Community Water System · PWS CO0101150
Thornton City Of
Thornton, Colorado 80229 - drinking water served from surface water sources to 226,465 people, tracked in EPA SDWIS and UCMR5.
- 226,465
- People served
- 36
- EPA violations
- 0
- Health-based
- 8 PFAS
- UCMR5 result
The verdict
EPA records 36 drinking-water violations at Thornton City Of - below the Colorado per-system average, and UCMR5 testing detected 8 PFAS compounds.
- 36
- Total EPA violations on record
- 0%
- Health-based (MCL / treatment failure)
- 226,465
- People served by this system
- 8
- PFAS compounds detected (UCMR5)
Water Quality Snapshot: Thornton City Of
Thornton City Of is a local-owned community water system that delivers drinking water to 226,465 residents in Thornton, Colorado (Adams County) through 42,530 service connections. Its water is drawn from surface water sources. EPA's Safe Drinking Water Information System records 36 total violations for this system , of which 0 (0%) are health-based, meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. A further 36 monitoring and reporting violations are on file. The most recent violation on record dates to 2023.
The most frequently cited contaminant at this system is Interim Enhanced Surface Water Treatment Rule, recorded in 17 violations (MR). Under EPA's UCMR5 PFAS monitoring program, 8 PFAS compounds were detected in samples collected from this system, with a maximum reported concentration of 12.6 ppt (parts per trillion). PFAS are persistent synthetic chemicals linked to health effects at very low exposure levels.
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%).
Thornton City Of's 36 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.
8 PFAS "forever chemicals" detected in testing under EPA's UCMR5 monitoring program.
System Details
- System Type
- Community
- Owner Type
- Local
- Connections
- 42,530
- County
- Adams
- School/Daycare
- No
- MCL Violations
- 0
- Monitoring Violations
- 36
- Treatment Tech Violations
- 0
Violation History
Contaminant violations recorded by EPA.
| Contaminant | Category | Count | Latest |
|---|---|---|---|
| Interim Enhanced Surface Water Treatment Rule | MR | 17 | 2023 |
| Lead and Copper Rule | MR | 7 | 2023 |
| Combined Radium (-226 and -228) | MR | 3 | 2022 |
| Combined Uranium | MR | 3 | 2022 |
| Gross Alpha, Excl. Radon and U | MR | 3 | 2022 |
| Diquat | MR | 3 | 2008 |
PFAS Testing Results (UCMR5)
Results from EPA's Fifth Unregulated Contaminant Monitoring Rule. 35 of 203 samples detected PFAS.
| Contaminant | Date | Result | MRL | Status |
|---|---|---|---|---|
| 9Cl-PF3ONS | 8/14/2023 | <2.00 ppt | 2.00 ppt | Not Detected |
| PFTrDA | 8/14/2023 | <7.00 ppt | 7.00 ppt | Not Detected |
| PFPeS | 8/14/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| NFDHA | 8/14/2023 | <20.00 ppt | 20.00 ppt | Not Detected |
| ADONA | 8/14/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFEESA | 8/14/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| HFPO-DA | 8/14/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| 4:2 FTS | 8/14/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| 6:2 FTS | 8/14/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFOS | 8/14/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFMBA | 8/14/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| 8:2 FTS | 8/14/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFMPA | 8/14/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| 11Cl-PF3OUdS | 8/14/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFHpS | 8/14/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFBA | 8/14/2023 | 8.10 ppt | 5.00 ppt | Detected |
| PFNA | 8/14/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFPeA | 8/14/2023 | 7.50 ppt | 3.00 ppt | Detected |
| NEtFOSAA | 8/14/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| NMeFOSAA | 8/14/2023 | <6.00 ppt | 6.00 ppt | Not Detected |
| PFHpA | 8/14/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHxS | 8/14/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFTA | 8/14/2023 | <8.00 ppt | 8.00 ppt | Not Detected |
| PFOA | 8/14/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFDA | 8/14/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFDoA | 8/14/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHxA | 8/14/2023 | 5.80 ppt | 3.00 ppt | Detected |
| PFUnA | 8/14/2023 | <2.00 ppt | 2.00 ppt | Not Detected |
| PFBS | 8/14/2023 | 3.60 ppt | 3.00 ppt | Detected |
| 9Cl-PF3ONS | 8/14/2023 | <2.00 ppt | 2.00 ppt | Not Detected |
| PFTA | 8/14/2023 | <8.00 ppt | 8.00 ppt | Not Detected |
| PFTrDA | 8/14/2023 | <7.00 ppt | 7.00 ppt | Not Detected |
| NEtFOSAA | 8/14/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| NMeFOSAA | 8/14/2023 | <6.00 ppt | 6.00 ppt | Not Detected |
| PFBS | 8/14/2023 | 3.10 ppt | 3.00 ppt | Detected |
| PFHxS | 8/14/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFNA | 8/14/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFOS | 8/14/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFOA | 8/14/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFDA | 8/14/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFDoA | 8/14/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHxA | 8/14/2023 | 4.10 ppt | 3.00 ppt | Detected |
| PFHpA | 8/14/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| 11Cl-PF3OUdS | 8/14/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| ADONA | 8/14/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| HFPO-DA | 8/14/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFBA | 8/14/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| 6:2 FTS | 8/14/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| 4:2 FTS | 8/14/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| 8:2 FTS | 8/14/2023 | <5.00 ppt | 5.00 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 Thornton City Of.
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 CO0101150 on SDWISSource: EPA SDWIS Federal Reports Search
Colorado Drinking Water Authority
Colorado Department of Public Health and Environment, Water Quality Control is the primacy agency that licenses and inspects Thornton City Of under EPA-delegated authority.
Open CO regulator portalSource: 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 |
|---|---|---|---|---|
| 2023 | Interim Enhanced Surface Water Treatment Rule | MR | 17 | SDWIS / CO0101150 / 0300 |
| 2023 | Lead and Copper Rule | MR | 7 | SDWIS / CO0101150 / 5000 |
| 2022 | Combined Radium (-226 and -228) | MR | 3 | SDWIS / CO0101150 / 4010 |
| 2022 | Combined Uranium | MR | 3 | SDWIS / CO0101150 / 4006 |
| 2022 | Gross Alpha, Excl. Radon and U | MR | 3 | SDWIS / CO0101150 / 4000 |
| 2008 | Diquat | MR | 3 | SDWIS / CO0101150 / 2032 |
How Thornton City Of Compares
Cross-reference this system's record against state averages and the federal MCL framework for context.
| Metric | Thornton City Of | Colorado avg | Federal benchmark |
|---|---|---|---|
| Total violations | 36 | 108.9 | SDWA compliance, any non-zero count is a recorded breach |
| Health-based violations | 0 | 13.9 | Indicates a contaminant exceeded a federal MCL |
| PFAS detection | 8 compounds | 60.1% | EPA final rule (2024): PFOA/PFOS MCL = 4.0 ppt |
| Population served | 226,465 | 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 Thornton City Of water safe to drink? ▼
How many people does Thornton City Of serve? ▼
What type of violations does Thornton City Of have? ▼
Has PFAS been detected in Thornton City Of water? ▼
What water source does Thornton City Of use? ▼
Where does this data come from? ▼
Read our methodology - how this data is sourced, computed, and verified.
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.