Help!!!

I built my dream home on a rocky hillside in upstate NY.

While excavating for the driveway I may have damaged my Maple tree.

The maple is about 30 years old and is perched on a rock outcropping.

It roots are sprawling in every direction for all to see before they
descend beneath the soil. It was necessary for the drive way to cut in
about 12 feet from the base of the tree.

In doing so, I remember encountering, and severing one root that was
about 3 inches in diameter. Looking back I'm afraid it might have been
the tap root for the tree. There isn't much soil beneath the tree
itself. The tree literally sits atop a rock. The soil was deepest
where I cut the driveway.

I wish I had the foresight to preserve any all encountered roots.

Long story short I retained the excavated area with a laid up dry
retaining wall and have watched the tree grow frailer with each
passing season.

That was three years ago. What might I do to save this handsome tree?

Feeding? Watering?

If anyone has advice I would appreciate some.

I'm concerned that one more year and I will have to remove the tree.

Thanks, Dante