The backfill pipe installation assembly uses {HEAD ~ a backfill hopper} to simultaneously install {TAIL ~ drainage pipe} above the trench floor and envelop the drainage pipe in backfill material to maintain the drainage pipe at a constant height above the trench floor 
to simultaneously install
The backfill pipe installation assembly uses { HEAD ~ a backfill hopper } to simultaneously install { TAIL ~ drainage pipe } above the trench floor and envelop the drainage pipe in backfill material to maintain the drainage pipe at a constant height above the trench floor
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH