Public water system · CA2900593
ActiveTwin Ridges Oak Tree School
At a glance
Twin Ridges Oak Tree School (PWSID CA2900593) is an active non-transient non-community water system in Nevada County, California. It reports serving 120 people through 8 service connections. Its primary water source is groundwater, and EPA lists it as owned by a local government. Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in February 2018.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
120
Service connections
8
Primary source
GW
Groundwater
System type
NTNCWS
Non-transient non-community water system
System record
How does Twin Ridges Oak Tree School compare with other water systems in Nevada County?
By EPA's size categories, Twin Ridges Oak Tree School is a very small system (500 people or fewer). Nevada County has 82 active public water systems. Its population served is well below the county average of 1,263 people per system, and accounts for 0.1% of the 103,540 people reported by systems filed under the county. Across California, the 7,479 active systems average 5,706 people each. Nationally, the average active non-transient non-community water system reports serving 430 people, so Twin Ridges Oak Tree School is well below that figure.
What does “non-transient non-community water system” mean?
A non-transient non-community water system regularly serves at least 25 of the same people for more than six months a year, but not where they live. Schools, factories, office buildings and hospitals with their own supply are typical examples. California has 1,466 active non-transient non-community water systems, 20% 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 Twin Ridges Oak Tree School?
EPA lists Twin Ridges Oak Tree School as owned by a local government. The CA state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 19 of the 82 active systems in Nevada County (23%) are also owned by a local government.
Does Twin Ridges Oak Tree School have drinking water violations?
Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in February 2018. The violations listed here began between July 1993 and February 2018. By type: 8 monitoring and reporting, 3 monitoring and 1 contaminant level above the legal limit. The contaminant or rule involved most often is Total coliform bacteria (TCR) (8 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 |
|---|---|---|---|---|
| 2018-02-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2017-05-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2016-10-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2015-02-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2011-04-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2011-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Monthly (TCR) · code 22 | Total coliform bacteria (TCR)code 3100 | Yes | Resolved |
| 2005-10-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2005-07-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2002-09-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2000-10-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 1997-11-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 1993-07-01 | Monitoring and reportingInitial Tap Sampling for Pb and Cu · code 51 | Lead and Copper Rulecode 5000 | 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.
Twin Ridges Oak Tree School: frequently asked questions
Who runs Twin Ridges Oak Tree School?
Twin Ridges Oak Tree School (PWSID CA2900593) is a non-transient non-community water system owned by a local government. It is regulated by the CA state drinking water program.
How many people does Twin Ridges Oak Tree School serve?
Twin Ridges Oak Tree School reports serving 120 people through 8 service connections in Nevada County, California.
Where does Twin Ridges Oak Tree School 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 Twin Ridges Oak Tree School have any drinking water violations?
Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in February 2018. 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 Twin Ridges Oak Tree School'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, one is health-based, and the most recent began in February 2018. For current results, consult EPA ECHO, or the CA state drinking water program.
Where can I find Twin Ridges Oak Tree School's water quality report?
The annual Consumer Confidence Report requirement applies to community water systems. Twin Ridges Oak Tree School is a non-transient non-community water system, so it is not required to publish one; like every public water system, it must notify the people it serves about violations under EPA's public notification rules.
Other water systems in Nevada County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Truckee-Donner PUD, Main | Nevada | 36,730 | Community | Groundwater |
| Nevada Id - E. George, Banner Mountain | Nevada | 17,154 | Community | Surface water |
| Nevada Id - Loma Rica | Nevada | 14,072 | Community | Surface water |
| Nevada Id - Lake Wildwood | Nevada | 9,108 | Community | Surface water |
| Nevada Id - Lake of Pines | Nevada | 6,870 | Community | Surface water |
| City of Grass Valley | Nevada | 4,947 | Community | 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, “Twin Ridges Oak Tree School, PWSID CA2900593, California”, https://aquacensus.com/water-systems/california/twin-ridges-oak-tree-school-ca2900593 (data as of October 1, 2026).