Page 439 - Trenchless Technology Piping Installation and Inspection

Planning and Safety Considerations for Trenchless Installation Methods 389

The risks that should be identified are those that affect perform-
ance, productivity, cost, schedule, quality, and safety. As with any
project, not exceeding the budget and remaining on schedule are the
primary goal. Risk management’s purpose is to identify all associated
risks to achieve this goal.
Many risks can be planned for if identified. There are still other
risks, however, which cannot be planned for, but still must be consid-
ered. Among those are

• Unknown or unexpected ground conditions
• Weather delays
• Unexpected/unplanned alignment or grade changes of pipe-
lines during pipe jacking
• Groundwater fluctuations and surface flooding
• Material shortages due to delay in shipping or supply

9.3.4 Utility Mapping
Any trenchless operation can have its own hazards. There are
always hazards to construction workers in any type of under-
ground construction; such as hazard of striking existing structures
or utilities underground. Coordination is required among several
parties and agencies prior to the start of the project. One of the first
tasks is locating all the existing utilities. The one-call service (the
811 number for most of the United States) is essential in locating
existing underground utilities; however, it would give the contrac-
tor an approximate alignment and no accuracy for the depth of
utility (see Fig. 9.2). The cost associated with identifying the exist-
ing underground utilities is small when compared to the cost of
striking a buried utility.
Additionally, visual checks and physical observations must
also be made of the planned construction path. Just as important in
identifying underground utilities is checking the site for evidence
of substructures such as manhole covers, valve box covers, meter
boxes, electrical transformers, conduits or drop lines from utility poles,
and pavement patches to determine if any utilities may have been
overlooked. Water and gas shutoffs attached to the houses or busi-
nesses in the area signify utility lines, even if they are not marked
by the one-call service. Depressions in the ground may indicate
that some type of excavation or trenching has taken place and,
although there may not be an obstruction present, there is a possi-
bility for some type of fill material that does not resemble the soil
structure around it.
Written procedures have to be followed for the probability of
striking an existing utility. Even if all of the checks and physical