California
Mono County drinking water quality
91 active public water systems serve 110,574 people in Mono County. 79 are compliant, 12 had at least one EPA violation in the past three years, 1 is a designated serious violator, and 6 carry a health flag.
Needs attention
Community water systems
18 systems, largest first| System | Serves | Status | Rules violated, 3 yr | Unresolved |
|---|---|---|---|---|
|
Mammoth Cwd |
8,234 | 1 | 0 | |
|
Mountain Meadows Mwc |
525 | 0 | 0 | |
|
Usmc Housing Coleville |
424 | 3 | 0 | |
|
Bridgeport Pud |
374 | 3 | 1 | |
|
June Lake Pud Down Canyon |
310 | 1 | 1 | |
|
Lower Rock Creek Mutual Water Co. |
310 | 1 | 1 | |
|
Usmc/mtn Warfare Trng Ctr Bridgeport |
300 | 1 | 0 | |
|
June Lake Pud Village |
263 | 1 | 1 | |
|
Crowley Lake Trailer Park |
230 | 1 | 1 | |
|
Lee Vining Public Utility District |
222 | 0 | 0 | |
|
Lundy Mutual Water Company |
200 | 0 | 0 | |
|
Crowley Lake Mutual Water Company |
175 | 0 | 0 | |
|
Birchim Community Service District |
150 | 0 | 0 | |
|
White Mountain Mutual Water Company |
142 | 0 | 0 | |
|
Wheeler Crest Csd |
86 | 0 | 0 | |
|
Sierra East HOA |
84 | 1 | 1 | |
|
Cold Water Canyon Mwc |
65 | 0 | 0 | |
|
Chalfant Valley West M.w.c. |
45 | 0 | 0 |
Non-community systems (73: schools, campgrounds, workplaces, restaurants)
These systems serve places people visit rather than homes.
Inactive systems (42, 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.