No agricultural activity, operation or facility, or appurtenances thereof, conducted or maintained for commercial purposes, and in a manner consistent with proper and accepted customs and standards, as established and followed by similar agricultural operations in and adjacent to the city, shall be or become a nuisance, private or public, due to any changed condition in or about the said area, after the same has been in operation for more than three years if it was not a nuisance at the time it began. (Ord. 343 §1, 1989).