Page 222 - Trenchless Technology Piping Installation and Inspection
P. 222

186    Cha pte r  F i v e


     5.3 Maxi-HDD Considerations
          Maxi-, and larger-size Midi-, HDD operations are commonly used for
          obstacle crossings, such as a river, lake, roadway, an environmentally
          sensitive area, and shore approaches, or a combination of such situa-
          tions (see Fig. 5.3). Product pipe selection (material, wall thickness,
          grade, coating, and others) is an important part of the HDD design
          process.
             The  American Society of Civil Engineers (ASCE) Manual of
          Practice (MOP) No. 108, Pipeline Design for Installation by Horizontal
          Directional Drilling, and American Society for Testing and Materials
          (ASTM F1962), Standard Guide for Use of Maxi Horizontal Directional
          Drilling for Placement of Polyethylene Pipe or Conduit Under Obstacles,
          Including River Crossings, provide overall guidelines for a Maxi-
          HDD operation, addressing preliminary site investigation, safety
          and environmental considerations, regulations and damage pre-
          vention, bore path layout and design, implementation, and inspec-
          tion and site cleanup (ASCE, 2005; ASTM, 2005).


          5.3.1  Site Investigation Requirements
          As in any construction project, the first step in an HDD installation
          is a thorough investigation of the site at which the work will be
          undertaken. As part of this investigation, a route must be selected
          with sufficient space for the various HDD equipment and opera-
          tions. Figures 5.4a and b illustrate the space requirements for the rig
          and product pipe sides of the operation. An appropriate site inves-
          tigation will also include both surface and subsurface surveys.
          Although each survey may be performed by different specialized
          engineering consultants, it is important that the results be integrated
          onto a single plan and profile drawing, which will be used by the
          contractor to price, plan, and execute the HDD operations. Accurate
          measurements for this drawing are important, as it will be used by
          the contractor for downhole navigation.
















          FIGURE 5.3  Maxi-HDD installation to cross beneath obstacles.
   217   218   219   220   221   222   223   224   225   226   227