Our builder installed, as a part of the "package", an irrigation system when our home was built last year. In the fall, we had the landcape company (the installers) shut it down for the winter. I've noticed that, over the winter, the irrigation lines are now exposed. Do I place more planting soil over it, then mulch? Or just mulch? The soil is pretty bad and I need to amend it this year before planting anything. Thanks!