Dont know if it works, but what does it look like to you?
(eladelantado.com)
Usually they put the lines 4' -6' deep i think so rodents and bugs shouldn't be an issue if the product purchased is rigid enough. It would be sharp rocks that would pose the biggest issue. To get around that you backfill with sand or pea gravel at least a foot below and above the lines. Similar to backfilling a septic drain field. Definitely wise to have forethought before installing such a spendy system.