Page 405 - Trenchless Technology Piping Installation and Inspection

Inspection and QA/QC for Trenchless Installation and Replacement Methods 355

The invert in the manholes must be removed to ease the pipe-
installation process and in such a fashion to accommodate
the invert replacement. Manhole inverts must be restored
upon completion with 3000-psi concrete so as to establish a
minimum 4-in.-thick manhole bottom.
4. Solid wall pipe must be produced with plain end construc-
tion for heat-joining (butt fusion) conforming to ASTM D
2657. The polyethylene pipe must be assembled and joined
at the site using the thermal butt-fusion method to provide
a leakproof and structurally sound joint. Threaded or sol-
vent-cement joints and connections are not permitted. The
butt-fused joint must have uniform roll back beads resulting
from the proper use of temperature and pressure during the
fusion process. The joint surfaces must be smooth. The joint
must be watertight and must have tensile strength equal to
that of the pipe. All defective joints must be cut out and
replaced.
5. Bypass pumping is required for this method when needed;
dewatering may be initiated prior to any pit excavation.
6. All laterals must be disconnected prior to pipe-bursting
operation.
7. Upsizing is only allowed if soil and site conditions are suita-
ble (new and existing pipe diameters considerations, mini-
mum depth of existing pipe is allowable, and if a minimum
distance to any existing utility or structure is followed).
Oversize Allowance
When using this method, the allowable oversize diameter is 1 in.
greater than the pipe radius.

Watertight Joints
Watertight pipe joints are very important to the integrity of the road-
bed. Every reasonable effort must be taken to ensure that watertight
joints are installed. Pipe must be constructed to prevent water leak-
age or earth infiltration throughout its entire length.
A watertight specification for each type of pipe material can be
obtained through each pipe material industry. Please refer to the
appropriate industry specifications for more detailed information.

Lubrication Fluids
Lubrication fluids may be used to facilitate the installation of new pipe.

Pipe Locating and Tracking
Pipe locating and tracking is not required for this method of pipe
installation. Figure 8.25 suggests a checklist for inspection of pipe-
replacement operations.