I have a 12"x12" metal box that was under some 30+ year old tile in my basement. Does anyone know what this is here for, and should access be maintained to it? Under the metal it is definitely hollow based on the sound from knocking on it, but there doesn't seem to be a good way to open it (and I'd prefer not to without some idea of what it could be).
The house is in Ohio and was built in the 1960s. The box is about 3 feet from the pipe cleanout & water regulator. It is flush with the slab other than the rust which is flaky and slightly above the concrete slab. There is a ~1mm thick layer of black tar that presumably used to cover the whole thing but is now only present in the top left corner.
Edit
Based on comments, I decided to pry up the metal plate. It was covering a metal grate the appears to just lead to pea gravel. Anyone know if pouring pea gravel and cement to fill the hold is acceptable? I'd like to put flooring over this.
Best Answer
From the size and location, it's most likely a sump for ground water drainage, where someone had a sump pump at one time. If your basement has never flooded, it might be that someone fixed whatever hydrological problem required a sump and pump, so they covered it over once it was not needed any longer.