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Water system · PWSID CA5010039

WESTERN HILLS WATER DISTRICT/DIABLO GRAN

PATTERSON, CA · ~2,000 people served

Check your exact address → PATTERSON overview
100
Excellent
PurityRadar safety score

PWSID

CA5010039

State

California

City

PATTERSON

Population served

2,000

Primary source

Surface water

Score history

No change since tracking began Jun 18, 2026.

Jun 18, 2026 · score 100 Jun 18, 2026 · score 100

2 score updates logged since tracking began Jun 18, 2026. Each future EPA re-score adds a point.

PFAS & contaminant readings

No PFAS detections are on record for this system from EPA’s UCMR5 monitoring (2023–25). Absence of a detection isn’t a guarantee — not every system was sampled, and this dataset doesn’t cover other contaminants.

Violations & enforcement

44

Violations on record

0

Unaddressed

32

Health-based

28

Enforcement actions

From EPA ECHO (SDWIS), most recent enforcement Mar 2021. Official EPA record →

Monitoring & reporting · Lead & Copper Rule began Jan 2018 Resolved
Max contaminant level (MCL) · Total trihalomethanes (TTHM) health-based began Jan 2017 Resolved
Max contaminant level (MCL) · Total trihalomethanes (TTHM) health-based began Oct 2016 Resolved
Monitoring & reporting · Lead & Copper Rule began Oct 2016 Resolved
Max contaminant level (MCL) · Total trihalomethanes (TTHM) health-based began Jul 2016 Resolved
Max contaminant level (MCL) · Total trihalomethanes (TTHM) health-based began Apr 2016 Resolved
Monitoring & reporting · Lead & Copper Rule began Oct 2015 Resolved
Max contaminant level (MCL) · Total trihalomethanes (TTHM) health-based began Jan 2015 Resolved
Max contaminant level (MCL) · Total trihalomethanes (TTHM) health-based began Oct 2014 Resolved
Max contaminant level (MCL) · Total trihalomethanes (TTHM) health-based began Jul 2014 Resolved
Monitoring & reporting · Bromate began Oct 2009 Resolved
Other · EPA contaminant 7000 began Jul 2009 Resolved

Recent enforcement actions

  • State action · SOX Mar 2021
  • State action · SOX Jul 2019
  • State action · SOX Jul 2019
  • State action · SFL Oct 2018
  • State action · SOX May 2018
  • State action · SOX Nov 2016
  • State action · SFL Oct 2016
  • State action · SOX Apr 2016

This profile is built from EPA public records for system CA5010039 — SDWIS violations and UCMR5 PFAS sampling. The score is system-level and can’t account for your home’s plumbing (older pipes can add lead at the tap). For health decisions, check your exact address, read the utility’s Consumer Confidence Report, and confirm with your provider.