County · California
Contra Costa County, California: drinking water records
This overview covers 43 ZIP codes and 43 community water systems in Contra Costa County. It also stands in for 2 ZIP codes whose utility has too little EPA data for a page of its own.
System population figures are summed from EPA registry records and can overlap where wholesalers and retail systems serve the same people. They are not a Census county-population estimate.
Water systems with the most complete records
| Water system | People served | PFAS survey results | PFAS found | Health-based violations | Lead, 9 in 10 homes at or below |
|---|---|---|---|---|---|
| Contra Costa Water District CA0710003 | 198,000 | 360 | 0 | 0 | 3.1 ppb |
| City of Antioch CA0710001 | 115,074 | 120 | 0 | 0 | 0 ppb |
| Brentwood CA0710004 | 64,513 | 420 | 0 | 0 | 0 ppb |
| City of Pittsburg CA0710008 | 62,500 | 120 | 0 | 0 | 0 ppb |
| Diablo Water District CA0710007 | 43,357 | 95 | 0 | 0 | 1.9 ppb |
| City of Martinez CA0710006 | 30,997 | 120 | 0 | 0 | 0 ppb |
| Golden State Water Company - Bay Point CA0710002 | 23,731 | 120 | 0 | 0 | 0 ppb |
| Town of Discovery Bay CA0710009 | 16,790 | 95 | 0 | 0 | 0 ppb |
| Vista Village MHP CO0107810 | 750 | 0 | 0 | 1 | 4 ppb |
| Willow Park Marina CA0707507 | 380 | 0 | 0 | 21 | 1.3 ppb |
| Orwood Resort CA0707545 | 350 | 0 | 0 | 1 | 0 ppb |
| Delta Mutual Water Company CA0707573 | 333 | 0 | 0 | 20 | 0 ppb |
| Oakley Mutual Water Company CA0706004 | 170 | 0 | 0 | 19 | 0 ppb |
| Russos Mobile Park CA0707601 | 110 | 0 | 0 | 1 | 0 ppb |
| Sandmound Mutual CA0707556 | 100 | 0 | 0 | 1 | 0 ppb |
| Bella Vista Water Sys CA0707589 | 93 | 0 | 0 | 14 | 6.5 ppb |
| Sandy Point Mobile Home Park CA0707597 | 67 | 0 | 0 | 1 | 1 ppb |
| Doubletree Ranch Water System CA0707615 | 66 | 0 | 0 | 7 | 0 ppb |
| Suntree Hollow Mobile Home Court ID5070049 | 60 | 0 | 0 | 12 | 1 ppb |
| Colonia Santa Maria CA0707517 | 32 | 0 | 0 | 1 | 0 ppb |
| Pleasantimes Mutual Water Co CA0707576 | 644 | 0 | 0 | 0 | 0.5 ppb |
| Clayton Palms Water CA0707603 | 549 | 0 | 0 | 0 | 4 ppb |
| Willow Mobile Home Park CA0707613 | 481 | 0 | 0 | 0 | 10 ppb |
| Riverview Water Association CA0707577 | 230 | 0 | 0 | 0 | 0 ppb |
| Camino Mobilehome CA0707598 | 210 | 0 | 0 | 0 | 0 ppb |
ZIP reports in Contra Costa County
No ZIP report in this county is published yet.
These ZIP codes are covered by this overview because their utility has too little EPA data for a separate page: 94511, 94516.
Sources and scope
EPA UCMR 5 occurrence data, samples collected 2023-01-03 – 2026-06-17, final release, August 2026 (file dated Aug 28, 2026); EPA SDWIS via ECHO, 2026Q2 extract (file dated Jul 9, 2026); EPA service-area boundaries v3.0; Census 2020 ZCTAs. Page generated 2026-09-03.
Counts cover the systems that report this county to EPA. A water system may cross county lines. "Found" means at least one result at or above the laboratory reporting level; it is not a compliance finding.