DIAMOND A MUTUAL WATER COMPANY
PWS ID: CA4900562 · SONOMA, California 95476
DIAMOND A MUTUAL WATER COMPANY serves 640 people in SONOMA, California using Groundwater water sources. It has 18 recorded EPA violations, including 3 health-based violations. No PFAS contamination was detected in UCMR5 testing.
Water Quality Snapshot: DIAMOND A MUTUAL WATER COMPANY
DIAMOND A MUTUAL WATER COMPANY is a private-owned community water system that delivers drinking water to 640 residents in SONOMA, California (Sonoma County) through 194 service connections. Its water is drawn from groundwater sources. EPA's Safe Drinking Water Information System records 18 total violations for this system , of which 3 (17%) are health-based — meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. A further 10 monitoring and reporting violations are on file. The most recent violation on record dates to 2024.
The most frequently cited contaminant at this system is Coliform (TCR), recorded in 6 violations (MR). This system has not yet been sampled under EPA's UCMR5 PFAS monitoring program, so no PFAS detection data is available here.
Across California, EPA tracks 7,249 public water systems serving 42,404,883 people, with 153,308 cumulative violations and 63,983 health-based violations on record. About 89% of systems in the state carry at least one violation, and state-wide the average per system is 21.1 violations. DIAMOND A MUTUAL WATER COMPANY's 18 violations sit below the California average. Statewide, 447 of 694 UCMR5-tested systems have reported PFAS detections (64.4%). All figures above are sourced directly from EPA SDWIS and UCMR5 public data releases and are updated as EPA publishes new reporting cycles.
System Details
- System Type
- Community
- Owner Type
- Private
- Connections
- 194
- County
- Sonoma
- School/Daycare
- No
- MCL Violations
- 2
- Monitoring Violations
- 10
- Treatment Tech Violations
- 1
Violation History
Contaminant violations recorded by EPA.
| Contaminant | Category | Count | Latest |
|---|---|---|---|
| Coliform (TCR) | MR | 6 | 2002 |
| Nitrate | MR | 2 | 2006 |
| Coliform (TCR) | MCL | 2 | 2014 |
| Gross Alpha, Excl. Radon and U | MR | 2 | 1981 |
| LEAD AND COPPER RULE REVISIONS | TT | 1 | 2024 |
| LEAD AND COPPER RULE REVISIONS | RPT | 1 | 2024 |
Verify This Water System
The figures above are aggregated from EPA's public databases. To verify the underlying records — or to file a complaint, request a Consumer Confidence Report, or check current monitoring status — go directly to the federal and state regulators that enforce the Safe Drinking Water Act for DIAMOND A MUTUAL WATER COMPANY.
EPA SDWIS — Federal Reports
EPA's Safe Drinking Water Information System (SDWIS) holds the federal compliance record for every regulated public water system. Open the system-level report by PWS ID:
View PWS ID CA4900562 on SDWISSource: EPA SDWIS Federal Reports Search
California Drinking Water Authority
California State Water Resources Control Board — Division of Drinking Water is the primacy agency that licenses and inspects DIAMOND A MUTUAL WATER COMPANY under EPA-delegated authority.
Open CA regulator portalSource: California State Water Resources Control Board — Division of Drinking Water
Violation Timeline
Each row links to the EPA SDWIS public record for verification. Cross-reference the contaminant code on EPA's federal report to see violation dates, return-to-compliance status, and enforcement actions.
| Year (latest) | Contaminant | Category | Count | EPA Record |
|---|---|---|---|---|
| 2024 | LEAD AND COPPER RULE REVISIONS | TT | 1 | SDWIS / CA4900562 / 5200 |
| 2024 | LEAD AND COPPER RULE REVISIONS | RPT | 1 | SDWIS / CA4900562 / 5200 |
| 2014 | Coliform (TCR) | MCL | 2 | SDWIS / CA4900562 / 3100 |
| 2006 | Nitrate | MR | 2 | SDWIS / CA4900562 / 1040 |
| 2002 | Coliform (TCR) | MR | 6 | SDWIS / CA4900562 / 3100 |
| 1981 | Gross Alpha, Excl. Radon and U | MR | 2 | SDWIS / CA4900562 / 4000 |
How DIAMOND A MUTUAL WATER COMPANY Compares
Cross-reference this system's record against state averages and the federal MCL framework for context.
| Metric | DIAMOND A MUTUAL WATER COMPANY | California avg | Federal benchmark |
|---|---|---|---|
| Total violations | 18 | 21.1 | SDWA compliance — any non-zero count is a recorded breach |
| Health-based violations | 3 | 8.8 | Indicates a contaminant exceeded a federal MCL |
| PFAS detection | None | 64.4% | EPA final rule (2024): PFOA/PFOS MCL = 4.0 ppt |
| Population served | 640 | 5,850 | Sizing context for compliance burden |
Sources: EPA SDWIS and EPA National Primary Drinking Water Regulations (40 CFR Part 141). State averages computed across 7,249 regulated public water systems in California.
Federal MCL reference — Safe Drinking Water Act thresholds ▼
| Contaminant | Federal MCL / Action Level | Note |
|---|---|---|
| Lead | 0 mg/L (Action Level: 0.015 mg/L) | Lead and Copper Rule treatment technique |
| Arsenic | 0.010 mg/L (10 ppb) | Health-based MCL since 2006 |
| Total Coliform | Treatment technique (RTCR) | Indicator organism, monitoring trigger |
| PFOA / PFOS (PFAS) | 4.0 ppt each (final 2024 rule) | Compliance deadline 2029 |
| Nitrate (as N) | 10 mg/L | Acute health risk for infants |
Frequently Asked Questions
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Related Data for California
Read our methodology — how this data is sourced, computed, and verified.