Fill pond to build on

[oldreptonian]

I have a small pond that I am intending to fill in/move. It is about 5x8ft and while I want to keep it in the garden I want to reshape it so that it effectively moves a few feet south.

To do this I intend to dig out a few feet to the south of the pond and fill in to the north.

The problem is that I intend to put a small greenhouse (around 6x6ft ish) over part of the infilled area. To do this I was planning on using edging or flag on edging to create a small retaining wall and then filling with sand/cement mix to around 150mm and then flags on top of that.

Does anyone have any advice as to what to backfill the pond with in order to support something like this?

Also any advice on my approach above for a greenhouse would be appreciated.

Many thanks

[seanandruby]

Fill in layers with dtp, 30/40 ml bedding layer then slabs. 150 sand cement too deep.

[oldreptonian]

Great thanks.

As I fill in the layers I think I'll have to tamp it down by hand as I won't be able to get a whacker into the section of old pond.

Thanks for the advice