We are working on a walapini near Asheville, NC in a small town called Old Fort. So far, the area to be dug is on a hill, and we are digging into the hill from a lower level of land below. There is a creek nearby that is a lot lower than where we are digging, but we have hit water about 5-6 feet down. Any suggestions on this? Also, any budget-minded suggestions to roofing/venting? Heat in winter?....average lows are in the 20's in the winter, but can get down to a little below zero. I know that we can get some average-joe plastic to cover the top, but what else might be a possibility that would hold up longer over time??.....thinking at least 5 years or so. Any really basic information.......simple to understand.....would be great. We need all the guidance we can get on this project, planning is necessary in any project.