Cheers Eric,
The situation does look serious.
I was enquiring because of the Palm tree dropped crown post.
When I was in England we used to add a system to the outlet of the septic tank.
Using a sump pump in the tanks final stage to pump the water into pipes dug under the lawn of the clients garden, in a herringbone fashion.
But the water could be directed anywhere including to trees etc.
It's probably already being done but I just thought I'd give it a mention.
It could be used even if you were on main sewer if a tank was fitted.
Every bit helps.
Nick.