can i use eastern hemlock to build a dock?

Answer 1

It's primary uses are for general construction, boxes and crates, retaining walls and pulp. You could build a dock with it, but you would have to have it treated and be vigilant in keeping up with the maintenance of it.

Answer 2

You might want to go with pressure treated wood naturally to build a dock. The link below is very informative, and will give you advice on environmental factors, permits, etc.