City of Thornton
EPA ID: CO0101150 · 226,465 people served · 11 ZIP codes
8 total violations across five years at City of Thornton — every finding closed, utility compliant today, 226,465 served.
Data: EPA SDWIS Last verified: 2026-04-02
Compliance Trajectory
Worsening · Risk tier: High · 95% chance of violation in next 12 months
Violations went from 4 (2022) to 2 (2024). The pattern suggests growing compliance challenges.
Service Area Map
Coverage area for City of Thornton Source: EPA SDWIS service area boundaries.
Service area boundary — Grade C
Service Area Demographics
The City of Thornton serves a community with a median household income of $88,714 and an estimated 384,418 residents across its service area.
🌊 Where Does Your Water Come From?
City of Thornton's water is drawn from rivers, lakes, or reservoirs. Surface water sources are more exposed to agricultural runoff, stormwater, and upstream discharges, but they typically receive more intensive treatment before reaching your tap.
About 1% of homes in Broomfield County, Colorado rely on private wells rather than public water systems. Private well owners are responsible for their own water testing and treatment.
Superfund Proximity Note: This service area ranks in the 70th percentile nationally for proximity to Superfund (NPL) sites.
Infrastructure Risk
Detected Contaminants
How City of Thornton compares to EPA limits
What This Means For You
Contaminant 1006 at 1 mg/L exceeds the EPA maximum of 0.006 mg/L. Cholesterol & blood sugar effects, liver damage. Consider reverse osmosis filtration.
Fecal Coliform at 4 presence exceeds the EPA maximum of presence.
Gross Alpha at 1 pCi/L exceeds the EPA maximum of pCi/L. Increased cancer risk from radioactive particles. Consider reverse osmosis filtration.
Stage 1 DBP Rule at 1 mg/L exceeds the EPA maximum of mg/L.
E. coli at 1 Zero tolerance (any positive sample triggers immediate action) exceeds the EPA maximum of Zero tolerance (any positive sample triggers immediate action). Severe GI illness; potentially fatal kidney failure in children. Consider UV disinfection (99.99%) filtration.
PFAS Detected in Service Area
PFAS ("forever chemicals") have been detected in water serving this system's area. 70 detections recorded. 18 exceed federal EPA limits (4 ppt for PFOA/PFOS).
Contaminant 1006 was detected in this water system. reverse osmosis filtration can reduce exposure.
Find a certified water filter →Comparable Water Systems
Similar-sized systems in Colorado
Estimated Remediation Costs
Average estimated costs across ZIP codes served by this system
Based on national averages for common remediation projects. Actual costs vary by property. Only issues flagged by EPA, FEMA, or state data for each ZIP code are included.
System Overview
City of Thornton (EPA ID: CO0101150) is a community water system in Colorado that serves approximately 226,465 people from surface water sources.
This system provides water to 11 ZIP codes across 5 communities.
Average Home Safety Score: C (68/100)
Based on water quality violations, lead levels, and radon risk across all ZIP codes served by this system.
Violation History
Recent Violations
| Date | Contaminant | Type | Status |
|---|---|---|---|
| March 1, 2024 | Fecal Coliform | Monitoring | Resolved |
| January 1, 2024 | Combined Radium | Monitoring | Resolved |
| November 1, 2023 | Fecal Coliform | Monitoring | Resolved |
| October 1, 2023 | Fecal Coliform | Monitoring | Resolved |
| September 1, 2023 | Fecal Coliform | Monitoring | Resolved |
| July 1, 2023 | Stage 1 DBP Rule | Monitoring | Resolved |
Contaminants Detected
The following contaminants have been flagged in EPA records for this water system:
| Contaminant | Category | Violations | Health-Based |
|---|---|---|---|
| Fecal Coliform | Microbiological | 4 | No |
| Contaminant 1006 | Other Violation | 1 | No |
| Gross Alpha | Radionuclides | 1 | No |
| Combined Radium | Radionuclides | 1 | No |
| Stage 1 DBP Rule | Treatment Failure | 1 | No |
| E. coli | Microbiological | 1 | No |
Lead & Copper
EPA Lead and Copper Rule sampling data for ZIP codes served by this system:
| ZIP Code | Lead Level | Exceeds Limit | Sample Date |
|---|---|---|---|
| 80233 | 0.0039 mg/L | No | N/A |
| 80234 | 0.0039 mg/L | No | N/A |
| 80260 | 0.0039 mg/L | No | N/A |
| 80241 | 0.0023 mg/L | No | N/A |
Radon Risk in Service Area
Dominant radon zone for ZIP codes served by this system: Zone 1 (High Risk)
The EPA recommends testing homes in Zone 1 and Zone 2 areas for radon.
Need help with your water quality?
Typical cost: Water test: typically $20–$50 (DIY kit) · Professional inspection: $150–$400
Find the Right Water FilterFree tip: Let cold water run for 2 minutes before drinking — this helps flush lead from your pipes.
ZIP Codes Served
Coverage: Service area ZIP codes sourced from EPA Community Water System Service Area Boundaries v3 (March 2026 release). These ZIPs reflect the actual deployment footprint recorded by CO or modeled from parcel and building-footprint data.
- 80023 — Broomfield
- 80216 — Denver
- 80221 — Denver
- 80229 — Denver
- 80233 — Denver
- 80234 — Denver
- 80241 — Thornton
- 80260 — Denver
- 80601 — Brighton
- 80602 — Brighton
- 80640 — Henderson
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View the full compliance record for City of Thornton (CO0101150) on EPA.gov.
Frequently Asked Questions
Is City of Thornton water safe to drink?
City of Thornton has only monitoring/reporting violations, which are procedural in nature. The system meets federal health-based standards.
How many people does City of Thornton serve?
City of Thornton serves approximately 226,465 people across 11 ZIP codes in Colorado.
Where does City of Thornton get its water?
The primary water source is surface water.
Contact Your Water Utility
Public-record contact information for the water utility serving this system. Use these channels to request water quality reports, ask about service, or report issues directly.
Contact information from Thornton Water Consumer Confidence Report.
ZipCheckup is not affiliated with this water utility, does not act as its agent, and does not provide customer support for it. Contact details shown are public-record information from CCR filings. For service issues, contact the utility directly using the information above.
Water Source & Treatment
Where this water originates and how it's treated before reaching your tap.
Source: Thornton Water Consumer Confidence Report.
ZipCheckup is not affiliated with this water utility. Treatment and source data are sourced from the utility's published CCR filings.
In 2002, the Colorado Department of Public Health and Environment (CDPHE) conducted a statewide Source Water Assessment for all municipal drinking water providers. The report identified potential sources of contaminants, such as gasoline storage tanks, wastewater plant discharges, mine drainages and others.
Treatment regime
How this utility classifies its treatment process and what each reported treatment chemical does.
Treatment chemicals and what each one does
Chemical names are reported verbatim by the utility. Purpose categories are ZipCheckup annotations based on standard drinking-water treatment practice.
Watershed exposure sources reported
Land-use and natural conditions identified in the utility's source-water assessment as potential contamination sources upstream of treatment.
Treatment classification and chemical list sourced from Thornton Water Consumer Confidence Report.
Treatment intensity is a ZipCheckup-derived classification based on the chemicals and processes the utility reports. Chemicals and contamination sources are taken verbatim from the utility's CCR filing. Routine federal monitoring and contaminant testing shown elsewhere on this page determine whether the water meets safety standards, not the treatment classification.
Federal UCMR5 PFAS Monitoring: Detected
This water system was tested under the federal EPA Unregulated Contaminant Monitoring Rule (UCMR5). PFAS compounds were detected below the current state-enforceable MCL.
Current MCL reflects the lowest state-enforceable limit (NYS 10 ppt for PFOA/PFOS, effective August 2020). The federal final MCL of 4 ppt for PFOA/PFOS (EPA April 2024 rule) is not enforceable until April 2029. Detections above 4 ppt but below 10 ppt are below current MCL but above the future federal limit.
Source: U.S. EPA UCMR5 (Unregulated Contaminant Monitoring Rule, 5th cycle) — per-system federal sampling, 2023–2025. EPA UCMR5 monitoring program →
PFAS Substances Detected in This System
This water system's Consumer Confidence Report disclosed the following PFAS compounds. Levels are from the utility's most recent reporting cycle.
In April 2024, EPA finalized the first National Primary Drinking Water Regulation for six PFAS. Public water systems have until 2029 to comply. EPA — PFAS regulation overview →
Source: Consumer Confidence Report disclosed by Thornton Water.
ZipCheckup is not affiliated with this water utility. PFAS detection data is sourced from public Consumer Confidence Reports filed by the utility itself.
Thornton has no lead service lines, and those findings have been submitted to the EPA.
Lead Service Line Replacement Tracker
This water utility's lead service line (LSL) replacement program is tracked from public Consumer Confidence Report filings. Email signup notifies subscribers when the utility files an updated replacement plan or progress milestone.
Thornton Water
ZipCheckup is not affiliated with this water utility. LSL replacement-program data is sourced from public CCR filings published by the utility. Subscription notifications are based on automated parsing of subsequent CCR releases.
Learn more about Lead and Copper Rule replacement requirements →
Lead Service Line Inventory
Service line breakdown reported under the federal Lead and Copper Rule Improvements (LCRI) inventory requirement:
This system reports zero confirmed lead service lines in its inventory. Unknown-material counts may still warrant verification.
Federal LCRI rule (effective October 2024) requires every public water system to inventory its service lines and complete lead-line replacement within 10 years.
Source: EPA SDWIS Federal Service Line Inventory (Phase 2) · Submitted 2026
ZipCheckup is not affiliated with the utility or state agency. Inventory figures render verbatim from the public LCRI submission cited above; ZipCheckup does not perform inspections or replacements.
Aesthetic water quality
These measurements describe the look, taste, and feel of the water this utility delivers. They are not contaminant violations — they sit alongside federal Secondary Maximum Contaminant Levels (SMCLs) which the EPA publishes as non-enforceable guidance.
Aesthetic measurements from Thornton Water Consumer Confidence Report.
Aesthetic measurements are reported by the utility from its annual sampling. EPA Secondary MCLs are advisory thresholds — values outside them indicate aesthetic concerns such as taste or appearance, not health violations. Federal contaminant testing is shown in the sections above.
Hard water detected in Thornton Water
Your utility reported water hardness of 183 ppm CaCO₃ (10.7 grains per gallon) in its most recent Consumer Confidence Report. This is in the hard range and may cause scale buildup, reduced appliance lifespan, and dry skin or hair.
There are three common approaches to treating hard water: salt-based ion-exchange softeners (most effective, require salt refills), salt-free conditioners (lower maintenance, scale prevention only), and reverse osmosis at the kitchen sink (cooking and drinking water only). Aquasana, EcoWater, Pelican, and SpringWell are among the major US brands.
Paid Partner. ZipCheckup earns commission on Aquasana purchases. We do not test water or verify product effectiveness for specific hardness levels — manufacturer claims are theirs alone. Consult a certified water-quality professional for personalized advice.
Hardness data parsed from this utility's most recent Consumer Confidence Report. Severity bands per USGS hard water classification.
Notable events and violations
This section summarizes events the utility chose to disclose in its most recent Consumer Confidence Report, plus any federal compliance violations the utility recorded against itself. Both lists are utility-authored — ZipCheckup does not audit, judge, or reorder them.
Federal compliance violations on record
These entries are taken verbatim from the utility's CCR violations section. EPA defines four broad violation categories: Maximum Contaminant Level (MCL), Treatment Technique (TT), Monitoring & Reporting (M&R), and Public Notification (PN).
-
monitoring · Backflow Prevention and Cross-Connection Control2024-08
During a sanitary survey, the inspector identified issues regarding how the city was implementing its Backflow Prevention and Cross-Connection Control program. The city failed to develop or implement a written BPCCC program.
Violations record from Thornton Water Consumer Confidence Report.
Notable events from the utility's CCR
These bullet entries are the utility's own narration of operational, regulatory, or infrastructure events during the reporting period.
- Completed an extensive survey to determine population size served, now approximately 225,000 people.
- Larimer County commissioners approved the permit to construct one of the final segments of the 70-mile pipeline from Cache la Poudre River.
- Determined that Thornton has no lead service lines.
- Began testing for lead and copper in schools and childcare facilities.
- Failed to meet Cross Connection Control and/or Backflow Prevention Requirements during a CDPHE sanitary survey in August 2024.
ZipCheckup note: items above reflect what the utility published in its most recent CCR. Federal violation records are also tracked separately by the EPA Safe Drinking Water Information System (SDWIS) — the SDWIS record is the authoritative federal source for any specific regulatory action.
How Water Systems Appear in Rankings
Water systems are evaluated by violation history, contaminant detections, and service population. Larger systems with more service connections appear in more rankings.
- #10 / 50 Highest Exposure Burden (Colorado)
Frequently Asked Questions
What You Can Do
Test your water
Home test kits can detect lead, bacteria, and other contaminants at your tap. Find the right filter →
Check your specific ZIP code
Water quality can vary within a system. View nearest ZIP report →
Contact your utility
City of Thornton (EPA ID: CO0101150) — request the latest Consumer Confidence Report or ask about specific contaminants.