Public water system · CA4100502
ActiveUc Elkus Ranch
At a glance
Uc Elkus Ranch (PWSID CA4100502) is an active transient non-community water system in San Mateo County, California. It reports serving 34 people through 6 service connections. Its primary water source is surface water, and EPA lists it as owned by a state government. Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in September 2018.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
34
Service connections
6
Primary source
SW
Surface water
System type
TNCWS
Transient non-community water system
System record
How does Uc Elkus Ranch compare with other water systems in San Mateo County?
By EPA's size categories, Uc Elkus Ranch is a very small system (500 people or fewer). San Mateo County has 51 active public water systems. Its population served is well below the county average of 15,363 people per system, and accounts for less than 0.1% of the 783,522 people reported by systems filed under the county. Across California, the 7,479 active systems average 5,706 people each. Nationally, the average active transient non-community water system reports serving 144 people, so Uc Elkus Ranch is well below that figure.
What does “transient non-community water system” mean?
A transient non-community water system serves places where people do not stay long, such as gas stations and campgrounds, and regularly serves at least 25 people a day for at least 60 days a year. California has 3,016 active transient non-community water systems, 40% of the state's 7,479 active systems. Surface water means the system draws its water from rivers, lakes, streams or reservoirs. 609 California systems (8.1%) list surface water as their primary source.
Who owns and regulates Uc Elkus Ranch?
EPA lists Uc Elkus Ranch as owned by a state 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. 5 of the 51 active systems in San Mateo County (9.8%) are also owned by a state government.
Does Uc Elkus Ranch have drinking water violations?
Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in September 2018. The violations listed here began between February 1984 and September 2018. By type: 8 public notice, recordkeeping or other, 2 monitoring and reporting, 1 monitoring and 1 required treatment not met. The contaminant or rule involved most often is Total coliform bacteria (TCR) (2 of them). EPA lists 8 as archived and 4 as resolved. Archived means the violation was not marked resolved but is more than five years past the end of the noncompliance period, so it no longer counts toward current compliance status. 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 |
|---|---|---|---|---|
| 2018-09-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2004-06-01 | Required treatment not metTreatment Technique (SWTR and GWR) · code 41 | Surface Water Treatment Rulecode 0200 | Yes | Resolved |
| 1996-07-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 1996-04-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 1984-09-01 | Public notice, recordkeeping or otherNotification, Public · code 06 | Not reported | No | Archived |
| 1984-08-01 | Public notice, recordkeeping or otherNotification, Public · code 06 | Not reported | No | Archived |
| 1984-07-01 | Public notice, recordkeeping or otherNotification, Public · code 06 | Not reported | No | Archived |
| 1984-06-01 | Public notice, recordkeeping or otherNotification, Public · code 06 | Not reported | No | Archived |
| 1984-05-01 | Public notice, recordkeeping or otherNotification, Public · code 06 | Not reported | No | Archived |
| 1984-04-01 | Public notice, recordkeeping or otherNotification, Public · code 06 | Not reported | No | Archived |
| 1984-03-01 | Public notice, recordkeeping or otherNotification, Public · code 06 | Not reported | No | Archived |
| 1984-02-01 | Public notice, recordkeeping or otherNotification, Public · code 06 | Not reported | No | Archived |
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.
Uc Elkus Ranch: frequently asked questions
Who runs Uc Elkus Ranch?
Uc Elkus Ranch (PWSID CA4100502) is a transient non-community water system owned by a state government. It is regulated by the CA state drinking water program.
How many people does Uc Elkus Ranch serve?
Uc Elkus Ranch reports serving 34 people through 6 service connections in San Mateo County, California.
Where does Uc Elkus Ranch get its water?
EPA SDWIS lists this system's primary water source as surface water. Surface water means the system draws its water from rivers, lakes, streams or reservoirs.
Does Uc Elkus Ranch 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 September 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 Uc Elkus Ranch'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 September 2018. For current results, consult EPA ECHO, or the CA state drinking water program.
Where can I find Uc Elkus Ranch's water quality report?
The annual Consumer Confidence Report requirement applies to community water systems. Uc Elkus Ranch is a 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 Mateo County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| City of Daly City | San Mateo | 104,901 | Community | Purchased surface water |
| California Water Service - San Mateo | San Mateo | 102,348 | Community | Purchased surface water |
| City of Redwood City | San Mateo | 92,819 | Community | Purchased surface water |
| California Water Service-S San Francisco | San Mateo | 64,146 | Community | Purchased surface water |
| California Water Service - Bear Gulch | San Mateo | 61,431 | Community | Surface water |
| City of San Bruno | San Mateo | 42,631 | Community | Purchased surface water |
Related pages
Working with water-system records? Pro adds alerts, change history and CSV export ($49/mo); Enterprise adds full national files, the API and an MCP server for AI tools.
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, “Uc Elkus Ranch, PWSID CA4100502, California”, https://aquacensus.com/water-systems/california/uc-elkus-ranch-ca4100502 (data as of October 1, 2026).