Boring - Trenchless International

Pumping station back in action
Per Aarsleff’s recently formed Pipe Technologies division has successfully
completed its first pipeline repair on a damaged pumping station discharge
pipeline at Bawdsey, on the East Suffolk coast in the United Kingdom. The
deformed and leaking cast iron pipeline was restored with CIPP.
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April 2010 - Trenchless International
The liner was turned inside out, pushed onto the outlet nozzle of the
inversion drum and held in place with special clamping bands.
Bawdsey land drainage
pumping station and its 450 mm diameter
discharge pipeline were built in
the late 1950s to serve an agricultural
catchment of nearly 13 square kilometres,
half of which lies at or below mean
sea level. The Bawdsey Pumping Station
automatically controls water levels
and discharges surface water drainage
through the pipeline, under a flood
defence embankment and into the tidal
estuary of the River Deben. The overall
pipe is about 30 metres long. However,
a 22 metre long section, from the pumping
station to the outfall, has deformed
under the weight of the embankment
and sunk about 250 mm into a shallow
‘U’ shape. When the pump operates at
its flow of 0.45 metres cubed per second
and pressure head of five metres, water
is forced out of the damaged pipe’s
open joints, jeopardising the integrity of
the flood defences.
A swallow hole appeared in the
embankment, forcing the Environment
Agency, which is responsible for the
embankment, and the East Suffolk
Internal Drainage Board (ESIDB), responsible
for Bawdsey Pumping Station, to act
quickly. The ESIDB is one of a consortium
of five boards making up the Water
Management Alliance (WMA), which
together protect about 1,220 square kilometres
of East Anglia. There was an
acute risk of an embankment breach
and the WMA looked at alternative repair
options.
“We had to act quickly and considered
various alternatives, including replacing
the entire section of pipe, but that would
have required major invasive surgery
to the embankment,” says WMA district
engineer Ian Hart.
“Instead we opted for a less invasive
option of relining the pipe without
the need for any excavation, in the
The liner was pushed through the
manhole and into the pipeline ready
for inversion.
spirit of modern, keyhole surgery.
I contacted Aarsleff and they confirmed
the feasibility of repairing the pipeline
in-situ with a tailor made liner. We then
appointed a local civil engineering contractor,
Breheny, to oversee the repair
as they had rebuilt the pumping station
in 2003–04. Aarsleff purpose-made the
liner to suit and installed it in a very slick
and professional operation.”
Breheny provided clear unobstructed
access to the pump house, removed
the pipeline inspection cover within the
pumping station and opened the outfall
flap valve to allow Aarsleff to make a
start on the lining during low tide. A thin
plastic pre-liner, with a blanked end,
was first inserted into the damaged
pipeline using compressed air to protect
the main resin-impregnated polyester
liner during installation. The main liner
was designed and made by Aarsleff’s
in-house designers to withstand the
positive and negative pressures and
the high flow rates generated when the
pump operates. It was made inside out
from resin impregnated thin layers of
special needle felt so that the outside
surface eventually became the inner
smooth bore surface when the liner was
inverted into the damaged pipeline. The
main liner was packed in flake ice during
delivery from the factory to the site to
prevent premature curing.
At the pump house the liner was
wound into the special inversion drum,
which was positioned close to the pump
house entrance. A length of liner, twice
the distance from the drum to the pipeline
manhole, was pulled out of the
drum. This protruding section was then
turned back on itself so the inside of
the liner was now on the outside. It was
pushed onto the outlet nozzle of the
inversion drum and held in place with
special clamping bands. The liner was
then lowered down into the manhole
and guided by hand a short distance
into the pre-liner and into the entrance
of the damaged 22 metre long pipeline.
The inversion drum was then pressurised
with compressed air, which forced
the liner, with its closed end, to rapidly
unwind from the drum and unfold and
invert itself through and out of the open
end of the damaged pipeline. The inversion
process only took a few seconds
with the air pressure forcing the liner
through the prelined damaged pipe and
against the wall, which effectively acted
as a former for the new lining.
A steam pressure hose was then
connected from a special boiler to the
inversion drum to heat up the liner. At
the same time a steam exhaust pipe
was also inserted into the exposed section
of liner protruding from the outfall.
Temperature probes were attached to the
liner, which was gradually heated by the
steam to 110°C and held for four hours to
cure the resin-impregnated, 13 mm thick
The special inversion drum with liner was
positioned close to the pump house entrance.
The inversion drum was pressurised with compressed air, which forced the liner to
unfold and invert itself through and out of the open end of the damaged pipeline.
liner. By using steam curing, the required
high temperature could be maintained,
even though the end of the liner was
submerged during high tide. The entire
liner inversion and curing process was
controlled and monitored by a computer
on board a self-contained lorry fitted with
highly advanced, purpose-built installation
equipment, including the boiler and
compressors, needed to perform the
No-Dig, CIPP process.
After curing and cooling, the ends
of the new liner, which formed a
self-supporting pipe within a pipe, were
cut off at the next low tide. Aarsleff’s
lining crew completed their work in just
one and half days and Breheny followed
on, restoring the outfall flap valve and
returning the pump house to full working
order. The repair to the Bawdsey
pipeline was completed without any
excavation or disturbance of the pipeline
and was done in a fraction of the
time and at a fraction of the cost it would
have taken using conventional, open-cut
pipe replacement methods.
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April 2010 - Trenchless International
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