Getting council permission to build underground may be a problem .
You  will have to think with imagination and be quick with decisions and to  think on your feet.
There will be challenges and hoops to dance threw as  they change the rules as you go.
Be methodical in your first  presentation and be quick to hand out a pen and paper and get them to do  there sums as to the engineering of the structure.
This will show there  talents or there foolishness to there objections.
If they don't have  the figures on them just say to use the existing figures and work them  back to the original results.
If they can not then they may not be  capable and there fore ask for some one who can do the sums.
If they get  really aggressive in there outbursts then ask for there qualifications as  they may not have any.
Remember to always to be polite and courteous as they hold the whip hand  and they know how to use it.
How do I know these things?
From experience with the Wollongong council when I tried to get a small cottage passed, and they cost me over $150,000 and nearly sent me broke. They actually sent my son broke with there incompetence.Names not changed to protect the identity of the offending council.
Extract from the Sydney morning herald.
Best of luck with your project.
The below article shows the extent of the problem of getting your  project passed, 
                                              Housing shortage will hurt the poor                                      
                 JACOB SAULWICK             
March 12, 2009          
THERE IS no lack of land in Australia, but a growing  shortage of housing.
A housing advisory group set up by the Government warned  yesterday that the country could face a shortfall of up to 1.5 million  homes in 20 years if construction did not increase.
They didn't need to set up an advisory group I would have told the government that for free. 
Cheers Stewart