Hi, we had a guy dig this hole, down to the soil clay pipe, he didn't come back, and we have decided to do things a different way, so i have started to fill the hole on top the clay pipe, i have poured Pea Gravel in the Gap i made in the centre of the pipe and surrounding it, and compacted it down, with my FOOT, both sides, do i go over the top the pipe with the Pea Gravel? and if so how high? or just back fill it?. thanks