Public water system · CO0107485
ActiveLongmont City of
At a glance
City of Longmont (PWSID CO0107485) is an active community water system in Boulder County, Colorado. It reports serving 104,178 people through 30,296 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 July 2022.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
104,178
Service connections
30,296
Primary source
SW
Surface water
System type
CWS
Community water system
System record
How does City of Longmont compare with other water systems in Boulder County?
By EPA's size categories, City of Longmont is a very large system (more than 100,000 people). Boulder County has 81 active public water systems, and City of Longmont is the 2nd-largest of them by population served. Its population served is about 19 times the county average of 5,397 people per system, and accounts for 24% of the 437,116 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 City of Longmont 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 City of Longmont?
EPA lists City of Longmont 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. 22 of the 81 active systems in Boulder County (27%) are also owned by a local government.
Does City of Longmont have drinking water violations?
Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in July 2022. The violations listed here began between January 2005 and July 2022. By type: 12 monitoring and reporting. The contaminants or rules involved are Haloacetic acids (HAA5), Total trihalomethanes (TTHM), Chlordane and Aldicarb sulfoxide. 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 |
|---|---|---|---|---|
| 2022-07-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Haloacetic acids (HAA5)code 2456 | No | Resolved |
| 2022-07-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Total trihalomethanes (TTHM)code 2950 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Chlordanecode 2959 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Aldicarb sulfoxidecode 2043 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | 2,4,5-TP (Silvex)code 2110 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Simazinecode 2037 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | 1,2-Dibromo-3-chloropropane (DBCP)code 2931 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Di(2-ethylhexyl) phthalatecode 2039 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Atrazinecode 2050 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Hexachlorocyclopentadienecode 2042 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Methoxychlorcode 2015 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Heptachlorcode 2065 | 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.
City of Longmont: frequently asked questions
Who runs City of Longmont?
City of Longmont (PWSID CO0107485) is a community water system owned by a local government. It is regulated by the CO state drinking water program.
How many people does City of Longmont serve?
City of Longmont reports serving 104,178 people through 30,296 service connections in Boulder County, Colorado.
Where does City of Longmont 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 City of Longmont 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 July 2022. 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 City of Longmont'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 July 2022. For current results, consult the system's annual water quality report, EPA ECHO, or the CO state drinking water program.
Where can I find City of Longmont's water quality report?
As a community water system, City of Longmont 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 Boulder County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Boulder City of | Boulder | 166,080 | Community | Surface water |
| Erie Town of | Boulder | 47,444 | Community | Surface water |
| Lafayette City of | Boulder | 28,700 | Community | Surface water |
| Louisville City of | Boulder | 20,975 | Community | Surface water |
| Left Hand Wd | Boulder | 20,280 | Community | Surface water |
| Superior Md No 1 | Boulder | 17,900 | 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, “Longmont City of, PWSID CO0107485, Colorado”, https://aquacensus.com/water-systems/colorado/longmont-city-of-co0107485 (data as of October 1, 2026).