Page 428 - Trenchless Technology Piping Installation and Inspection

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FIGURE 9.1 Staging HDD equipment to minimize environmental impacts.

The design engineer must fully understand the trenchless tech-
nology that has been chosen and have a set of realistic expectations.
Setting realistic expectations can be difficult since the pipe is installed
horizontally and may go through different ground conditions empha-
sizing the need for obtaining good subsurface information during the
planning phase.
Accurate surface monitoring must be undertaken by the project
owner, public agency, or the contractor as a proof that the trenchless
operation did not affect the nearby structure. Sometimes the cost of
repairing pavement heave or settlement may be less expensive than
reinstatement of ground during open-cut construction which could
impact local business and traffic in a much more disruptive way. Proj-
ect engineers and owners need to consider that during a trenchless
technology project, there is a possibility of ground movement that
may show in the surface in terms of settlement or heave. The extent
of settlement or heave on the surface is dependent on many factors,
including type of trenchless method used, pipe diameter, experience
of operator, equipment used, depth of installation, and soil conditions.
With proper geotechnical investigations, planning, and contractor
and method selection, the possibility and/or extent of surface/ground
movements can be reduced tremendously.