I am searching for expert opinion (possible witness). I have home on
Lake Minnetonka in Orono, Minnesota. Last year I constructed a
permanent dock structure (two 40 X 20 slips, pier style piling 10"
diameter).

This past winter I had damage do to ice movement on the lake. I was
not provided a permitted to de-ice (using a bubbler) do a new
moratorium on the lake by the Lake Minnetonka Conservatory District.
My neighbor (within 20ft of my dock) was grandfathered a permit he
de-iced which opened water around my  pilings/dock which allowed the
ice to move toward shore damaging my dock.

With that crib tic explanation I am searching for expert opinion that
the ice movement was due to neighbor over de-ice.

Hello,

   By what you've provided it's provisionally "plausible" that broken
ice from your neighbor collided with your dock and damaged it. But
without much greater detail I think it'd be a stretch to expect anyone
on Google Answers to expertly support your assertion.

   Here's something you could do: Survey other homes along the
shoreline. Ask for anecdotes from owners pertaining to property damage
due to broken ice. If you can demonstrate a strong relationship
between broken ice and property damage, then you may be able to at
least have your neighbor's de-icing permit revoked in the future. As
for the existing damage, I don't see how it would be your neighbor's
legal responsibility, as long as the permit was granted legally.

   In fact, if broken ice is a liability along your lake, then how is
it that the spring thaw doesn't wreak havoc on a yearly basis? Why
hold your neighbor responsible for something that Nature itself will
impose with the changing of the seasons?

I grew up on the shores of the Duluth Harbor and spent many years
watching the movemnts of the ice and the way that the ice behaves. 
When you have ice all the way up to a piling it will move that piling
with the force of a train.  It was irrelevant as to whether your
neighbor was de-iced or not, either way if the ice felt like moving it
was going to move, and there was nothing that was going to stop it.  I
have been standing on the ice of the Duluth Harbor when as a result of
temperature expansion the ice decided that it had to be 18" to further
south-east than it was.  The force of the ice suddenly shifting threw
me to the ground, shot rocks along the shore line into the air, and
knocked pictures, ect. off walls in teh houses along shore.  The only
way that your neighbors deicing would have any effect on ice damage to
the piling of your dock would be if ALL of your neighbors were
de-icing with the only stress point remaining for the ice to work on
being your dock.  I hope that this answer is helpful.