decomissioning a septic tank

Hi guys,
We are in Perth and have finally decided to go ahead with our reno. We are connected to mains sewage about 5 years ago but we never decomissioned our septic tank. Now the law states b4 any building over an old septic the septic has to be drained and filled in and you have to have the receipt of a licensed person to show the council and water authority you have done it. Anyway I dug up the old tank and all the waste has turned solid (compost by now) so cant be pumped out. Do you think it would be ok to back fill and compact down, the council states that the bottom of the tank needs to be broken up but I dont see how we can get to the bottom as 3/4 full with composted poo. Any hints?
Cheers Seamus


More...