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Nicasio, CA Tap Water Quality 2026

Water quality report for Nicasio, CA — PFAS, lead and copper results, violation history and state inspection findings from EPA SDWIS.

A look at Nicasio's drinking water using EPA enforcement records: violations, lead and copper results, PFAS sampling and state inspection findings.

Main Utility: Nicasio Valley Ranch Mutual PWSID: CA2100579 Updated: 2026 Q2
✅

No federal limits exceeded on record

Lead is 4.00 ppb, 27% of the action level and no violations are open. PFAS has never been sampled at this system.

C

Nicasio earns a C for water quality

Graded on violations and lead, with state inspection findings. PFAS not tested.

Lead: 4.00 ppb — 27% of the federal action level
PFAS never sampled at this system
12 violations since 2015, 9 health-based
No violations currently open
Nicasio's lead level vs. all California community water systems
0 ppb5 ppb10 ppb15 ppb
Lead level: 4.00 ppb — 27% of the federal action level
✓ Lower lead than 26% of California utilities
Population Served
29
~14 connections
Water Source
Groundwater
Drawn from wells — SDWIS source code GW
Active Violations
0
12 since 2015, all resolved

Lead & Copper Testing

Lead (Pb)
90th percentile of tap samples collected across the distribution system
27% of EPA action level
4.00 ppb
Action level: 15 ppb
Copper (Cu)
90th percentile of tap samples. SDWIS reports a copper figure only when a system exceeds the action level, so any value here is an exceedance.
134.6% of EPA action level
1,750 ppb
Action level: 1,300 ppb
The 90th-percentile lead result is 4.00 ppb, 27% of the 15 ppb federal action level. The action level is a treatment trigger, not a legal maximum, and it is measured across sampled taps rather than at any single home. Copper reached the action level here; a copper figure appears in SDWIS only when a system triggers it.

Contaminant Violations (2015–Present)

ContaminantTypeMeasuredLimitPeriodStatus
TTHM MCL EXCEEDANCE 0.096 MG/L 0.080 mg/L 2021 Resolved
Arsenic MONITORING AND REPORTING — 0.010 mg/L 2020 Resolved
Arsenic MONITORING AND REPORTING — 0.010 mg/L 2020 Resolved
— OTHER — — 2019 Resolved
TTHM MCL EXCEEDANCE 140 UG/L 0.080 mg/L 2019 Resolved
TTHM MCL EXCEEDANCE 81 UG/L 0.080 mg/L 2019 Resolved
TTHM MCL EXCEEDANCE 89 UG/L 0.080 mg/L 2018 Resolved
TTHM MCL EXCEEDANCE 98 UG/L 0.080 mg/L 2018 Resolved
TTHM MCL EXCEEDANCE 130 UG/L 0.080 mg/L 2017 Resolved
TTHM MCL EXCEEDANCE 101 MG/L 0.080 mg/L 2015 Resolved
TTHM MCL EXCEEDANCE 0.13 MG/L 0.080 mg/L 2015 Resolved
TTHM MCL EXCEEDANCE 0.084 MG/L 0.080 mg/L 2015 Resolved
Understanding violation types MCL violations mean a contaminant exceeded the federal maximum limit — the most serious type.
TT (Treatment Technique) violations mean required treatment procedures weren't followed, but don't necessarily mean contamination occurred.

Violation History

12 violations are on record since 2015, of which 9 were health-based. All have been resolved and none remain open.

About the Main Water System

Utility Nicasio Valley Ranch Mutual
PWSID CA2100579
Water source Groundwater — Drawn from wells — SDWIS source code GW
Population served 29
Service connections 14
Systems serving this area 1
Regulator State primacy agency
Data through 2026 Q2 — EPA SDWIS

Frequently Asked Questions

Is Nicasio tap water safe to drink? ▼
No federal limit is exceeded on record. No violations are currently open. Lead is 4.00 ppb, 27% of the action level.
Does Nicasio water have PFAS? ▼
This system has never been sampled for PFAS. EPA's national monitoring covered systems serving 3,300 people or more, so no results exist — which is not evidence that none is present.
Who supplies water to Nicasio? ▼
Nicasio Valley Ranch Mutual (PWSID CA2100579). Groundwater. Drawn from wells — SDWIS source code GW
When was this system last inspected? ▼
It was last inspected on 2023-03-22. No significant deficiencies were recorded.

What Should Nicasio Residents Do?

1
Read your annual water report
Your supplier publishes a Consumer Confidence Report each July covering the prior year.
2
Check for a lead service line
Lead reaches tap water mainly through service lines and household plumbing. Suppliers now publish an inventory identifying lead lines.
3
Flush before drinking
If water has sat in pipes more than six hours, run the cold tap for two minutes before drinking or cooking.

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