I could give you some hint on its construction but nothing about standards. In fact, I would be interested myself how to follow that up and with whom as I doubt the local council is good enough.

We used to make these @1000cubic meters and the bottom part (cone with column studs) weighted around 125 tonnes and was heat treated to 1100 degrees Celsius prior to seat it on the support columns.

How about:

BS EN 1993-4-1:2007

Eurocode 3. Design of steel structures. Silos

http://www.techstreet.com/cgi-bin/detail?doc_no=BS_EN|1993_4_1_2007&product_id=1402447

How big is this tank gonna be?

As I see the code book ain't cheap and at this stage it looks as if the support columns might have to be extended up on the side of the tank (meaning the cone and the lower end of the cylinder has to be the same gage) if the tank is a monster size.