Gripe of the day - What is yours?

[rowdy]

Just got home from work. Met the contractors this morning before I left, and searched for a reason for the collapse.
When I moved into the property, the previous tenant erected a terribly built utility room on the side of the house, as has been done with every house in the street. I immediately tore it down and re built it.
However, the previous tenant took the downpipe from the house and diverted it into a blue water butt (the kind used on building sites to fill with water to knock up with) that was just left to fill up and overflow with nowhere for the rain water to go.

When I rebuilt the utility room, I dug down to the footings of the house and built up a kind of French drain, creating a channel with engineering bricks and concreting inside the channel with a fall to the waste drain about a meter along the house and filling it with shingle thus creating a run off and somewhere for the rain water to go. The outside tap is above this and after running it for a period it appears that over time this has now failed and allowed the water to disperse into the ground.

Now, what neither I or the contractor can quite understand is how and where tue sheer amount of soil, a mixture of sandy loam, clay and such has disappeared to.
There are working sand pits still, around a mile ir so from my home. The property was built 100 years ago originally for workers that were building the local railway line so whether there was some historic mining for materials I don’t know. Maybe there is a fissure under the ground somewhere below the property, but to put in perspective quite how much ground has disappeared, the contractor has ordered 17 bulk bags of shingle and type 1 mot! Which to me seems excessive for rain water run off from the narrow end of the house (pitched barn end, approx 4m length of gutter.