Q.Blue Atlas Cedar
Are blue atlas cedar roots invasive and how far away from a pool could a 25-30 year old tree be without risking roots damaging pool?

Certified GKH Gardening Expert
I would not plant it any less than about 25 or 30 feet from the pool. They have quite the root system, and it will damage foundation or any other structure nearby. Though the roots can be found deeper, most will stay closer to the surface. This is no good for being near a pool.
Even planting that far away, the tree can reach about 40 ft across. This means that even if you satisfy the root room requirement, you may still be looking at the branches to overhang the pool.
https://www.gardeningknowhow.com/ornamental/trees/cedar/caring-blue-atlas-cedars.htm