Arizona Stormwater Laws and Regulations
The state operates under the Arizona Pollutant Discharge Elimination System, through NPDES Permit (AZG2002-002) and state regulation Arizona Administrative Code (A.A.C.) R18-9-A905. There is a phase II MS4 general permit to address stormwater runoff from new development and redevelopment projects that "disturb greater than or equal to one acre, including projects less than one acre that are part of a larger common plan of development or sale, and discharge into the small MS4." The standards are only applicable in regulated MS4 areas, and Indian Lands are exempted.
Excerpt- Arizona Department of Environmental Quality Stormwater Page
On December 05, 2002, Arizona became one of 45 states with authorization from EPA to operate the NPDES Permit Program (Section 402 of the Clean Water Act) on the state level under the Arizona Pollutant Discharge Elimination System (AZPDES) Permit Program. All facilities that discharge pollutants from any point source into waters of the United States (navigable waters) are required to obtain or seek coverage under an AZPDES permit. Pollutants can enter waters of the United States from a variety of pathways, including agricultural, domestic and industrial sources. For regulatory purposes these sources are generally categorized as either point source or nonpoint sources.
Arizona is authorized to issue NOIs for construction and industrial activities under AZPDES. An AZPDES permit is required for any point source discharge of pollutants to a water of the United States. Because stormwater runoff can transport pollutants to either a municipal separate storm sewer system or to a water of the United States, permits are required for those discharges. Most stormwater discharges are permitted under various general permits. However, an individual permit is required when the general permit requirements do not accurately represent the activity at a facility and a permit is customized to the site. An individual permit may be necessary if the Limitations of Coverage section of a general permit does not allow the facility's discharge to be covered within the general permit. It is the responsibility of every applicant to determine if any of the Limitations of Coverage apply to the facility seeking a general permit.