Tapcensus

Chlorine (MRDL) violations in Montana

10 active public water systems in Montana had a Chlorine (MRDL) violation in the past three years, 2 of them in the latest quarter of EPA's data. What Chlorine (MRDL) is and why it matters.

Health effects: Acute high-dose exposure to chlorinated water can cause eye and nose irritation, stomach discomfort, and nausea. Chronic exposure above the MRDL is primarily a concern because elevated chlorine accelerates formation of trihalomethanes and haloacetic acids, which are associated with increased cancer risk over time.

Systems with a Chlorine (MRDL) violation

Latest quarter first, then largest first
SystemServesStatusRules violated, 3 yrUnresolved
Busby Community Water System
County 		535 2 1
Ashland Community Water System
County 		210 3 0
ST Ignatius (mission) So.side
County 		356 2 0
Lame Deer High School
County 		291 5 2
Pretty Eagle School
County 		188 3 0
Arlee
County 		124 2 0
Mission Dam Water System
County 		87 2 0
Schley Water System
County 		85 2 0
Dixon (old Agency)
County 		72 2 0
Blackfeet Dorm. Water System
County 		66 2 1
About this data

A system is counted once if any of its violations in the past three years involved Chlorine (MRDL), including monitoring and reporting lapses. Rules violated and status in the table are for the whole system, not Chlorine (MRDL) alone.

Source: the U.S. EPA's Enforcement and Compliance History Online system (ECHO), which publishes the federal Safe Drinking Water Information System. EPA's terms and values are shown as published. The Montana records are from EPA's data refresh of Oct 7, 2026; EPA refreshes this data quarterly, and states report to EPA with a lag of three to six months, so the newest violations may not appear yet.