PWSID CA2100579
NICASIO VALLEY RANCH MUTUAL
Community water system based in Nicasio, CA
Service area on file with EPA: Marin County. EPA's recorded service area can be incomplete for regional authorities. The cities and counties above are what the utility has filed with EPA; the utility may serve additional areas.
- Population served
- 36
- Source
- Groundwater
- Status
- Active
At a glance
2 above the safety limit, 1 detection to watch
-
Copper was found above the federal safety limit. Long-term high exposure can affect the liver and kidneys.
Most recent lead and copper test · See details below
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EPA's Lead and Copper Rule Improvements treat galvanized service lines as lead, because galvanized iron pipe installed downstream of an old lead component absorbs and continues to release lead for years after the lead source is removed.
From the utility's published inventory · See details below
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Public health experts agree no amount of lead in drinking water is safe. Even low levels can affect children's brain development.
Most recent lead and copper test · See details below
-
CDC's My Water's Fluoride listing does not report this system as fluoridating its drinking water.
Per CDC My Water's Fluoride · See details below
Past 5 years: 2 health-based violations on file, all marked Resolved or Archived. See compliance history below.
Risk classification follows EPA's published values for safe drinking water, with caution and concern bands reviewed by a clinician. Past resolved violations do not influence this card. See methodology.
Lead service line inventory
Lead or galvanized-requiring-replacement service lines confirmed in this system
NICASIO VALLEY RANCH MUTUAL reports 0 confirmed lead service lines, 1 galvanized requiring replacement, 12 non-lead, 0 unknown (total 13) in the EPA SDWIS service line inventory (2026Q1).
- 0 confirmed lead service lines
- 1 galvanized requiring replacement (LCRI treats these as lead)
- 0 unknown (0.0% of total)
- 12 confirmed non-lead (92.3%)
- 13 total service lines in the system
Why this is a health concern. A galvanized iron service line that was ever installed downstream of a historic lead component (a lead service line, a lead gooseneck connector, or lead solder) absorbed lead into its corrosion layer over decades. The pipe continues to release that accumulated lead into water for years after the upstream lead source is removed. That is why EPA's LCRI treats GRR lines as lead and requires their replacement on the same 10-year schedule as confirmed lead lines. Read our plain-English lead guide.
What to do if your service line might be lead
- Ask your utility to check the service-line classification for your specific address. Many utilities provide a public address-lookup tool linked from the inventory page.
- Get on the replacement queue. Under the LCRI, utilities must replace all lead and galvanized-requiring- replacement lines within 10 years (clock generally starts November 2027). Some prioritize requests.
- Until the line is replaced: flush the tap 30 seconds after long stagnation, use cold water for drinking and cooking, and consider an NSF/ANSI 53 lead-rated tap filter.
- Talk to your clinician about a blood lead test for anyone in the home, especially a pregnant person or a child under 6. Lead in drinking water guide.
Inventory data sourced from NICASIO VALLEY RANCH MUTUAL ( retrieved May 24, 2026 ; curator confidence: high ). Confirmed against the original source automatically each month; see methodology.
Lead and copper test results
The most recent measurement per contaminant from EPA's Lead and Copper Rule sampling.
Why only lead and copper, and not arsenic, nitrate, or others?
EPA's bulk SDWIS download is the only nationwide per-system sample data they publish, and it only includes the Lead and Copper Rule table. Values for other regulated contaminants (TTHMs, nitrate, arsenic, etc.) appear on this page only when they trigger a violation. For the full per-system contaminant suite, see the utility's annual Consumer Confidence Report (link further down the page).
Data from EPA SDWIS (Lead and Copper Rule sample table) , last refreshed May 24, 2026.
Fluoride
Per CDC My Water's Fluoride
NICASIO VALLEY RANCH MUTUAL does not add fluoride to its drinking water.
This system has not reported adding fluoride to its water on CDC's My Water's Fluoride listing. Natural fluoride may still be present at trace levels from the source water; the utility's annual water quality report has the latest measured concentration.
Source: CDC My Water's Fluoride, listed under Nicasio Valley Ranch Mutual (Marin County). Verify on CDC's site .
Area context
Marin County, CA (2020 data)
- Community water systems
- 1 of 13 add fluoride
- Population on fluoridated water
- 182,575 of 190,383 (95.9%)
California statewide (2020 data)
- Population on fluoridated water
- 21,879,582 of 38,051,212 (57.5%)
- Community water systems adding fluoride
- 417 of 3,057
Data from CDC My Water's Fluoride (per-system status) , last refreshed May 19, 2026.
Data from CDC Water Fluoridation Reporting System (state and county aggregates) , last refreshed May 16, 2026.
Recorded contaminant measurements (from violations)
When this system exceeded a regulatory limit and EPA recorded the measured value, that value is shown here. These are not routine sample results: they are the values the violation was triggered on.
| Period | Contaminant | Measured | Federal MCL | Status |
|---|---|---|---|---|
| October 1, 2021 | Tthm | 0.096MG/L | 0.08 MG/L | Health-based |
| October 1, 2021 | Tthm | 0.096MG/L | 0.08 MG/L | Health-based |
Data from EPA SDWIS (violation records) , last refreshed May 24, 2026.
Compliance history
EPA-recorded violations against this system over the last 5 years.
How to read this section
Health-based violations are when a measured limit was exceeded; the measured concentration is shown alongside the EPA federal limit where SDWIS published it. Monitoring and reporting items are paperwork issues (missed sample dates, late filings) that do not themselves indicate unsafe water.
2 resolved health-based violations in the last 5 years
All 2 health-based violations in the last 5 years are marked Resolved or Archived. Past violations do not represent current water quality.
| Period start | Contaminant | What happened | Measured level | Status |
|---|---|---|---|---|
| October 1, 2021 | Tthm | Maximum Contaminant Level Violation, Average | 0.096 MG/L
MCL 0.080 MG/L | Resolved |
| October 1, 2021 | Tthm | Maximum Contaminant Level Violation, Average | 0.096 MG/L
MCL 0.080 MG/L | Resolved |
17 older violation s (5-10 years ago) · 10 health-based, 7 paperwork , all resolved
| Period start | Relates to | Item | Measured level | Status |
|---|---|---|---|---|
| July 1, 2020 | Arsenic | Monitoring, Regular | — | Resolved |
| July 1, 2020 | Arsenic | Monitoring, Regular | — | Resolved |
| May 1, 2020 | Arsenic | Monitoring, Regular | — | Resolved |
| May 1, 2020 | Arsenic | Monitoring, Regular | — | Resolved |
| October 1, 2019 | — | Variance/Exemption/Other Compliance | — | Resolved |
| October 1, 2019 | — | Variance/Exemption/Other Compliance | — | Resolved |
| October 1, 2019 | — | Variance/Exemption/Other Compliance | — | Resolved |
| July 1, 2019 | Tthm | Maximum Contaminant Level Violation, Average | 140 UG/L
MCL 0.080 UG/L | Resolved |
| July 1, 2019 | Tthm | Maximum Contaminant Level Violation, Average | 140 UG/L
MCL 0.080 UG/L | Resolved |
| April 1, 2019 | Tthm | Maximum Contaminant Level Violation, Average | 81 UG/L
MCL 0.080 UG/L | Resolved |
| April 1, 2019 | Tthm | Maximum Contaminant Level Violation, Average | 81 UG/L
MCL 0.080 UG/L | Resolved |
| October 1, 2018 | Tthm | Maximum Contaminant Level Violation, Average | 89 UG/L
MCL 0.080 UG/L | Resolved |
| October 1, 2018 | Tthm | Maximum Contaminant Level Violation, Average | 89 UG/L
MCL 0.080 UG/L | Resolved |
| July 1, 2018 | Tthm | Maximum Contaminant Level Violation, Average | 98 UG/L
MCL 0.080 UG/L | Resolved |
| July 1, 2018 | Tthm | Maximum Contaminant Level Violation, Average | 98 UG/L
MCL 0.080 UG/L | Resolved |
| October 1, 2017 | Tthm | Maximum Contaminant Level Violation, Average | 130 UG/L
MCL 0.080 UG/L | Resolved |
| October 1, 2017 | Tthm | Maximum Contaminant Level Violation, Average | 130 UG/L
MCL 0.080 UG/L | Resolved |
Data from EPA SDWIS (violation records) , last refreshed May 24, 2026.
Where to see every contaminant this utility tested for
EPA's bulk SDWIS dataset gives MyTapWater.us per-system measured values for lead and copper, plus violation records for everything else. To see every regulated contaminant this utility tested for in the past year (TTHMs, HAA5, nitrate, arsenic, fluoride, chromium, etc.) with measured values, read the utility's Consumer Confidence Report (CCR).
Every community water system is required by EPA to publish a CCR annually, by July 1, listing every contaminant they sampled, the measured value, the federal limit, and any health-based exceedances. Most utilities post the report online; some mail it with your bill.
How to find NICASIO VALLEY RANCH MUTUAL's CCR:
- Search the web for "NICASIO VALLEY RANCH MUTUAL consumer confidence report" . The PDF is usually on the utility's own website.
- Or call the utility directly. Their phone number is in the contact section below.
Other water systems in Marin County, CA
Compare nearby utilities by population served.
- MARIN MUNICIPAL WATER DISTRICT
187k served · Marin County
- NORTH MARIN WATER DISTRICT
62k served · Marin County
- NPS GGNRA
18k served · Marin County
- BOLINAS COMMUNITY PUD
2,483 served · Marin County
- NORTH MARIN WD - PT. REYES
1,841 served · Marin County
Contact this utility
Public administrative contact information for this water system, as filed with the EPA. Use this to ask about your service line, request your home's lead status, or report a water quality issue.
- Administrator
- WOLFSON, LEANNE
- Phone
- 415-269-3690
- lcwolfson@gmail.com
- Mailing address
- P.O. Box 151NICASIO, CA 94946
Where this page's data comes from
Bundle released 2026-Q2, regenerated May 24, 2026. Each section above also shows its own source date so you can tell at a glance how fresh that part of the page is.
- EPA SDWIS bulk download — last refreshed May 24, 2026 (system info, violations, lead and copper samples).
- Lead service line inventory — last refreshed May 24, 2026 (from the utility's reported inventory).
- CDC My Water's Fluoride — last refreshed May 19, 2026 (per-system Yes/No fluoridation status).
- CDC Water Fluoridation Reporting System — last refreshed May 16, 2026 (state and county fluoridation aggregates).
Every value on this page is cross-verified before publication; read our methodology for the verification steps and corrections process.