Seabed backfill plow and method

A method of backfilling spoil into a seabed trench comprising using a plow comprising a chassis comprising a single elongated member defining a longitudinal axis along a continuous portion of the elongated member and aligned in a direction of anticipated movement of the chassis during launch or retrieval, a tool end disposed at a first end of the elongated member, and a skid end disposed opposite the first end of the elongated member and situated lower than the tool end of the elongated member;

• a skid disposed proximate to, and configured to, support the skid end of said chassis above the seabed;
• moldboards mounted on said chassis forward of said skid proximate the tool end, said moldboards sized and oriented to span the trench and funnel spoil disposed on the seabed laterally of the trench toward the center of the trench as the plow travels forward on the seabed;
• and a blade mounted on and spanning bottom edges of said moldboards, the blade configured to collect the spoil in its path as the plow travels forward on the seabed, said blade having a passage at a rear apex thereof configured to dispense spoil collected by said blade and funneled by said moldboards to said passage on top of a pipe disposed in the trench below said passage;
• the method comprising:
• propelling the blade to travel forward on the seabed substantially parallel to the longitudinal axis and collect spoil along the sides of the trench;
• using the moldboards to funnel the collected spoil toward a rear apex of the blade;
• and
• allowing the funneled spoil to be discharged through an opening in the blade apex and onto a top surface of a pipe disposed in the trench.

A method of backfilling spoil into a seabed trench comprising:

• propelling a backfill plow on the deck of a vessel toward and across a fulcrum on a stern of the vessel, the backfill plow comprising a chassis comprising a single elongated member defining a longitudinal axis along a continuous portion of the elongated member and aligned in a direction of anticipated movement of the chassis during launch or retrieval, a tool end disposed at a first end of the elongated member, and a skid end disposed opposite the first end of the elongated member and situated lower than the tool end of the elongated member;
• a skid disposed proximate to, and configured to, support the skid end of said chassis above the seabed;
• moldboards mounted on said chassis forward of said skid proximate the tool end, said moldboards sized and oriented to span the trench and funnel spoil disposed on the seabed laterally of the trench toward the center of the trench as the plow travels forward on the seabed;
• and a blade mounted on and spanning bottom edges of said moldboards, the blade configured to collect the spoil in its path as the plow travels forward on the seabed, said blade having a passage at a rear apex thereof configured to dispense spoil collected by said blade and funneled by said moldboards to said passage on top of a pipe disposed in the trench below said passage;
• allowing the backfill plow to rotate about the fulcrum as the backfill plow crosses the fulcrum and is released from the fulcrum into the sea;
• lowering the released backfill plow at a towing line end to the seabed;
• and
• towing the backfill plow to backfill the trench by using the moldboards to funnel the collected spoil toward a rear apex of the blade of the released backfill plow and allowing the funneled spoil to be discharged through an opening in the blade apex and onto a top surface of a pipe disposed in the trench.