standing water beneath a concrete basement floor
After years of living with a flooding basement, we had a waterproofing company dig a perimeter trench in the basement, leading to a sump with a pump. For two years, we joyed at the dryness of the basement and, especially, the sound of water filling the sump and being pumped out (often at 5 gallons/min). With the flooding problem out of the way, we hired a contractor to finish the basement (new walls, new wiring, new carpeted floors in the living space, a new tile floor in the bathroom, etc.. . ) During the renovation, the plumber discovered that the sewage pipes beneath the concrete basement floor had corroded badly; these were the pipes leading out to the sewer and connected to pipes coming down the walls. So, the plumber dug out a large area of the basement, an area about 6 ft x 12 ft and to a depth of several feet, to lay PVC pipe. During the dig, he had to remove the black plastic tubing along the drainage trench. He then filled in the entire area with gravel stone, then put down a concrete floor.
Several months later, we had a hard rain, 2" in 24 hours, and I noticed a large area of wet floor in the basement. Even more discouraging, very little water reached the sump pump over the next 48 hours.
I fear that the plumber screwed up the drainage system that worked so well before he dug up the basement. He said that he did what was necessary and refused to admit that his construction was responsible for either the wetness or the lack of sump pump activity. So I called back the waterproofing company, and they dug through the floor at selected locations to ascertain the problem. We saw that the black pipe in their trench had been crushed, that the underfloor was not full of gravel (to the underside of the concrete floor) and, worst of all, there was standing water under the floor, probably extending the entire area of the dig.
The waterproofing people suggested re-routing the trench around the dig (which I will do). But I worry that the area that was (partially) filled with gravel will now become ‘lake basement’ after every rain, and the water – not able to ‘run uphill’ to the re-routed drainage trench, will sit for month evaporating and corroding everything accessible. It seems to me that the dig area should have been – and should be – filled with concrete, compacted soil or something that would not have become a lake, something that would have prevented water from collecting at a depth lower than the drainage trench. However, I don’t know the rules of construction in such circumstances, so I’m appealing for help from the experts on this matter. What should have been the correct procedure for filling in the hole? How should the drainage trench have been repaired? And, what should we do now to prevent water damage in the future?
ILS^2
