CA / Mariposa
CA · Tap water records
Mariposa tap water, in plain English
Here is what the EPA's own data shows about tap water in Mariposa. According to EPA SDWIS data retrieved June 2026, Mariposa is served by 5 active community water systems, together reported to serve about 3,695 people.
As of June 2026, EPA records show 54 violations across the community water system(s) serving Mariposa, going back to the earliest EPA record. 40 of these are classified by the EPA as health-based (a contaminant recorded above the limit the EPA tracks); the rest are monitoring or reporting violations. Each is listed by system below, with its status.
What the EPA has on record, by system
Mariposa Public Utility Dist
2,000 served · surface water · PWSID CA2210001 - Health-based Total Haloacetic Acids (HAA5): a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 26 times between January 2004 and October 2012. The EPA record lists a level of 0.0708 MG/L; the limit (MCL) is 0.06 MG/L. All have since returned to compliance, per EPA records.
- Health-based TTHM: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 12 times between January 2004 and July 2012. The EPA record lists a level of 0.081 MG/L; the limit (MCL) is 0.08 MG/L. All have since returned to compliance, per EPA records.
Ponderosa Basin Mutual Wtr Co
798 served · groundwater · PWSID CA2210002 - Monitoring Lead and Copper Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in October 2024. EPA records do not show all of these as returned to compliance.
Yosemite West Water System
420 served · groundwater · PWSID CA2210924 - Monitoring Lead and Copper Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times between March 2004 and October 2025. EPA records do not show all of these as returned to compliance.
Mariposa Pines Mutual
284 served · groundwater · PWSID CA2210906 - Health-based LEAD AND COPPER RULE REVISIONS: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded once in October 2024. The EPA record for these does not include a measured level. EPA records do not show all of these as returned to compliance.
- Health-based Coliform (TCR): a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded once in October 2015. The EPA record for these does not include a measured level. All have since returned to compliance, per EPA records.
- Monitoring LEAD AND COPPER RULE REVISIONS: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in October 2024. EPA records do not show all of these as returned to compliance.
- Monitoring Consumer Confidence Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in July 2024. All have since returned to compliance, per EPA records.
- Monitoring Lead and Copper Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times between January 1996 and October 2020. All have since returned to compliance, per EPA records.
- Monitoring Nitrate: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. All have since returned to compliance, per EPA records.
- Monitoring Revised Total Coliform Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in April 2016. All have since returned to compliance, per EPA records.
Mpwd-Coulterville Csa 1
193 served · groundwater · PWSID CA2210901 - Monitoring Revised Total Coliform Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times between February 2019 and February 2022. All have since returned to compliance, per EPA records.
- Monitoring Coliform (TCR): a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in September 2015. All have since returned to compliance, per EPA records.
- Monitoring Lead and Copper Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 1996. All have since returned to compliance, per EPA records.
What this means
A health-based violation means a contaminant was recorded above the limit the EPA tracks for it. A monitoring or reporting violation means a required test or report was late or missed — not that a contaminant was measured above a limit. “Returned to compliance” means the EPA recorded the issue as resolved.
This page summarizes the EPA's own records and does not assess whether your water is safe to drink. For the most current details, you can verify every record directly with the EPA, and contact your water system with questions.
Source: U.S. EPA Envirofacts SDWIS, retrieved June 2026. Records cover the EPA's full reporting history for these systems. Verify at EPA ECHO.