Page 418 - Trenchless Technology Piping Installation and Inspection

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• Quality Level D: The minimum level of information is based on
existing utility records. Such information is primarily useful
for the purposes of project planning and route selection only.
• Quality Level C: In addition to the information from Quality
Level D, this level includes information obtained from a site
visit and a survey of ground surface features, such as man-
holes, valve boxes, posts, and the like, and correlation of this
information with existing utility records. As a result, the pres-
ence of additional belowground utilities, or erroneously
recorded location information of utility lines, may be deter-
mined. Although such information may be adequate for areas
with minimal belowground facilities, or where possible repair
is not a major issue, this quality level would typically not be
sufficient for proceeding with trenchless construction in
established areas.
• Quality Level B: In addition to the information from Quality
Level C, for more useful and reliable information, Quality
Level B surface locators are used to identify and mark the
existing utility lines.
• Quality Level A: In addition to the information from Quality
Level B, the highest quality level (Quality Level A) includes
the use of minimal destructive equipment (such as vacuum
potholing) at critical points to expose the utility to determine
the precise horizontal and vertical position of underground
utilities, as well as the type, size, condition, material, and
other characteristics.
The reader is referred to the referenced ASCE standard for a more in-
depth discussion of SUE. However, it is apparent that varying levels
of existing utility location may be applicable depending on the specif-
ics and objectives of the trenchless project. During the planning phase,
the design engineer or owner should decide what quality level of
information for underground utility is consistent with the project
needs and relate that with their risk management strategy. The SUE
process offers some potential benefits, such as avoiding conflicts with
other existing utilities, reducing delays in the construction schedule,
eliminating additional construction costs, and reducing inconve-
niences to the general public.
The level of utility quality information is an important decision
that should be made and obtained as early as possible during the
planning and design phase of the project.

9.2.3 Geotechnical Investigations
A second phase of subsurface investigation for trenchless installation
projects involves determination of soil conditions. Once the proposed
alignment has been identified, a geotechnical investigation should be