pondliner under marble countertop?

[Lynn Harrison]

Hello, I need a solution for making darn sure a bathroom vanity top is waterproof. It is in a small trailer. The main electrical box backs out under the vanity. The sink will be 2 feet away from it but I am still concerned in case of too much spillage on the countertop.

I have a nice piece of marble cut to fit the vanity. I am wondering if I can use pond liner under the marble or if it needs a completely stiff surface. The pond liner would be sitting on a rough plywood surface. The marble is about 4 feet by 16 1/2 inches and is 3/4 inch thick. Fairly heavy- I can't see it moving much once sliconed down, but I suppose the rubber pond liner might accentuate any vibration.

It's either that or hardiboard, but I'm not too keen on the hardiboard idea as a seal on the edges might fail over time.

Anyone know the answer on this one? Or have a better idea? And no, I can't move the electrical box.