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are generally consistent with that reported by Rogers (1995), indi-
cating that ground displacements are unlikely to cause problems at
distances greater than 2–3 diameters from the pipe alignment. Utili-
ties that are closer to the bursting head than these distances should
be exposed prior to bursting so the vibration from the bursting
operation would be isolated or reduced prior to reaching the utility
in question.
6.9.5 Bypass Pumping
One of the objectives of the bursting project team (owner, engineer,
contractor, etc.) is to minimize customers’ service interruptions. The
key for achieving this objective is the bypass pumping system. For
water applications, the system should be able to deliver the needed
flow volume with the specified pressure to the customers. For gravity
applications, the system should be able to adequately pump the
upstream flow and discharge it to the manhole downstream of the
run being burst. The plan should ensure that the bypass system has
adequate pumping capacity to handle the flow with emergency
backup pumps to ensure no interruption to existing services. The
bypass pipes and fittings should have sufficient strength to withstand
the surge water pressures. Contractual arrangements between the
owner and contractor should be made regarding responsibility for
maintaining service to customers.
6.9.6 Dewatering
The pulling and the insertion shafts should be dry during installation
to avoid disturbing bursting operations. Installation of a dewatering
sump pump at one corner of the shaft is required. If the pipe invert
is significantly below the GWT in sandy or silty soils, a more elabo-
rate dewatering system is recommended such as well-point system,
deep wells, or larger sump and pump system. As the water level is
drawn down, soil particles tend to travel with the water toward the
dewatering system undermining utilities and structures. Therefore,
as it is the case with every dewatering system, the contractor should
take all necessary measures to prevent the migration of the soil par-
ticles from underneath nearby buildings and utilities. Since the dis-
charge flow volume in this case is expected to be large, a suitable
discharge permit in compliance with the EPA requirements may be
necessary. If a sump pump is used, preliminary treatment of flow to
reduce the sediments before discharging into water streams may be
required.
6.9.7 Ground Movement Monitoring
The safety of nearby utilities, buildings, and structures due to ground
movement is always important. For extremely challenging pipe-
bursting operations (Class C, Table 6.1), preconstruction survey and