5 Things You Need to Know About PA's MS4 PAG-13 Permit Updates

Posted by Shawn Fassl on Tuesday, April 29, 2025

Pennsylvania's Department of Environmental Protection (PA DEP) has recently announced updates to the PAG-13 General Permit for Discharges of Stormwater from Small Municipal Separate Storm Sewer Systems (MS4s). These changes aim to enhance stormwater management practices and ensure compliance with federal and state regulations.

What is the PAG-13 General Permit?

The PAG-13 General Permit regulates stormwater discharges from small MS4s. This permit is designed to minimize pollutants entering our waterways from urban and developed areas. It outlines specific Best Management Practices (BMPs) and requirements that municipalities must implement to protect water quality. DEP anticipates that the new PAG-13 permit will become effective on October 1, 2026. MS4 municipalities that are seeking to obtain new coverage or continue existing coverage under PAG-13 will need to submit a Notice of Intent (NOI) to the appropriate PA DEP Regional Office by September 30, 2026.

5 Key Updates to the PAG-13 Permit

The PAG-13 General Permit updates have significantly shifted focus towards stormwater runoff volume management, rather than pollution prevent/reduction. Here are some of the critical changes:

1. Shift to Volume Management Objective (VMO):
• The updated permit moves from primarily focusing on sediment and nutrient reduction to emphasizing a stormwater runoff VMO. This indicates a greater focus for controlling the sheer volume of stormwater runoff to reduce pollution.
• This requires an updated local ordinance to be consistent with the 2028 model ordinance.
2. Volume Management Plan (VMP):
• MS4s, especially those discharging to tributaries of the Chesapeake Bay or facing specific water quality impairments, are now required to prepare and submit a VMP. This plan details how the MS4 will achieve the defined VMO.
• Existing MS4s must submit the VMP by September 30, 2028, and begin its implementation upon PA DEP approval.
3. MEP Calculator Spreadsheet:
• The PA DEP provides a Maximum Extent Practicable (MEP) Calculator Spreadsheet to assist MS4s in determining their VMO. This tool helps quantify the volume management requirements.
4. Volume Management Credit:
• The permit outlines how municipalities can obtain "Volume Management Credit" for implementing various stormwater management practices.
• There are specifications regarding what activities can and cannot be used to obtain these credits. For example, there are specific credit values given to the planting of new native trees within urban areas.
5. Increased Focus on Green Infrastructure:
• The focus on volume management strongly promotes the use of green infrastructure. Green infrastructure practices, such as rain gardens and permeable pavement, are very effective at reducing the volume of stormwater runoff.

What These Changes Mean for Municipalities:

• Increased Investment: Municipalities may need to allocate additional resources to implement enhanced BMPs and monitoring requirements.
• Enhanced Planning: More comprehensive planning and analysis will be needed to meet the volume management and TMDL requirements.
• Collaboration: Increased collaboration with other municipalities, watershed organizations, and environmental agencies will be essential for effective stormwater management. Incentives will be provided for collaborations with other MS4s.
• Proactive Approach: Municipalities should take a proactive approach to reviewing their existing stormwater management programs and identifying areas for improvement.

New PAG-13 General Permit Timeline

1. March 19, 2025: End of public comment period
2. September 30, 2026: Notice of Intent (NOI) application submission deadline
3. October 1, 2026: Anticipated PAG-13 effective date
4. September 30, 2028: Volume Management Plan and local ordinance updates deadline

Need help or have questions with:

• Expertise to help you navigate permit changes and develop effective plans to comply with new regulatory requirements.
• Resourcing funding options for implementation of MS4 projects.
• Assistance with volume management design, project implementation and other regulatory or permitting requirements.

We’re here to help for all of your MS4 permit questions and assistance!

 

Categories: Municipal Infrastructure

Tagged: Stormwater