I recently had a 2nd access door to my crawl space cut in the rear of my home. The ground level under my home is about 2 ft lower than the ground level surrounding my home, so the brick mason dug about 3-4 ft down (to allow for the bottom of the floor), cut the door, built a retaining wall, & filled the bottom with sand. The recessed area flooded when it rained & the water began to spill over into my crawl space. The contractor then put mortar in the bottom topped with sand and tried to seal the retaining wall with roofing tar, but the area still flooded. The contractor said the problem has something to do with the clay soil that was used to build up the area when my home was built, but is unsure exactly why the water keeps seeping in. This project has become more complicated & more expensive than I anticipated. Any suggestions on what's going on & how to fix it.