Public water system record
Western Hills Water District/Diablo Gran
Serves Diablo Grande, Stanislaus County, CA · 2,000 people served
Federal records show 2 health-based violations and 2 monitoring/reporting issues for Western Hills Water District/Diablo Gran in the last ten years. The most serious issue in this window was a resolved Total Trihalomethanes (TTHMs) violation.
System profile
- Health-based violations, last 10 years
- 2
- Resolved
- 2
- Unresolved
- 0
- Any acute record
- No
- Monitoring issues, last 10 years
- 2
Key facts
- Western Hills Water District/Diablo Gran draws water from 1 surface water intake.
- Highest measured level in the last 10 years: Total Trihalomethanes (TTHMs), 0.109 mg/L, federal limit 0.08 mg/L (1.4 times the limit), 2016.
- Most recent formal enforcement: compliance order (no penalty) by California, October 2018.
- Record on file since 2004, with 31 health-based violations before October 19, 2016.
- Lead pipe inventory: 0 lead and 0 unknown out of 613 service lines.
Check whether Western Hills Water District/Diablo Gran serves your address
Health-based violations
Since October 2016Violation data reflects EPA records through March 2026. For the most current status, visit the EPA ECHO database.
| Contaminant | Rule family | Start date | Status | Acute |
|---|---|---|---|---|
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.086 mg/L, federal limit 0.08 mg/L (1.1 times the limit)
|
220 | Jan 1, 2017 | Resolved | No |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.109 mg/L, federal limit 0.08 mg/L (1.4 times the limit)
|
220 | Oct 1, 2016 | Resolved | No |
Monitoring and reporting issues
Since October 2016Missed tests or reports, not contaminants found above a limit.
| Issue | Start date | Status |
|---|---|---|
|
Lead and Copper Rule
Monitoring and reporting
|
Jan 1, 2018 | Resolved |
|
Lead and Copper Rule
Monitoring and reporting
|
Oct 1, 2016 | Resolved |
Full record since 2004
EPA's records for Western Hills Water District/Diablo Gran go back to 2004. Before October 19, 2016 they list 31 health-based violations (31 resolved) and 11 monitoring or reporting violations.
| Violations that began in | Health-based | Monitoring and reporting |
|---|---|---|
| 2000s | 25 | 9 |
| 2010 to October 18, 2016 | 6 | 2 |
| October 19, 2016 to 2019 | 1 | 1 |
Most recent health-based violation before October 19, 2016: Total Trihalomethanes (TTHMs), began October 2016, Resolved.
Show all 31 health-based violations before October 19, 2016
| Contaminant | Start date | Status |
|---|---|---|
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.109 mg/L, federal limit 0.08 mg/L (1.4 times the limit)
|
Oct 1, 2016 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.122 mg/L, federal limit 0.08 mg/L (1.5 times the limit)
|
Jul 1, 2016 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.135 mg/L, federal limit 0.08 mg/L (1.7 times the limit)
|
Apr 1, 2016 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.115 mg/L, federal limit 0.08 mg/L (1.4 times the limit)
|
Jan 1, 2015 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.114 mg/L, federal limit 0.08 mg/L (1.4 times the limit)
|
Oct 1, 2014 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.106 mg/L, federal limit 0.08 mg/L (1.3 times the limit)
|
Jul 1, 2014 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.095 mg/L, federal limit 0.08 mg/L (1.2 times the limit)
|
Jul 1, 2009 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1043 mg/L, federal limit 0.08 mg/L (1.3 times the limit)
|
Apr 1, 2009 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1073 mg/L, federal limit 0.08 mg/L (1.3 times the limit)
|
Jan 1, 2009 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1068 mg/L, federal limit 0.08 mg/L (1.3 times the limit)
|
Oct 1, 2008 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1008 mg/L, federal limit 0.08 mg/L (1.3 times the limit)
|
Jul 1, 2008 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1018 mg/L, federal limit 0.08 mg/L (1.3 times the limit)
|
Apr 1, 2008 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0956 mg/L, federal limit 0.08 mg/L (1.2 times the limit)
|
Jan 1, 2008 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0973 mg/L, federal limit 0.08 mg/L (1.2 times the limit)
|
Oct 1, 2007 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0895 mg/L, federal limit 0.08 mg/L (1.1 times the limit)
|
Jul 1, 2007 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.102 mg/L, federal limit 0.08 mg/L (1.3 times the limit)
|
Jul 1, 2006 | Resolved |
|
Surface Water Treatment Rule
Treatment technique failure
|
May 1, 2006 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.061 mg/L, federal limit 0.06 mg/L (at or just above the limit)
|
Apr 1, 2006 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1388 mg/L, federal limit 0.08 mg/L (1.7 times the limit)
|
Apr 1, 2006 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.151 mg/L, federal limit 0.08 mg/L (1.9 times the limit)
|
Jan 1, 2006 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.079 mg/L, federal limit 0.06 mg/L (1.3 times the limit)
|
Jan 1, 2006 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1725 mg/L, federal limit 0.08 mg/L (2.2 times the limit)
|
Oct 1, 2005 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0928 mg/L, federal limit 0.06 mg/L (1.5 times the limit)
|
Oct 1, 2005 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0955 mg/L, federal limit 0.06 mg/L (1.6 times the limit)
|
Jul 1, 2005 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.17 mg/L, federal limit 0.08 mg/L (2.1 times the limit)
|
Jul 1, 2005 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0828 mg/L, federal limit 0.06 mg/L (1.4 times the limit)
|
Apr 1, 2005 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1575 mg/L, federal limit 0.08 mg/L (2 times the limit)
|
Apr 1, 2005 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0793 mg/L, federal limit 0.06 mg/L (1.3 times the limit)
|
Jan 1, 2005 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1443 mg/L, federal limit 0.08 mg/L (1.8 times the limit)
|
Jan 1, 2005 | Resolved |
|
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.082 mg/L, federal limit 0.06 mg/L (1.4 times the limit)
|
Oct 1, 2004 | Resolved |
|
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1318 mg/L, federal limit 0.08 mg/L (1.6 times the limit)
|
Oct 1, 2004 | Resolved |
Enforcement actions
California regulators took 11 formal enforcement actions against Western Hills Water District/Diablo Gran between 2005 and 2018. The most recent was a compliance order (no penalty) in October 2018.
| Date | By | Action | Violations covered |
|---|---|---|---|
| Oct 19, 2018 | California | Compliance order (no penalty) | 1 violation: Lead and Copper Rule |
| Oct 1, 2016 | California | Compliance order (no penalty) | 1 violation: Lead and Copper Rule |
| Feb 3, 2016 | California | Compliance order (no penalty) | 1 violation: Lead and Copper Rule |
| Oct 23, 2014 | California | Compliance order (no penalty) | 7 violations (7 health-based): Total Trihalomethanes (TTHMs) |
| Dec 31, 2009 | California | Compliance order (no penalty) | 1 violation: CARBON, TOTAL |
| Jun 23, 2009 | California | Compliance order (no penalty) | 1 violation (1 health-based): Surface Water Treatment Rule |
| Jul 21, 2008 | California | Compliance order (no penalty) | 5 violations (1 health-based): Surface Water Treatment Rule, Total Coliform, Total Trihalomethanes (TTHMs) |
| Jun 20, 2008 | California | Administrative penalty | 1 violation (1 health-based): Total Trihalomethanes (TTHMs) |
| Feb 7, 2008 | California | Compliance order (no penalty) | 5 violations (5 health-based): Total Trihalomethanes (TTHMs) |
| Nov 14, 2007 | California | Compliance order (no penalty) | 8 violations (8 health-based): Total Trihalomethanes (TTHMs) |
| Aug 23, 2005 | California | Compliance order (no penalty) | 1 violation: Consumer Confidence Rule |
What the violations mean
Total Trihalomethanes (TTHMs)
2 incidentsDisinfection byproduct levels exceeded the federal limit
Long-term TTHM exposure may increase bladder cancer risk
Where the water comes from
Western Hills Water District/Diablo Gran draws water from 1 surface water intake.
Annual water quality report
Western Hills Water District/Diablo Gran must give its customers an annual water quality report (Consumer Confidence Report) by July 1, with the levels its tests found in the previous year.
Where the state allows it, systems serving fewer than 10,000 people may publish the report in a local newspaper or news site instead of mailing it, and must provide a copy on request.
Find a posted report with EPA's Consumer Confidence Report search
Testing your own water
To test the water at your tap, or a private well this record does not cover, use a laboratory certified for drinking water by California.
Certified drinking water labs by state EPA guidance for private wells