If I have a wasp colony nesting somwhere under my deck and want to keep them from coming back next yr what can I do short of spraying them or block up hole and suffocate them?

Well from what I have read about the nature of wasps, yellow jackets, and the likes is that they never use the same nest twice from one year to the next. They even tell you to put up "dummy" nests in and around the areas of your home that you want to be wasp free. So I think my advice would be to just leave them alonefor now. And be sure to just leave their nest intact so that it will be a reminder of past usage.