Water quality: Municipal MS4 urban area maps

On March 24, 2022, the US Census Bureau finalized Urban Area Criteria for the 2020 Census. Census urbanized areas are the primary factor EPA and states use to determine regulated small MS4 areas. The division is following the developments and is awaiting information from EPA on how the new criteria will impact MS4 permitting. View the 2020 Census 2020 Urban Area Reference Map online. Populations for each urban area can be accessed through the map viewer and are also provided in this Excel File.