Yes I would agree, if there is concern for the enviroment then go electric.

Saying that there is no impact to the lake/pond enviroment may be jumping the gun a bit. 5 yrs is nothing in relation to evolution. The impact will start @ the bottom & work its way up. This could take decades or more, who knows. It would of course depend on the amounts ect.
I don't know, but I do know that OIL in water is BAD. Still we fly & love it, compaired to the worlds major industry polluting we (Model Float Pilots) are just a grain of sand on a large beach.