Page 278 - Trenchless Technology Piping Installation and Inspection

242 Cha pte r S i x

design engineer must therefore identify and locate these existing util-
ities as accurately as possible. However, the exact location of these
utilities will be identified during the construction phase through
visual locating, such as vacuum potholing. The identification of
nearby utilities is critical for the following reasons:

• The presence of nearby utilities may eliminate pipe bursting
as a viable construction method.
• Existing utilities may affect the location of insertion and
pulling/jacking shafts.
• Allows protection of existing utilities from the ground move-
ment of the bursting operation.
• Reduces the risk of injuries and fatalities to the workers and
public by avoiding damage to existing utilities.
• Contractors need to know the number of utilities to be
exposed, to be properly reflected in their bid.
See Chap. 9 for more information on utility locating.

6.8.2 Investigation of Existing Pipe and Site Conditions
Investigation of the existing pipe condition assists in selecting the
suitable renewal technique and provides the exact location of the lat-
eral connections. The nature and condition of the existing pipe may
render pipe bursting as an unsuitable solution. The presence of sags
in the pipeline may require correction prior to bursting. The existing
pipe (diameter, material, and conditions) and the diameter of the new
pipe guide the contractor in the selection of an appropriate type of
bursting system, size, and accessories, and should, therefore, be
reflected in the bid documents. The site conditions and surface fea-
tures may affect the locations of the insertion and pulling shafts, stag-
ing area for fused pipe, traffic control planes, and layout for the
required bursting system components.

6.8.3 Insertion and Pulling Shaft Requirements
When planning for shaft locations, the engineer identifies locations
where excavation is required to replace manholes, valves, lateral
connections, or fittings. If excavation at the manhole location is not
necessary or feasible, shaft excavation at other locations may be
considered. In selecting the location of these shafts, the engineer has
to consider the following:

• Sufficient staging area for the replacement pipe to avoid
blocking driveways and intersecting roads.