"MS4 regulated service area" or "service area" means for Phase II permittees, the drainage area served by the permittee's MS4 that is located within an urbanized area as determined by the 2010 decennial census performed by the Bureau of the Census. 

Why is the 2020 Census data not being used? or language similar to what is seen on VADEQ Permit portal "in "urbanized areas" (as defined by the latest decennial census)"?