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Community Water System · PWS CA4100512

Loma Mar Mutual

Loma Mar, California 94021 - drinking water served from surface water sources to 65 people, tracked in EPA SDWIS and UCMR5.

65
People served
67
EPA violations
24
Health-based
Untested
UCMR5 result

The verdict

EPA records 67 drinking-water violations at Loma Mar Mutual, 36% of them health-based - above the California per-system average.

67
Total EPA violations on record
36%
Health-based (MCL / treatment failure)
65
People served by this system
N/A
PFAS compounds detected (UCMR5)

Water Quality Snapshot: Loma Mar Mutual

Loma Mar Mutual is a private-owned community water system that delivers drinking water to 65 residents in Loma Mar, California (San Mateo County) through 34 service connections. Its water is drawn from surface water sources. EPA's Safe Drinking Water Information System records 67 total violations for this system , of which 24 (36%) are health-based, meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. A further 9 monitoring and reporting violations are on file. The most recent violation on record dates to 2016.

The most frequently cited contaminant at this system is Surface Water Treatment Rule, recorded in 17 violations (TT, health-based). 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. Statewide, 447 of 694 UCMR5-tested systems have reported PFAS detections (64.4%).

Loma Mar Mutual's 67 violations sit above the California average.

All figures above are sourced directly from EPA SDWIS and UCMR5 public data releases and are updated as EPA publishes new reporting cycles.

Population Served
65
Total Violations
67
Health-Based Violations
24
Water Source
Surface Water

System Details

System Type
Community
Owner Type
Private
Connections
34
County
San Mateo
School/Daycare
No
MCL Violations
5
Monitoring Violations
9
Treatment Tech Violations
19

Violation History

Contaminant violations recorded by EPA.

Contaminant Category Count Latest
Surface Water Treatment Rule TT 17 2016
Coliform (TCR) MR 7 2006
Consumer Confidence Rule Other 3 2003
TTHM MCL 2 2016
Gross Alpha, Excl. Radon and U MR 2 1981
Interim Enhanced Surface Water Treatment Rule TT 2 2005
Coliform (TCR) MCL 2 2003
Mercury MCL 1 1980

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 Loma Mar Mutual.

Federal Source of Truth

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 CA4100512 on SDWIS

Source: EPA SDWIS Federal Reports Search

State Regulator

California Drinking Water Authority

California State Water Resources Control Board, Division of Drinking Water is the primacy agency that licenses and inspects Loma Mar Mutual under EPA-delegated authority.

Open CA regulator portal

Source: 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
2016 Surface Water Treatment Rule TT 17 SDWIS / CA4100512 / 0200
2016 TTHM MCL 2 SDWIS / CA4100512 / 2950
2006 Coliform (TCR) MR 7 SDWIS / CA4100512 / 3100
2005 Interim Enhanced Surface Water Treatment Rule TT 2 SDWIS / CA4100512 / 0300
2003 Consumer Confidence Rule Other 3 SDWIS / CA4100512 / 7000
2003 Coliform (TCR) MCL 2 SDWIS / CA4100512 / 3100
1981 Gross Alpha, Excl. Radon and U MR 2 SDWIS / CA4100512 / 4000
1980 Mercury MCL 1 SDWIS / CA4100512 / 1035

How Loma Mar Mutual Compares

Cross-reference this system's record against state averages and the federal MCL framework for context.

Metric Loma Mar Mutual California avg Federal benchmark
Total violations 67 21.1 SDWA compliance, any non-zero count is a recorded breach
Health-based violations 24 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 65 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 (EPA proposed extending to 2031, not yet final as of May 2026)
Nitrate (as N) 10 mg/L Acute health risk for infants

Frequently Asked Questions

Is Loma Mar Mutual water safe to drink? ▼
Loma Mar Mutual (PWS ID: CA4100512) has 67 recorded violations in the EPA SDWIS database. No PFAS contamination was detected in UCMR5 testing. This system serves 65 people using Surface Water sources.
How many people does Loma Mar Mutual serve? ▼
Loma Mar Mutual serves 65 people in Loma Mar, California. It is a Private-owned system using Surface Water water sources with 34 service connections.
What type of violations does Loma Mar Mutual have? ▼
Loma Mar Mutual has 67 total violations: 24 health-based violations (MCL exceedances or treatment failures), 9 monitoring/reporting violations, and 19 treatment technique violations. Health-based violations indicate contaminant levels exceeded EPA safe limits.
Has PFAS been detected in Loma Mar Mutual water? ▼
No PFAS testing data is available for Loma Mar Mutual under the EPA's UCMR5 monitoring program.
What water source does Loma Mar Mutual use? ▼
Loma Mar Mutual uses Surface Water as its primary water source. It is classified as a Community Water System (CWS), serving residential populations year-round.
Where does this data come from? ▼
All data comes from the EPA Safe Drinking Water Information System (SDWIS) and the UCMR5 PFAS monitoring program. SDWIS tracks compliance for all public water systems regulated under the Safe Drinking Water Act.
Data Sources: EPA Safe Drinking Water Information System (SDWIS), Q4 2025. This data is provided for informational purposes only.

Read our methodology - how this data is sourced, computed, and verified.

Data sourced from EPA SDWIS and UCMR5 PFAS monitoring data. See our methodology for details. Retrieved and formatted by PlainWater Editorial

Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This system's figures are rendered directly from EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.