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Community Water System · PWS CO0107485

Longmont City Of

Longmont, Colorado 80501 - drinking water served from surface water sources to 102,866 people, tracked in EPA SDWIS and UCMR5.

102,866
People served
78
EPA violations
2
Health-based
No PFAS
UCMR5 result

The verdict

EPA records 78 drinking-water violations at Longmont City Of, 3% of them health-based - below the Colorado per-system average.

78
Total EPA violations on record
3%
Health-based (MCL / treatment failure)
102,866
People served by this system
0
PFAS compounds detected (UCMR5)

Water Quality Snapshot: Longmont City Of

Longmont City Of is a local-owned community water system that delivers drinking water to 102,866 residents in Longmont, Colorado (Boulder County) through 29,697 service connections. Its water is drawn from surface water sources. EPA's Safe Drinking Water Information System records 78 total violations for this system , of which 2 (3%) are health-based, meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. A further 75 monitoring and reporting violations are on file. The most recent violation on record dates to 2022.

The most frequently cited contaminant at this system is TTHM, recorded in 3 violations (MR). This system was sampled under EPA's UCMR5 PFAS monitoring program and no PFAS compounds were detected above the minimum reporting level.

Across Colorado, EPA tracks 2,193 public water systems serving 7,473,456 people, with 238,796 cumulative violations and 30,589 health-based violations on record. About 93% of systems in the state carry at least one violation, and state-wide the average per system is 108.9 violations. Statewide, 98 of 163 UCMR5-tested systems have reported PFAS detections (60.1%).

Longmont City Of's 78 violations sit below the Colorado average.

All figures above are sourced directly from EPA SDWIS and UCMR5 public data releases and are updated as EPA publishes new reporting cycles.

Population Served
102,866
Total Violations
78
Health-Based Violations
2
Water Source
Surface Water

System Details

System Type
Community
Owner Type
Local
Connections
29,697
County
Boulder
School/Daycare
No
MCL Violations
0
Monitoring Violations
75
Treatment Tech Violations
2

Violation History

Contaminant violations recorded by EPA.

Contaminant Category Count Latest
TTHM MR 3 2022
Total Haloacetic Acids (HAA5) MR 3 2022
Endrin MR 2 2005
Diquat MR 2 2005
Endothall MR 2 2005
Di(2-ethylhexyl) adipate MR 2 2005
Di(2-ethylhexyl) phthalate MR 2 2005
Picloram MR 2 2005
Aldicarb sulfone MR 2 2005
Carbofuran MR 2 2005
Aldicarb MR 2 2005
Atrazine MR 2 2005
LASSO MR 2 2005
2,4-D MR 2 2005
HEXACHLOROBENZENE MR 2 2005
Benzo(a)pyrene MR 2 2005
1,2-DIBROMO-3-CHLOROPROPANE MR 2 2005
ETHYLENE DIBROMIDE MR 2 2005
Total Polychlorinated Biphenyls (PCB) MR 2 2005
Dalapon MR 2 2005
2,4,5-TP MR 2 2005
Simazine MR 2 2005
Methoxychlor MR 2 2005
Heptachlor MR 2 2005
Aldicarb sulfoxide MR 2 2005
Chlordane MR 2 2005
Toxaphene MR 2 2005
Heptachlor epoxide MR 2 2005
Surface Water Treatment Rule TT 2 1995
Dinoseb MR 2 2005

PFAS Testing Results (UCMR5)

Results from EPA's Fifth Unregulated Contaminant Monitoring Rule. 0 of 116 samples detected PFAS.

Contaminant Date Result MRL Status
PFHpA 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFUnA 8/7/2023 <2.00 ppt 2.00 ppt Not Detected
PFHxA 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFDoA 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFDA 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFOA 8/7/2023 <4.00 ppt 4.00 ppt Not Detected
PFOS 8/7/2023 <4.00 ppt 4.00 ppt Not Detected
11Cl-PF3OUdS 8/7/2023 <5.00 ppt 5.00 ppt Not Detected
PFHxS 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
NMeFOSAA 8/7/2023 <6.00 ppt 6.00 ppt Not Detected
NEtFOSAA 8/7/2023 <5.00 ppt 5.00 ppt Not Detected
PFHpS 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFTrDA 8/7/2023 <7.00 ppt 7.00 ppt Not Detected
PFTA 8/7/2023 <8.00 ppt 8.00 ppt Not Detected
PFNA 8/7/2023 <4.00 ppt 4.00 ppt Not Detected
PFPeA 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFBS 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
NFDHA 8/7/2023 <20.00 ppt 20.00 ppt Not Detected
9Cl-PF3ONS 8/7/2023 <2.00 ppt 2.00 ppt Not Detected
PFMBA 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFPeS 8/7/2023 <4.00 ppt 4.00 ppt Not Detected
PFMPA 8/7/2023 <4.00 ppt 4.00 ppt Not Detected
8:2 FTS 8/7/2023 <5.00 ppt 5.00 ppt Not Detected
4:2 FTS 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
6:2 FTS 8/7/2023 <5.00 ppt 5.00 ppt Not Detected
PFBA 8/7/2023 <5.00 ppt 5.00 ppt Not Detected
HFPO-DA 8/7/2023 <5.00 ppt 5.00 ppt Not Detected
ADONA 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFEESA 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
4:2 FTS 5/1/2023 <3.00 ppt 3.00 ppt Not Detected
PFHxA 5/1/2023 <3.00 ppt 3.00 ppt Not Detected
11Cl-PF3OUdS 5/1/2023 <5.00 ppt 5.00 ppt Not Detected
ADONA 5/1/2023 <3.00 ppt 3.00 ppt Not Detected
HFPO-DA 5/1/2023 <5.00 ppt 5.00 ppt Not Detected
PFEESA 5/1/2023 <3.00 ppt 3.00 ppt Not Detected
6:2 FTS 5/1/2023 <5.00 ppt 5.00 ppt Not Detected
PFOA 5/1/2023 <4.00 ppt 4.00 ppt Not Detected
8:2 FTS 5/1/2023 <5.00 ppt 5.00 ppt Not Detected
PFMPA 5/1/2023 <4.00 ppt 4.00 ppt Not Detected
PFPeA 5/1/2023 <3.00 ppt 3.00 ppt Not Detected
PFMBA 5/1/2023 <3.00 ppt 3.00 ppt Not Detected
PFBA 5/1/2023 <5.00 ppt 5.00 ppt Not Detected
PFDA 5/1/2023 <3.00 ppt 3.00 ppt Not Detected
9Cl-PF3ONS 5/1/2023 <2.00 ppt 2.00 ppt Not Detected
PFOS 5/1/2023 <4.00 ppt 4.00 ppt Not Detected
PFNA 5/1/2023 <4.00 ppt 4.00 ppt Not Detected
PFHxS 5/1/2023 <3.00 ppt 3.00 ppt Not Detected
PFHpA 5/1/2023 <3.00 ppt 3.00 ppt Not Detected
PFBS 5/1/2023 <3.00 ppt 3.00 ppt Not Detected
NMeFOSAA 5/1/2023 <6.00 ppt 6.00 ppt Not Detected

Verify This Water System

The figures above are aggregated from EPA's public databases. To verify the underlying records, or to file a complaint, request a Consumer Confidence Report, or check current monitoring status, go directly to the federal and state regulators that enforce the Safe Drinking Water Act for Longmont City Of.

Federal Source of Truth

EPA SDWIS, Federal Reports

EPA's Safe Drinking Water Information System (SDWIS) holds the federal compliance record for every regulated public water system. Open the system-level report by PWS ID:

View PWS ID CO0107485 on SDWIS

Source: EPA SDWIS Federal Reports Search

State Regulator

Colorado Drinking Water Authority

Colorado Department of Public Health and Environment, Water Quality Control is the primacy agency that licenses and inspects Longmont City Of under EPA-delegated authority.

Open CO regulator portal

Source: Colorado Department of Public Health and Environment, Water Quality Control

Violation Timeline

Each row links to the EPA SDWIS public record for verification. Cross-reference the contaminant code on EPA's federal report to see violation dates, return-to-compliance status, and enforcement actions.

Year (latest) Contaminant Category Count EPA Record
2022 TTHM MR 3 SDWIS / CO0107485 / 2950
2022 Total Haloacetic Acids (HAA5) MR 3 SDWIS / CO0107485 / 2456
2005 Endrin MR 2 SDWIS / CO0107485 / 2005
2005 Diquat MR 2 SDWIS / CO0107485 / 2032
2005 Endothall MR 2 SDWIS / CO0107485 / 2033
2005 Di(2-ethylhexyl) adipate MR 2 SDWIS / CO0107485 / 2035
2005 Di(2-ethylhexyl) phthalate MR 2 SDWIS / CO0107485 / 2039
2005 Picloram MR 2 SDWIS / CO0107485 / 2040
2005 Aldicarb sulfone MR 2 SDWIS / CO0107485 / 2044
2005 Carbofuran MR 2 SDWIS / CO0107485 / 2046
2005 Aldicarb MR 2 SDWIS / CO0107485 / 2047
2005 Atrazine MR 2 SDWIS / CO0107485 / 2050
2005 LASSO MR 2 SDWIS / CO0107485 / 2051
2005 2,4-D MR 2 SDWIS / CO0107485 / 2105
2005 HEXACHLOROBENZENE MR 2 SDWIS / CO0107485 / 2274

How Longmont City Of Compares

Cross-reference this system's record against state averages and the federal MCL framework for context.

Metric Longmont City Of Colorado avg Federal benchmark
Total violations 78 108.9 SDWA compliance, any non-zero count is a recorded breach
Health-based violations 2 13.9 Indicates a contaminant exceeded a federal MCL
PFAS detection None 60.1% EPA final rule (2024): PFOA/PFOS MCL = 4.0 ppt
Population served 102,866 3,408 Sizing context for compliance burden

Sources: EPA SDWIS and EPA National Primary Drinking Water Regulations (40 CFR Part 141). State averages computed across 2,193 regulated public water systems in Colorado.

Federal MCL reference, Safe Drinking Water Act thresholds ▼
Contaminant Federal MCL / Action Level Note
Lead 0 mg/L (Action Level: 0.015 mg/L) Lead and Copper Rule treatment technique
Arsenic 0.010 mg/L (10 ppb) Health-based MCL since 2006
Total Coliform Treatment technique (RTCR) Indicator organism, monitoring trigger
PFOA / PFOS (PFAS) 4.0 ppt each (final 2024 rule) Compliance deadline 2029 (EPA proposed extending to 2031, not yet final as of May 2026)
Nitrate (as N) 10 mg/L Acute health risk for infants

Frequently Asked Questions

Is Longmont City Of water safe to drink? ▼
Longmont City Of (PWS ID: CO0107485) has 78 recorded violations in the EPA SDWIS database. No PFAS contamination was detected in UCMR5 testing. This system serves 102,866 people using Surface Water sources.
How many people does Longmont City Of serve? ▼
Longmont City Of serves 102,866 people in Longmont, Colorado. It is a Local-owned system using Surface Water water sources with 29,697 service connections.
What type of violations does Longmont City Of have? ▼
Longmont City Of has 78 total violations: 2 health-based violations (MCL exceedances or treatment failures), 75 monitoring/reporting violations, and 2 treatment technique violations. Health-based violations indicate contaminant levels exceeded EPA safe limits.
Has PFAS been detected in Longmont City Of water? ▼
No. Longmont City Of was tested for PFAS under the EPA's UCMR5 monitoring program and no PFAS contamination was detected.
What water source does Longmont City Of use? ▼
Longmont City Of uses Surface Water as its primary water source. It is classified as a Community Water System (CWS), serving residential populations year-round.
Where does this data come from? ▼
All data comes from the EPA Safe Drinking Water Information System (SDWIS) and the UCMR5 PFAS monitoring program. SDWIS tracks compliance for all public water systems regulated under the Safe Drinking Water Act.
Data Sources: EPA Safe Drinking Water Information System (SDWIS), Q4 2025. PFAS data from EPA UCMR5 monitoring program (2023-2025). This data is provided for informational purposes only.

Read our methodology - how this data is sourced, computed, and verified.

Data sourced from EPA SDWIS and UCMR5 PFAS monitoring data. See our methodology for details. Retrieved and formatted by PlainWater Editorial

Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This system's figures are rendered directly from EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.