Public water system · CA2100579
ActiveNicasio Valley Ranch Mutual
At a glance
Nicasio Valley Ranch Mutual (PWSID CA2100579) is an active community water system in Marin County, California. It reports serving 36 people through 14 service connections. Its primary water source is groundwater, and EPA lists it as privately owned. Of the 12 most recent violations in EPA's records, 9 are health-based, and the most recent began in October 2021.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
36
Service connections
14
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does Nicasio Valley Ranch Mutual compare with other water systems in Marin County?
By EPA's size categories, Nicasio Valley Ranch Mutual is a very small system (500 people or fewer). Marin County has 46 active public water systems. Its population served is well below the county average of 6,203 people per system, and accounts for less than 0.1% of the 285,353 people reported by systems filed under the county. Across California, the 7,479 active systems average 5,706 people each. Nationally, the average active community water system reports serving 6,703 people, so Nicasio Valley Ranch Mutual is well below that figure.
What does “community water system” mean?
A community water system serves at least 15 connections used by year-round residents, or regularly serves at least 25 year-round residents. Homes, apartments and mobile-home parks are served by these. California has 2,997 active community water systems, 40% of the state's 7,479 active systems. Groundwater means the system draws its water from wells or springs fed by underground aquifers. 6,179 California systems (83%) list groundwater as their primary source.
Who owns and regulates Nicasio Valley Ranch Mutual?
EPA lists Nicasio Valley Ranch Mutual as privately owned. The CA state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 22 of the 46 active systems in Marin County (48%) are also privately owned.
Does Nicasio Valley Ranch Mutual have drinking water violations?
Of the 12 most recent violations in EPA's records, 9 are health-based, and the most recent began in October 2021. The violations listed here began between April 2015 and October 2021. By type: 9 contaminant level above the legal limit, 2 monitoring and reporting and 1 public notice, recordkeeping or other. The contaminant or rule involved most often is Total trihalomethanes (TTHM) (9 of them). EPA lists 12 as resolved. Resolved means at least one resolving action is on record: the system returned to compliance, the rule no longer applies, or no further action was needed.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2021-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2020-07-01 | Monitoring and reportingMonitoring, Regular · code 03 | Arseniccode 1005 | No | Resolved |
| 2020-05-01 | Monitoring and reportingMonitoring, Regular · code 03 | Arseniccode 1005 | No | Resolved |
| 2019-10-01 | Public notice, recordkeeping or otherVariance/Exemption/Other Compliance · code 08 | Not reported | No | Resolved |
| 2019-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2019-04-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2018-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2018-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2017-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2015-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2015-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2015-04-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
The 12 most recent violations in EPA's records, newest first.Labels and codes come from EPA's SDWIS reference tables. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found. "Health-based" marks violations of a legal limit or required treatment.
Nicasio Valley Ranch Mutual: frequently asked questions
Who runs Nicasio Valley Ranch Mutual?
Nicasio Valley Ranch Mutual (PWSID CA2100579) is a community water system privately owned. It is regulated by the CA state drinking water program.
How many people does Nicasio Valley Ranch Mutual serve?
Nicasio Valley Ranch Mutual reports serving 36 people through 14 service connections in Marin County, California.
Where does Nicasio Valley Ranch Mutual get its water?
EPA SDWIS lists this system's primary water source as groundwater. Groundwater means the system draws its water from wells or springs fed by underground aquifers.
Does Nicasio Valley Ranch Mutual have any drinking water violations?
Of the 12 most recent violations in EPA's records, 9 are health-based, and the most recent began in October 2021. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found.
Is Nicasio Valley Ranch Mutual's water safe to drink?
AquaCensus shows EPA compliance records, not current water test results, so it cannot say whether the water is safe at a given moment. Of the 12 most recent violations in EPA's records, 9 are health-based, and the most recent began in October 2021. For current results, consult the system's annual water quality report, EPA ECHO, or the CA state drinking water program.
Where can I find Nicasio Valley Ranch Mutual's water quality report?
As a community water system, Nicasio Valley Ranch Mutual must deliver an annual water quality report, called a Consumer Confidence Report, to its customers by July 1 each year, covering the previous calendar year. The system can provide a copy on request.
Other water systems in Marin County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Marin Municipal Water District | Marin | 186,895 | Community | Surface water |
| North Marin Water District | Marin | 61,691 | Community | Surface water |
| Nps Ggnra | Marin | 18,447 | Community | Purchased surface water |
| Bolinas Community PUD | Marin | 2,483 | Community | Surface water |
| North Marin Wd - Pt. Reyes | Marin | 1,841 | Community | Groundwater |
| Csp - Angel Island St Park | Marin | 1,622 | Transient non-community | Groundwater |
Related pages
Working with water-system records? Pro adds alerts, change history and CSV export ($49/mo); Enterprise adds full national files, the API and an MCP server for AI tools.
About this data
Source: U.S. EPA Safe Drinking Water Information System (SDWIS) and SDWA violation records, via EPA ECHO, as published October 1, 2026 — AquaCensus refreshes it quarterly. See the methodology for how records are matched, cleaned and scored.
Cite as: AquaCensus, “Nicasio Valley Ranch Mutual, PWSID CA2100579, California”, https://aquacensus.com/water-systems/california/nicasio-valley-ranch-mutual-ca2100579 (data as of October 1, 2026).