Page 70 - Trenchless Technology Piping Installation and Inspection

40 Cha pte r O n e

all the data, including geotechnical reports and soil bore information
to the contractor. This will help the contractor to make adjustments in
machine selection and installation methods.
The following are examples of these risks with more information
provided in Chap. 10.

• Borehole collapse/subsidence.
• Ground displacement/upheaval.
• Ground vibrations damaging nearby utilities and struc-
tures.
• Excessive fluid pressures (such as in HDD operations)
damaging/breaking nearby utilities.
• Excessive use of torque/thrust.
• Use of forward thrust power in HDD operations to ream the
borehole (this practice may heave the ground, damage the
pavement, and damage nearby utilities).
• Striking underground utilities during reaming and pullback
operations (such as HDD method). It should be noted that in
HDD operations, the back-reaming and installation of prod-
uct pipe may take a shallower profile than original planned
borehole.
• Lack of keeping a safe distance from parallel and crossing
utilities.
• Lack of proper entry/access/exit pit excavation and support
systems.
• Risks involved in operating boring and jacking machines and
use of hydraulic and air hoses, and power tools.
• Confined space entries.
• Work zone traffic accidents.
• Fall into shafts and pits.
• Overhead power lines.
• Striking natural obstacles (tree roots, boulders, etc.) and man-
made obstacles (mass of concrete, abandoned underground
tanks, and other structures).
• Ground variability and mix-face conditions.
• Exceeding jacking capacity or torque capacity of boring
machines (such as machine upset in horizontal auger boring).
• Exceeding jacking capacity of the thrust block or backstop.
• Exceeding jacking capacity or pulling capacity of the product
pipe.
• Uncovered or unmarked surface potholes.