WESTERN HILLS WATER DISTRICT/DIABLO GRAN
PWSID: CA5010039 · Patterson, CA · Serves 2,000 people
WESTERN HILLS WATER DISTRICT/DIABLO GRAN has 8 health-based violations out of 8 total. Health violations indicate contaminant levels exceeded EPA limits or required treatment was not followed.
WESTERN HILLS WATER DISTRICT/DIABLO GRAN (PWSID CA5010039) is a cws water system drawing from a surface water source, regulated by the EPA Safe Drinking Water Information System (SDWIS) under the Safe Drinking Water Act. It serves approximately 2,000 people in Patterson, CA, and is subject to primacy enforcement by the California drinking-water program.
The system's federal compliance record contains 8 total violations, with 8 classified as health-based (MCL exceedances or treatment-technique failures). 2 distinct contaminants have been cited, including Total Trihalomethanes (TTHM), Arsenic. Recorded violations span 2006–2017.
A historical violation does not necessarily describe current water quality, systems must notify customers and remediate, and monitoring-type violations often reflect reporting lapses rather than contamination. The most authoritative real-time source is the utility's annual Consumer Confidence Report. For enforcement history and corrective-action orders, consult EPA ECHO and the California state drinking-water program's public portal.
System Details
- EPA ID (PWSID)
- CA5010039
- System Type
- CWS
- Water Source
- Surface Water
- Location
- Patterson, CA
- Population Served
- 2,000
- Health Violations
- Yes (8)
What contaminants are in this water system?
| Contaminant | Violations | Health-Based |
|---|---|---|
| Total Trihalomethanes (TTHM) | 7 | 7 |
| Arsenic | 1 | 1 |
Violation History (8)
| Contaminant | Health | Date |
|---|---|---|
| Total Trihalomethanes (TTHM) | Yes | Jan 1, 2017 |
| Total Trihalomethanes (TTHM) | Yes | Oct 1, 2016 |
| Total Trihalomethanes (TTHM) | Yes | Jul 1, 2016 |
| Total Trihalomethanes (TTHM) | Yes | Apr 1, 2016 |
| Total Trihalomethanes (TTHM) | Yes | Jan 1, 2015 |
| Total Trihalomethanes (TTHM) | Yes | Oct 1, 2014 |
| Total Trihalomethanes (TTHM) | Yes | Jul 1, 2014 |
| Arsenic | Yes | May 1, 2006 |
Frequently Asked Questions
Is WESTERN HILLS WATER DISTRICT/DIABLO GRAN water safe to drink?
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What violations does WESTERN HILLS WATER DISTRICT/DIABLO GRAN have?
What contaminants have been found in WESTERN HILLS WATER DISTRICT/DIABLO GRAN water?
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About This Data
Water system data is from the EPA Safe Drinking Water Information System (SDWIS). Health-based violations include Maximum Contaminant Level (MCL) and Treatment Technique (TT) violations that may pose a direct risk to public health. Violation records may span multiple years.
Source: U.S. Environmental Protection Agency, SDWIS Federal Reporting Services U.S. Environmental Protection Agency, SDWIS Federal Reporting Services
Read our methodology - how this data is sourced, computed, and verified.