The previous owner routed a downspout into a treewell so when it rained, the treewell filled with about 150-200 gallons of water. That water worked it's way into the mortar joints of the fireplace chimney about 20' away and then into the cleanout pit which has it's access door in the basement. Now the rain fills the pit and spills out the door. Fortunately, we have a floating slab basement so I can divert much of the spillage into the 1" trench but the underfloor area saturates eventually. When it does, the water then spills onto the basement floor. One idea I had was to install a 1-1 1/2" PVC pipe into the cement block wall fireplace chimney and route it to a nearby sump pump well. Is there any other way to seal the below ground level mortar joints besides digging down outside and sealing them externally with mortar? Any ideas would be appreciated.