WINDSOR, CA · Sonoma County

MOUNT WESKE ESTATES MUTUAL WATER COMPANY Water System

Inactive system

This water system is marked inactive in EPA’s federal records as of August 30, 2018. 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 Sonoma County, CA.

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 California’s official records. Always confirm current status with California before making decisions based on this information.

System facts

System ID (PWSID): CA4900643
System type: Community Water System
Population served: 26
Service connections: 24
Ownership: privately owned
Water source: groundwater (wells)

MOUNT WESKE ESTATES MUTUAL WATER COMPANY is one of 3,951 community water systems in California in the 500 or fewer people size category, formerly serving 26 people from groundwater.

EPA's federal records list this system as inactive in 2018; the record below is historical.

As of August 1, 2026, its federal record holds 14 entries between 1981 and 2017, all of which EPA lists as closed. Nothing has been added since 2017.

Of the 14, 1 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 inorganic chemicals, the Miscellaneous Other Rules, and the Radionuclides and Revised Rad Rule.

Violation history

Maximum Contaminant Level Violation, Average
Health-based
Arsenic
October 1, 2017 – December 31, 2017
Archived
Maximum Contaminant Level Violation, Average
Health-based
Arsenic
October 1, 2016 – December 31, 2016
Archived
Maximum Contaminant Level Violation, Average
Health-based
Arsenic
July 1, 2016 – September 30, 2016
Archived
Maximum Contaminant Level Violation, Average
Health-based
Arsenic
January 1, 2016 – March 31, 2016
Archived
Maximum Contaminant Level Violation, Average
Health-based
Arsenic
July 1, 2015 – September 30, 2015
Archived
Maximum Contaminant Level Violation, Average
Health-based
Arsenic
April 1, 2014 – June 30, 2014
Archived
Maximum Contaminant Level Violation, Average
Health-based
Arsenic
July 1, 2012 – September 30, 2012
Archived
Maximum Contaminant Level Violation, Average
Health-based
Arsenic
April 1, 2011 – June 30, 2011
Archived
Maximum Contaminant Level Violation, Average
Health-based
Arsenic
January 1, 2008 – March 31, 2008
Archived
Notification, Public
—
No contaminant on record
September 1, 1984 – September 30, 1984
Archived
Notification, Public
—
No contaminant on record
July 1, 1984 – July 31, 1984
Archived
Maximum Contaminant Level Violation, Single Sample
Health-based
Arsenic
July 29, 1982 – June 28, 1983
Archived
Maximum Contaminant Level Violation, Single Sample
Health-based
Arsenic
June 23, 1982 – July 22, 1982
Archived
Monitoring, Regular
—
Gross Alpha, Excl. Radon and U
October 1, 1981 – September 30, 1982
Archived

Archived closed in EPA's records (typically due to age or a data correction)

Period	Violation	Contaminant / rule	Health-based	Status
October 1, 2017 – December 31, 2017	Maximum Contaminant Level Violation, Average	Arsenic	Health-based	Archived
October 1, 2016 – December 31, 2016	Maximum Contaminant Level Violation, Average	Arsenic	Health-based	Archived
July 1, 2016 – September 30, 2016	Maximum Contaminant Level Violation, Average	Arsenic	Health-based	Archived
January 1, 2016 – March 31, 2016	Maximum Contaminant Level Violation, Average	Arsenic	Health-based	Archived
July 1, 2015 – September 30, 2015	Maximum Contaminant Level Violation, Average	Arsenic	Health-based	Archived
April 1, 2014 – June 30, 2014	Maximum Contaminant Level Violation, Average	Arsenic	Health-based	Archived
July 1, 2012 – September 30, 2012	Maximum Contaminant Level Violation, Average	Arsenic	Health-based	Archived
April 1, 2011 – June 30, 2011	Maximum Contaminant Level Violation, Average	Arsenic	Health-based	Archived
January 1, 2008 – March 31, 2008	Maximum Contaminant Level Violation, Average	Arsenic	Health-based	Archived
September 1, 1984 – September 30, 1984	Notification, Public	—	—	Archived
July 1, 1984 – July 31, 1984	Notification, Public	—	—	Archived
July 29, 1982 – June 28, 1983	Maximum Contaminant Level Violation, Single Sample	Arsenic	Health-based	Archived
June 23, 1982 – July 22, 1982	Maximum Contaminant Level Violation, Single Sample	Arsenic	Health-based	Archived
October 1, 1981 – September 30, 1982	Monitoring, Regular	Gross Alpha, Excl. Radon and U	—	Archived

Archived closed in EPA's records (typically due to age or a data correction)

Enforcement actions

June 2, 2009State Administrative/Compliance Order without penalty issued86 linked violations

Last known contact on file (system is inactive)

HARTLINE, CRAIG

707-431-6113

WINDSOR, CA 95492