Industrial stormwater permitting is a critical part of environmental protection under the Clean Water Act (CWA) and state regulations. In the case of Arizona, the Arizona Department of Environmental Quality (ADEQ) is responsible for issuing and enforcing the Industrial Stormwater Multi-Sector General Permit (MSGP). The Clean Water Act (CWA) establishes the basic structure for regulating discharges of pollutants into U.S. waters. ADEQ’s 2019 Industrial Stormwater MSGP is designed to reduce pollutants from industrial stormwater runoff, ensuring that stormwater discharges meet the required quality standards for surface waters.
The MSGP categorizes industrial activities into
29 sectors, each with its own set of requirements for stormwater management. These sectors range from manufacturing to mining, transportation, and more. Rather than requiring treatment of stormwater, the MSGP focuses on the implementation of Best Management Practices (BMPs) to minimize the pollutants that stormwater can carry. These can include structural controls (e.g., stormwater ponds, drainage systems) and operational controls (e.g., proper waste handling, spill prevention), for more information visit
AZDEQ.
When is Permit Coverage Required?
- Discharge to Protected Surface Waters: If the facility’s stormwater runoff is directed into or could potentially reach protected surface waters (such as rivers, lakes or streams) directly or through a conveyance system, (like a ditch, storm drain, or street) then permit coverage is required.
- Sector-Related Activities: Industrial activity must fall under one of the sectors outlined in the MSGP. Each sector has its own criteria for stormwater discharges and management practices.
When is Permit Coverage Not Required?
- No Discharge to Protected Surface Waters: If the industrial stormwater runoff does not discharge to surface waters that are protected under the CWA — meaning the stormwater is not reaching these waters, either directly or through a conveyance — then stormwater permit coverage is not necessary.
- No Pathway to Surface Waters: If there is no direct or indirect pathway (like a stormwater system or a ditch) for stormwater to reach surface waters, the facility is not required to obtain a stormwater permit under the MSGP. For example, if the stormwater is contained onsite or directed to a non-protected area, it may not require a permit. For more information, refer to the ADEQ website on No Discharge Certificates (NDCs) or No Exposure Certificates (NECs).
In April 2024, ADEQ announced the proposed changes associated with the reissuance of the 2019 MSGP. These proposed changes to the current MSGP are outlined below.
Proposed Changes
- Consideration of stormwater control measure enhancements for major storm events when selecting and designing control measures.
- Metal Translators:
- Permit requires analysis of total recoverable metals, but some surface water quality standards (SWQS) are for dissolved metals.
- Reissued permit will use translators to set total recoverable action levels.
- Action levels will be added to general analytical monitoring.
- Action levels will be set at the lowest applicable acute water quality standard.
- Additional Implementation Measures (AIM) for Action Level Exceedances.
Permittees are required to maintain an up-to-date Stormwater Pollution Prevention Plan (SWPPP) which outlines the steps a facility will take to prevent pollutants in stormwater runoff from entering protected surface waters. A SWPPP is essential for facilities covered under the MSGP and serves as a framework for BMPs. With the finalization of the new 2024 MSGP, facilities should review the following key components to ensure the facility SWPPP is up to date.
Key Components of a Stormwater Pollution Prevention Plan (SWPPP)
- Facility Information
- Site Description
- Pollution Prevention Team
- Identification of Pollutant Sources
- Best Management Practices (BMPs)
- Monitoring and Inspections
- Corrective Actions and Annual Updates
- Recordkeeping and Reporting
- Certification and Signature
What Does This All Mean?
ADEQ has reissued the MSGP effective on January 16th, 2025. To maintain permit coverage, all current MSGP holders must submit a new notice of intent (NOI) in myDEQ within 90 days. In order to submit the NOI by the April 16th deadline, the facility SWPPP must be certified that it is up to date and align with the requirements of the new 2024 MSGP. There is no time like the present! It is essential facilities review their SWPPP and make sure it is up to date.
