Question
I want to install an in-ground swimming pool.  How close can I dig to a mature Oak tree without hurting the tree?

Answer
Digging inside the dripline will cause dieback of the foliage. The dripline is the distance the branches extent out to. Also DO NOT let any machinery drive on the area of the dripline--this includes piling up of soil dug for the pool. Machinery or soil piled up will compact the soil and damage the roots. I hope this answers your question.