A lady asked me to replace her old "bridge" with a new one. The old one had a ridiculous arch in it that cause many people to slip and fall if it was even slightly wet. I wish I had taken a picture of it. I put three 2×4's underneath and tapered them at the ends to meet the ground. I am always surprised by how inexpensive deck wood is. At Lowe's, a 12 foot board was only 5 bucks. I think that's cheap, but maybe I'm wrong.