Massive Roots Growing in Drainage Pipe

The drain hole outside my house does not drain well. We found a contractor to improve the drain. When the drain pipe was cut, the hole was almost occluded by tree roots. The root size was huge. Three quarter of the diameter of the drain pipe is occupied by the main roots and there are plenty of rootlets. It is amazing to see the monster root that grow and grow and we did not know until we have drainage problem. The tree has been there for 7 or 8 years now. The power of tree. Simply amazing.