MASON CITY: EPA violation history, explained

MASON CITY has a health-based violation on record, but none in the last five years - an older issue, not necessarily a current one. Population served: 2,393, over 1,080 connections.

Ranked against every other system in this dataset

MASON CITY has 17 violations on record in total, 15 of thems health-based - ranking it 1,282th of 12,903 systems by violation count, the 90th percentile nationally.

Against the IL average

IL's 560 covered systems average 5.0 health-based violations each; MASON CITY carries 15, more than typical for the state. See the lead and copper guide for why lead counts differently.

Most recent violation on record

MASON CITY's most recent violation on record is dated 2025-02-07, with the most recent health-based one dated 2009-01-07. Last reported to EPA: 05/27/2026.

The concern categories on record

MASON CITY's flagged contaminants and rule violations, grouped by what they actually mean for a filter choice rather than left as EPA's raw code list:

• Other regulated metals - flagged from: Arsenic

The most severe category on record is other regulated metals, which points toward a reverse osmosis-class filter if you want to address it directly.

What MASON CITY's record does not cover

This is what MASON CITY reported to its state primacy agency and EPA under the Safe Drinking Water Act - real regulatory record, not a lab test of your specific tap. Water quality can still change between the meter and the faucet - household plumbing sits outside what a record of 17 logged violations can see. The guide to what this data misses covers that gap.