Public water system · CA0707573
ActiveDelta Mutual Water Company
At a glance
Delta Mutual Water Company (PWSID CA0707573) is an active community water system in Contra Costa County, California. It reports serving 333 people through 119 service connections. Its primary water source is groundwater, and EPA lists it as privately owned. Of the 12 most recent violations in EPA's records, 12 are health-based, and the most recent began in July 2025.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
333
Service connections
119
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does Delta Mutual Water Company compare with other water systems in Contra Costa County?
By EPA's size categories, Delta Mutual Water Company is a very small system (500 people or fewer). Contra Costa County has 84 active public water systems. Its population served is well below the county average of 6,726 people per system, and accounts for less than 0.1% of the 564,952 people reported by systems filed under the county. Across California, the 7,479 active systems average 5,706 people each. Nationally, the average active community water system reports serving 6,703 people, so Delta Mutual Water Company is well below that figure.
What does “community water system” mean?
A community water system serves at least 15 connections used by year-round residents, or regularly serves at least 25 year-round residents. Homes, apartments and mobile-home parks are served by these. California has 2,997 active community water systems, 40% of the state's 7,479 active systems. Groundwater means the system draws its water from wells or springs fed by underground aquifers. 6,179 California systems (83%) list groundwater as their primary source.
Who owns and regulates Delta Mutual Water Company?
EPA lists Delta Mutual Water Company as privately owned. The CA state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 57 of the 84 active systems in Contra Costa County (68%) are also privately owned.
Does Delta Mutual Water Company have drinking water violations?
Of the 12 most recent violations in EPA's records, 12 are health-based, and the most recent began in July 2025. The violations listed here began between January 2022 and July 2025. By type: 12 contaminant level above the legal limit. The contaminant or rule involved most often is Arsenic (12 of them). EPA lists 12 as archived. Archived means the violation was not marked resolved but is more than five years past the end of the noncompliance period, so it no longer counts toward current compliance status.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2025-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Arseniccode 1005 | Yes | Archived |
| 2025-04-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Arseniccode 1005 | Yes | Archived |
| 2025-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Arseniccode 1005 | Yes | Archived |
| 2024-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Arseniccode 1005 | Yes | Archived |
| 2023-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Arseniccode 1005 | Yes | Archived |
| 2023-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Arseniccode 1005 | Yes | Archived |
| 2023-04-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Arseniccode 1005 | Yes | Archived |
| 2023-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Arseniccode 1005 | Yes | Archived |
| 2022-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Arseniccode 1005 | Yes | Archived |
| 2022-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Arseniccode 1005 | Yes | Archived |
| 2022-04-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Arseniccode 1005 | Yes | Archived |
| 2022-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Arseniccode 1005 | Yes | Archived |
The 12 most recent violations in EPA's records, newest first.Labels and codes come from EPA's SDWIS reference tables. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found. "Health-based" marks violations of a legal limit or required treatment.
Delta Mutual Water Company: frequently asked questions
Who runs Delta Mutual Water Company?
Delta Mutual Water Company (PWSID CA0707573) is a community water system privately owned. It is regulated by the CA state drinking water program.
How many people does Delta Mutual Water Company serve?
Delta Mutual Water Company reports serving 333 people through 119 service connections in Contra Costa County, California.
Where does Delta Mutual Water Company get its water?
EPA SDWIS lists this system's primary water source as groundwater. Groundwater means the system draws its water from wells or springs fed by underground aquifers.
Does Delta Mutual Water Company have any drinking water violations?
Of the 12 most recent violations in EPA's records, 12 are health-based, and the most recent began in July 2025. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found.
Is Delta Mutual Water Company's water safe to drink?
AquaCensus shows EPA compliance records, not current water test results, so it cannot say whether the water is safe at a given moment. Of the 12 most recent violations in EPA's records, 12 are health-based, and the most recent began in July 2025. For current results, consult the system's annual water quality report, EPA ECHO, or the CA state drinking water program.
Where can I find Delta Mutual Water Company's water quality report?
As a community water system, Delta Mutual Water Company must deliver an annual water quality report, called a Consumer Confidence Report, to its customers by July 1 each year, covering the previous calendar year. The system can provide a copy on request.
Other water systems in Contra Costa County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Contra Costa Water District | Contra Costa | 198,000 | Community | Surface water |
| City of Antioch | Contra Costa | 115,074 | Community | Surface water |
| Brentwood | Contra Costa | 64,513 | Community | Purchased surface water |
| City of Pittsburg | Contra Costa | 62,500 | Community | Purchased surface water |
| Diablo Water District | Contra Costa | 43,357 | Community | Purchased surface water |
| City of Martinez | Contra Costa | 30,997 | Community | Purchased surface water |
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About this data
Source: U.S. EPA Safe Drinking Water Information System (SDWIS) and SDWA violation records, via EPA ECHO, as published October 1, 2026 — AquaCensus refreshes it quarterly. See the methodology for how records are matched, cleaned and scored.
Cite as: AquaCensus, “Delta Mutual Water Company, PWSID CA0707573, California”, https://aquacensus.com/water-systems/california/delta-mutual-water-company-ca0707573 (data as of October 1, 2026).