Page 79 - Trenchless Technology Piping Installation and Inspection

Existing Pipeline Renewal and Replacement Methods 49

establish the conditions and limitations of the project along with set-
ting the project priorities. Many of these factors may be available
through existing pipe records, such as original installation data
such as, age of the existing pipe, type and class of existing pipe mate-
rial, diameter, profile and alignment, size of trench, and backfill
materials, bedding, and compaction, history of pipe problems with
solutions provided (such as leaks or collapse, overflow, and types of
repairs and/or actions taken in the past).

Screening of Alternatives
This activity will provide a general screening of potential solutions
based upon the technical conditions and needs of the project. The
purpose of this activity is to further eliminate candidate solutions,
and identify the type of design data that must be collected for the
project to proceed.

Data Collection
This activity includes investigations that provide the information
required to evaluate and screen candidate alternatives for consider-
ation in the design phase. Data collection may provide information
relating to flow conditions, physical conditions, subsurface condi-
tions, and existing pipe conditions. Surface survey, geotechnical
investigations, and internal cleaning and subsequent inspection of
existing pipe (with use of CCTV or other methods) will accomplish
this goal.

Evaluation and Selection of Alternatives
This activity includes the final screening of alternatives and the selec-
tion of alternatives for proceeding into design. The final screening is
based upon the preliminary known data in addition to the data col-
lected during this activity.

2.2.2 Design Process
Pipe-renewal design involves a set of equations considering factors
such as groundwater, soil, traffic loads, and other loadings condi-
tion. As for any structural design, there are many variables and
parameters used in the design of the pipe wall thickness, including
material properties, pipe geometry, and loading conditions, includ-
ing assumptions for a safety factor and long-term material proper-
ties, which provide the required performance requirements to resist
the loads. There is no single design equation that can be used for all
different conditions that must be taken into account for the proper
design of a pipeline renewal and replacement method. For proper
design, it is necessary to divide these conditions into different
groups.