in proper term, an 'underground' drain is call sub-soil drainage. It works by draining excess water from soil to your common drain. Basically it's a perforated pvc pipe with layer of membrane wrap around it. It is usually place abt 5'-8' top grass level depending on the level of your common drain. All soil need some sort of drainage to drain excess water.

If someone say no need for such area even it's just a small lawn patch, I think something is wrong there, especially when we are in Malaysia where rain is constant. Beside for all new development, most likely the land you are sitting on is of yellow soil/clay like soil, so it cannot absorb water so much.

Good luck to you!

This post has been edited by maxim concept: Jul 10 2011, 03:14 PM