My house was built in 1951. A trench, I am not sure for what purpose, was created inside the basement at the base of 2 of the walls. The trench is about 6" wide and 6" deep and runs around 1 short side and the long front side of my ranch style home (inside the basement along the base of the walls). It is filled with gravel (the top 6" below floor level are empty, and then the gravel begins--I don't know how deep the gravel is and I assume it goes right to dirt). From living in my house I have noticed that in really wet springs water will accumulate in this trench, so I guess it is to prevent flooding in the basement.

My issue is that I would like to seal this trench in order to prevent radon gas from coming in. I am going to have a radon remediation unit installed so I want to seal the trench first.

What would be the best way to ensure that there is no cracking, no future water problems, and an equal radon barrier to that of the rest of the floor? In short, I am trying to find the best way to eliminate the trench in a way that one would never know it had existed.

Thank you for your expertise,
Anya

I will assume you had the area tested for radon. Positive? Someone put in a french drain inside-is it connected to a sump pump or outside drain? Depending on how the water is coming in, you may be able to put more gravel -57 stone is used- to bring it up to within 2 inches of the floor and then lay aluminum flashing over the gravel and then mix up some quikcrete on top and smooth it off. Make sure you don't block any drains.