Public water system · CA2610001
ActiveMammoth Cwd
At a glance
Mammoth Cwd (PWSID CA2610001) is an active community water system in Mono County, California. It reports serving 8,234 people through 3,818 service connections. Its primary water source is surface water, and EPA lists it as owned by a local government. EPA's records list 5 violations for this system; 3 are health-based, and the most recent began in January 2023.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
8,234
Service connections
3,818
Primary source
SW
Surface water
System type
CWS
Community water system
System record
How does Mammoth Cwd compare with other water systems in Mono County?
By EPA's size categories, Mammoth Cwd is a medium system (3,301 to 10,000 people). Mono County has 84 active public water systems, and Mammoth Cwd is the largest of them by population served. Its population served is about 19 times the county average of 424 people per system, and accounts for 23% of the 35,602 people reported by systems filed under the county. 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 Mammoth Cwd is about 23% above 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. 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 Mammoth Cwd?
EPA lists Mammoth Cwd 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 84 active systems in Mono County (23%) are also owned by a local government.
Does Mammoth Cwd have drinking water violations?
EPA's records list 5 violations for this system; 3 are health-based, and the most recent began in January 2023. The violations listed here began between June 1991 and January 2023. By type: 2 monitoring and reporting, 2 required treatment not met and 1 contaminant level above the legal limit. The contaminant or rule involved most often is Surface Water Treatment Rule (2 of them). EPA lists 5 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 |
|---|---|---|---|---|
| 2023-01-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Haloacetic acids (HAA5)code 2456 | No | Resolved |
| 2023-01-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Total trihalomethanes (TTHM)code 2950 | No | Resolved |
| 2016-08-01 | Required treatment not metTreatment Technique (SWTR and GWR) · code 41 | Surface Water Treatment Rulecode 0200 | Yes | Resolved |
| 1992-09-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Monthly (TCR) · code 22 | Total coliform bacteria (TCR)code 3100 | Yes | Resolved |
| 1991-06-01 | Required treatment not metTreatment Technique (SWTR and GWR) · code 41 | Surface Water Treatment Rulecode 0200 | Yes | Resolved |
All 5 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.
Mammoth Cwd: frequently asked questions
Who runs Mammoth Cwd?
Mammoth Cwd (PWSID CA2610001) is a community water system owned by a local government. It is regulated by the CA state drinking water program.
How many people does Mammoth Cwd serve?
Mammoth Cwd reports serving 8,234 people through 3,818 service connections in Mono County, California.
Where does Mammoth Cwd 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 Mammoth Cwd have any drinking water violations?
EPA's records list 5 violations for this system; 3 are health-based, and the most recent began in January 2023. 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 Mammoth Cwd'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 5 violations for this system; 3 are health-based, and the most recent began in January 2023. For current results, consult the system's annual water quality report, EPA ECHO, or the CA state drinking water program.
Where can I find Mammoth Cwd's water quality report?
As a community water system, Mammoth Cwd 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 Mono County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Mammoth Mountain Ski Area - Outpost 14 | Mono | 7,736 | Non-transient non-community | Groundwater |
| June Lake PUD - Down Canyon | Mono | 2,810 | Community | Surface water |
| June Lake PUD Village | Mono | 2,763 | Community | Surface water |
| Usmc/Mtn Warfare Trng Ctr - Bridgeport | Mono | 1,200 | Community | Groundwater |
| Mammoth Lakes Basin | Mono | 1,000 | Transient non-community | Groundwater |
| East Fork Campground | Mono | 750 | Transient non-community | Groundwater |
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, “Mammoth Cwd, PWSID CA2610001, California”, https://aquacensus.com/water-systems/california/mammoth-cwd-ca2610001 (data as of October 1, 2026).