Cross country cave-in is normal for MT & ND when bacfilling during the snow season. Alrhough not recommended, the proceedure protects the integrity of the pipe itself. It is mostly a unsightly visual impact however it should have some oversight so plugs can be set for traffic or cattle untill full settlement is complete. To be concerned with removing the snow requires more risk to safety and integrity in most cases. basically the snow melts under the backfill on top and then the snow settles slowley around the pipe. Pipelines need room to flex when under hydrotest and to flex under the pressure of the snow gives more cushing then the melt slowly fills the voids around the pipe. Next, the void migrates to the top of the ditch line and a rebackfill fill the top void.