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States → EPA Region 9 — Tribal Water Systems

Community Water System · PWS 090605046

Colusa Northern System

Colusa, EPA Region 9 — Tribal Water Systems 95932-4018 - drinking water served from groundwater sources to 67 people, tracked in EPA SDWIS and UCMR5.

67
People served
385
EPA violations
0
Health-based
Untested
UCMR5 result

The verdict

EPA records 385 drinking-water violations at Colusa Northern System.

385
Total EPA violations on record
0%
Health-based (MCL / treatment failure)
67
People served by this system
N/A
PFAS compounds detected (UCMR5)

Water Quality Snapshot: Colusa Northern System

Colusa Northern System is a native american-owned community water system that delivers drinking water to 67 residents in Colusa, EPA Region 9 — Tribal Water Systems through 13 service connections. Its water is drawn from groundwater sources. EPA's Safe Drinking Water Information System records 385 total violations for this system , of which 0 (0%) are health-based, meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. A further 149 monitoring and reporting violations are on file. The most recent violation on record dates to 2005.

The most frequently cited contaminant at this system is Nitrate, recorded in 5 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 9 — 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
67
Total Violations
385
Health-Based Violations
0
Water Source
Groundwater

System Details

System Type
Community
Owner Type
Native American
Connections
13
School/Daycare
No
MCL Violations
0
Monitoring Violations
149
Treatment Tech Violations
0

Violation History

Contaminant violations recorded by EPA.

Contaminant Category Count Latest
Nitrate MR 5 2004
Consumer Confidence Rule Other 5 2005
Coliform (TCR) MR 4 1996
BHC-GAMMA MR 3 2004
Methoxychlor MR 3 2004
Toxaphene MR 3 2004
Atrazine MR 3 2004
LASSO MR 3 2004
Heptachlor MR 3 2004
Heptachlor epoxide MR 3 2004
2,4-D MR 3 2004
2,4,5-TP MR 3 2004
Pentachlorophenol MR 3 2004
Total Polychlorinated Biphenyls (PCB) MR 3 2004
ETHYLENE DIBROMIDE MR 3 2004
Xylenes, Total MR 3 2004
Chlordane MR 3 2004
Carbofuran MR 3 2004
1,2-DIBROMO-3-CHLOROPROPANE MR 3 2004
Arsenic MR 2 2001
Cadmium MR 2 2001
Chromium MR 2 2001
Fluoride MR 2 2001
CYANIDE MR 2 2004
Endrin MR 2 2004
Dalapon MR 2 2004
Diquat MR 2 2004
Endothall MR 2 2004
Glyphosate MR 2 2004
OXAMYL MR 2 2004

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 Colusa Northern System.

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 090605046 on SDWIS

Source: EPA SDWIS Federal Reports Search

State Regulator

EPA Region 9 — Tribal Water Systems Drinking Water Authority

EPA Region 9 — 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 09 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
2005 Consumer Confidence Rule Other 5 SDWIS / 090605046 / 7000
2004 Nitrate MR 5 SDWIS / 090605046 / 1040
2004 BHC-GAMMA MR 3 SDWIS / 090605046 / 2010
2004 Methoxychlor MR 3 SDWIS / 090605046 / 2015
2004 Toxaphene MR 3 SDWIS / 090605046 / 2020
2004 Atrazine MR 3 SDWIS / 090605046 / 2050
2004 LASSO MR 3 SDWIS / 090605046 / 2051
2004 Heptachlor MR 3 SDWIS / 090605046 / 2065
2004 Heptachlor epoxide MR 3 SDWIS / 090605046 / 2067
2004 2,4-D MR 3 SDWIS / 090605046 / 2105
2004 2,4,5-TP MR 3 SDWIS / 090605046 / 2110
2004 Pentachlorophenol MR 3 SDWIS / 090605046 / 2326
2004 Total Polychlorinated Biphenyls (PCB) MR 3 SDWIS / 090605046 / 2383
2004 ETHYLENE DIBROMIDE MR 3 SDWIS / 090605046 / 2946
2004 Xylenes, Total MR 3 SDWIS / 090605046 / 2955

How Colusa Northern System Compares

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

Metric Colusa Northern System EPA Region 9 — Tribal Water Systems avg Federal benchmark
Total violations 385 - SDWA compliance, any non-zero count is a recorded breach
Health-based violations 0 - Indicates a contaminant exceeded a federal MCL
PFAS detection None - EPA final rule (2024): PFOA/PFOS MCL = 4.0 ppt
Population served 67 - 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 9 — 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 Colusa Northern System water safe to drink? ▼
Colusa Northern System (PWS ID: 090605046) has 385 recorded violations in the EPA SDWIS database. No PFAS contamination was detected in UCMR5 testing. This system serves 67 people using Groundwater sources.
How many people does Colusa Northern System serve? ▼
Colusa Northern System serves 67 people in Colusa, EPA Region 9 — Tribal Water Systems. It is a Native American-owned system using Groundwater water sources with 13 service connections.
What type of violations does Colusa Northern System have? ▼
Colusa Northern System has 385 total violations: 0 health-based violations (MCL exceedances or treatment failures), 149 monitoring/reporting violations, and 0 treatment technique violations. Health-based violations indicate contaminant levels exceeded EPA safe limits.
Has PFAS been detected in Colusa Northern System water? ▼
No PFAS testing data is available for Colusa Northern System under the EPA's UCMR5 monitoring program.
What water source does Colusa Northern System use? ▼
Colusa Northern System 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.