Just a heads up, if it's the Outdoor Products PU tarp I'm thinking of, it's specifically listed as "water resistant" not "waterproof".
If it's the blue one they sell at WalMart, I'm sure it's the same.
I doubt is has a DWR treatment on the nylon side, but the PU coating is going to be just as waterproof as any other polyurethane. The only stitching it has is around the perimeter, so that's the only place it would leak.