If I'm targeting white bass I usually fish bridge pilings with a pair of green submersible lights. If I'm after crappie, I'll usually pick out a tangle of structure on or very near a drop in water that is typically 20 feet deep or so. Crappie can be caught around the pilings but our bridges on KY Lake and Barkley are much bigger than the typical 2-4 lane highways bridges and don't hold nearly as many crappie as whites.