I built a house on a sloping site approx 10 years ago. I wanted to raise one section at the base of the site near the road exit. I asked the excavator at the time to strip back the topsoil, increase the depth of the subsoil and replace the same topsoil again. When i got back the job was complete and he said he had to use additional topsoil i had on the site. No problems of course until he is paid and out the gate. Soil settles, rain comes and year after year a person cannot even walk the lawn its so wet and soggy. The surrounding lawn is bone dry except for the raised section. I decided to dig some deep trial holes in the area in question and this confirmed the worst. So now i have a later of topsoil, a layer of subsoil (10″) and then the original topsoil again below that. Firstly would this explain the wet ground and secondly have i any option except the obvious and strip back the ground again?
If the compacted layer had been broken at the time of earth-moving before the last layer of topsoil was laid, there would be no problem and the challenge now is to find a way to break the layer and allow water through.
Over a small area you could dig holes at 2-metre centres and fill with stone to within 15cm of the surface topping off with soil. If the are is larger, you will need to lay land drains with stone around them to take the water off the compacted layer.