Working out sub surface irrigration

I am applying for a permit for a wastewater treatment plant to local council

I had the plumber out and notified him that I was using the biolitiyx system

He talked to the council and due to landslip category on the land M2 I have to lay out 100 mtrs (1000sq mtrs) of sub surface irrigration which seems alot to me .Does anyone know the formula to work this out ? I thought it was 15

I am on two and half acres but there is alot of trees on the block

I was also told if I cant come up with something suitable that they can knock back the permit to build the house(even though I have a planning permit issued) which is a bit scarey

Can I use a composite toilet and a grey water system would that help ?


Any ideas to help me would be great


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