When you start to dig deeper and deeper then you will discover just how useful it is to be wearing a strong pair of welly boots if you reach a clay layer. This is because if it rains then the hole will start to fill with water from above and /or it will start to seep from below. I found paddling around in soggy clay turned it into sticky “glue” after a few minutes and I could hardly lift my feet or get out of the hole! The bags of clay were so heavy I used a wheel barrow to move them ready for transporting to the local council tip. You may need to bale out the water if it gets too deep of course. As I went deeper and deeper I kept checking with a long straight batten and spirit level that the wooden (final water level) pegs had not been displaced. At the same time I made sure that I included a “shelf” of clay/soil in different areas where we would place various water plants later. This could range from 15 to 25 cm down according to your choice of plants. There was a gentle slope opposite the abyss hole to allow some creatures, like frogs and newts, to crawl out if needed.
To be continued...