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Community Water System · PWS CA4100540

Oku Incorporated

Pescadero, California 94060 - drinking water served from groundwater sources to 35 people, tracked in EPA SDWIS and UCMR5.

35
People served
94
EPA violations
9
Health-based
Untested
UCMR5 result

The verdict

EPA records 94 drinking-water violations at Oku Incorporated, 10% of them health-based - above the California per-system average.

94
Total EPA violations on record
10%
Health-based (MCL / treatment failure)
35
People served by this system
N/A
PFAS compounds detected (UCMR5)

Water Quality Snapshot: Oku Incorporated

Oku Incorporated is a private-owned community water system that delivers drinking water to 35 residents in Pescadero, California (San Mateo County) through 10 service connections. Its water is drawn from groundwater sources. EPA's Safe Drinking Water Information System records 94 total violations for this system , of which 9 (10%) are health-based, meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. A further 78 monitoring and reporting violations are on file. The most recent violation on record dates to 2021.

The most frequently cited contaminant at this system is Radium-228, 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. Statewide, 447 of 694 UCMR5-tested systems have reported PFAS detections (64.4%).

Oku Incorporated's 94 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
35
Total Violations
94
Health-Based Violations
9
Water Source
Groundwater

System Details

System Type
Community
Owner Type
Private
Connections
10
County
San Mateo
School/Daycare
No
MCL Violations
4
Monitoring Violations
78
Treatment Tech Violations
5

Violation History

Contaminant violations recorded by EPA.

Contaminant Category Count Latest
Radium-228 MR 6 2021
Interim Enhanced Surface Water Treatment Rule TT 3 2010
Lead and Copper Rule MR 3 2003
TTHM MCL 2 2011
Coliform (TCR) MR 2 2006
Surface Water Treatment Rule TT 2 1996
Arsenic MR 2 2019
Barium MR 2 2019
Chromium MR 2 2019
Mercury MR 2 2019
Nickel MR 2 2019
Thallium, Total MR 2 2019
cis-1,2-Dichloroethylene MR 2 2019
Xylenes, Total MR 2 2019
DICHLOROMETHANE MR 2 2019
o-Dichlorobenzene MR 2 2019
p-Dichlorobenzene MR 2 2019
Vinyl chloride MR 2 2019
trans-1,2-Dichloroethylene MR 2 2019
1,2-Dichloroethane MR 2 2019
1,1,1-Trichloroethane MR 2 2019
Carbon tetrachloride MR 2 2019
1,2-Dichloropropane MR 2 2019
Trichloroethylene MR 2 2019
Toluene MR 2 2019
Ethylbenzene MR 2 2019
Styrene MR 2 2019
Cadmium MR 2 2019
Benzene MR 2 2019
Antimony, Total MR 2 2019

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 Oku Incorporated.

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 CA4100540 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 Oku Incorporated 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
2021 Radium-228 MR 6 SDWIS / CA4100540 / 4030
2019 Arsenic MR 2 SDWIS / CA4100540 / 1005
2019 Barium MR 2 SDWIS / CA4100540 / 1010
2019 Chromium MR 2 SDWIS / CA4100540 / 1020
2019 Mercury MR 2 SDWIS / CA4100540 / 1035
2019 Nickel MR 2 SDWIS / CA4100540 / 1036
2019 Thallium, Total MR 2 SDWIS / CA4100540 / 1085
2019 cis-1,2-Dichloroethylene MR 2 SDWIS / CA4100540 / 2380
2019 Xylenes, Total MR 2 SDWIS / CA4100540 / 2955
2019 DICHLOROMETHANE MR 2 SDWIS / CA4100540 / 2964
2019 o-Dichlorobenzene MR 2 SDWIS / CA4100540 / 2968
2019 p-Dichlorobenzene MR 2 SDWIS / CA4100540 / 2969
2019 Vinyl chloride MR 2 SDWIS / CA4100540 / 2976
2019 trans-1,2-Dichloroethylene MR 2 SDWIS / CA4100540 / 2979
2019 1,2-Dichloroethane MR 2 SDWIS / CA4100540 / 2980

How Oku Incorporated Compares

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

Metric Oku Incorporated California avg Federal benchmark
Total violations 94 21.1 SDWA compliance, any non-zero count is a recorded breach
Health-based violations 9 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 35 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 Oku Incorporated water safe to drink? ▼
Oku Incorporated (PWS ID: CA4100540) has 94 recorded violations in the EPA SDWIS database. No PFAS contamination was detected in UCMR5 testing. This system serves 35 people using Groundwater sources.
How many people does Oku Incorporated serve? ▼
Oku Incorporated serves 35 people in Pescadero, California. It is a Private-owned system using Groundwater water sources with 10 service connections.
What type of violations does Oku Incorporated have? ▼
Oku Incorporated has 94 total violations: 9 health-based violations (MCL exceedances or treatment failures), 78 monitoring/reporting violations, and 5 treatment technique violations. Health-based violations indicate contaminant levels exceeded EPA safe limits.
Has PFAS been detected in Oku Incorporated water? ▼
No PFAS testing data is available for Oku Incorporated under the EPA's UCMR5 monitoring program.
What water source does Oku Incorporated use? ▼
Oku Incorporated uses Groundwater 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.