Rick, I have superior drainage, except for my bog area where everything drains to. That entire lower area stays wet even after months of drought. So where the cold frame was in the photos and where the tunnels were has very good drainage. For the cold frames I often use leaves and grass clippings or compost to insulate the sides, for the tunnels they were just left out in the open most of the time, when really cold weather was expected I used bagged leaves or threw a cover over them.
