[TowerTalk] Engineering advice on above ground foundation

[Rudy Bakalov]

I have a rather complex situation that certainly can benefit from the collective wisdom and experience of this reflector.
My property has a very high water table and as a result my builder and I decided to build the tower foundation mostly above ground. Specifically, we dug a hole, filled it with compacted gravel that is above the water table, covered the gravel with very thick sheets of plastic, and inserted 2' styrofoam boards around the base. Then we poured the concrete.  As a result, only about 1.5' of the foundation is below ground, 3.5' are above.  The overall dimensions are 10' x 10' x 5'.
Now I wonder what are the additional engineering issues we need to address to make sure the foundation will last and the 90' AN Wireless tower will stay up.  Currently, we have identified the following next steps:
1) Waterproof the concrete using silica based solutions, such as Penetron, Xypex, etc. as permanent solution against water getting into the foundation2) Add extra waterproofing using tar/asphalt-like solutions to make sure we have extra protection should cracks emerge3) Add styrofoam boards to prevent against freezing (it gets as cold as -25F in Ontario)4) Backfill around the structure to create a mound that takes the rain and melting snow water away from the concrete. I have also proposed we layer more plastic sheets about a foot below the mound surface to make sure no water gets near the foundation
Any further comments and suggestions will be greatly appreciated.
Rudy N2WQ