Public water system · 090605047
ActiveColusa Southern System
At a glance
Colusa Southern System (PWSID 090605047) is an active community water system in California. It reports serving 3,474 people through 31 service connections. Its primary water source is groundwater, and EPA lists it as Native American-owned. Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in July 2005.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
3,474
Service connections
31
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does Colusa Southern System compare with other water systems in California?
By EPA's size categories, Colusa Southern System is a medium system (3,301 to 10,000 people). Across California, the 7,479 active systems average 5,706 people each. Nationally, the average active community water system reports serving 6,703 people, so Colusa Southern System is about half of that figure.
What does “community water system” mean?
A community water system serves at least 15 connections used by year-round residents, or regularly serves at least 25 year-round residents. Homes, apartments and mobile-home parks are served by these. California has 2,997 active community water systems, 40% of the state's 7,479 active systems. Groundwater means the system draws its water from wells or springs fed by underground aquifers. 6,179 California systems (83%) list groundwater as their primary source.
Who owns and regulates Colusa Southern System?
EPA lists Colusa Southern System as Native American-owned. The EPA Region 09 is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act.
Does Colusa Southern System have drinking water violations?
Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in July 2005. The violations listed here began between January 2004 and July 2005. By type: 10 monitoring and reporting and 2 public notice, recordkeeping or other. The contaminant or rule involved most often is Consumer Confidence Rule (2 of them). EPA lists 12 as resolved. Resolved means at least one resolving action is on record: the system returned to compliance, the rule no longer applies, or no further action was needed.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2005-07-01 | Public notice, recordkeeping or otherConsumer Confidence Report Complete Failure to Report · code 71 | Consumer Confidence Rulecode 7000 | No | Resolved |
| 2004-07-01 | Public notice, recordkeeping or otherConsumer Confidence Report Complete Failure to Report · code 71 | Consumer Confidence Rulecode 7000 | No | Resolved |
| 2004-01-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Total trihalomethanes (TTHM)code 2950 | No | Resolved |
| 2004-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Vinyl chloridecode 2976 | No | Resolved |
| 2004-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Heptachlor epoxidecode 2067 | No | Resolved |
| 2004-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Heptachlorcode 2065 | No | Resolved |
| 2004-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Methoxychlorcode 2015 | No | Resolved |
| 2004-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | 1,1-Dichloroethylenecode 2977 | No | Resolved |
| 2004-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Trichloroethylenecode 2984 | No | Resolved |
| 2004-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Benzenecode 2990 | No | Resolved |
| 2004-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Dichloromethanecode 2964 | No | Resolved |
| 2004-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Toluenecode 2991 | No | Resolved |
The 12 most recent violations in EPA's records, newest first.Labels and codes come from EPA's SDWIS reference tables. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found. "Health-based" marks violations of a legal limit or required treatment.
Colusa Southern System: frequently asked questions
Who runs Colusa Southern System?
Colusa Southern System (PWSID 090605047) is a community water system Native American-owned. It is regulated by the EPA Region 09.
How many people does Colusa Southern System serve?
Colusa Southern System reports serving 3,474 people through 31 service connections in California.
Where does Colusa Southern System get its water?
EPA SDWIS lists this system's primary water source as groundwater. Groundwater means the system draws its water from wells or springs fed by underground aquifers.
Does Colusa Southern System have any drinking water violations?
Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in July 2005. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found.
Is Colusa Southern System's water safe to drink?
AquaCensus shows EPA compliance records, not current water test results, so it cannot say whether the water is safe at a given moment. Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in July 2005. For current results, consult the system's annual water quality report, EPA ECHO, or the EPA Region 09.
Where can I find Colusa Southern System's water quality report?
As a community water system, Colusa Southern System must deliver an annual water quality report, called a Consumer Confidence Report, to its customers by July 1 each year, covering the previous calendar year. The system can provide a copy on request.
Other water systems in California
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Los Angeles-City, Dept. of Water & Power | Los Angeles | 3,875,566 | Community | Surface water |
| East Bay MUD | Alameda | 1,442,800 | Community | Surface water |
| San Diego, City of | San Diego | 1,385,379 | Community | Surface water |
| San Jose Water | Santa Clara | 1,039,920 | Community | Surface water |
| Sfpuc City Distribution Division | San Francisco | 848,019 | Community | Purchased surface water |
| Eastern Municipal Wd | Riverside | 666,581 | Community | Purchased surface water |
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About this data
Source: U.S. EPA Safe Drinking Water Information System (SDWIS) and SDWA violation records, via EPA ECHO, as published October 1, 2026 — AquaCensus refreshes it quarterly. See the methodology for how records are matched, cleaned and scored.
Cite as: AquaCensus, “Colusa Southern System, PWSID 090605047, California”, https://aquacensus.com/water-systems/california/colusa-southern-system-090605047 (data as of October 1, 2026).