Page 76 - Trenchless Technology Piping Installation and Inspection

46 Cha pte r T w o

Circular Rectangular Elliptical Pipe arch Metal box culvert Arch
FIGURE 2.1 Common existing pipe shapes.

environmental, hydraulic, and social conditions, which often lead
to emergency repairs. Table 2.1 provides a summary of factors to
consider, grouped under surface, subsurface, and existing pipeline
conditions, pipe service requirements, constructability. and strengths
and limitations, when a project is considered for trenchless renewal
and/or replacement.
The pipeline renewal and replacement method selection process
is indeed a complicated one. As mentioned above, many parameters
and factors must be considered to reach an optimum solution. The
decision must be made during the planning phase and reevaluated
during the design and preconstruction phase of the project. The
project owner and design engineer must identify the appropriate solu-
tions and consult with contractors and technology providers during
the design and preconstruction phase. However, the decision-mak-
ing process should not be left to contractors to be decided in the
bidding phase.

2.2 Planning Trenchless Renewal/Replacement Project
The total process of a construction project includes project definition,
preliminary planning, project design, procurement of major items,
project construction, and project startup. During the project defini-
tion, preliminary planning, and project design stages, major decisions
are made concerning overall project size and complexity, project loca-
tion, time constraints, level of quality, and costs.
Generally speaking, planning is done by all the parties in different
stages of a construction project, but the initial planning is typically
done by the project owner using the services of an engineer. The proj-
ect background may also have a great impact on the planning process
itself. The planning phase for a conventional project can proceed in a
more regulated and ordered fashion than that for an emergency pipe
repair or replacement due to a collapse in a roadway (see Fig. 2.2). In
an accelerated schedule such as for an emergency, the priority of
speed of completion may outweigh all other priorities. This may lead
to selection of a project delivery system and contracting method that
allows a greater focus on speed, such as design-build, cost plus, and
the like, with a much higher cost to accelerate operations.