BigSki, I wouldn't think so... the lean-to will be heated & the tunnel has a cement pad above it that I had poured a year ago. The length of the tunnel will be about 11FT, probably be quite cool though.
Ed, tunnel width is 5ft, so yes to a dirt ramp @10 - 12 degree grade & a narrow walkway with stairs for me to travel too.
I'm just about done the 1st 14" cut as far back as I want to go for now, cut an entry ramp to get down to lower level to make another 16" cut. And then go across the length to the basement on that 2nd level, digging the face of the wall till I reach the house basement. Then I'll dig down to the 7ft entrance level that I want at the basement opening and work my way back from there maintaining the 10 - 12 degree incline on one side.... hard to explain