Trenching or digging to repair sewer mainlines is by far the most invasive approach.  The process involves heavy earth moving equipment used to dig a hole three or four feet wide, ten or more feet down and as long as the section of pipe intended to be replaced.  Any trees, landscape, retaining walls, or anything else in the path of the trench need to be removed.  Once work on the sewer has been completed and the dirt back filled there is still a large patch of yard that needs to be rehabilitated.

There are benefits to trenching, and in some circumstances, no option other than trenching.  Both the pipe bursting method and the liner method require a host pipe.  If the existing mainline or host pipe has completely collapsed neither the bursting method or lining method are achievable.