Sub-Surface Water

Hi,

Yesterday I was searching for roots from trees that were removed when my block was cleared last year. I knew where they were located and started poking around only to find water down about 10cm. My block has a fall of 2m from back to front and we have not had any significant rain in the past months. I know where old trees once stood, it can leave damp conditions for quite a while being clay but my father said there is a water spring in this area but can't remember exactly the whereabouts. My worry is what trouble am I in for once my house is built(Concrete slab)? The soil tests from the builder shows that a H1 slab is required but I had another test from a different builder who said a H2 was required and both didn't mention any water problems. Anyone had this before and will it be a problem down the track e.g. rising damp?

Regards,

Jasper 26