The Pennsylvania Department of Environmental Protection's Bureau of Watershed Management issues MS4 permits. These permits govern storm water discharges from small Municipal Separate Storm Sewer Systems (MS4). As an MS4 permittee, Radnor Township must comply with 6 Minimum Control Measures (MCM's):

• MCM #1: Public Education and Outreach on Storm Water Impacts
• MCM #2: Public Involvement /Participation
• MCM #3: Illicit Discharge Detection and Elimination (IDD&E)
• MCM #4: Construction Site Storm Water Runoff Control
• MCM #5: Post-Construction Storm Water Management in New Development and Redevelopment
• MCM #6: Pollution Prevention / Good Housekeeping for Municipal Operation