Question
We have recently moved to the east end of long island and I am discovering there is an area in our garden that it is soggy and holds and the soil smells foul.we had top soil put in but I think he compacted it with a machine.all the other areas drain well and have sand below.what should we do??

Answer
"Soggy" and "foul" sounds like a compost pile gone bad.

Absolutely without a doubt, the odor is produced by anaerobes -- bacteria that thrive in the absence of air, a condition that is produced by too much water and lack of drainage.

Sand may lie underneath, but the barrier between the sand and the decaying organic matter above it will prevent air from flowing down and killing the smelly anaerobes and their waste.

We don't like the way anaerobic bacteria smell because they are sometimes  pathogens.  This isn't just unpleasant.  It's potentially unhealthy.  The cause may be something as simple as buried fish parts or too many leaves.  While anaerobic composting is a perfectly legitimate system, it does take longer.  But the fact that you have a drainage problem is still a problem, and it should be taken care of.

I would ask your landscaper to drill through into the sand and allow the water to escape.  A dry well may be needed, diversion of water may be needed -- it is impossible to solve reliably without an on-site visit.  Compacting the soil of course is not going to solve the problem; don't ask the person who "solved" this that way for further solutions as they simply are not familiar with the situation.  If possible, I would contact the previous owners; now that you have taken ownership of the property, they may have something helpful to say about this that will lead to an intelligent decision.  People at the East End DO NOT have this problem; as you know, sand is only inches from the surface, and sand NEVER compacts.  Keep me posted,

L.I.G.