Modesto Water Quality
California
According to EPA SDWIS, Modesto, California is served by 16 community water systems covering about 239,487 people. The same extract lists 6 health-based violation records, most recently coded 4006 in 2020. Counts are historical EPA registry rows, not a current compliance or drinkability score.
Drinking water in Modesto, California is delivered through 16 EPA-regulated community water systems serving an estimated 239,487 people. Each system is tracked in the EPA Safe Drinking Water Information System (SDWIS) under the Safe Drinking Water Act, which requires testing for regulated contaminants, consumer notification of violations, and publication of an annual Consumer Confidence Report.
PlainEnviro's health-based SDWIS extract shows 6 violation records across the 16 active community systems shown here. Monitoring and reporting records are not present in the extract. The records carry 2 distinct EPA contaminant codes: Combined Uranium, Nitrate. 11 TRI-reporting industrial facilities are also located within the city limits.
A past EPA health-based registry row does not describe water delivered today or current compliance status; utilities notify customers and remediate under state primacy oversight when required. For current water-quality status and treatment practices, review your local utility's most recent Consumer Confidence Report or contact the California drinking water program. All records above reflect federal EPA SDWIS data and are not independently verified against state databases.
Community Water Systems
| System Name | Pop. Served | Violations | Status |
|---|---|---|---|
| MODESTO, CITY OF | 218,771 | 0 | Clean |
| CITY OF MODESTO - SALIDA | 14,537 | 0 | Clean |
| CITY OF MODESTO - DEL RIO | 1,327 | 0 | Clean |
| CITY OF MODESTO - SOUTH TURLOCK | 1,099 | 0 | Clean |
| CITY OF MODESTO - GRAYSON | 914 | 2 | Health |
| HILLSVIEW HOMES | 887 | 0 | Clean |
| RIVERDALE PARK TRACT CSD | 610 | 4 | Health |
| BUENA VISTA MIGRANT CENTER | 455 | 0 | Clean |
| PARK HEIGHTS MUTUAL WATER CO | 250 | 0 | Clean |
| CITY OF MODESTO - WALNUT MANOR | 175 | 0 | Clean |
| CITY OF MODESTO - NORTH TURLOCK | 172 | 0 | Clean |
| CITY OF MODESTO - CENTRAL TURLOCK | 119 | 0 | Clean |
| MORNINGSIDE MOBILEHOME PARK | 67 | 0 | Clean |
| COUNTRY WESTERN MHRV | 55 | 0 | Clean |
| RIVER ROAD MUTUAL WATER COMPANY | 26 | 0 | Clean |
| MODESTO IRRIGATION DISTRICT | 23 | 0 | Clean |
Does this city have health-based water violations?
These health-based records can represent Maximum Contaminant Level (MCL), Treatment Technique (TT), or Maximum Residual Disinfectant Level (MRDL) categories. A historical record does not establish that water is currently unsafe.
| Water system | Contaminant | Begin Date |
|---|---|---|
| RIVERDALE PARK TRACT CSD | Combined Uranium | 2020-10-01 |
| RIVERDALE PARK TRACT CSD | Combined Uranium | 2016-07-01 |
| RIVERDALE PARK TRACT CSD | Combined Uranium | 2016-04-01 |
| RIVERDALE PARK TRACT CSD | Combined Uranium | 2016-01-01 |
| CITY OF MODESTO - GRAYSON | Nitrate | 1995-07-01 |
| CITY OF MODESTO - GRAYSON | Nitrate | 1995-04-01 |
What are Modesto's health-based records for?
Modesto's health-based violation records carry 2 distinct EPA codes: some name a substance, others the drinking-water rule that was breached. Counts are records on file in the EPA SDWIS extract, not current test results.
| Contaminant | Records | Systems |
|---|---|---|
| Combined Uranium | 4 | 1 |
| Nitrate | 2 | 1 |
TRI Facilities in Modesto
| Facility | Total Releases |
|---|---|
| Blue Diamond Growers | 168.8K lbs |
| Crystal Creamery Inc. | 78.6K lbs |
| Custom Marble & Onyx | 17.6K lbs |
| Gallo Glass Co | 16.0K lbs |
| Enviro Tech Chemical Services Inc. | 8.7K lbs |
| Southern Counties Oil Co. LP D.b.a. Sc Fuels | 7.5K lbs |
| Usalco Modesto Plant LLC | 765 lbs |
| Pacific Star Chemical LLC D.b.a. Northstar Chemical | 104 lbs |
| Frito Lay Inc. | 0 lbs |
| Nestle USA Inc | 0 lbs |
Frequently Asked Questions
What does EPA SDWIS list for drinking water in Modesto, California? ▼
How many water violations does Modesto have in this EPA extract? ▼
What contaminants were found in Modesto water? ▼
How many water systems serve Modesto? ▼
Where does Modesto get its drinking water? ▼
Are there pollution sources near Modesto? ▼
How does Modesto compare in California?
Of the 909 California places with at least one community water system on file, Modesto ranks #23 by number of systems (16).
Either side of it: Thermal (17), Los Gatos (16), Napa (16), Rosemead (15)
About This Data
Figures here are the current EPA SDWIS extract joined to the 16 community water systems whose service area lists Modesto, ranked against the 909 California places with at least one system on file. Data current as of 2026-08-25.
Water system data comes from the EPA's Safe Drinking Water Information System (SDWIS). PlainEnviro's violation fetch is restricted upstream to records EPA flags as health-based and then joined to active community water systems. Monitoring and reporting violations are not included.
A health-based violation row in this extract is a historical EPA registry entry. It does not describe water delivered today or current compliance status. Many records are later resolved, and public water systems notify customers when required. For current conditions, contact your local water utility or the state drinking water program.
TRI facility data comes from the EPA Toxic Release Inventory. Facilities shown are those that self-report to the TRI program. PlainEnviro presents this data without advocacy framing.
Read our methodology - how this data is sourced, computed, and verified.