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Public water system record

Delta Mutual Water Company

Serves an area of Contra Costa County, CA · 333 people served

Federal records show 20 health-based violations and 1 monitoring/reporting issue for Delta Mutual Water Company in the last ten years. The most serious issue in this window was a Arsenic violation that EPA lists as archived, not resolved.

  • CA0707573
  • OAKLEY
  • CA
  • 333 served

System profile

Source water Groundwater
ZIP 94561
EPA system ID CA0707573

Verify this system on EPA ECHO →

Health-based violations, last 10 years
20
Resolved
0
Unresolved
0
Archived by EPA
20
Any acute record
No
Monitoring issues, last 10 years
1

Key facts

  • Delta Mutual Water Company draws water from 3 wells.
  • Highest measured level in the last 10 years: Arsenic, 0.013 mg/L, federal limit 0.01 mg/L (1.3 times the limit), 2025.
  • Most recent formal enforcement: compliance order (no penalty) by California, January 2020.
  • Record on file since 1980, with 1 health-based violation before October 19, 2016.
  • Lead pipe inventory: 0 lead and 0 unknown out of 129 service lines.

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Health-based violations

Since October 2016

Violation data reflects EPA records through March 2026. For the most current status, visit the EPA ECHO database.

Contaminant Rule family Start date Status Acute
Arsenic
Contaminant limit exceeded
Measured 0.013 mg/L, federal limit 0.01 mg/L (1.3 times the limit)
 330 Jul 1, 2025 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.011 mg/L, federal limit 0.01 mg/L (1.1 times the limit)
 330 Apr 1, 2025 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.011 mg/L, federal limit 0.01 mg/L (1.1 times the limit)
 330 Jan 1, 2025 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.012 mg/L, federal limit 0.01 mg/L (1.2 times the limit)
 330 Oct 1, 2024 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.011 mg/L, federal limit 0.01 mg/L (1.1 times the limit)
 330 Oct 1, 2023 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.011 mg/L, federal limit 0.01 mg/L (1.1 times the limit)
 330 Jul 1, 2023 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.011 mg/L, federal limit 0.01 mg/L (1.1 times the limit)
 330 Apr 1, 2023 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.011 mg/L, federal limit 0.01 mg/L (1.1 times the limit)
 330 Jan 1, 2023 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.011 mg/L, federal limit 0.01 mg/L (1.1 times the limit)
 330 Oct 1, 2022 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.012 mg/L, federal limit 0.01 mg/L (1.2 times the limit)
 330 Jul 1, 2022 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.012 mg/L, federal limit 0.01 mg/L (1.2 times the limit)
 330 Apr 1, 2022 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.012 mg/L, federal limit 0.01 mg/L (1.2 times the limit)
 330 Jan 1, 2022 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.012 mg/L, federal limit 0.01 mg/L (1.2 times the limit)
 330 Oct 1, 2021 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.012 mg/L, federal limit 0.01 mg/L (1.2 times the limit)
 330 Jul 1, 2021 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.013 mg/L, federal limit 0.01 mg/L (1.3 times the limit)
 330 Apr 1, 2021 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.013 mg/L, federal limit 0.01 mg/L (1.3 times the limit)
 330 Jan 1, 2021 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.011 mg/L, federal limit 0.01 mg/L (1.1 times the limit)
 330 Oct 1, 2020 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.012 mg/L, federal limit 0.01 mg/L (1.2 times the limit)
 330 Jul 1, 2020 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.011 mg/L, federal limit 0.01 mg/L (1.1 times the limit)
 330 Apr 1, 2020 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No
Arsenic
Contaminant limit exceeded
Measured 0.012 mg/L, federal limit 0.01 mg/L (1.2 times the limit)
 330 Jan 1, 2020 Archived
Violation period ended. EPA no longer counts it toward current compliance, but no fix was formally recorded.
 No

Monitoring and reporting issues

Since October 2016

Missed tests or reports, not contaminants found above a limit.

Issue Start date Status
Nitrate
Monitoring and reporting
 Jan 1, 2017 Resolved

Full record since 1980

EPA's records for Delta Mutual Water Company go back to 1980. Before October 19, 2016 they list 1 health-based violation (1 resolved) and 3 monitoring or reporting violations.

Violations that began in Health-based Monitoring and reporting
1980s 0 3
2000s 1 0
October 19, 2016 to 2019 0 1
2020s 20 0

Most recent health-based violation before October 19, 2016: Total Coliform (acute), began April 2004, Resolved.

Show the health-based violation before October 19, 2016
Contaminant Start date Status
Total Coliform (acute)
Contaminant limit exceeded
 Apr 1, 2004 Resolved

Enforcement actions

California regulators took 2 formal enforcement actions against Delta Mutual Water Company between 2018 and 2020. The most recent was a compliance order (no penalty) in January 2020.

Date By Action Violations covered
Jan 31, 2020 California Compliance order (no penalty) 20 violations (20 health-based): Arsenic
Aug 30, 2018 California Compliance order (no penalty) 1 violation: Nitrate

What the violations mean

Arsenic

20 incidents

Arsenic exceeded the federal limit

Long-term arsenic exposure is linked to cancer and cardiovascular effects

Where the water comes from

Delta Mutual Water Company draws water from 3 wells.

Annual water quality report

Delta Mutual Water Company 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.

Systems serving 500 or fewer people may meet the rule by telling customers the report is available on request, so you may need to ask Delta Mutual Water Company for a copy.

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