Division of Water Pollution Control
Attn: Permit Section
PO Box 19276
Springfield, Illinois 62794-9276
General NPDES Permit for SW Discharges from Industrial Activities
Only reference to measurable storm events in quarterly visual monitoring.
Your visual observation must be made on samples collected as soon as practical, but not to exceed 1 hour of when the runoff or snowmelt begins discharging from your facility. All samples must be collected from a storm event discharge that is greater than 0.1 inch in magnitude and that occurs at least 72 hours from the previously measurable (greater than 0.1 inch rainfall) storm event. The observation must document: color, odor, clarity, floating solids, settled solids, suspended solids, foam, oil sheen, and other obvious indicators of storm water pollution. If visual observations indicate any unnatural color, odor, turbidity, floatable material, oil sheen or other indicators of storm water pollution, the permittee shall obtain a sample and monitor for the parameter or the list of pollutants in Part E.5.d.
Magnitude: greater than 0.1 inches
Interval Between Storms: at least 72 hours