California
Mariposa County drinking water quality
68 active public water systems serve 25,753 people in Mariposa County. 49 are compliant, 19 had at least one EPA violation in the past three years, 0 are designated serious violators, and 3 carry a health flag.
Needs attention
Community water systems
11 systems, largest first| System | Serves | Status | Rules violated, 3 yr | Unresolved |
|---|---|---|---|---|
|
Mariposa Public Utility Dist |
2,000 | 0 | 0 | |
|
Yosemite Nps-Yosemite Valley |
1,000 | 1 | 0 | |
|
Ponderosa Basin Mutual Wtr CO |
798 | 1 | 1 | |
|
Yosemite Nps-El Portal |
635 | 0 | 0 | |
|
Yosemite West Water System |
420 | 1 | 1 | |
|
Mariposa Pines Mutual |
294 | 2 | 1 | |
|
Mpwd-Coulterville Csa 1 |
193 | 0 | 0 | |
|
Yosemite Nps-Wawona |
150 | 1 | 0 | |
|
Yosemite Terrace Estates |
130 | 2 | 1 | |
|
McClure Boat Club, Inc. |
36 | 0 | 0 | |
|
Cedar Lodge |
28 | 1 | 0 |
Non-community systems (57: schools, campgrounds, workplaces, restaurants)
These systems serve places people visit rather than homes.
Inactive systems (131, no longer operating or reporting)
Kept for the record and excluded from the county totals above. Browse inactive systems.
About this data
Totals cover active systems. Systems serving more than one county are counted in each county. EPA counts the rules a system was in violation of, not the individual violations; one rule can carry several.
Source: the U.S. EPA's Enforcement and Compliance History Online system (ECHO), which publishes the federal Safe Drinking Water Information System. EPA's terms and values are shown as published. The California records are from EPA's data refresh of Oct 7, 2026; EPA refreshes this data quarterly, and states report to EPA with a lag of three to six months, so the newest violations may not appear yet. Retrieved from ECHO on Oct 11, 2026.