Method of launching long pipelines and retrieving support means therefor

A method of launching a pipeline from an on-shore site into a body of water, said method comprising the steps of:

• supporting said pipeline at said on-shore site with a plurality of ground engaging movable support means spaced along a length of said pipeline, said means of said plurality of support means being connected together by a support connecting line;
• providing a plurality of floats, one of said floats being attached to each of said support means, each of said floats having a buoyancy greater than a combined weight of the float plus the support means to which it is attached, so that said support means will float after it is disengaged from said pipeline;
• positioning a shallow draft barge off-shore from said site;
• deploying a main launching line seaward from a seaward end of said barge to a main buoy located at a position in said body of water where said body of water has a depth sufficient to allow a launch vessel to approach said main buoy, said main launching line being provided with sufficient buoyancy means to hold said main launching line above a floor of said body of water;
• connecting a pipeline launch line between a landward end of said barge and a seaward end of said pipeline;
• connecting a support means launch line between said landward end of said barge and a seaward end of said support connecting line;
• connecting a seaward end of said main launching line to said launch vessel;
• moving said launch vessel seaward and thereby towing said pipeline and said support connecting line into said body of water;
• applying a retarding force to said pipeline and thereby maintaining a tension force on said pipeline, as said pipeline is towed, sufficient to hold said pipeline above said floor of said body of water;
• connecting a trailing tow line between a trailing tow vessel and said landward end of said pipeline after said landward end of said pipeline is towed into said body of water a distance such that said landward end of said pipeline is at a position on said body of water having a depth sufficient to float said trailing tow vessel;
• applying a tensional retarding force to said trailing tow line and said pipeline by means of said trailing tow vessel to hold said pipeline above said floor of said body of water;
• connecting a leading tow line between a leading tow vessel and said seaward end of said pipeline;
• disconnecting said pipeline launch line and said support means launch line from said pipeline and said support connecting line, respectively;
• and
• disengaging said support means from said pipeline thereby allowing said support means to float to the surface of said body of water.