PlainWater
States → EPA Region 10 — Tribal Water Systems

Community Water System · PWS 105300021

McCoy Lake

Wellpinit, EPA Region 10 — Tribal Water Systems 99040 - drinking water served from groundwater sources to 325 people, tracked in EPA SDWIS and UCMR5.

325
People served
433
EPA violations
7
Health-based
Untested
UCMR5 result

The verdict

EPA records 433 drinking-water violations at McCoy Lake, 2% of them health-based.

433
Total EPA violations on record
2%
Health-based (MCL / treatment failure)
325
People served by this system
N/A
PFAS compounds detected (UCMR5)

Water Quality Snapshot: McCoy Lake

McCoy Lake is a native american-owned community water system that delivers drinking water to 325 residents in Wellpinit, EPA Region 10 — Tribal Water Systems through 90 service connections. Its water is drawn from groundwater sources. EPA's Safe Drinking Water Information System records 433 total violations for this system , of which 7 (2%) are health-based, meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. A further 397 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 Coliform (TCR), recorded in 58 violations (MR). This system has not yet been sampled under EPA's UCMR5 PFAS monitoring program, so no PFAS detection data is available here.

EPA Region 10 — Tribal Water Systems has thousands of regulated public water systems tracked by EPA under the Safe Drinking Water Act.

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
325
Total Violations
433
Health-Based Violations
7
Water Source
Groundwater

System Details

System Type
Community
Owner Type
Native American
Connections
90
School/Daycare
No
MCL Violations
0
Monitoring Violations
397
Treatment Tech Violations
7

Violation History

Contaminant violations recorded by EPA.

Contaminant Category Count Latest
Coliform (TCR) MR 58 2015
Consumer Confidence Rule Other 17 2019
Gross Alpha, Excl. Radon and U MR 14 2020
Nitrate MR 14 2019
Revised Total Coliform Rule MON 9 2022
Atrazine MR 6 2008
Benzene MR 6 2008
Groundwater Rule TT 6 2025
BHC-GAMMA MR 5 2008
Carbofuran MR 5 2008
Chlordane MR 5 2008
Dalapon MR 5 2008
Di(2-ethylhexyl) adipate MR 5 2008
Diquat MR 5 2008
Endrin MR 5 2008
ETHYLENE DIBROMIDE MR 5 2008
Glyphosate MR 5 2008
Heptachlor MR 5 2008
Heptachlor epoxide MR 5 2008
HEXACHLOROBENZENE MR 5 2008
Hexachlorocyclopentadiene MR 5 2008
Methoxychlor MR 5 2008
OXAMYL MR 5 2008
Picloram MR 5 2008
Total Polychlorinated Biphenyls (PCB) MR 5 2008
2,4-D MR 5 2008
1,2,4-Trichlorobenzene MR 5 2008
o-Dichlorobenzene MR 5 2008
p-Dichlorobenzene MR 5 2008
trans-1,2-Dichloroethylene MR 5 2008

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 McCoy Lake.

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 105300021 on SDWIS

Source: EPA SDWIS Federal Reports Search

State Regulator

EPA Region 10 — Tribal Water Systems Drinking Water Authority

EPA Region 10 — Tribal Water Systems's primacy agency administers the Safe Drinking Water Act locally. Search EPA SDWIS for the current state contact, or use the state's public health or environment department portal.

Find 10 regulator via EPA SDWIS

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 Groundwater Rule TT 6 SDWIS / 105300021 / 0700
2025 Public Notice Other 2 SDWIS / 105300021 / 7500
2024 LEAD AND COPPER RULE REVISIONS TT 1 SDWIS / 105300021 / 5200
2023 Revised Total Coliform Rule RPT 5 SDWIS / 105300021 / 8000
2022 Revised Total Coliform Rule MON 9 SDWIS / 105300021 / 8000
2020 Gross Alpha, Excl. Radon and U MR 14 SDWIS / 105300021 / 4000
2020 Combined Radium (-226 and -228) MR 5 SDWIS / 105300021 / 4010
2020 Combined Uranium MR 3 SDWIS / 105300021 / 4006
2020 Arsenic MR 2 SDWIS / 105300021 / 1005
2019 Consumer Confidence Rule Other 17 SDWIS / 105300021 / 7000
2019 Nitrate MR 14 SDWIS / 105300021 / 1040
2016 Lead and Copper Rule MR 3 SDWIS / 105300021 / 5000
2015 Coliform (TCR) MR 58 SDWIS / 105300021 / 3100
2011 Mercury MR 3 SDWIS / 105300021 / 1035
2008 Atrazine MR 6 SDWIS / 105300021 / 2050

How McCoy Lake Compares

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

Metric McCoy Lake EPA Region 10 — Tribal Water Systems avg Federal benchmark
Total violations 433 - SDWA compliance, any non-zero count is a recorded breach
Health-based violations 7 - Indicates a contaminant exceeded a federal MCL
PFAS detection None - EPA final rule (2024): PFOA/PFOS MCL = 4.0 ppt
Population served 325 - Sizing context for compliance burden

Sources: EPA SDWIS and EPA National Primary Drinking Water Regulations (40 CFR Part 141). State averages computed across all regulated public water systems in EPA Region 10 — Tribal Water Systems.

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 McCoy Lake water safe to drink? ▼
McCoy Lake (PWS ID: 105300021) has 433 recorded violations in the EPA SDWIS database. No PFAS contamination was detected in UCMR5 testing. This system serves 325 people using Groundwater sources.
How many people does McCoy Lake serve? ▼
McCoy Lake serves 325 people in Wellpinit, EPA Region 10 — Tribal Water Systems. It is a Native American-owned system using Groundwater water sources with 90 service connections.
What type of violations does McCoy Lake have? ▼
McCoy Lake has 433 total violations: 7 health-based violations (MCL exceedances or treatment failures), 397 monitoring/reporting violations, and 7 treatment technique violations. Health-based violations indicate contaminant levels exceeded EPA safe limits.
Has PFAS been detected in McCoy Lake water? ▼
No PFAS testing data is available for McCoy Lake under the EPA's UCMR5 monitoring program.
What water source does McCoy Lake use? ▼
McCoy Lake 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.