Water Quality Technical Report — MADISON WATER UTILITY, WI
- PWSID
- WI1130224
- Population
- 272,000
- Source
- Groundwater
- Data Period
- —
- Last Updated
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Summary
MADISON WATER UTILITY serves approximately 272,000 people in MADISON, Wisconsin. Based on contaminant analyses from DNR, WQP, EPA ECHO, EPA UCMR5, 3 contaminants have been measured above federal EPA standards (MCL) and 8 exceed health-based guidelines. The most significant finding is PFHxS (Perfluorohexane Sulfonate) at 23 ng/L, which is 2.3x the EPA legal limit. Data is drawn from source-level compliance monitoring and covers 2014 through 2026. Results reflect conditions at the point of collection (wells, treatment plants), not necessarily at the tap.
Key Findings
- Lead (90th percentile): Below the legal limit but above health-based guidelines (2023 reading). From your water system's testing.
- Uranium: Below the legal limit but above health-based guidelines (2026 reading). From your water system's testing.
- Tetrachloroethylene (PCE): Below the legal limit but above health-based guidelines (2026 reading). From your water system's testing.
- Benzene: Below the legal limit but above health-based guidelines (2025 reading). From your water system's testing.
Understanding the two thresholds
EPA Legal Limit (MCL)
The highest level of a contaminant allowed by federal law. Utilities that exceed this threshold face enforcement action. Limits balance health risk against the cost of treatment, so they are not always set at levels considered safe by independent researchers.
Health Guideline
The level below which independent researchers (CalEPA, WHO, EWG) believe there is no known health risk. Guidelines are not legally enforceable but are typically stricter than legal limits — often by 10x or more for contaminants like arsenic and lead.
A reading can be below the EPA limit (legally compliant) while still exceeding health guidelines (above levels considered safe by independent researchers).
Above Federal Standard
These contaminants were measured at levels above the federal Maximum Contaminant Level (MCL) in source-level compliance monitoring. Formal compliance determinations may differ — the EPA evaluates running averages, per-entry-point samples, and other criteria before declaring a violation.
PFAS Hazard Index: 2.30 — exceeds limit of 1.0
EPA 2024 PFAS Rule — Hazard Index across PFHxS, PFNA, HFPO-DA, PFBS. A Hazard Index of 1.0 or higher exceeds the federal Maximum Contaminant Level for the PFAS mixture. Systems have until 2029 to achieve compliance with this standard.
Partial Hazard Index based on 2 of 4 regulated compounds with monitoring data. The actual Hazard Index may be higher if the other compounds are present but untested.
- PFHxS: 23 ng/L ÷ 10 ng/L HBWC = 2.3
- PFBS: 2.9 ng/L ÷ 2000 ng/L HBWC = 0.0014
| Contaminant | Result | Unit | Health Guideline | EPA Legal Limit | Source | Sample Date |
|---|---|---|---|---|---|---|
| PFHxS (Perfluorohexane Sulfonate) Associated with thyroid disease, reproductive effects, and immune system changes. Per-source breakdown (10 sampling locations)
| 23 | ng/L | 10 | 10 | DNR | |
| PFOS (Perfluorooctane Sulfonate) Linked to liver damage, thyroid disease, immune system effects, and increased cholesterol. Classified as a possible human carcinogen. Per-source breakdown (7 sampling locations)
| 6.2 | ng/L | 0 | 4 | DNR | |
| PFOA (Perfluorooctanoic Acid) Associated with kidney cancer, testicular cancer, thyroid disease, and developmental effects. Classified as a possible human carcinogen. Per-source breakdown (8 sampling locations)
| 4.3 | ng/L | 0 | 4 | DNR |
EPA Violation Records
The following violation records exist in EPA's federal compliance database for this system. We do not have corresponding monitoring data for these contaminants in our database.
Exceeds Health Guidelines
These contaminants were detected below the EPA legal limit but above a health-based guideline from a public health agency (CalEPA OEHHA, WHO, or similar). Health guidelines are non-enforceable research-backed targets that are often stricter than the legal limit.
| Contaminant | Result | Unit | Health Guideline | EPA Legal Limit | Source | Sample Date |
|---|---|---|---|---|---|---|
| Tetrachloroethylene (PCE) Liver problems, increased risk of cancer | 1.5 | ug/L | 0.06 | 5 | DNR | |
| Arsenic Skin damage, circulatory problems, increased risk of cancer | 6.7 | ug/L | 0.004 | 10 | DNR | |
| Lead (90th Percentile) Developmental delays in children, kidney damage, high blood pressure. There is no safe level of lead exposure. | 1.8 | ug/L | 0.2 | 15 Pending rule: LCRI 2024 — Action level drops from 15 → 10 µg/L effective 2027; full lead service line replacement within 10 years (EPA Lead & Copper Rule Improvements, October 2024) | EPA ECHO | (2+ years ago) |
| Uranium Increased risk of cancer, kidney toxicity | 1.6 | ug/L | 0.5 | 30 | DNR | |
| Benzene Anemia, decrease in blood platelets, increased risk of cancer | 390 | ng/L | 150 | 5000 | DNR |
PFAS: 10.5 ng/L detected.
Per- and polyfluoroalkyl substances (PFAS) are a group of manufactured chemicals that persist in the environment and accumulate in the human body. The EPA set enforceable limits for six PFAS compounds in April 2024, with a compliance deadline of 2029. PFAS compounds measured above EPA standards appear in the Above Federal Standard section above. The value shown in the heading is the combined PFOA + PFOS concentration reported by Wisconsin DNR (a legacy 2016 EPA Health Advisory metric, not a current MCL).
| Contaminant | Result | Unit | Health Guideline | EPA Legal Limit | Source | Sample Date |
|---|---|---|---|---|---|---|
| PFBA (Perfluorobutanoic Acid) Shorter-chain PFAS with faster elimination. Thyroid effects in animal studies. Per-source breakdown (8 sampling locations)
| 3.7 | ng/L | Not published | Not regulated | DNR | |
| PFBS (Perfluorobutane Sulfonate) Thyroid effects, reproductive and developmental effects, kidney effects. Per-source breakdown (8 sampling locations)
| 2.9 | ng/L | Not published | Regulated via Hazard Index (HBWC 2,000 ng/L) | DNR | |
| PFHxA (Perfluorohexanoic Acid) Limited toxicological data. Potential liver and developmental effects. Per-source breakdown (8 sampling locations)
| 2 | ng/L | Not published | Not regulated | DNR |
Microplastics
Microplastics have been documented in raw and treated drinking water worldwide, but federal regulations do not currently require testing — so there is no data specific to this system. Standardized methods and rules are in progress.
Other Regulated Contaminants
These contaminants were detected within federal standards (EPA Maximum Contaminant Levels). They are presented for transparency.
Total Trihalomethanes (TTHMs) (LRAA): 2.94 ug/L — within limit of 80 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, system-wide, based on 12 samples across 4 quarters (2025Q2 · 2025Q3 · 2025Q4 · 2026Q1).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
Haloacetic Acids (HAA5) (LRAA): 1.41 ug/L — within limit of 60 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, system-wide, based on 8 samples across 4 quarters (2025Q2 · 2025Q3 · 2025Q4 · 2026Q1).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
| Contaminant | Result | Unit | Health Guideline | EPA Legal Limit | Source | Sample Date |
|---|---|---|---|---|---|---|
| Chlorine (free) Eye/nose irritation, stomach discomfort Per-source breakdown (18 sampling locations)
| 530 | ug/L | 4000 | 4000 | DNR | |
| Chlorine (total residual) Eye/nose irritation, stomach discomfort | 430 | ug/L | 4000 | 4000 | DNR | |
| Fluoride (natural) Bone disease, mottled teeth in children | 711 | ug/L | 4000 | 4000 | DNR | |
| Combined Radium (226+228) Increased risk of cancer Per-source breakdown (8 sampling locations)
| 3.07 | pCi/L | 0 | 5 | DNR | |
| Gross Alpha Radiation (excluding Radon and Uranium) Increased risk of cancer | 3.96 | pCi/L | Not published | 15 | DNR | |
| Trichloroethylene (TCE) Liver problems, increased risk of cancer | 370 | ng/L | 1700 | 5000 | DNR | |
| cis-1,2-Dichloroethylene Liver damage, immune system effects | 520 | ng/L | 70000 | 70000 | DNR | |
| Barium Increase in blood pressure Per-source breakdown (19 sampling locations)
| 24 | ug/L | 1000 | 2000 | DNR | |
| Selenium Hair or fingernail loss, numbness, circulation problems | 1.4 | ug/L | 50 | 50 | DNR | |
| Nitrate (as N) Blue baby syndrome in infants Per-source breakdown (15 sampling locations)
| 2.3 | mg/L | 10 | 10(as N) | DNR | |
| Chromium (total) Note: total chromium includes the harmless trivalent form (Cr-III). The toxic hexavalent form (Cr-VI) has no federal MCL; California set a 10 µg/L Cr-VI MCL in 2014. Allergic dermatitis | 1.3 | ug/L | 100 | 100 | DNR | |
| Nitrite (as N) Blue baby syndrome in infants | 12.8 | ug/L | 1000 | 1000(as N) | DNR | |
| Total Xylenes Short-term: nervous system effects. Long-term: damage to the nervous system, liver, and kidneys. | 740 | ng/L | 500000 | 10000000 | DNR | |
| 1,1-Dichloroethylene Liver problems | 180 | ng/L | 7000 | 7000 | DNR | (21 months ago) |
| Atrazine Cardiovascular system or reproductive problems | 31 | ng/L | 150 | 3000 | DNR | (2+ years ago) |
| Beryllium Intestinal lesions | 198 | ng/L | 4000 | 4000 | DNR | (4+ years ago) |
Unregulated Detected Contaminants
These contaminants were detected but do not have a federal Maximum Contaminant Level. They are monitored for awareness, not compliance.
PFAS — Per- and Polyfluoroalkyl Substances
| Contaminant | Result | Unit | Health Guideline | EPA Legal Limit | Source | Sample Date |
|---|---|---|---|---|---|---|
| PFPeA (Perfluoropentanoic Acid) Limited toxicity data. Shorter-chain PFAS. Per-source breakdown (8 sampling locations)
| 2 | ng/L | Not published | Not regulated | DNR | |
| PFPeS (Perfluoropentane Sulfonate) Limited toxicity data. Short-chain PFAS. | 0.71 | ng/L | Not published | Not regulated | DNR | (3+ years ago) |
| PFHpA (Perfluoroheptanoic Acid) Limited human data. Part of the broader PFAS family; persistence and bioaccumulation suspected. | 0.52 | ng/L | Not published | Not regulated | DNR | (3+ years ago) |
| 6:2 FTS (6:2 Fluorotelomer Sulfonate) Limited human data. Potential thyroid and liver effects. | 5.6 | ng/L | Not published | Not regulated | DNR | (3+ years ago) |
VOCs — Volatile Organic Compounds
| Contaminant | Result | Unit | Health Guideline | EPA Legal Limit | Source | Sample Date |
|---|---|---|---|---|---|---|
| Trichlorofluoromethane Cardiac sensitization, central nervous system depression at high levels. Per-source breakdown (5 sampling locations)
| 530 | ng/L | Not published | Not regulated | DNR | |
| Metolachlor Liver, kidney problems | 12 | ng/L | 10000 | Not regulated | DNR | (2+ years ago) |
| 1,1-Dichloroethane Liver and kidney effects in animal studies. | 110 | ng/L | Not published | Not regulated | DNR | (3+ years ago) |
| Chloromethane Nervous system effects, liver and kidney damage at high exposure. | 450 | ng/L | Not published | Not regulated | DNR | (4+ years ago) |
Inorganics — Metals and Minerals
| Contaminant | Result | Unit | Health Guideline | EPA Legal Limit | Source | Sample Date |
|---|---|---|---|---|---|---|
| Silver Prolonged high exposure can cause argyria (blue-gray skin discoloration) but is not associated with cancer or organ damage. EPA has no enforceable health-based MCL for silver. | 160 | ng/L | 0.1 mg/L | 100000 | DNR | |
| Nickel Allergic dermatitis, lung and nasal effects | 2.4 | ug/L | 12 | Not regulated | DNR |
Other Substances
| Contaminant | Result | Unit | Health Guideline | EPA Legal Limit | Source | Sample Date |
|---|---|---|---|---|---|---|
| Copper (90th Percentile) Gastrointestinal distress at high levels. Long-term exposure can cause liver or kidney damage. Per-source breakdown (19 sampling locations)
| 6.4 | ug/L | 300 | 1300 | DNR | |
| Styrene | 430 | ng/L | — | — | DNR | |
| Trichlorotrifluoroethane Freon | 540 | ng/L | — | — | DNR | (5+ years ago) |
Radionuclides — Radioactive Elements
| Contaminant | Result | Unit | Health Guideline | EPA Legal Limit | Source | Sample Date |
|---|---|---|---|---|---|---|
| Radon Radon is a known human carcinogen. Inhalation of radon released from water during showering and other household use is the primary exposure route; ingestion contributes a smaller stomach cancer risk. | 223 | pCi/L | 300 | Not regulated | DNR | (4+ years ago) |
Other Potential Contaminants
Not detecting a contaminant does not prove it isn't present — it only means the laboratory didn't test for it, or tested below the reporting limit. Many substances of emerging concern are not routinely monitored because federal regulations haven't caught up to the science.
- Pharmaceuticals and personal care products (PPCPs) — USGS Emerging Contaminants program · Kolpin et al. (USGS FS-2006-3013)
- Unregulated PFAS compounds — EPA PFAS rule (2024) · EPA UCMR monitoring
- 1,4-Dioxane — EPA technical fact sheet
- Hexavalent chromium (Cr-VI) — EPA chromium in drinking water · California OEHHA PHG
- Unregulated disinfection byproducts — EPA Stage 1 / Stage 2 DBPR
- Endocrine disruptors — EPA Endocrine Disruptor Screening Program
Compliance History
Formal EPA and DNR compliance events on record for this utility. Includes all events from the last 10 years plus any unresolved violations regardless of age. Health-based violations are legally enforceable thresholds that were exceeded; procedural events are monitoring or reporting lapses that don't indicate contamination by themselves.
Oct 17, 2024 – ongoing
Jul 1, 1992 – ongoing
Oct 17, 2024 – ongoing
Source: EPA ECHO enforcement and violation records (via Envirofacts / SDWIS Federal Reports).
Action Steps
This system has contaminants above a legal limit or multiple health guidelines. The following steps are concrete things a homeowner or facility operator can do right now — starting with the most important non-commercial options.
- Request the utility's Consumer Confidence Report (CCR). The CCR compares utility-reported readings to the federal legal limits and is independent of this site. Utilities must make it available on request. EPA CCR search.
- Get a certified tap test. A state-certified laboratory can test your tap for a specific contaminant or a broader panel. A single-contaminant test runs in the low tens of dollars; a comprehensive panel runs several hundred. Ask for the EPA-certified lab list from Wisconsin DNR. Wisconsin DNR lab certification.
- Consider point-of-use filtration. For the specific contaminants detected in this system, the exceedance sections above list the technology categories (reverse osmosis, granular activated carbon, ion exchange, etc.) that target each class. Those are category-level descriptions — the right choice depends on the contaminant profile, budget, and installation constraints.
- Contact the utility directly. Ask about the specific contaminants you're concerned about and request the most recent sampling data. The EPA SDWIS portal lists utility contact details. EPA SDWIS system lookup.
- Check the utility's lead service line inventory. Under the Lead and Copper Rule Revisions (LCRR, 2024), utilities must publish a service line inventory identifying lines flagged as lead, galvanized-requiring-replacement, or unknown material. If your service line is flagged or unknown, the utility is required to replace it on a scheduled timeline. EPA Lead and Copper Rule Improvements.
Frequently Asked Questions
What contaminants are in MADISON water?
Based on available public monitoring data, 165 contaminants have been tested in MADISON's water supply. 43 were detected above reporting limits. The most notable detections include Chlorine (free), Chlorine (total residual), Fluoride (natural). This data comes from source-level compliance monitoring at wells and treatment plants.
Does MADISON water meet EPA standards?
Based on available public monitoring data, 3 contaminants were measured above federal EPA standards in source-level monitoring. This does not necessarily indicate a formal violation — the EPA uses running averages and other criteria for compliance determinations. Data comes from wells and treatment plants, not tap-level measurements.
Is MADISON WI water safe to drink?
Based on source-level compliance monitoring, 3 contaminants were measured above federal standards. However, compliance monitoring tests water at wells and treatment plants, not at individual taps. An on-site test is the only way to know what reaches your tap, as conditions can vary based on plumbing, blending, and distribution.
Does MADISON water have PFAS?
Yes, PFAS compounds have been detected in source monitoring for MADISON's water supply: PFBS (Perfluorobutane Sulfonate) (2.9 ng/L), PFHxS (Perfluorohexane Sulfonate) (23 ng/L), PFOS (Perfluorooctane Sulfonate) (6.2 ng/L), PFOA (Perfluorooctanoic Acid) (4.3 ng/L). PFAS are a group of manufactured chemicals that do not break down in the environment. The EPA set enforceable limits for several PFAS compounds in 2024.
Does MADISON water have lead?
No. MADISON's most recent Lead and Copper Rule testing found a 90th-percentile lead level of 0.0018 mg/L, which is below the EPA action level of 0.015 mg/L. That means at the systemwide level, lead is not exceeding the enforcement threshold. Lead levels can still vary significantly by individual building — older homes and schools with legacy plumbing can have much higher readings than the system average.
Cross-check against the official record
This report is our read of the public monitoring data. Every Wisconsin utility also publishes an annual Consumer Confidence Report (CCR) — a plain-language summary written by the utility itself, usually mailed with a water bill or posted on the utility's website. If anything in this report surprises you, request MADISON WATER UTILITY's latest CCR directly from the utility, or browse the underlying compliance data on the Wisconsin DNR portal.
Data Sources and Methodology
- Wisconsin DNR Compliance Monitoring
State-level drinking water compliance testing. Covers all regulated contaminants for community water systems. Source-level monitoring at wells and treatment plants. Individual result links are provided for each contaminant in the tables above.
- Water Quality Portal
Cooperative service by USGS, EPA, and NWQMC. Regional groundwater monitoring data from nearby wells — may not reflect this specific utility.
- EPA ECHO Lead & Copper Rule
90th percentile measurements from EPA Enforcement and Compliance History Online. Based on tap-level sampling at high-risk sites.
- EPA UCMR5
Unregulated Contaminant Monitoring Rule, Fifth cycle. Per-analyte PFAS results from utility-level sampling.
Definitions
- Maximum Contaminant Level (MCL)
- The highest level of a contaminant allowed in drinking water, set by the EPA. MCLs are legally enforceable standards.
- Maximum Contaminant Level Goal (MCLG)
- The level of a contaminant below which there is no known or expected health risk. MCLGs are non-enforceable public health goals.
- Action Level
- The concentration of a contaminant which, if exceeded, triggers treatment or other requirements. Used for lead and copper.
- Health Advisory
- Non-enforceable guidelines set by the EPA providing information on contaminants that can cause health effects at certain exposure levels.
- Total Dissolved Solids (TDS)
- A measure of all dissolved minerals, salts, and organic matter in water, expressed in mg/L (ppm). Not a health hazard but affects taste and indicates overall mineral content.
- PFAS
- Per- and polyfluoroalkyl substances. A group of manufactured chemicals that do not break down in the environment. The EPA set enforceable limits for several PFAS compounds in 2024.
- Non-Detect (ND)
- The contaminant was tested for but not found above the laboratory's reporting limit. This does not mean zero — it means below the detection threshold.
- VOCs (Volatile Organic Compounds)
- Chemicals that evaporate easily and can contaminate groundwater. Sources include gasoline, industrial solvents, and dry cleaning fluids. Some are regulated by the EPA; many are monitored but not yet regulated.
Download Data
Cite This Report
WaterAdvantage. "Water Quality Technical Report: MADISON, WI (WI1130224)." WaterAdvantage.org, 2026-04-14. https://www.wateradvantage.org/report/WI1130224/detail
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