Air Qualityi
Water Systemsi
Water Violationsi
8TRI Facilitiesi
Active NPDESi
Air Quality — McHenry County (2025)i
AQSThe Air Quality Index measures how clean or polluted the air is on a given day. AQI is reported at the county level. A score of 0–50 is considered good; 51–100 is moderate; above 100 may be unhealthy for sensitive groups.
Median AQI
PM2.5 Daysi
118Ozone Daysi
154Drinking Wateri
SDWISPublic water systems registered to serve this area. Community systems (CWS) provide water to residents year-round. Transient systems serve places like gas stations or restaurants. Violations indicate a system failed to meet federal drinking water standards.
Community Systemsi
1Active Systemsi
2Recent Violationsi
8Recent Violations (Last 5 Years)
UNION
Toxic Release Inventory (TRI)i
TRIFactories, refineries, and other industrial facilities that use or store hazardous chemicals are required to report their releases annually to the EPA. Being listed here does not mean a violation occurred — it means the facility is transparently tracking its chemical usage.
Reporting Facilitiesi
2With Chemical Datai
1Total Reported Releasesi
2.3K lbsWastewater & Stormwater Permits (NPDES)i
NPDESUnder the Clean Water Act, any facility that discharges wastewater or stormwater into rivers, lakes, or streams must hold an NPDES permit. "Effective" means the permit is currently active and the facility is authorized to discharge under its permit conditions.
Active Permitsi
4Expired / Terminatedi
4Cleanup Sites (Brownfields)i
EPA BrownfieldsFormer industrial or commercial properties where contamination has been found. "Remedy Complete" means cleanup is finished. "Construction Complete" means cleanup infrastructure is built but monitoring continues. "In Progress" means the site is still being investigated or cleaned up.
Leaking Underground Storage Tanksi
IL EPAUnderground storage tanks (commonly at gas stations) can leak fuel and chemicals into soil and groundwater. "Open" means the leak is still being investigated or cleaned up. "Closed" means the site received a No Further Remediation (NFR) letter — cleanup is done.