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Community Water System · PWS CA4100509

County Service Area 7

Redwood City, California 94063 - drinking water served from surface water sources to 300 people, tracked in EPA SDWIS and UCMR5.

300
People served
84
EPA violations
13
Health-based
Untested
UCMR5 result

The verdict

EPA records 84 drinking-water violations at County Service Area 7, 15% of them health-based - above the California per-system average.

84
Total EPA violations on record
15%
Health-based (MCL / treatment failure)
300
People served by this system
N/A
PFAS compounds detected (UCMR5)

Water Quality Snapshot: County Service Area 7

County Service Area 7 is a local-owned community water system that delivers drinking water to 300 residents in Redwood City, California (San Mateo County) through 68 service connections. Its water is drawn from surface water sources. EPA's Safe Drinking Water Information System records 84 total violations for this system , of which 13 (15%) are health-based, meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. A further 45 monitoring and reporting violations are on file. The most recent violation on record dates to 2025.

The most frequently cited contaminant at this system is TTHM, recorded in 8 violations (MCL, 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%).

County Service Area 7's 84 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
300
Total Violations
84
Health-Based Violations
13
Water Source
Surface Water

System Details

System Type
Community
Owner Type
Local
Connections
68
County
San Mateo
School/Daycare
No
MCL Violations
12
Monitoring Violations
45
Treatment Tech Violations
1

Violation History

Contaminant violations recorded by EPA.

Contaminant Category Count Latest
TTHM MCL 8 2018
Total Haloacetic Acids (HAA5) MCL 4 2025
Toluene MR 2 2004
Benzene MR 2 2004
Ethylbenzene MR 2 2004
DICHLOROMETHANE MR 2 2004
Tetrachloroethylene MR 2 2004
1,1,1-Trichloroethane MR 2 2004
1,1,2-Trichloroethane MR 2 2004
1,2-Dichloroethane MR 2 2004
o-Dichlorobenzene MR 2 2004
1,2-Dichloropropane MR 2 2004
p-Dichlorobenzene MR 2 2004
Vinyl chloride MR 2 2004
Styrene MR 2 2004
Xylenes, Total MR 2 2004
Gross Alpha, Excl. Radon and U MR 2 1981
Carbon tetrachloride MR 2 2004
CHLOROBENZENE MR 2 2004
1,2,4-Trichlorobenzene MR 2 2004
trans-1,2-Dichloroethylene MR 2 2004
1,1-Dichloroethylene MR 2 2004
Trichloroethylene MR 2 2004
cis-1,2-Dichloroethylene MR 2 2004
Lead and Copper Rule MR 1 1993
Surface Water Treatment Rule TT 1 1992

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 County Service Area 7.

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 CA4100509 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 County Service Area 7 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
2025 Total Haloacetic Acids (HAA5) MCL 4 SDWIS / CA4100509 / 2456
2018 TTHM MCL 8 SDWIS / CA4100509 / 2950
2004 Toluene MR 2 SDWIS / CA4100509 / 2991
2004 Benzene MR 2 SDWIS / CA4100509 / 2990
2004 Ethylbenzene MR 2 SDWIS / CA4100509 / 2992
2004 DICHLOROMETHANE MR 2 SDWIS / CA4100509 / 2964
2004 Tetrachloroethylene MR 2 SDWIS / CA4100509 / 2987
2004 1,1,1-Trichloroethane MR 2 SDWIS / CA4100509 / 2981
2004 1,1,2-Trichloroethane MR 2 SDWIS / CA4100509 / 2985
2004 1,2-Dichloroethane MR 2 SDWIS / CA4100509 / 2980
2004 o-Dichlorobenzene MR 2 SDWIS / CA4100509 / 2968
2004 1,2-Dichloropropane MR 2 SDWIS / CA4100509 / 2983
2004 p-Dichlorobenzene MR 2 SDWIS / CA4100509 / 2969
2004 Vinyl chloride MR 2 SDWIS / CA4100509 / 2976
2004 Styrene MR 2 SDWIS / CA4100509 / 2996

How County Service Area 7 Compares

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

Metric County Service Area 7 California avg Federal benchmark
Total violations 84 21.1 SDWA compliance, any non-zero count is a recorded breach
Health-based violations 13 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 300 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 County Service Area 7 water safe to drink? ▼
County Service Area 7 (PWS ID: CA4100509) has 84 recorded violations in the EPA SDWIS database. No PFAS contamination was detected in UCMR5 testing. This system serves 300 people using Surface Water sources.
How many people does County Service Area 7 serve? ▼
County Service Area 7 serves 300 people in Redwood City, California. It is a Local-owned system using Surface Water water sources with 68 service connections.
What type of violations does County Service Area 7 have? ▼
County Service Area 7 has 84 total violations: 13 health-based violations (MCL exceedances or treatment failures), 45 monitoring/reporting violations, and 1 treatment technique violations. Health-based violations indicate contaminant levels exceeded EPA safe limits.
Has PFAS been detected in County Service Area 7 water? ▼
No PFAS testing data is available for County Service Area 7 under the EPA's UCMR5 monitoring program.
What water source does County Service Area 7 use? ▼
County Service Area 7 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.