Next step, 3 inch hole for radon mitigation.

Start by placing the 3” pipe on the floor and drawing a circle around it.piping lay out The pipe needs to be at least 3” in diameter or you will not be able to get your hand down in the hole to remove the dirt, gravel, clay, etc.….  If you have a concrete core drill machine it will make your job a lot easier, if not you will bedrill concrete holes drilling several holes around the circle to chisel out the concrete for the radon pit. Make sure you drill it out just outside your circle as you need make sure the pipe fits in the hole easily. Placing a vacuum cleaner near this will make clean up a lot easier and you will not be breathing  all the dust, I do not recommend pouring water on it as the dust cement will turn hard if not cleaned up quickly.     A 1” SDS rotary hammer drill makes this much easier and with the chisel attachment makes everything better, but if you only have a regular drill go ahead and get out the safety glasses, hammer and chisel, the next hour is going to be long.