Western Hills Water District/Diablo Gran
PWSID: CA5010039
This system has no unresolved violations. The most recent violation on record was 2018-01-01.
This system has more violations on record than 87% of water systems in California.
Violation trend: 0.0 per year over the last 5 years, down from 1.0 per year in the previous 5.
System Details
| Population Served | 2,000 |
| Service Connections | 596 |
| Water Source | Surface Water |
| System Type | Community Water System |
| Owner | Local Government |
| Status | Active |
| City | Patterson |
| EPA ZIP on File | 95363 |
Lead & Copper Testing
| Contaminant | Level | EPA Action Level | Status |
|---|---|---|---|
| Lead (90th percentile) | 0.0000 mg/L | 0.015 mg/L | Below Action Level |
| Lead (90th percentile) | 0.0000 mg/L | 0.015 mg/L | Below Action Level |
| Lead (90th percentile) | 0.0000 mg/L | 0.015 mg/L | Below Action Level |
| Lead (90th percentile) | 0.0000 mg/L | 0.015 mg/L | Below Action Level |
| Lead (90th percentile) | 0.0000 mg/L | 0.015 mg/L | Below Action Level |
| Lead (90th percentile) | 0.0000 mg/L | 0.015 mg/L | Below Action Level |
| Lead (90th percentile) | 0.0000 mg/L | 0.015 mg/L | Below Action Level |
| Lead (90th percentile) | 0.0000 mg/L | 0.015 mg/L | Below Action Level |
| Lead (90th percentile) | 0.0000 mg/L | 0.015 mg/L | Below Action Level |
Violation History (14 total)
| Contaminant | Violation | Date | Health-Based | Status |
|---|---|---|---|---|
| 5000 | MR | 2018-01-01 | Returned to Compliance | |
| 2950 | MCL Measured: 0.0860 MG/L (limit: 0.0800 MG/L) | 2017-01-01 | Yes | Returned to Compliance |
| 2950 | MCL Measured: 0.1090 MG/L (limit: 0.0800 MG/L) | 2016-10-01 | Yes | Returned to Compliance |
| 5000 | MR | 2016-10-01 | Returned to Compliance | |
| 2950 | MCL Measured: 0.1220 MG/L (limit: 0.0800 MG/L) | 2016-07-01 | Yes | Returned to Compliance |
| 2950 | MCL Measured: 0.1350 MG/L (limit: 0.0800 MG/L) | 2016-04-01 | Yes | Returned to Compliance |
| 5000 | MR | 2015-10-01 | Returned to Compliance | |
| 2950 | MCL Measured: 0.1150 MG/L (limit: 0.0800 MG/L) | 2015-01-01 | Yes | Returned to Compliance |
| 2950 | MCL Measured: 0.1140 MG/L (limit: 0.0800 MG/L) | 2014-10-01 | Yes | Returned to Compliance |
| 2950 | MCL Measured: 0.1060 MG/L (limit: 0.0800 MG/L) | 2014-07-01 | Yes | Returned to Compliance |
| 2920 | MR | 2009-10-01 | Major | Returned to Compliance |
| 7000 | Other | 2009-07-01 | Returned to Compliance | |
| 0200 | TT | 2006-05-01 | Yes | Returned to Compliance |
| 7000 | Other | 2005-07-01 | Returned to Compliance |
Understanding This Water System's Record
Western Hills Water District/Diablo Gran is a community water system water system that draws from surface water sources and serves a population of 2,000 in Patterson, California. This page shows its complete compliance history as reported to the EPA's Safe Drinking Water Information System (SDWIS), the federal database that tracks every public water system in the United States.
What Do These Violations Mean?
Health-based violations mean the system exceeded an EPA maximum contaminant level (MCL) or failed to provide required treatment. These indicate potential health risks from contaminants like lead, arsenic, bacteria, nitrates, or disinfection byproducts. Non-health-based violations involve monitoring, reporting, or procedural requirements — the system missed a testing deadline or failed to notify customers, but contaminant levels were not necessarily unsafe.
What Should You Do?
Your water utility is required to publish an annual Consumer Confidence Report (CCR) that details test results and any violations. If your system has active health-based violations, consider a certified water filter rated for the specific contaminants involved. The contaminant guides on this site explain health risks and filter options for common pollutants. For the most current results, contact your water utility directly — EPA data can lag weeks or months behind real-time testing.