Public water system · CA4000590
ActiveCounty of Monterey-Lake Nacimiento
At a glance
County of Monterey-Lake Nacimiento (PWSID CA4000590) is an active non-transient non-community water system in San Luis Obispo County, California. It reports serving 1,521 people through 323 service connections. Its primary water source is groundwater under influence of surface water, and EPA lists it as privately owned. EPA's records list 6 violations for this system; none is health-based, and the most recent began in October 2020.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
1,521
Service connections
323
Primary source
GU
Groundwater under influence of surface water
System type
NTNCWS
Non-transient non-community water system
System record
How does County of Monterey-Lake Nacimiento compare with other water systems in San Luis Obispo County?
By EPA's size categories, County of Monterey-Lake Nacimiento is a small system (501 to 3,300 people). San Luis Obispo County has 171 active public water systems. Its population served is about 25% below the county average of 2,038 people per system, and accounts for 0.4% of the 348,510 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 County of Monterey-Lake Nacimiento is about 3.5 times 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 under the influence of surface water is well or spring water that the regulator has found to be affected by nearby surface water, so it is regulated under the surface-water treatment rules. 105 California systems (1.4%) list groundwater under influence of surface water as their primary source.
Who owns and regulates County of Monterey-Lake Nacimiento?
EPA lists County of Monterey-Lake Nacimiento as privately owned. 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. 130 of the 171 active systems in San Luis Obispo County (76%) are also privately owned.
Does County of Monterey-Lake Nacimiento have drinking water violations?
EPA's records list 6 violations for this system; none is health-based, and the most recent began in October 2020. The violations listed here began between July 2003 and October 2020. By type: 4 monitoring and reporting and 2 public notice, recordkeeping or other. The contaminant or rule involved most often is Total coliform bacteria (TCR) (3 of them). EPA lists 6 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 |
|---|---|---|---|---|
| 2020-10-01 | Monitoring and reportingFollow-up Or Routine LCR Tap M/R · code 52 | Lead and Copper Rulecode 5000 | No | Resolved |
| 2005-07-01 | Public notice, recordkeeping or otherConsumer Confidence Report Complete Failure to Report · code 71 | Consumer Confidence Rulecode 7000 | No | Resolved |
| 2005-03-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2004-12-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2003-07-01 | Public notice, recordkeeping or otherConsumer Confidence Report Complete Failure to Report · code 71 | Consumer Confidence Rulecode 7000 | No | Resolved |
All 6 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.
County of Monterey-Lake Nacimiento: frequently asked questions
Who runs County of Monterey-Lake Nacimiento?
County of Monterey-Lake Nacimiento (PWSID CA4000590) is a non-transient non-community water system privately owned. It is regulated by the CA state drinking water program.
How many people does County of Monterey-Lake Nacimiento serve?
County of Monterey-Lake Nacimiento reports serving 1,521 people through 323 service connections in San Luis Obispo County, California.
Where does County of Monterey-Lake Nacimiento get its water?
EPA SDWIS lists this system's primary water source as groundwater under influence of surface water. Groundwater under the influence of surface water is well or spring water that the regulator has found to be affected by nearby surface water, so it is regulated under the surface-water treatment rules.
Does County of Monterey-Lake Nacimiento have any drinking water violations?
EPA's records list 6 violations for this system; none is health-based, and the most recent began in October 2020. 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 County of Monterey-Lake Nacimiento'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. EPA's records list 6 violations for this system; none is health-based, and the most recent began in October 2020. For current results, consult EPA ECHO, or the CA state drinking water program.
Where can I find County of Monterey-Lake Nacimiento's water quality report?
The annual Consumer Confidence Report requirement applies to community water systems. County of Monterey-Lake Nacimiento 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 San Luis Obispo County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Santa Margarita Recreation Area | San Luis Obispo | 50,001 | Transient non-community | Groundwater |
| San Luis Obispo Water Department | San Luis Obispo | 47,788 | Community | Surface water |
| City of Paso Robles Water Division | San Luis Obispo | 31,176 | Community | Surface water |
| Atascadero Mutual Water Co | San Luis Obispo | 30,618 | Community | Groundwater |
| City of Arroyo Grande Utilities Division | San Luis Obispo | 17,963 | Community | Purchased surface water |
| California Mens Colony | San Luis Obispo | 15,000 | 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, “County of Monterey-Lake Nacimiento, PWSID CA4000590, California”, https://aquacensus.com/water-systems/california/county-of-monterey-lake-nacimiento-ca4000590 (data as of October 1, 2026).