I'm trying to run a new 4" dryer duct outside. I've run into an issue with space. The diameter of the hole in the photo is a little over 4". I've test fit a section of 4" duct and it fit nicely so the diameter is correct. The issue is that I'm not sure how much of the shown wood I can cut. I'm already right up against the subfloor and it looks like I'm going to have to cut some of the concrete that is showing right at the bottom of the hole. One of my main questions is what is the piece of wood right above the drill hole? In general can I cut the 4" through here?