Question
I have 2 spruce trees, approx 30 feet tall.  They are located on the north side of Lake Ontario (I don't know the hardiness rating for that part of Canada) and are approx 200 feet from the edge of the lake itself.  Grade is going to be raised around them by between 5 to 8 feet. I understand a radiating system of tile or pipes, perforated to allow air to travel, can be installed. They are attached to vertical pipes to bring air down.  It is then filled with stones and covered so as to prevent soil etc from clogging the system.  My question is what are the chances for survival of these trees?  It will cost $3,000 to install and I am quite willing to try if there is a a better than 50/50 chance for success.  Any help would be appreciated.

Answer
WOW - what a challenge.  I would suggest you hire a local arborist for a consult.  I doubt you'll get a 50% success from this "pipe" method or any other mechanical method.  It would be closer to 20:80 mortality, if I had to lay odds. The sheer weight* of 5 to 8 feet of soil/gravel will crush the roots, and the collar of the tree, if also covered by gravel/dirt, will be prone to rot & disease.

* 1 cubic foot of dirt weighs about 40-50#, and gravel is actually heavier, at 100#/cubic ft., so a column of gravel 8 feet tall would weighs 800 lbs! Times the surface area of a tree with a 15-foot dripline, and you're talking about 700 s.f. x 800 lbs, or 280 tons of gravel!  I am also assuming you cover ALL of the tree area...

I have seen "pits" created with retaining walls at the drip zone, to save California Live Oaks, but success is illusive (and expensive!)  A 5 to 8 ft. retaining wall completely around a tree this size (15' radius, at 94 ft circumference x 5' tall) could easily run $5,000 per tree.  If you go with this option, I would use a "gravity" stacked wall (Allan Block/Castle/Versa-Lok style), and not a poured-in-place type.  You are also creating a "bathtub" for leaf litter and junk, that now become a maintenance issue.  Plus, it will look odd.

For that kind of money, I would consider a professional tree-mover, that will dig up the trees (30' isn't that big for the pros), bring up the grade, and re-plant at the new grade.  Your success rate will actually be better, at about 50:50. A local arborist in Lake Ontario can suggest an outfit, or you can do a google search.

My bottom-line advise -- You may end up spending a ton of money, and they die anyway.  Consider either moving/raising them up, or replacing them with large new tree, after you re-grade.  Large boxed pines, at about 15 to 20 ft tall run about $1,000 to $1,500 in our area. A tree mover with a tree-spade may be able to get you one or BIGGER for less.  Spend your $3,000 on replacement trees.

http://www.popularmechanics.com/home/improvement/lawn-garden/1273551

By the way, the north side of Lake Ontario is a Plant Hardiness zone 6.

Hope it helps ~Marc