WESTERN HILLS WATER DISTRICT/DIABLO GRAN
California - Community Water System - PWSID: CA5010039
System Information
| PWSID | CA5010039 |
| System Name | WESTERN HILLS WATER DISTRICT/DIABLO GRAN |
| System Type | Community Water System |
| Water Source | Surface Water |
| Activity Status | Active |
| Owner Type | Local |
| EPA Region | 09 |
| Serves School | No |
| Wholesaler | No |
| First Reported | Jun 24, 1999 |
| Last Reported | Mar 20, 2026 |
Location & Contact
| State | California |
| City | PATTERSON |
| ZIP Code | 95363 |
| Address | 9501 Morton Davis Drive |
| Organization | KOVICH, MARK |
| Phone | 408-396-2511 |
Population & Service
| Population Served | 2,000 |
| Service Connections | 596 |
Drinking Water Violations (87)
This water system has 87 violations recorded in the EPA SDWIS database.
| Begin Date | End Date | Contaminant | Category | Health-Based | Major | Measured | Federal MCL | State MCL | Status | Return to Compliance | Rule |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Jan 1, 2018 | - | MR | No | No | - | TT | - | Resolved | Mar 16, 2021 | - | |
| Jan 1, 2018 | - | MR | No | No | - | TT | - | Resolved | Mar 16, 2021 | - | |
| Jan 1, 2017 | Mar 31, 2017 | MCL | Yes | No | .086 MG/L | 0.080 mg/L | .08 | Resolved | Mar 31, 2017 | - | |
| Jan 1, 2017 | Mar 31, 2017 | MCL | Yes | No | .086 MG/L | 0.080 mg/L | .08 | Resolved | Mar 31, 2017 | - | |
| Oct 1, 2016 | - | MR | No | No | - | TT | - | Resolved | Nov 1, 2016 | - | |
| Oct 1, 2016 | Dec 31, 2016 | MCL | Yes | No | .109 MG/L | 0.080 mg/L | .08 | Resolved | Dec 31, 2016 | - | |
| Oct 1, 2016 | Dec 31, 2016 | MCL | Yes | No | .109 MG/L | 0.080 mg/L | .08 | Resolved | Dec 31, 2016 | - | |
| Oct 1, 2016 | - | MR | No | No | - | TT | - | Resolved | Nov 1, 2016 | - | |
| Jul 1, 2016 | Sep 30, 2016 | MCL | Yes | No | .122 MG/L | 0.080 mg/L | .08 | Resolved | Sep 30, 2016 | - | |
| Jul 1, 2016 | Sep 30, 2016 | MCL | Yes | No | .122 MG/L | 0.080 mg/L | .08 | Resolved | Sep 30, 2016 | - | |
| Apr 1, 2016 | Jun 30, 2016 | MCL | Yes | No | .135 MG/L | 0.080 mg/L | .08 | Resolved | Jun 30, 2016 | - | |
| Apr 1, 2016 | Jun 30, 2016 | MCL | Yes | No | .135 MG/L | 0.080 mg/L | .08 | Resolved | Jun 30, 2016 | - | |
| Oct 1, 2015 | - | MR | No | No | - | TT | - | Resolved | Apr 30, 2016 | - | |
| Oct 1, 2015 | - | MR | No | No | - | TT | - | Resolved | Apr 30, 2016 | - | |
| Jan 1, 2015 | Mar 31, 2015 | MCL | Yes | No | .115 MG/L | 0.080 mg/L | .08 | Resolved | Mar 31, 2015 | - | |
| Jan 1, 2015 | Mar 31, 2015 | MCL | Yes | No | .115 MG/L | 0.080 mg/L | .08 | Resolved | Mar 31, 2015 | - | |
| Oct 1, 2014 | Dec 31, 2014 | MCL | Yes | No | .114 MG/L | 0.080 mg/L | .08 | Resolved | Dec 31, 2014 | - | |
| Oct 1, 2014 | Dec 31, 2014 | MCL | Yes | No | .114 MG/L | 0.080 mg/L | .08 | Resolved | Dec 31, 2014 | - | |
| Jul 1, 2014 | Sep 30, 2014 | MCL | Yes | No | .106 MG/L | 0.080 mg/L | .08 | Resolved | Sep 30, 2014 | - | |
| Jul 1, 2014 | Sep 30, 2014 | MCL | Yes | No | .106 MG/L | 0.080 mg/L | .08 | Resolved | Sep 30, 2014 | - | |
| Oct 1, 2009 | Dec 31, 2009 | MR | No | Yes | - | TT | - | Resolved | Dec 31, 2009 | - | |
| Oct 1, 2009 | Dec 31, 2009 | MR | No | Yes | - | TT | - | Resolved | Dec 31, 2009 | - | |
| Jul 1, 2009 | - | Other | No | No | - | - | - | Resolved | Jul 2, 2009 | - | |
| Jul 1, 2009 | Sep 30, 2009 | MCL | Yes | No | .095 MG/L | 0.080 mg/L | .08 | Resolved | Sep 30, 2009 | - | |
| Jul 1, 2009 | Sep 30, 2009 | MCL | Yes | No | .095 MG/L | 0.080 mg/L | .08 | Resolved | Sep 30, 2009 | - | |
| Apr 1, 2009 | Jun 30, 2009 | MCL | Yes | No | .1043 MG/L | 0.080 mg/L | .08 | Resolved | Jun 30, 2009 | - | |
| Jan 1, 2009 | Mar 31, 2009 | MCL | Yes | No | .1073 MG/L | 0.080 mg/L | .08 | Resolved | Mar 31, 2009 | - | |
| Jan 1, 2009 | Mar 31, 2009 | MCL | Yes | No | .1073 MG/L | 0.080 mg/L | .08 | Resolved | Mar 31, 2009 | - | |
| Oct 1, 2008 | Dec 31, 2008 | MCL | Yes | No | .1068 MG/L | 0.080 mg/L | .08 | Resolved | Dec 31, 2008 | - | |
| Oct 1, 2008 | Dec 31, 2008 | MCL | Yes | No | .1068 MG/L | 0.080 mg/L | .08 | Resolved | Dec 31, 2008 | - | |
| Jul 1, 2008 | Sep 30, 2008 | MCL | Yes | No | .1008 MG/L | 0.080 mg/L | .08 | Resolved | Sep 30, 2008 | - | |
| Jul 1, 2008 | Sep 30, 2008 | MCL | Yes | No | .1008 MG/L | 0.080 mg/L | .08 | Resolved | Sep 30, 2008 | - | |
| Jun 1, 2008 | Jun 30, 2008 | MR | No | Yes | - | - | - | Resolved | Jun 30, 2008 | - | |
| Jun 1, 2008 | Jun 30, 2008 | MR | No | Yes | - | - | - | Resolved | Jun 30, 2008 | - | |
| Jun 1, 2008 | Jun 30, 2008 | MR | No | No | - | 5% of samples | - | Resolved | Jun 30, 2008 | - | |
| Jun 1, 2008 | Jun 30, 2008 | MR | No | No | - | 5% of samples | - | Resolved | Jun 30, 2008 | - | |
| May 1, 2008 | May 31, 2008 | MR | No | No | - | 5% of samples | - | Resolved | May 31, 2008 | - | |
| May 1, 2008 | May 31, 2008 | MR | No | No | - | 5% of samples | - | Resolved | May 31, 2008 | - | |
| May 1, 2008 | May 31, 2008 | MR | No | Yes | - | - | - | Resolved | May 31, 2008 | - | |
| May 1, 2008 | May 31, 2008 | MR | No | Yes | - | - | - | Resolved | May 31, 2008 | - | |
| Apr 1, 2008 | Jun 30, 2008 | MCL | Yes | No | .1018 MG/L | 0.080 mg/L | .08 | Resolved | Jun 30, 2008 | - | |
| Apr 1, 2008 | Jun 30, 2008 | MCL | Yes | No | .1018 MG/L | 0.080 mg/L | .08 | Resolved | Jun 30, 2008 | - | |
| Jan 1, 2008 | Mar 31, 2008 | MCL | Yes | No | .0956 MG/L | 0.080 mg/L | .08 | Resolved | Mar 31, 2008 | - | |
| Jan 1, 2008 | Mar 31, 2008 | MCL | Yes | No | .0956 MG/L | 0.080 mg/L | .08 | Resolved | Mar 31, 2008 | - | |
| Oct 1, 2007 | Dec 31, 2007 | MCL | Yes | No | .0973 MG/L | 0.080 mg/L | .08 | Resolved | Dec 31, 2007 | - | |
| Oct 1, 2007 | Dec 31, 2007 | MCL | Yes | No | .0973 MG/L | 0.080 mg/L | .08 | Resolved | Dec 31, 2007 | - | |
| Jul 1, 2007 | Sep 30, 2007 | MCL | Yes | No | .0895 MG/L | 0.080 mg/L | .08 | Resolved | Sep 30, 2007 | - | |
| Jul 1, 2006 | Sep 30, 2006 | MCL | Yes | No | .102 MG/L | 0.080 mg/L | .08 | Resolved | Sep 30, 2006 | - | |
| Jul 1, 2006 | Sep 30, 2006 | MCL | Yes | No | .102 MG/L | 0.080 mg/L | .08 | Resolved | Sep 30, 2006 | - | |
| May 1, 2006 | Jun 27, 2009 | TT | Yes | No | - | - | - | Resolved | Jun 27, 2009 | - |
About This Water System
Public water system data comes from the EPA Safe Drinking Water Information System (SDWIS). Systems with violations must notify customers. Contact your water utility for the latest annual water quality report.