Tried deep root watering on a dying maple and the ground cracked open

So I got called out to look at a 40 foot silver maple in a client's yard in Rochester that was dropping leaves in July. I figured it was drought stress, so I drilled a few holes around the drip line and stuck a soil needle down about 18 inches. Pulled it back up and the soil down there was bone dry and rock hard, like concrete. I ran water slow for about two hours and next morning there were three cracks in the lawn running out from the holes. Turns out the tree was planted over old construction fill and the roots never got past the top 8 inches. Anyone run into fill dirt like this and is it even worth trying to save the tree at this point?