Page 288 - Trenchless Technology Piping Installation and Inspection

252 Cha pte r S i x

6.9 Construction Considerations
Once the owner has accepted a bid, based upon the bidding process,
a notice to proceed is issued. Then, typically, the contractor takes the
following steps:

• Preconstruction survey
• Cleaning or pigging of line, if necessary
• CCTV inspection, if necessary
• Excavations at services for temporary bypass
• Setting up temporary bypass with connections to customers
• Excavation of insertion and pulling shafts
• Joining (fusing or assembling) individual new pipe sections,
as necessary
• Setting up the winch or hydraulic pulling unit and insertion
of pulling cable or pulling rods inside the existing pipe
• Installation of hoses through the new pipe to attach to burst-
ing head (air supply hoses or hydraulic hoses for pneumatic
or hydraulic systems respectively), as appropriate
• Connection of bursting head to pulling cable or rod
• Pipe bursting and replacement with new pipe
• Removal of bursting head and hoses from the pipe
• Post installation inspection
• Pipeline chlorination, flushing, and testing if it is not prechlo-
rinated (for potable water pipes)
• Reconnection of services and reinstating manhole connections
• Site restoration and project close out
It should be noted that, if allowed by the water agency and local,
city and state guidelines, prechlorination of potable pipe saves installa-
tion time and bypass pumping. In this method, prechlorination and
testing is conducted above ground, and left to stand for 24 hours. Then,
new pipe is flushed, and pulling head is welded to the pipe to keep
pipe ends sealed hygienically. After completion of bursting operation,
a super chlorinated swab is passed through the new pipe. After removal
of swab, the new pipe is flushed and commissioned, and service later-
als are connected. Usually one water sample is taken after commission-
ing and another after 24 hours of commissioning (see Fig. 6.9).
Butt fusion of HDPE replacement pipe is carried out prior to the
bursting operation, so that all fused joints can be chlorinated (for
waterlines), checked, and tested. The pipe should not be dragged
over the ground, and rollers, pipe cutouts, or slings should be used
for both insertion and transportation of the pipe. The ends of water or
gas pipes should be capped to prevent the entry of contaminants.