Water Quality Technical Report — ROCK ISLAND, IL
- PWSID
- IL1610650
- Population
- 39,018
- Source
- Surface Water
- Data Period
- —
- Last Updated
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Summary
ROCK ISLAND serves approximately 39,018 people in ROCK ISLAND, Illinois. Based on contaminant analyses from DNR, WQP, EPA ECHO, EPA UCMR5, 0 contaminants have been measured above federal EPA standards (MCL) and 0 exceed health-based guidelines. No contaminants were measured above federal EPA standards in recent compliance monitoring. Data is drawn from source-level compliance monitoring and covers 1995 through 2026. Results reflect conditions at the point of collection (wells, treatment plants), not necessarily at the tap.
Key Findings
- PFAS Detected: PFAS compounds were detected in monitoring data for this system.
- Arsenic (nearby groundwater): Below the legal limit but above health-based guidelines (2014 reading). From regional groundwater monitoring, not your tap.
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).
PFAS
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.
| 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. | 9.3 | ng/L | Not published | Not regulated | DNR | |
| PFBS (Perfluorobutane Sulfonate) Thyroid effects, reproductive and developmental effects, kidney effects. | 0.9 | 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. | 0.9 | ng/L | Not published | Not regulated | DNR | |
| PFHxS (Perfluorohexane Sulfonate) Associated with thyroid disease, reproductive effects, and immune system changes. | 0.9 | ng/L | 10 | 10 | DNR | |
| PFOA (Perfluorooctanoic Acid) Associated with kidney cancer, testicular cancer, thyroid disease, and developmental effects. Classified as a possible human carcinogen. | 2.3 | ng/L | 0 | 4 | DNR | |
| PFOS (Perfluorooctane Sulfonate) Linked to liver damage, thyroid disease, immune system effects, and increased cholesterol. Classified as a possible human carcinogen. | 1.7 | ng/L | 0 | 4 | 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): 53.78 ug/L — within limit of 80 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HT1, based on 4 samples across 4 quarters (2025Q4 · 2026Q1 · 2026Q2 · 2026Q3).
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.
Total Trihalomethanes (TTHMs) (LRAA): 37.28 ug/L — within limit of 80 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HH1, based on 4 samples across 4 quarters (2025Q4 · 2026Q1 · 2026Q2 · 2026Q3).
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.
Total Trihalomethanes (TTHMs) (LRAA): 37.25 ug/L — within limit of 80 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HT2, based on 4 samples across 4 quarters (2025Q4 · 2026Q1 · 2026Q2 · 2026Q3).
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.
Total Trihalomethanes (TTHMs) (LRAA): 34.80 ug/L — within limit of 80 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2DBP1, based on 4 samples across 4 quarters (2025Q4 · 2026Q1 · 2026Q2 · 2026Q3).
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): 33.85 ug/L — within limit of 60 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HH1, based on 4 samples across 4 quarters (2025Q4 · 2026Q1 · 2026Q2 · 2026Q3).
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): 37.90 ug/L — within limit of 60 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HT2, based on 4 samples across 4 quarters (2025Q4 · 2026Q1 · 2026Q2 · 2026Q3).
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): 32.70 ug/L — within limit of 60 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2DBP1, based on 4 samples across 4 quarters (2025Q4 · 2026Q1 · 2026Q2 · 2026Q3).
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): 38.90 ug/L — within limit of 60 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HT1, based on 4 samples across 4 quarters (2025Q4 · 2026Q1 · 2026Q2 · 2026Q3).
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 |
|---|---|---|---|---|---|---|
| Nitrate (as N) Blue baby syndrome in infants | 965 | ug/L | 10000 | 10000(as N) | DNR | |
| Barium Increase in blood pressure | 44.3 | ug/L | 1000 | 2000 | DNR | |
| Fluoride (natural) Bone disease, mottled teeth in children | 591 | ug/L | 4000 | 4000 | DNR | |
| Arsenic Skin damage, circulatory problems, increased risk of cancer | 200 | ng/L | 4 | 10000 | WQP | (12+ years ago) |
| 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 | 150 | ng/L | 100000 | 100000 | WQP | (19+ 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.
Other Substances
| Contaminant | Result | Unit | Health Guideline | EPA Legal Limit | Source | Sample Date |
|---|---|---|---|---|---|---|
| Lead (90th Percentile) Developmental delays in children, kidney damage, high blood pressure. There is no safe level of lead exposure. | 0 | ng/L | 200 | 15000 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 | |
| Copper (90th Percentile) Gastrointestinal distress at high levels. Long-term exposure can cause liver or kidney damage. Per-source breakdown (71 sampling locations)
| 45.5 | ug/L | 300 | 1300 | DNR | |
| Toc | 6.8 | mg/L | — | — | DNR |
PFAS — Per- and Polyfluoroalkyl Substances
| Contaminant | Result | Unit | Health Guideline | EPA Legal Limit | Source | Sample Date |
|---|---|---|---|---|---|---|
| PFHpA (Perfluoroheptanoic Acid) Limited human data. Part of the broader PFAS family; persistence and bioaccumulation suspected. | 0.5 | ng/L | Not published | Not regulated | DNR | |
| PFPeA (Perfluoropentanoic Acid) Limited toxicity data. Shorter-chain PFAS. | 0.9 | ng/L | Not published | Not regulated | DNR |
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.
Jan 1, 2026 – Mar 31, 2026
Jul 1, 2025 – ongoing
Oct 1, 2023 – ongoing
Apr 1, 2023 – Jun 30, 2023
Apr 1, 2020 – Jun 30, 2020
Apr 1, 2020 – Jun 30, 2020
Apr 1, 2020 – Jun 30, 2020
Apr 1, 2020 – Jun 30, 2020
Apr 1, 2020 – Jun 30, 2020
Apr 1, 2020 – Jun 30, 2020
Apr 1, 2020 – Jun 30, 2020
Apr 1, 2020 – Jun 30, 2020
Apr 1, 2020 – Jun 30, 2020
Apr 1, 2020 – Jun 30, 2020
Apr 1, 2020 – Jun 30, 2020
Apr 1, 2020 – Jun 30, 2020
Apr 1, 2020 – Jun 30, 2020
Apr 1, 2020 – Jun 30, 2020
Apr 1, 2020 – Jun 30, 2020
Apr 1, 2020 – Jun 30, 2020
+ 16 older events in the 10-year window not shown
Source: EPA ECHO enforcement and violation records (via Envirofacts / SDWIS Federal Reports).
Routine Maintenance
Nothing in this system's current readings crosses a legal limit or a health guideline. Water systems still change over time, so the following is a baseline of habits worth keeping.
- Check the utility's annual Consumer Confidence Report. Utilities publish CCRs every July covering the prior calendar year. They include sampling data the utility collected itself, which complements the independent data on this page. EPA CCR search.
- Notice changes in taste, odor, or color. Chlorine smells, metallic tastes, and rust discoloration are worth flagging to the utility even when readings are in range — they can signal distribution-system events that sampling catches on a delay.
- Consider an independent tap test. A state-certified laboratory can test your tap water for a specific contaminant or a broader panel. Especially valuable for smaller systems with limited monitoring data. Illinois certified labs (EPA directory).
- Point-of-use filtration is optional. When readings are within guidelines, any additional filtration is a personal preference — choose based on taste, hardness, or a specific contaminant you want extra assurance on.
Frequently Asked Questions
What contaminants are in ROCK ISLAND water?
Based on available public monitoring data, 41 contaminants have been tested in ROCK ISLAND's water supply. 16 were detected above reporting limits. The most notable detections include Haloacetic Acids (HAA5), Total Trihalomethanes (TTHMs), PFHpA (Perfluoroheptanoic Acid). This data comes from source-level compliance monitoring at wells and treatment plants.
Does ROCK ISLAND water meet EPA standards?
Based on available public monitoring data, no contaminants were measured above federal EPA standards in recent compliance monitoring. This assessment is based on source-level monitoring data (wells and treatment plants), not tap-level measurements.
Is ROCK ISLAND, IL water safe to drink?
Based on source-level compliance monitoring, all tested contaminants were within 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 ROCK ISLAND water have PFAS?
Yes, PFAS compounds have been detected in source monitoring for ROCK ISLAND's water supply: PFOS (Perfluorooctane Sulfonate) (1.7 ng/L), PFBA (Perfluorobutanoic Acid) (9.3 ng/L), PFHxS (Perfluorohexane Sulfonate) (0.9 ng/L), PFBS (Perfluorobutane Sulfonate) (0.9 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 ROCK ISLAND water have lead?
No. ROCK ISLAND's most recent Lead and Copper Rule testing found a 90th-percentile lead level of 0 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 Illinoisutility 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 ROCK ISLAND's latest CCR directly from the utility, or browse the underlying compliance data published by Illinois EPA.
Data Sources and Methodology
- Illinois EPA 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: ROCK ISLAND, IL (IL1610650)." WaterAdvantage.org, 2026-11-02. https://www.wateradvantage.org/report/IL1610650/detail
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