YELLOWTAIL, MT · Big Horn County

YELLOWTAIL DAM MK UPPER SYSTEM Water System

Inactive system

This water system is marked inactive in EPA’s federal records as of November 17, 2022. It is no longer an operating public water system under this PWSID, and no compliance deadlines — including the 2027 Consumer Confidence Report rule — apply to it.

If you are a resident looking for your current water provider, see water systems in Big Horn County, MT.

Data sourced from the EPA ECHO database (SDWA bulk download), last refreshed August 1, 2026. This is a record-keeping and public-information tool — it does not replace Montana’s official records. Always confirm current status with Montana before making decisions based on this information.

System facts

System ID (PWSID): MT0002531
System type: Community Water System
Population served: 40
Service connections: 12
Ownership: federal government
Water source: groundwater (wells)

YELLOWTAIL DAM MK UPPER SYSTEM is one of 1,084 community water systems in Montana in the 500 or fewer people size category, formerly serving 40 people from groundwater.

EPA's federal records list this system as inactive in 2022; the record below is historical.

As of August 1, 2026, its federal record holds 31 entries between 1995 and 2015, all of which EPA lists as closed. Nothing has been added since 2015.

Of the 31, 28 are monitoring and reporting requirements — the category that accounts for about four in five of all violations in EPA's national dataset — rather than findings about the water itself. The record involves synthetic organic chemicals, inorganic chemicals, and the Consumer Confidence Rule.

Violation history

Lead Consumer Notice
—
Lead and Copper Rule
December 30, 2015 – February 1, 2016
Resolved
Consumer Confidence Report Complete Failure to Report
—
Consumer Confidence Rule
July 1, 2012 – July 20, 2012
Resolved
Monitoring, Regular
—
Nitrate-Nitrite
January 1, 2005 – December 31, 2005
Resolved
Monitoring, Regular
—
Nitrate-Nitrite
January 1, 2003 – December 31, 2003
Resolved
Consumer Confidence Report Complete Failure to Report
—
Consumer Confidence Rule
July 1, 2002 – October 2, 2003
Resolved
Monitoring, Regular
—
Pentachlorophenol
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
Benzene
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
Heptachlor epoxide
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
2,4-D
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
HEXACHLOROBENZENE
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
Trichloroethylene
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
Barium
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
Fluoride
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
Mercury
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
Nickel
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
Antimony, Total
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
Beryllium, Total
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
BHC-GAMMA
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
Toxaphene
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
OXAMYL
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
Di(2-ethylhexyl) phthalate
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
Dinoseb
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
Aldicarb sulfoxide
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
Aldicarb
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
Atrazine
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
LASSO
January 1, 2002 – December 31, 2004
Resolved
Monitoring, Regular
—
Heptachlor
January 1, 2002 – December 31, 2004
Resolved
Consumer Confidence Report Complete Failure to Report
—
Consumer Confidence Rule
July 1, 2000 – August 19, 2004
Resolved
Monitoring, Routine Major (TCR)
—
Coliform (TCR)
September 1, 1997 – September 30, 1997
Resolved
Monitoring, Routine Major (TCR)
—
Coliform (TCR)
April 1, 1997 – April 30, 1997
Resolved
Monitoring, Routine Major (TCR)
—
Coliform (TCR)
April 1, 1995 – April 30, 1995
Resolved

Resolved addressed and confirmed by the state

Period	Violation	Contaminant / rule	Health-based	Status
December 30, 2015 – February 1, 2016	Lead Consumer Notice	Lead and Copper Rule	—	Resolved
July 1, 2012 – July 20, 2012	Consumer Confidence Report Complete Failure to Report	Consumer Confidence Rule	—	Resolved
January 1, 2005 – December 31, 2005	Monitoring, Regular	Nitrate-Nitrite	—	Resolved
January 1, 2003 – December 31, 2003	Monitoring, Regular	Nitrate-Nitrite	—	Resolved
July 1, 2002 – October 2, 2003	Consumer Confidence Report Complete Failure to Report	Consumer Confidence Rule	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	Pentachlorophenol	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	Benzene	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	Heptachlor epoxide	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	2,4-D	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	HEXACHLOROBENZENE	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	Trichloroethylene	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	Barium	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	Fluoride	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	Mercury	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	Nickel	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	Antimony, Total	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	Beryllium, Total	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	BHC-GAMMA	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	Toxaphene	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	OXAMYL	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	Di(2-ethylhexyl) phthalate	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	Dinoseb	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	Aldicarb sulfoxide	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	Aldicarb	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	Atrazine	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	LASSO	—	Resolved
January 1, 2002 – December 31, 2004	Monitoring, Regular	Heptachlor	—	Resolved
July 1, 2000 – August 19, 2004	Consumer Confidence Report Complete Failure to Report	Consumer Confidence Rule	—	Resolved
September 1, 1997 – September 30, 1997	Monitoring, Routine Major (TCR)	Coliform (TCR)	—	Resolved
April 1, 1997 – April 30, 1997	Monitoring, Routine Major (TCR)	Coliform (TCR)	—	Resolved
April 1, 1995 – April 30, 1995	Monitoring, Routine Major (TCR)	Coliform (TCR)	—	Resolved

Resolved addressed and confirmed by the state

Enforcement actions

February 6, 2018State Public Notification received1 linked violation
January 25, 2018State Compliance achieved1 linked violation
January 23, 2018State Violation/Reminder Notice1 linked violation
January 23, 2018State Public Notification requested1 linked violation
February 16, 2016State Compliance achieved1 linked violation
February 1, 2016State Compliance achieved1 linked violation
February 1, 2016State Violation/Reminder Notice1 linked violation
February 10, 2014State Public Notification received1 linked violation
January 24, 2014State Public Notification requested1 linked violation
January 24, 2014State Violation/Reminder Notice1 linked violation
January 15, 2014State Compliance achieved1 linked violation
January 15, 2014State Public Notification requested1 linked violation
January 15, 2014State Violation/Reminder Notice1 linked violation
July 20, 2012State Compliance achieved1 linked violation
January 14, 2011State Violation/Reminder Notice1 linked violation
May 15, 2009State Compliance achieved1 linked violation
May 15, 2009State Compliance achieved1 linked violation
May 15, 2009State Compliance achieved1 linked violation
May 15, 2009State Compliance achieved1 linked violation
August 5, 2008State Public Notification requested1 linked violation
August 5, 2008State Violation/Reminder Notice1 linked violation
July 31, 2008State Compliance achieved1 linked violation
January 18, 2007State Compliance achieved1 linked violation
January 14, 2007State Violation/Reminder Notice1 linked violation
January 14, 2007State Public Notification requested1 linked violation
February 14, 2006State Compliance achieved1 linked violation
February 10, 2006State Violation/Reminder Notice1 linked violation
November 22, 2005State Compliance achieved1 linked violation
September 27, 2005State Public Notification requested4 linked violations
June 7, 2005State Compliance achieved14 linked violations
June 6, 2005State Compliance achieved49 linked violations
April 15, 2005State Public Notification requested22 linked violations
April 14, 2005State Public Notification requested58 linked violations
August 19, 2004State Compliance achieved1 linked violation
May 12, 2004State Violation/Reminder Notice1 linked violation
May 12, 2004State Public Notification requested1 linked violation
December 23, 2002State Violation/Reminder Notice1 linked violation

Last known contact on file (system is inactive)

BYRNES, MICHAEL

406-666-3201

YELLOWTAIL, MT 59035