When a swine facility exists prior to the construction of a habitable structure or designation of a park as a city, county, state or federal park that would otherwise be located within the separation distance for a waste retention lagoon or pond or the separation distance for land on which manure or wastewater from the facility has been or is being applied, the separation distance requirement shall not apply to such structure or park since the owner of such structure or park is expected to know and understand that such structure or park, if located in that location, will be subject to agricultural sights, sounds, odors and other characteristics of farming from the preexisting swine facility.