Tapcensus

Interim Enhanced Surface Water Treatment Rule violations in Montana

5 active public water systems in Montana had a Interim Enhanced Surface Water Treatment Rule violation in the past three years, 1 of them in the latest quarter of EPA's data. What Interim Enhanced Surface Water Treatment Rule is and why it matters.

Health effects: Violations indicate failure to meet treatment technique requirements that reduce exposure to Cryptosporidium, Giardia, and other microbial pathogens. Cryptosporidium poses the greatest risk to immunocompromised individuals, infants, and the elderly, and can cause severe or fatal illness in vulnerable populations.

Systems with a Interim Enhanced Surface Water Treatment Rule violation

Latest quarter first, then largest first
SystemServesStatusRules violated, 3 yrUnresolved
Crow Agency Water System
County 		2,057 7 2
Havre City of
Havre · Hill County 		9,921 5 0
Libby City of
Libby · Lincoln County 		4,892 1 0
Two Medicine Water East Glacier
County 		1,504 3 1
Hysham Town of
Hysham · Treasure County 		262 4 0
About this data

A system is counted once if any of its violations in the past three years involved Interim Enhanced Surface Water Treatment Rule, including monitoring and reporting lapses. Rules violated and status in the table are for the whole system, not Interim Enhanced Surface Water Treatment Rule 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.