To realize just how spongy the ground is around the swampland of Louisiana, you really have to be down there. Semis going by on the highway, you can feel the ground move up and down. I had to turn down the sensitivity of my car alarm on vibrations, because of ground flex from passing semis. The highways themselves need patching far more often, because the ground isn't a solid as you would think. It surprises me none at all, that the ties are rotting. Even though they are chemically treated to prevent it, over time that breaks down.