Retaining wall removal and replacement around mature maple tree
A couple of things to keep in mind if you replace that aged wall. If the new wall is not exactly as deep as the present one, and extends deeper, it will damage the tree's root system. The roots system of a tree in general are primarily in the top 18" of soil. Also, maple trees are very shallow-rooted. Any digging will damage roots, and subsequently the tree.
Construction worker foot traffic and their equipment and supplies re heavy and compact soil. Compacted soil does not allow water--and oxygen--to get down to roots. This can kill trees. Steps can be taken to reduce the compaction during construction, such as mulch paths, plywood or similar, and storing construction materials not flat on the ground. Construction materials includes stone, sand, and mulch piles. The roots of a tree can extend out 1 1/2 times the height of a tree, though the bulk of roots are within the dripline (at the edge of leaf canopy.)
It's important not to raise the soil level around a tree too much, as that can suffocate the roots quickly.
Here are some more points to consider:
Due to the tree roots buckling the existing patio, the patio is being replaced. I am assuming the landscaper doing the work is aware of the issues facing the tree. In your opinion, can this project be done to limit the chances of killing the tree. This tree was mature when we moved here 35 years ago. So we estimate it is at least 50 years old.
We would not necessarily assume that the landscaper is aware or knowledgable about protection of the tree, but you could share with them the info above.
We cannot say from afar how much disruption the replacement of your patio will be for the tree. For the best outcome we would suggest having a certified arborist out for a consultation at your site. A certified arborist is a tree health expert credentialed by the International Society of Arboriculture. They can evaluate your situation and make recommendations or perhaps suggest possible changes for best results.
Most larger tree companies have arborists on staff, but you can also search for one at www.treesaregood.org