Contra Costa Water District
EPA ID: CA0710003 · 198,000 people served · 29 ZIP codes
Current EPA status: Contra Costa Water District, 2 open violations, 198,000 people served.
Data: EPA SDWIS Last verified: 2026-04-02
Compliance Trajectory
Worsening · Risk tier: High · 95% chance of violation in next 12 months
Violations went from 2 (2022) to 15 (2025). The pattern suggests growing compliance challenges.
Service Area Map
Coverage area for Contra Costa Water District Source: EPA SDWIS service area boundaries.
Service area boundary — Grade B
Service Area Demographics
The Contra Costa Water District serves a community with a median household income of $130,644 and an estimated 817,212 residents across its service area. Approximately 62% of housing stock was built before 1986, which increases the likelihood of lead service lines and older plumbing.
🌊 Where Does Your Water Come From?
Contra Costa Water District's water is drawn from rivers, lakes, or reservoirs. Surface water sources are more exposed to agricultural runoff, stormwater, and upstream discharges, but they typically receive more intensive treatment before reaching your tap.
About 1% of homes in Contra Costa County, California rely on private wells rather than public water systems. Private well owners are responsible for their own water testing and treatment.
Superfund Proximity Note: This service area ranks in the 60th percentile nationally for proximity to Superfund (NPL) sites.
Infrastructure Risk
Detected Contaminants
How Contra Costa Water District compares to EPA limits
What This Means For You
Stage 1 DBP Rule at 2 mg/L exceeds the EPA maximum of mg/L.
Stage 2 DBP Rule at 2 mg/L exceeds the EPA maximum of mg/L.
PFAS Detected in Service Area
PFAS ("forever chemicals") have been detected in water serving this system's area. 25 detections recorded. 6 exceed federal EPA limits (4 ppt for PFOA/PFOS). 2 exceed state limits.
Comparable Water Systems
Similar-sized systems in California
Estimated Remediation Costs
Average estimated costs across ZIP codes served by this system
Based on national averages for common remediation projects. Actual costs vary by property. Only issues flagged by EPA, FEMA, or state data for each ZIP code are included.
System Overview
Contra Costa Water District (EPA ID: CA0710003) is a community water system in California that serves approximately 198,000 people from surface water sources.
This system provides water to 29 ZIP codes across 19 communities.
Average Home Safety Score: B (78/100)
Based on water quality violations, lead levels, and radon risk across all ZIP codes served by this system.
Violation History
Recent Violations
| Date | Contaminant | Type | Status |
|---|---|---|---|
| October 17, 2024 | Stage 2 DBP Rule | Health-based | Unresolved |
| October 17, 2024 | Stage 2 DBP Rule | Monitoring | Unresolved |
| October 1, 2024 | Stage 1 DBP Rule | Monitoring | Resolved |
| October 1, 2023 | Stage 1 DBP Rule | Monitoring | Unresolved |
Contaminants Detected
The following contaminants have been flagged in EPA records for this water system:
| Contaminant | Category | Violations | Health-Based |
|---|---|---|---|
| Stage 1 DBP Rule | Treatment Failure | 2 | No |
| Stage 2 DBP Rule | Treatment Failure | 2 | Yes |
Lead & Copper
EPA Lead and Copper Rule sampling data for ZIP codes served by this system:
| ZIP Code | Lead Level | Exceeds Limit | Sample Date |
|---|---|---|---|
| 94518 | 0.0031 mg/L | No | N/A |
| 94519 | 0.0031 mg/L | No | N/A |
| 94520 | 0.0031 mg/L | No | N/A |
| 94521 | 0.0031 mg/L | No | N/A |
| 94522 | 0.0031 mg/L | No | N/A |
| 94524 | 0.0031 mg/L | No | N/A |
| 94527 | 0.0031 mg/L | No | N/A |
| 94529 | 0.0031 mg/L | No | N/A |
| 94511 | 0.0005 mg/L | No | N/A |
Radon Risk in Service Area
Dominant radon zone for ZIP codes served by this system: Zone 2 (Moderate Risk)
The EPA recommends testing homes in Zone 1 and Zone 2 areas for radon.
Need help with your water quality?
Typical cost: Water test: typically $20–$50 (DIY kit) · Professional inspection: $150–$400
Find the Right Water FilterFree tip: Let cold water run for 2 minutes before drinking — this helps flush lead from your pipes.
ZIP Codes Served
Coverage: 25 ZIP codes confirmed via EPA Community Water System Service Area Boundaries v3 plus 4 additional ZIPs inferred from SDWIS registry data. The EPA-confirmed set is the most reliable; SDWIS-inferred entries may be narrower than the real deployment area.
- 94506 — Danville
- 94509 — Antioch
- 94511 — Bethel Island
- 94513 — Brentwood
- 94517 — Clayton
- 94518 — Concord
- 94519 — Concord
- 94520 — Concord
- 94521 — Concord
- 94522 — Concord
- 94523 — Pleasant Hill
- 94524 — Concord
- 94525 — Crockett
- 94527 — Concord
- 94529 — Concord
- 94531 — Antioch
- 94547 — Hercules
- 94548 — Knightsen
- 94549 — Lafayette
- 94551 — Livermore
- 94553 — Martinez
- 94561 — Oakley
- 94565 — Pittsburg
- 94569 — Port Costa
- 94588 — Pleasanton
- 94596 — Walnut Creek
- 94597 — Walnut Creek
- 94598 — Walnut Creek
- 95219 — Stockton
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View the full compliance record for Contra Costa Water District (CA0710003) on EPA.gov.
Frequently Asked Questions
Is Contra Costa Water District water safe to drink?
Contra Costa Water District has recorded 1 health-based violation in the past 5 years. While the system is required to treat water to meet federal standards, you may want to consider additional precautions such as a certified water filter.
How many people does Contra Costa Water District serve?
Contra Costa Water District serves approximately 198,000 people across 29 ZIP codes in California.
Where does Contra Costa Water District get its water?
The primary water source is surface water.
Federal UCMR5 PFAS Monitoring: Tested Clean
This water system was tested under the federal EPA Unregulated Contaminant Monitoring Rule (UCMR5). No PFAS compounds were detected.
Current MCL reflects the lowest state-enforceable limit (NYS 10 ppt for PFOA/PFOS, effective August 2020). The federal final MCL of 4 ppt for PFOA/PFOS (EPA April 2024 rule) is not enforceable until April 2029. Detections above 4 ppt but below 10 ppt are below current MCL but above the future federal limit.
Source: U.S. EPA UCMR5 (Unregulated Contaminant Monitoring Rule, 5th cycle) — per-system federal sampling, 2023–2025. EPA UCMR5 monitoring program →
Lead Service Line Inventory
Service line breakdown reported under the federal Lead and Copper Rule Improvements (LCRI) inventory requirement:
This system reports zero confirmed lead service lines in its inventory. Unknown-material counts may still warrant verification.
Federal LCRI rule (effective October 2024) requires every public water system to inventory its service lines and complete lead-line replacement within 10 years.
Source: EPA SDWIS Federal Service Line Inventory (Phase 2) · Submitted 2026
ZipCheckup is not affiliated with the utility or state agency. Inventory figures render verbatim from the public LCRI submission cited above; ZipCheckup does not perform inspections or replacements.
Frequently Asked Questions
What You Can Do
Test your water
Home test kits can detect lead, bacteria, and other contaminants at your tap. Find the right filter →
Check your specific ZIP code
Water quality can vary within a system. View nearest ZIP report →
Contact your utility
Contra Costa Water District (EPA ID: CA0710003) — request the latest Consumer Confidence Report or ask about specific contaminants.