Rangersedge,
It must be a fairly large creek if you are able to get enough sand/gravel to make it worth while. Therefore with that much running water the stream should be safe unless there has been some major chemical leaching from manufactoring ect. upstream. Any lifeforms brought in with the sand/gravel other than fish should benifit your new lake. If it were mine I would do as you said & store it close by long enough to let any errant minnows or fish eggs die before utilizing.
Ric
