Is WESTERN HILLS WATER DISTRICT/DIABLO GRAN required to publish a Consumer Confidence Report?

Yes. WESTERN HILLS WATER DISTRICT/DIABLO GRAN is a community water system, and federal rules (40 CFR 141 Subpart O) require every community water system to publish a Consumer Confidence Report each year.

When is WESTERN HILLS WATER DISTRICT/DIABLO GRAN’s next Consumer Confidence Report due?

WESTERN HILLS WATER DISTRICT/DIABLO GRAN’s next Consumer Confidence Report is due by July 1, 2027. The report covers calendar year 2026.

What is a Consumer Confidence Report?

A Consumer Confidence Report (CCR) is the annual drinking water quality report that community water systems must provide to the people they serve. It lists the contaminants detected in the system’s water during the year, where the water comes from, and how the results compare with federal limits. EPA’s revised CCR rule takes effect January 1, 2027, and the first reports in the new format are due July 1, 2027.

PATTERSON, CA · Stanislaus County

WESTERN HILLS WATER DISTRICT/DIABLO GRAN Water System

Consumer Confidence Report status

WESTERN HILLS WATER DISTRICT/DIABLO GRAN must publish a Consumer Confidence Report — the annual drinking water quality report covering calendar year 2026 — by July 1, 2027.

As of August 1, 2026, EPA's federal records show no open violations for WESTERN HILLS WATER DISTRICT/DIABLO GRAN.

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): CA5010039
System type: Community Water System
Population served: 2,000
Service connections: 596
Ownership: local government
Water source: surface water (rivers, lakes, or reservoirs)

WESTERN HILLS WATER DISTRICT/DIABLO GRAN is one of 728 community water systems in California in the 501 to 3,300 people size category, serving 2,000 people from surface water.

As of August 1, 2026, its federal record holds 17 entries between 2004 and 2018, all of which EPA lists as closed. Nothing has been added since 2018.

Of the 17, 4 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 the Stage 1 Disinfectants and Disinfection Byproducts Rule, the Stage 2 Disinfectants and Disinfection Byproducts Rule, and the Consumer Confidence Rule.

Violation history

Follow-up Or Routine LCR Tap M/R
—
Lead and Copper Rule
January 1, 2018 – March 16, 2021
Resolved
Maximum Contaminant Level Violation, Average
Health-based
TTHM
October 1, 2016 – December 31, 2016
Resolved
Maximum Contaminant Level Violation, Average
Health-based
TTHM
April 1, 2016 – June 30, 2016
Resolved
Consumer Confidence Report Complete Failure to Report
—
Consumer Confidence Rule
July 1, 2009 – July 2, 2009
Resolved
Monitoring, Routine Major (TCR)
—
Coliform (TCR)
June 1, 2008 – June 30, 2008
Resolved
Monitoring of Treatment (SWTR-Filter)
—
Surface Water Treatment Rule
May 1, 2008 – May 31, 2008
Resolved
Monitoring, Routine Major (TCR)
—
Coliform (TCR)
May 1, 2008 – May 31, 2008
Resolved
Maximum Contaminant Level Violation, Average
Health-based
TTHM
April 1, 2008 – June 30, 2008
Resolved
Maximum Contaminant Level Violation, Average
Health-based
TTHM
January 1, 2008 – March 31, 2008
Resolved
Maximum Contaminant Level Violation, Average
Health-based
TTHM
October 1, 2007 – December 31, 2007
Resolved
Maximum Contaminant Level Violation, Average
Health-based
Total Haloacetic Acids (HAA5)
January 1, 2006 – March 31, 2006
Resolved
Consumer Confidence Report Complete Failure to Report
—
Consumer Confidence Rule
July 1, 2005 – August 23, 2005
Resolved
Maximum Contaminant Level Violation, Average
Health-based
TTHM
July 1, 2005 – September 30, 2005
Resolved
Maximum Contaminant Level Violation, Average
Health-based
Total Haloacetic Acids (HAA5)
July 1, 2005 – September 30, 2005
Resolved
Maximum Contaminant Level Violation, Average
Health-based
Total Haloacetic Acids (HAA5)
April 1, 2005 – June 30, 2005
Resolved
Maximum Contaminant Level Violation, Average
Health-based
TTHM
January 1, 2005 – March 31, 2005
Resolved
Maximum Contaminant Level Violation, Average
Health-based
Total Haloacetic Acids (HAA5)
October 1, 2004 – December 31, 2004
Resolved

Resolved addressed and confirmed by the state

Period	Violation	Contaminant / rule	Health-based	Status
January 1, 2018 – March 16, 2021	Follow-up Or Routine LCR Tap M/R	Lead and Copper Rule	—	Resolved
October 1, 2016 – December 31, 2016	Maximum Contaminant Level Violation, Average	TTHM	Health-based	Resolved
April 1, 2016 – June 30, 2016	Maximum Contaminant Level Violation, Average	TTHM	Health-based	Resolved
July 1, 2009 – July 2, 2009	Consumer Confidence Report Complete Failure to Report	Consumer Confidence Rule	—	Resolved
June 1, 2008 – June 30, 2008	Monitoring, Routine Major (TCR)	Coliform (TCR)	—	Resolved
May 1, 2008 – May 31, 2008	Monitoring of Treatment (SWTR-Filter)	Surface Water Treatment Rule	—	Resolved
May 1, 2008 – May 31, 2008	Monitoring, Routine Major (TCR)	Coliform (TCR)	—	Resolved
April 1, 2008 – June 30, 2008	Maximum Contaminant Level Violation, Average	TTHM	Health-based	Resolved
January 1, 2008 – March 31, 2008	Maximum Contaminant Level Violation, Average	TTHM	Health-based	Resolved
October 1, 2007 – December 31, 2007	Maximum Contaminant Level Violation, Average	TTHM	Health-based	Resolved
January 1, 2006 – March 31, 2006	Maximum Contaminant Level Violation, Average	Total Haloacetic Acids (HAA5)	Health-based	Resolved
July 1, 2005 – August 23, 2005	Consumer Confidence Report Complete Failure to Report	Consumer Confidence Rule	—	Resolved
July 1, 2005 – September 30, 2005	Maximum Contaminant Level Violation, Average	TTHM	Health-based	Resolved
July 1, 2005 – September 30, 2005	Maximum Contaminant Level Violation, Average	Total Haloacetic Acids (HAA5)	Health-based	Resolved
April 1, 2005 – June 30, 2005	Maximum Contaminant Level Violation, Average	Total Haloacetic Acids (HAA5)	Health-based	Resolved
January 1, 2005 – March 31, 2005	Maximum Contaminant Level Violation, Average	TTHM	Health-based	Resolved
October 1, 2004 – December 31, 2004	Maximum Contaminant Level Violation, Average	Total Haloacetic Acids (HAA5)	Health-based	Resolved

Resolved addressed and confirmed by the state

Enforcement actions

March 16, 2021State Compliance achieved2 linked violations
July 16, 2019State Compliance achieved1 linked violation
July 16, 2019State Compliance achieved1 linked violation
October 19, 2018State Administrative/Compliance Order without penalty issued1 linked violation
May 10, 2018State Compliance achieved7 linked violations
November 1, 2016State Compliance achieved1 linked violation
October 1, 2016State Administrative/Compliance Order without penalty issued1 linked violation
April 30, 2016State Compliance achieved1 linked violation
February 3, 2016State Administrative/Compliance Order without penalty issued1 linked violation
October 23, 2014State Administrative/Compliance Order without penalty issued7 linked violations
March 31, 2010State Compliance achieved24 linked violations
July 21, 2008State Compliance achieved7 linked violations
July 21, 2008State Administrative/Compliance Order without penalty issued6 linked violations
August 23, 2005State Administrative/Compliance Order without penalty issued2 linked violations
December 30, 2004State Compliance achieved2 linked violations
November 30, 2004State Compliance achieved1 linked violation

Common questions

Is WESTERN HILLS WATER DISTRICT/DIABLO GRAN required to publish a Consumer Confidence Report?: Yes. WESTERN HILLS WATER DISTRICT/DIABLO GRAN is a community water system, and federal rules (40 CFR 141 Subpart O) require every community water system to publish a Consumer Confidence Report each year.
When is WESTERN HILLS WATER DISTRICT/DIABLO GRAN’s next Consumer Confidence Report due?: WESTERN HILLS WATER DISTRICT/DIABLO GRAN’s next Consumer Confidence Report is due by July 1, 2027. The report covers calendar year 2026.
Does WESTERN HILLS WATER DISTRICT/DIABLO GRAN have any open drinking water violations on record?: As of August 1, 2026, EPA's federal records show no open violations for WESTERN HILLS WATER DISTRICT/DIABLO GRAN.
What is a Consumer Confidence Report?: A Consumer Confidence Report (CCR) is the annual drinking water quality report that community water systems must provide to the people they serve. It lists the contaminants detected in the system’s water during the year, where the water comes from, and how the results compare with federal limits. EPA’s revised CCR rule takes effect January 1, 2027, and the first reports in the new format are due July 1, 2027.

Contact

KOVICH, MARK

408-828-7007

PATTERSON, CA 95363