Arsenic violations in California
113 active public water systems in California had a Arsenic violation in the past three years, 24 of them in the latest quarter of EPA's data. What Arsenic is and why it matters.
Systems with a Arsenic violation
Latest quarter first, then largest first| System | Serves | Status | Rules violated, 3 yr | Unresolved |
|---|---|---|---|---|
|
Hughson, City of Hughson · Stanislaus County |
7,977 | 2 | 1 | |
|
Tule River Reservation Main Tule River Reservation · County |
2,560 | 9 | 2 | |
|
LE Grand Comm Services Dist Merced County |
1,739 | 2 | 1 | |
|
Laguna Seca Recreation WS Monterey County |
1,248 | 2 | 1 | |
|
Knoll Enterprises San Bernardino County |
500 | 6 | 2 | |
|
Primex Farms Water System Kern County |
450 | 1 | 0 | |
|
South Kaweah Mutual Water Company Tulare County |
384 | 3 | 1 | |
|
Musco Family Olive CO San Joaquin County |
348 | 1 | 0 | |
|
Lactalis Heritage Dairy Tulare County |
295 | 3 | 1 | |
|
MD 08 North Fork Water System Madera County |
264 | 1 | 0 | |
|
Sierra Linda Mutual Water CO Madera County |
200 | 3 | 1 | |
|
MD 24 Teaford Meadow Lakes Madera County |
150 | 1 | 0 | |
|
Cedar Valley Mutual Water CO Madera County |
137 | 2 | 1 | |
|
Bar-Len Mwc San Bernardino County |
126 | 5 | 2 | |
|
Austin Industrial Park Water System San Joaquin County |
125 | 1 | 0 | |
|
HI Desert Mwc San Bernardino County |
112 | 4 | 2 | |
|
Yosemite Forks Est Mutual Madera County |
110 | 1 | 0 | |
|
MD 42 Still Meadow Madera County |
100 | 2 | 0 | |
|
Gico Management San Joaquin County |
60 | 1 | 0 | |
|
Gemperle Egg Ranch Merced County |
55 | 2 | 0 | |
|
Century Mobile Home Park San Joaquin County |
50 | 1 | 0 | |
|
V & P Trailer Court Water System San Joaquin County |
35 | 2 | 0 | |
|
Sunny Road Water System San Joaquin County |
34 | 1 | 0 | |
|
Martinez Apartments San Joaquin County |
26 | 2 | 0 | |
|
Corona, City of Corona · Riverside County |
169,380 | 6 | 0 | |
|
City of Sunnyvale Sunnyvale · Santa Clara County |
157,566 | 5 | 0 | |
|
Norco, City of Norco · Riverside County |
25,068 | 5 | 0 | |
|
Castroville Community Services District Monterey County |
7,515 | 2 | 0 | |
|
Quechan Casino Resort County |
2,950 | 6 | 0 | |
|
Land Projects Mutual Water Co. Los Angeles County |
2,800 | 1 | 0 | |
|
Richgrove Community Services District Tulare County |
1,617 | 8 | 3 | |
|
Grimmway Enterprises-Malaga Water System Kern County |
1,200 | 2 | 0 | |
|
North Edwards WD Kern County |
1,105 | 3 | 2 | |
|
Baker Community Services District San Bernardino County |
1,000 | 3 | 1 | |
|
Rosamond School Water System Kern County |
940 | 1 | 0 | |
|
Lakeside Park Association El Dorado County |
924 | 5 | 1 | |
|
Madison Service Dist Yolo County |
876 | 8 | 1 | |
|
Coyote Valley System County |
850 | 5 | 0 | |
|
Tranquillity Irrigation District Fresno County |
686 | 3 | 1 | |
|
Echo Valley School WS Monterey County |
579 | 1 | 0 | |
|
Colusa Co. Wwd #1 Grimes Colusa County |
512 | 2 | 1 | |
|
Madera MH & RV Park Madera County |
450 | 5 | 0 | |
|
Twin Lakes Resort San Diego County |
400 | 5 | 2 | |
|
Willow Park Marina Contra Costa County |
380 | 1 | 0 | |
|
Havasu Water Company County |
361 | 11 | 4 | |
|
Sharondale Mesa HOA Riverside County |
340 | 3 | 0 | |
|
Delta Mutual Water Company Contra Costa County |
333 | 1 | 0 | |
|
Rand Communities Water District Kern County |
303 | 4 | 3 | |
|
Salmon Creek Middle School Sonoma County |
300 | 2 | 0 | |
|
The Lodge at Sonoma Sonoma County |
300 | 1 | 0 |
About this data
A system is counted once if any of its violations in the past three years involved Arsenic, including monitoring and reporting lapses. Rules violated and status in the table are for the whole system, not Arsenic alone.
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.