No soakaway

[stevefx]

I bought a bungalow in april 2004.It was built in 2002 but has not been lived in and was the show bungalow of the 7 built as such was built first.Last week i started on the garden by digging a trench at the bottom to erect a retaining wall the level the garden and i came across a pipe laying about 2cm below.I followed it to one of the gutter downpipes. I then dug all pipes front and rear and found that they go about 1m then stop.I`m now worried about this causing subsidence.I Know that there is an underground culvert and the ground drain exstremely well and is not boggy,Any help is much appreciated as before this i never gave SW drainage a second thaugth