHS INC REFINERY LAUREL	LAUREL, Yellowstone, MT	Pass	State
2026-04-27	CHS INC REFINERY LAUREL	LAUREL, Yellowstone, MT	Pass	State
2026-04-09	COLSTRIP STEAM ELECTRIC STATION	COLSTRIP, Rosebud, MT	Pass	State
2026-04-09	COLSTRIP STEAM ELECTRIC STATION	COLSTRIP, Rosebud, MT	Pass	State
2026-04-09	COLSTRIP STEAM ELECTRIC STATION	COLSTRIP, Rosebud, MT	Pass	State
2026-04-09	COLSTRIP STEAM ELECTRIC STATION	COLSTRIP, Rosebud, MT	Pass	State
2026-04-08	COLSTRIP STEAM ELECTRIC STATION	COLSTRIP, Rosebud, MT	Pass	State
2026-04-08	COLSTRIP STEAM ELECTRIC STATION	COLSTRIP, Rosebud, MT	Pass	State
2026-04-01	CALUMET MONTANA REFINING — high-priority violation on file	GREAT FALLS, Cascade, MT	Pass	State
2026-04-01	CALUMET MONTANA REFINING — high-priority violation on file	GREAT FALLS, Cascade, MT	Pass	State
2026-04-01	CALUMET MONTANA REFINING — high-priority violation on file	GREAT FALLS, Cascade, MT	Pass	State
2026-04-01	CALUMET MONTANA REFINING — high-priority violation on file	GREAT FALLS, Cascade, MT	Pass	State
2026-03-31	MSU - CENTRAL HEATING PLANT	BOZEMAN, Gallatin, MT	Pass	State
2026-03-13	BASIN CREEK POWER SERVICES	BUTTE, Silver Bow, MT	Pass	State
2026-03-13	BASIN CREEK POWER SERVICES	BUTTE, Silver Bow, MT	Pass	State
2026-03-13	BASIN CREEK POWER SERVICES	BUTTE, Silver Bow, MT	Pass	State
2026-03-13	BASIN CREEK POWER SERVICES	BUTTE, Silver Bow, MT	Pass	State
2026-03-13	BASIN CREEK POWER SERVICES	BUTTE, Silver Bow, MT	Pass	State
2026-03-13	BASIN CREEK POWER SERVICES	BUTTE, Silver Bow, MT	Pass	State
2026-03-13	BASIN CREEK POWER SERVICES	BUTTE, Silver Bow, MT	Pass	State
2026-03-13	BASIN CREEK POWER SERVICES	BUTTE, Silver Bow, MT	Pass	State
2026-03-13	BASIN CREEK POWER SERVICES	BUTTE, Silver Bow, MT	Pass	State
2026-03-13	BASIN CREEK POWER SERVICES	BUTTE, Silver Bow, MT	Pass	State
2026-03-10	WILLISTON BASIN - LITTLE BEAVER	BAKER, Fallon, MT	Pass	State
2026-03-10	WILLISTON BASIN - LITTLE BEAVER	BAKER, Fallon, MT	Pass	State
2026-03-10	BOZEMAN PRODUCT TERMINAL	BOZEMAN, Gallatin, MT	Pass	State
2026-03-09	TRIDENT	THREE FORKS, Gallatin, MT	Pass	State
2026-02-17	PAR MONTANA BILLINGS REFINERY	BILLINGS, Yellowstone, MT	Pass	State
2026-02-09	CALUMET MONTANA REFINING — high-priority violation on file	GREAT FALLS, Cascade, MT	Pass	State
2026-02-09	CALUMET MONTANA REFINING — high-priority violation on file	GREAT FALLS, Cascade, MT	Pass	State
2026-02-09	CALUMET MONTANA REFINING — high-priority violation on file	GREAT FALLS, Cascade, MT	Pass	State
2026-02-02	NORTH MOULTON FIELD	SHELBY, Toole, MT	Pass	State
2026-01-29	COLSTRIP STEAM ELECTRIC STATION	COLSTRIP, Rosebud, MT	Pass	State
2026-01-29	PAR MONTANA BILLINGS REFINERY	BILLINGS, Yellowstone, MT	Pass	State
2026-01-27	DAVE GATES GENERATING STATION AT MILL CREEK	ANACONDA, Deer Lodge, MT	Pass	State
2026-01-27	DAVE GATES GENERATING STATION AT MILL CREEK	ANACONDA, Deer Lodge, MT	Pass	State
2026-01-27	DAVE GATES GENERATING STATION AT MILL CREEK	ANACONDA, Deer Lodge, MT	Pass	State
2026-01-27	DAVE GATES GENERATING STATION AT MILL CREEK	ANACONDA, Deer Lodge, MT	Pass	State
2026-01-27	DAVE GATES GENERATING STATION AT MILL CREEK	ANACONDA, Deer Lodge, MT	Pass	State
2026-01-27	DAVE GATES GENERATING STATION AT MILL CREEK	ANACONDA, Deer Lodge, MT	Pass	State
2026-01-27	DAVE GATES GENERATING STATION AT MILL CREEK	ANACONDA, Deer Lodge, MT	Pass	State
2026-01-23	KRAKEN CENTRAL SITE	SIDNEY, Richland, MT	Pass	State
2026-01-23	KRAKEN CENTRAL SITE	SIDNEY, Richland, MT	Pass	State
2026-01-23	KRAKEN CENTRAL SITE	SIDNEY, Richland, MT	Pass	State
2026-01-23	KRAKEN CENTRAL SITE	SIDNEY, Richland, MT	Pass	State
2026-01-13	COLSTRIP ENERGY LTD PARTNERSHIP	COLSTRIP, Rosebud, MT	Pass	State
2026-01-13	COLSTRIP ENERGY LTD PARTNERSHIP	COLSTRIP, Rosebud, MT	Pass	State
2026-01-13	COLSTRIP ENERGY LTD PARTNERSHIP	COLSTRIP, Rosebud, MT	Pass	State
2026-01-07	WILLISTON BASIN - HATHAWAY STATION	HATHAWAY, Rosebud, MT	Pass	State
2026-01-07	WILLISTON BASIN - HATHAWAY STATION	HATHAWAY, Rosebud, MT	Pass	State
2026-01-07	WILLISTON BASIN - LITTLE BEAVER	BAKER, Fallon, MT	Pass	State
2026-01-07	WILLISTON BASIN - LITTLE BEAVER	BAKER, Fallon, MT	Pass	State
2026-01-07	WILLISTON BASIN - CABIN CREEK	BAKER, Fallon, MT	Pass	State
2026-01-07	WILLISTON BASIN - CABIN CREEK	BAKER, Fallon, MT	Pass	State
2026-01-07	BILLINGS REFINERY	BILLINGS, Yellowstone, MT	Pass	State
2026-01-06	CALUMET MONTANA REFINING — high-priority violation on file	GREAT FALLS, Cascade, MT	Pass	State
2026-01-06	BAINVILLE STATION	BAINVILLE, Roosevelt, MT	Pass	State

Dates as filed by the agency that recorded the stack test. Figures from EPA’s ICIS-AIR download.