Community Water System · PWS IA1750048
Mason City Water Department
Operator location Mason City, Iowa - larger served population (> 3,309) at 27,338 people served; 647 SDWIS violations on record from groundwater sources.
- 27,338
- People served (this PWS)
- 647
- EPA violations (this PWS)
- 68
- Health-based (this PWS)
- No PFAS
- UCMR5 (this PWS)
Mason City Water Department standing, high SDWIS violation third
27,338 people served (SDWIS) - larger served population (> 3,309). Corpus terciles use 29,740 systems serving 500+ (the sitemap cohort). Health-based share 11% is middle-third health share (≤ 23%). UCMR5: UCMR5 tested, none detected. Population rank #2,031 of 29,740 among systems serving 500+.
The verdict
Mason City Water Department sits in the upper third of the sitemap cohort by violation count (647), so the tables below sample a dense compliance trail rather than a near-clean ledger. Population served is large (27,338; larger served population (> 3,309)), so household exposure scale sits behind the violation mix. Health-based share is 11% (middle-third health share (≤ 23%)). UCMR5 tested this system and reported no PFAS above the minimum reporting level.
- #2,031 of 29,740
- Population · /systems
- #20 of 545
- Population · IA
- 647
- Total EPA violations on record
- 11%
- Health-based (MCL / treatment failure)
Population ordinals match the sitemap cohort (systems serving 500+, population_served DESC). See methodology · corpus placement.
System Details
- System Type
- Community
- Owner Type
- Local
- Connections
- 19,000
- County
- Cerro Gordo
- School/Daycare
- No
- MCL Violations
- 68
- Monitoring Violations
- 429
- Treatment Tech Violations
- 0
Violation History
Contaminant violations recorded by EPA.
| Contaminant | Category | Count | Latest |
|---|---|---|---|
| Combined Radium (-226 and -228) | Other | 123 | 2003 |
| Combined Radium (-226 and -228) | MCL | 43 | 2004 |
| Coliform (TCR) | MCL | 25 | 2012 |
| Consumer Confidence Rule | Other | 17 | 2004 |
| Carbon tetrachloride | MR | 12 | 1995 |
| p-Dichlorobenzene | MR | 12 | 1995 |
| 1,1-Dichloroethylene | MR | 12 | 1995 |
| trans-1,2-Dichloroethylene | MR | 12 | 1995 |
| DICHLOROMETHANE | MR | 12 | 1995 |
| 1,2-Dichloropropane | MR | 12 | 1995 |
| CHLOROBENZENE | MR | 12 | 1995 |
| 1,2,4-Trichlorobenzene | MR | 12 | 1995 |
| Trichloroethylene | MR | 12 | 1995 |
| Xylenes, Total | MR | 12 | 1995 |
| LASSO | MR | 12 | 1995 |
| Benzo(a)pyrene | MR | 12 | 1995 |
| 2,4-D | MR | 12 | 1995 |
| Dalapon | MR | 12 | 1995 |
| Di(2-ethylhexyl) adipate | MR | 12 | 1995 |
| Di(2-ethylhexyl) phthalate | MR | 12 | 1995 |
| Pentachlorophenol | MR | 12 | 1995 |
| Simazine | MR | 12 | 1995 |
| 2,4,5-TP | MR | 12 | 1995 |
| cis-1,2-Dichloroethylene | MR | 12 | 1995 |
| Ethylbenzene | MR | 12 | 1995 |
| Styrene | MR | 12 | 1995 |
| Tetrachloroethylene | MR | 12 | 1995 |
| Toluene | MR | 12 | 1995 |
| Atrazine | MR | 12 | 1995 |
| Dinoseb | MR | 12 | 1995 |
Violation Count vs. the National Corpus
Mason City Water Department has 647 recorded EPA violations, 97% of the 29,740 public water systems serving 500+ people nationwide carry fewer, and 3% carry more. 11% of this system's own violations are health-based (68 of 647), and it ranks #2,031 of 29,740 by population served among that same cohort.
EPA violations vs. the national water-system corpus
Public water systems serving 500+ people (EPA SDWIS)
647 Higher than most more violations than 97% of 29,740 water systems
the national water-system corpus, bucketed by value
Each bar is a band; taller bars hold more water systems. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count and share, and where it sits relative to this entry.
Source EPA SDWIS · 2026-05-15
PFAS Testing Results (UCMR5)
Results from EPA's Fifth Unregulated Contaminant Monitoring Rule. 0 of 58 samples detected PFAS.
| Contaminant | Date | Result | MRL | Status |
|---|---|---|---|---|
| NEtFOSAA | 7/17/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| 8:2 FTS | 7/17/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFMBA | 7/17/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| NMeFOSAA | 7/17/2024 | <6.00 ppt | 6.00 ppt | Not Detected |
| 6:2 FTS | 7/17/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFTA | 7/17/2024 | <8.00 ppt | 8.00 ppt | Not Detected |
| PFHpS | 7/17/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFPeS | 7/17/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFTrDA | 7/17/2024 | <7.00 ppt | 7.00 ppt | Not Detected |
| PFEESA | 7/17/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFPeA | 7/17/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFOS | 7/17/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFNA | 7/17/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFHxS | 7/17/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHpA | 7/17/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFBS | 7/17/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| 11Cl-PF3OUdS | 7/17/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFDoA | 7/17/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| NFDHA | 7/17/2024 | <20.00 ppt | 20.00 ppt | Not Detected |
| PFMPA | 7/17/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFUnA | 7/17/2024 | <2.00 ppt | 2.00 ppt | Not Detected |
| 9Cl-PF3ONS | 7/17/2024 | <2.00 ppt | 2.00 ppt | Not Detected |
| ADONA | 7/17/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFDA | 7/17/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| HFPO-DA | 7/17/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFBA | 7/17/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFOA | 7/17/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| 4:2 FTS | 7/17/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHxA | 7/17/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| HFPO-DA | 1/10/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFPeA | 1/10/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| 6:2 FTS | 1/10/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| 8:2 FTS | 1/10/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFMPA | 1/10/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFBA | 1/10/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFMBA | 1/10/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFEESA | 1/10/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFPeS | 1/10/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFHpS | 1/10/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| ADONA | 1/10/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| NEtFOSAA | 1/10/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFOS | 1/10/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFTrDA | 1/10/2024 | <7.00 ppt | 7.00 ppt | Not Detected |
| PFTA | 1/10/2024 | <8.00 ppt | 8.00 ppt | Not Detected |
| NMeFOSAA | 1/10/2024 | <6.00 ppt | 6.00 ppt | Not Detected |
| PFHxS | 1/10/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| 4:2 FTS | 1/10/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| NFDHA | 1/10/2024 | <20.00 ppt | 20.00 ppt | Not Detected |
| PFDA | 1/10/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHpA | 1/10/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
Population served record for Mason City Water Department
EPA SDWIS lists 27,338 people served and 19,000 connections for this PWS, confirm the service-area footprint on the federal report before comparing to municipal census totals.
Sources: EPA SDWIS
Nationwide peers
647 violations · 27,338 served: nearest cross-state SDWIS matches.
Cross-state systems with comparable violation load
Nearest cross-state community systems (500+ served) by total SDWIS violations on record.
Cross-state systems with similar served population
Nearest cross-state systems by EPA SDWIS population_served (same 500+ sitemap gate).
What to do with Mason City Water Department
Use this system's EPA-reported record as a starting filter, not a final verdict.
- See how every tracked system in Iowa compares on the same EPA violation measures. Iowa systems
- Check whether PFAS was detected at this system under UCMR5 testing. PFAS guide
- Find and compare another public water system by name or PWSID. Search systems
EPA SDWIS and UCMR5 figures are informational only, not a substitute for a certified lab test of your own tap water.