Public water system · CA0710003
ActiveContra Costa Water District
At a glance
Contra Costa Water District (PWSID CA0710003) is an active community water system in Contra Costa County, California. It reports serving 198,000 people through 60,730 service connections. Its primary water source is surface water, and EPA lists it as owned by a local government. EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in February 1999.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
198,000
Service connections
60,730
Primary source
SW
Surface water
System type
CWS
Community water system
System record
How does Contra Costa Water District compare with other water systems in Contra Costa County?
By EPA's size categories, Contra Costa Water District is a very large system (more than 100,000 people). Contra Costa County has 84 active public water systems, and Contra Costa Water District is the largest of them by population served. Its population served is about 29 times the county average of 6,726 people per system, and accounts for 35% 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 Contra Costa Water District is about 30 times 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. Surface water means the system draws its water from rivers, lakes, streams or reservoirs. 609 California systems (8.1%) list surface water as their primary source.
Who owns and regulates Contra Costa Water District?
EPA lists Contra Costa Water District as owned by a local government. 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. 25 of the 84 active systems in Contra Costa County (30%) are also owned by a local government.
Does Contra Costa Water District have drinking water violations?
EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in February 1999. The violations listed here began between October 1989 and February 1999. By type: 1 required treatment not met and 1 public notice, recordkeeping or other. The contaminant or rule involved is Surface Water Treatment Rule. EPA lists 1 as resolved and 1 as archived. Resolved means at least one resolving action is on record: the system returned to compliance, the rule no longer applies, or no further action was needed. 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 |
|---|---|---|---|---|
| 1999-02-01 | Required treatment not metTreatment Technique (SWTR and GWR) · code 41 | Surface Water Treatment Rulecode 0200 | Yes | Resolved |
| 1989-10-01 | Public notice, recordkeeping or otherNotification, Public · code 06 | Not reported | No | Archived |
All 2 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.
Contra Costa Water District: frequently asked questions
Who runs Contra Costa Water District?
Contra Costa Water District (PWSID CA0710003) is a community water system owned by a local government. It is regulated by the CA state drinking water program.
How many people does Contra Costa Water District serve?
Contra Costa Water District reports serving 198,000 people through 60,730 service connections in Contra Costa County, California.
Where does Contra Costa Water District get its water?
EPA SDWIS lists this system's primary water source as surface water. Surface water means the system draws its water from rivers, lakes, streams or reservoirs.
Does Contra Costa Water District have any drinking water violations?
EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in February 1999. 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 Contra Costa Water District'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. EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in February 1999. For current results, consult the system's annual water quality report, EPA ECHO, or the CA state drinking water program.
Where can I find Contra Costa Water District's water quality report?
As a community water system, Contra Costa Water District 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 |
|---|---|---|---|---|
| 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 |
| Golden State Water Company - Bay Point | Contra Costa | 23,731 | 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, “Contra Costa Water District, PWSID CA0710003, California”, https://aquacensus.com/water-systems/california/contra-costa-water-district-ca0710003 (data as of October 1, 2026).