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Water: Stormwater

Urbanized Area Maps for NPDES MS4 Phase II Stormwater Permits

2010 Urbanized Areas

According to the 1999 Phase II Stormwater Rule, the universe of the regulated small MS4 program expands every ten years based on the decennial Census definition of urbanized area.

The U.S. Census Bureau recently completed the maps of 2010 urbanized areas. These maps can be used to assist authorized states (and EPA Regional Offices for unauthorized states) as they  determine which new MS4s are located in the 2010 urbanized area and would require coverage (4 pp, 295K, About PDF) by an MS4s permit.  Municipalities can also use these maps to determine which parts of their jurisdiction are located in the 2010 urbanized area where the MS4 program would apply.  Interested parties can now access regional PDF maps that depict urbanized areas across the United States. The maps are organized by the name of the urbanized area.  Within each urbanized area folder is a series of PDFs that depict the urbanized area. The first PDF contains a reference map and additional detailed maps, while the remaining PDFs are individual copies of the detailed maps contained in the first file (note: smaller urbanized areas may contain only one map). The reference maps can be accessed from the following link:

Census 2010 Urban Area Reference Maps

Please note: The urbanized area and urban cluster are both outlined in green on the reference maps, so it's difficult to distinguish them, however the urbanized areas are labeled in regular font and the urban clusters are slightly italicized. EPA’s small MS4 program applies in the urbanized areas.

The Census Bureau also provides a series of files relating the 2010 urban areas to counties, incorporated places, and zip codes to help identify the correct urban area.

The original GIS shapefiles used to generate the maps can be downloaded from the Census 2010 Urban Area website under “boundaries and shapefiles.”

2000 Urbanized Areas

EPA developed a set of digitized maps for each urbanized area (3 pp, 422K, About PDF) as defined by the 2000 US Census.  While these old 2000 maps have been superseded by the new 2010 Census data, they are still available upon request.  To obtain copies of these maps please send an email to npdesbox-request@epa.gov and include the state and urbanized area that you are requesting.


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