Arizona Department of Environmental Quality
1110 West Washington Street - 5415 A1
Phoenix, Arizona 85007

Arizona Pollutant Discharge Elimination System General Permit for Stormwater Discharges Associated with Industrial Activities from Non-Mining Facilities to the Waters of the United States Measurable Storm Events

All required monitoring must be performed on a storm event that results in a discharge from the facility (“measurable storm event”) that follows the preceding measurable storm event by at least 72 hours (3 calendar days). The 72 hour (3 day) storm interval does not apply if the permittee is able to document that less than a 72 hour interval is representative for local storm events during the sampling period. In the case of snowmelt, the monitoring must be performed at a time when a measurable discharge occurs at the site.

For each monitoring event, except snowmelt monitoring, you must identify the date and duration (in hours) of the rainfall event, rainfall total (in inches) for that rainfall event, and time (in days) since the previous measurable storm event. For snowmelt monitoring, you must identify the date of the sampling event.

Magnitude: results in actual discharge

Interval between storms: 72 hours, unless less than 72 hours is representative

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