An MS4 located in an incorporated place or county with a population of 250,000 or more, as determined by the latest U.S. Census.
LARGE MUNICIPAL SEPARATE STORM SEWER SYSTEM (MS4
Meaning of LARGE MUNICIPAL SEPARATE STORM SEWER SYSTEM (MS4 in English
Environmental engineering English vocabulary. Английский словарь экологического инжиниринга. 2012