Water Quality: Mariposa, CA
6 water systems • 3,755 people served
Multiple Health ViolationsWater Quality Summary
Mariposa is served by 6 public water systems with a combined service population of 3,755 people, and has 53 EPA Safe Drinking Water Act violations on record. Critically, 40 of those are health-based violations, meaning one or more contaminants were detected above EPA-established safe levels — a serious public health concern. Mariposa's violation count is 10% above the national average for California. Contaminants associated with violations include Gross Alpha, Stage 2 DBP, TTHM, Total Haloacetic Acids (HAA5).
Contaminants Found
Alpha-emitting radioactive particles increase cancer risk, particularly from bone and other internal cancers.
Common source: Natural uranium and radium in geological formations
EPA limit: 15 pCi/L (excluding radon and uranium)
Trihalomethanes and haloacetic acids that increase cancer risk and may cause adverse reproductive outcomes.
Common source: Chlorine disinfection reacting with natural organic matter in source water
EPA limit: TTHM: 0.080 mg/L; HAA5: 0.060 mg/L
Total trihalomethanes are linked to increased risk of bladder cancer and adverse reproductive outcomes.
Common source: Reaction of chlorine disinfectants with naturally occurring organic matter in water
EPA limit: 0.080 mg/L (80 ppb)
Haloacetic acids are associated with increased cancer risk and potential reproductive and developmental effects.
Common source: Reaction of chlorine disinfectants with organic matter in treated water
EPA limit: 0.060 mg/L (60 ppb)
Water Systems Serving Mariposa
| System Name | PWSID | Source | Population | Violations |
|---|---|---|---|---|
| MARIPOSA PUBLIC UTILITY DIST | CA2210001 | Surface Water | 2,000 | 38 |
| PONDEROSA BASIN MUTUAL WTR CO | CA2210002 | Groundwater | 798 | 1 |
| YOSEMITE WEST WATER SYSTEM | CA2210924 | Groundwater | 420 | 1 |
| MARIPOSA PINES MUTUAL | CA2210906 | Groundwater | 284 | 9 |
| MPWD-COULTERVILLE CSA 1 | CA2210901 | Groundwater | 193 | 4 |
| CDF & FP - MT. BULLION | CA2210851 | Groundwater | 60 | 0 |
Concerned About Your Water?
A home water filter can remove common contaminants. NSF-certified filters are tested against EPA standards.
Consider a reverse osmosis system for comprehensive filtration or a carbon filter for basic improvement.
Other Cities in California
Data Sources
Drinking water violation data from the EPA Safe Drinking Water Information System (SDWIS). Data includes all recorded violations for active community water systems.