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Water system · PWSID CA4910012

SONOMA, CITY OF

SONOMA, CA · ~11,725 people served

Check your exact address → SONOMA overview
78
Good
PurityRadar safety score

PWSID

CA4910012

State

California

City

SONOMA

Population served

11,725

Primary source

Groundwater

Score history

▼ 22 points — the score moved from 100 to 78 on Jun 18, 2026, as newly published EPA data was incorporated.

Jun 18, 2026 · score 100 Jun 18, 2026 · score 78

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

PFAS & contaminant readings

Latest detections from EPA’s UCMR5 monitoring (through Jan 2024). Levels in parts per trillion (ppt).

PFOA

Perfluorooctanoic acid

6.2 ppt

limit 4 ppt

Above EPA limit · 1.5×

Lithium

29,000 ppt

limit —

No federal limit

PFHxA

6.1 ppt

limit —

No federal limit

Violations & enforcement

9

Violations on record

1

Unaddressed

1

Health-based

12

Enforcement actions

From EPA ECHO (SDWIS), most recent enforcement Sep 2024. Official EPA record →

Reporting · EPA contaminant 5200 began Jul 2025 Unaddressed
Monitoring & reporting · Arsenic began Apr 2021 Resolved
Monitoring & reporting · Haloacetic acids (HAA5) began Jan 2020 Resolved
Monitoring & reporting · Total trihalomethanes (TTHM) began Jan 2020 Resolved
Monitoring · Lead & Copper Rule began Nov 2017 Resolved
Max contaminant level (MCL) · Total coliform health-based began Jan 2010 Resolved
Monitoring & reporting · Total trihalomethanes (TTHM) began Apr 2006 Resolved
Monitoring & reporting · Haloacetic acids (HAA5) began Apr 2006 Resolved
Monitoring & reporting · Nitrate began Jan 2006 Resolved

Recent enforcement actions

  • State action · SOX Sep 2024
  • State action · SOX Sep 2024
  • State action · SOX Sep 2024
  • State action · SFL Sep 2021
  • State action · SFL Mar 2021
  • State action · SFJ Mar 2021
  • State action · SOX Mar 2018
  • State action · SFL Apr 2010

This profile is built from EPA public records for system CA4910012 — 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.