Forced to pay 2-5 lakhs for maintenance

I stay in a flat which is constructed badly that it is 10 feet below the road. We have already paid 1 lakh plus in the past for maintenance. Our flat is in Chennai Virugumbakkam which got drowned during the recent December floods and it is recovered now spending some lakhs of amount only to drain water. Now the association members have come up with few ideas like raising the flat on either side of it just to walk out if there is a flood in future again. They claim 2 lakhs to 5 lakhs and we are retired and cannot afford to pay so much though it is our own flat. Few association members threatened that they would cut the water supply if we don't pay money and threatened that they will take legal action against us for not paying money. I happened to consult one of my friend who is a civil engineer, he saw the flat construction and made it clear it this raising of base on either side of the flat is not going to solve the problem in anyway. please advice I would like to take it legally and how to proceed