Public water system · CO0118010
ActiveCastle Rock Town of
At a glance
Town of Castle Rock (PWSID CO0118010) is an active community water system in Douglas County, Colorado. It reports serving 110,298 people through 27,865 service connections. Its primary water source is surface water, and EPA lists it as owned by a local government. Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in June 2025.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
110,298
Service connections
27,865
Primary source
SW
Surface water
System type
CWS
Community water system
System record
How does Town of Castle Rock compare with other water systems in Douglas County?
By EPA's size categories, Town of Castle Rock is a very large system (more than 100,000 people). Douglas County has 74 active public water systems, and Town of Castle Rock is the largest of them by population served. Its population served is about 19 times the county average of 5,694 people per system, and accounts for 26% of the 421,335 people reported by systems filed under the county. Across Colorado, the 2,207 active systems average 3,400 people each. Nationally, the average active community water system reports serving 6,703 people, so Town of Castle Rock is about 16 times 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. Colorado has 1,068 active community water systems, 48% of the state's 2,207 active systems. Surface water means the system draws its water from rivers, lakes, streams or reservoirs. 228 Colorado systems (10%) list surface water as their primary source.
Who owns and regulates Town of Castle Rock?
EPA lists Town of Castle Rock as owned by a local government. The CO state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 25 of the 74 active systems in Douglas County (34%) are also owned by a local government.
Does Town of Castle Rock have drinking water violations?
Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in June 2025. The violations listed here began between April 2008 and June 2025. By type: 12 monitoring and reporting. The contaminant or rule involved most often is Surface Water Treatment Rule (5 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 |
|---|---|---|---|---|
| 2025-06-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Resolved |
| 2025-05-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Resolved |
| 2022-04-01 | Monitoring and reportingMonitoring, Regular · code 03 | Combined Uraniumcode 4006 | No | Resolved |
| 2022-04-01 | Monitoring and reportingMonitoring, Regular · code 03 | Combined Radium (-226 and -228)code 4010 | No | Resolved |
| 2022-04-01 | Monitoring and reportingMonitoring, Regular · code 03 | Combined Radium (-226 and -228)code 4010 | No | Resolved |
| 2022-04-01 | Monitoring and reportingMonitoring, Regular · code 03 | Gross alpha (excluding radon and uranium)code 4000 | No | Resolved |
| 2022-04-01 | Monitoring and reportingMonitoring, Regular · code 03 | Gross alpha (excluding radon and uranium)code 4000 | No | Resolved |
| 2022-04-01 | Monitoring and reportingMonitoring, Regular · code 03 | Combined Uraniumcode 4006 | No | Resolved |
| 2019-05-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Resolved |
| 2013-10-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Resolved |
| 2013-09-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Resolved |
| 2008-04-01 | Monitoring and reportingMonitoring, Regular · code 03 | Nitritecode 1041 | 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.
Town of Castle Rock: frequently asked questions
Who runs Town of Castle Rock?
Town of Castle Rock (PWSID CO0118010) is a community water system owned by a local government. It is regulated by the CO state drinking water program.
How many people does Town of Castle Rock serve?
Town of Castle Rock reports serving 110,298 people through 27,865 service connections in Douglas County, Colorado.
Where does Town of Castle Rock 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 Town of Castle Rock 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 June 2025. 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 Town of Castle Rock'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 June 2025. For current results, consult the system's annual water quality report, EPA ECHO, or the CO state drinking water program.
Where can I find Town of Castle Rock's water quality report?
As a community water system, Town of Castle Rock 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 Douglas County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Highlands Ranch Wsd | Douglas | 103,444 | Community | Surface water |
| Parker Wsd | Douglas | 75,949 | Community | Surface water |
| Meridian Md | Douglas | 23,415 | Community | Purchased surface water |
| Stonegate Md | Douglas | 15,295 | Community | Purchased surface water |
| Roxborough Wsd | Douglas | 13,765 | Community | Surface water |
| Pinery Wwd | Douglas | 12,901 | 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, “Castle Rock Town of, PWSID CO0118010, Colorado”, https://aquacensus.com/water-systems/colorado/castle-rock-town-of-co0118010 (data as of October 1, 2026).