He is there already when you are coming in and without knowing you are bumping him. You need to go in much earlier and stay put until maybe even an hour after dark. He is aware of your presence and staying bedded all day. Hunting in the valley would not work because of thermals changing through out the day. You will need to figure out a completely different access and exit route that will not encroach his travel corridor.. What you are doing now is only going to eventually bump him out of there for good. It is odd that you have bumped him so many times without blowing him out of there. There must be does holding him there at this time. Your window is short now so you need to come up with a plan now. Good Luck.