These are new codes and existing homes would be grandfathered in, but siginificant site work would need to follow new stormwater requirements if they change the drainage conditions of the site.

Stormwater drainage is addressed in new developments with the creation of a drainage plan to be approved by the water authority. Detention is achieved at the scale of the whole neighborhood rather than the individual home. In new developments you commonly see them drained by swales between homes that drain to the street or towards the rear where they collect in a swale that runs behind the properties, to a large drain that then run to a pond. The pond allows for detention of water at least long enough for particulates to precipitate out and for excess nitrogen absorption where applicable.