EPA Air · stack tests by county and year

Air-emissions stack tests in Rosebud County, Montana, 2025

20Stack 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 Rosebud 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 Rosebud County facility page.

Air-emissions stack tests in Rosebud County, other years

Air-emissions stack tests recorded in Rosebud County, Montana, 2025

Date	Facility	Kind	Agency
2025-12-24	COLSTRIP STEAM ELECTRIC STATION	Pass	State
2025-12-24	COLSTRIP STEAM ELECTRIC STATION	Pass	State
2025-10-24	COLSTRIP STEAM ELECTRIC STATION	Pass	State
2025-10-16	COLSTRIP STEAM ELECTRIC STATION	Pass	State
2025-10-16	COLSTRIP STEAM ELECTRIC STATION	Pass	State
2025-08-07	COLSTRIP STEAM ELECTRIC STATION	Pass	State
2025-08-07	COLSTRIP STEAM ELECTRIC STATION	Pass	State
2025-07-21	WILLISTON BASIN - HATHAWAY STATION	Pass	State
2025-05-20	COLSTRIP STEAM ELECTRIC STATION	Pass	State
2025-05-20	COLSTRIP STEAM ELECTRIC STATION	Pass	State
2025-05-14	WILLISTON BASIN - HATHAWAY STATION	Pass	State
2025-05-02	COLSTRIP STEAM ELECTRIC STATION	Pass	State
2025-04-29	COLSTRIP STEAM ELECTRIC STATION	Pass	State
2025-04-29	COLSTRIP STEAM ELECTRIC STATION	Pass	State
2025-04-29	COLSTRIP STEAM ELECTRIC STATION	Pass	State
2025-04-29	COLSTRIP STEAM ELECTRIC STATION	Pass	State
2025-04-10	COLSTRIP STEAM ELECTRIC STATION	Pass	State
2025-04-10	COLSTRIP STEAM ELECTRIC STATION	Pass	State
2025-04-07	COLSTRIP STEAM ELECTRIC STATION	Pass	State
2025-04-07	COLSTRIP STEAM ELECTRIC STATION	Pass	State

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

What this page shows

This page covers Clean Air Act facilities in the EPA air register with stack tests in Rosebud county, MT, for 2025. It lists 20 stack tests recorded in 2025.