PA Department of Environmental ProtectionMunicipalities and other entities, such as universities and prisons, that meet certain standards must obtain NPDES permit coverage for discharges of stormwater from their municipal separate storm sewer system (MS4s). The part of the municipality regulated by the permittee's MS4 permit is the portion of the municipality designated by the 2010 Census as urbanized area, plus any additional areas designated by the 2020 Census as urban areas with a population of 50,000 or more. This dataset was created using two shapefiles from the Census Bureau. The census data is a snapshot in time. When data from the 2030 Census becomes available a new dataset will be created. This dataset shows the current area regulated by MS4 permits throughout the state.ArcGIS FeatureLayerhttps://hub.arcgis.com/datasets/565615e7cc22438884556fdc13dc3cae_0engPennsylvania Department of Environmental ProtectionPublicMS4 Regulated Areas [Pennsylvania]Web servicesPennsylvaniaLast Modified: 2026-01-08