Page 396 - Trenchless Technology Piping Installation and Inspection

346 Cha pte r Ei g h t

To help with future locating of installed pipes, installation of a
trace wire on plastic pipes and submission of an as-built (both plan
and profile) for all installations are required. In locations where the
road surface is elevated, the minimum depth of the bore must be
measured from the lowest side of the pavement surface.

Method
1. The ends of each section of HDPE pipe must be inspected and
cleaned as necessary to be free of debris immediately prior to
joining the pipes by means of thermal butt-fusion. The poly-
ethylene pipe must be of the same type, grade, and class of
the polyethylene compound used in the process. This process
provides joint weld strength equal to or greater than the
tensile strength of the pipe.
2. The handling of the joined pipeline must be in such a manner
that the pipe is not damaged by dragging it over sharp or jag-
ged objects. Sections of the pipes with cuts and gouges
exceeding 10 percent of the pipe wall thickness or kinked sec-
tions must be removed and the ends rejoined.
3. HDPE pipes must be stored on level ground, free of sharp
objects, which could damage the pipe. Stacking of the poly-
ethylene pipe must be limited to a height that will not cause
excessive deformation, bending, or warping of the bottom
layers of pipes under anticipated temperature condition.
4. Sufficient space must be allocated to fabricate and layout the
product pipeline into one continuous pipe length, thus ena-
bling the pull back to be conducted during a single operation.
If space considerations are discovered that make this impos-
sible, the permit applicant must obtain specific alternative
instructions from the design engineer.
5. Sufficient space is required on the rig side of the machine to
safely set up and perform the operation.
6. The drill path alignment must be as straight as possible to min-
imize the frictional resistance during pullback and maximize
the length of the pipe that can be installed during a single pull.
7. The minimum radius of curvature of HDD path must be 1200
times the nominal diameter of the pipe to be installed.
8. The required piping must be assembled in a manner that does
not obstruct adjacent roadways or public activities. The con-
tractor must erect temporary fencing around the entry and
exit pipe staging areas.
9. Several prereams may be employed to gradually enlarge the
borehole to the desired diameter and reduce road surface heav-
ing potential. No backream diameter increase must exceed 1.5