[Cob] foundation on unstable caly with high water table

[Christo Markham * CobSolutions]

We want to build a small cob studio, 5metersx 7meters. 
The problem is we are here in the Netherlands far below sealevel. 
With unstable clay ground and a very high water table after 40 centimeters we hit water. Any suggestions for the foundation? 
We are thinking of dumping as much sand as we can to get something in between the water and the floor.
Typically they drive 20 meter piles in the grond to build the foundation ringwalls onto. This isn't possible as we are only accesable with wheelbarrows.