This concept is the same as building a four plex on a one acre lot.  You would have one well and one septic on each acre.  That's plenty of space to separate the well and septic system.  This floor plan just separates the four units into individual units that still share a well and septic system.  No difference than one four plex.  It seems to be a smart way to build.  Fire risk is also reduced since each unit is stand alone.  The builder has been very responsible in this new approach.  I would be happy to own one of their four plex s.