on a small section of a house, the area is about 8x12 of grass. it always looks excellent. last year and this year we've had a ton of rain, and i noticed there were sink holes developing. when you walk across it, in spots, you'll go down litterally 4-5 inches. it really made the lawn look terrible this year, weeds developed in the soil areas where the holes are, etc. customer told me some years back there was a huge tree in front, and the roots are now rotting away. how would you fix this? if i just add soil, even compacted the soil afterwards, wouldn't it do the same thing eventually? do you have to rip the lawn up and dig these roots out?