I was hoping someone could give me some insight as to why at one clients house, pipes are coming to the surface after winter. It happens in certain areas of his property, not the entire property. Pipes can rise to the surface (only thing holding them completely popping out is the grass/roots) as much as 1' per winter. The client burried a conduit for wire to his cabano that intitally was around 2 1/2 ' deep and that come completely to the surface after a few years. Valve boxes raise out of the ground by about a foot every winter as well. The soil is clay.