this house i'm working on (backyard patio) is about a year old. the yard wasnt pitched that great, and we fixed that....but, we notice along the foundation, that there are some spots that are real spongy(clay). i have a heavy compactor, but it doesnt help. you can step on these spots, and see the soil flex, yet it is dry on the surface, and moist below. i've dug down a few spots, but i dont want to put 2' of gravel in there. will this clay dry up and harden? or will it settle?