PROJECT FOCUS
The biggest risk for us was a section going
into the sewer out of alignment.
"However, design tolerance was built-in
to enable slight adjustments to be made and
calculations were carried out to determine
heave induced by excavation. Everything
worked perfectly."
Grouting
Temporary shelters and acoustic
curtains were installed to minimise
odour and noise
Precision-welding in the tunnel was to
standards usually associated with very
high-pressure pipelines
A temporary metal and rubber cage
was created to support the Ham Sewer
14 Water & Wastewater Treatment January 2014
The space between the liner and the existing
brick was grouted through pre-formed grout
holes using cementitious grout, to ensure
there were no voids and that the loads from
the TBM works would be transferred onto
the new structural lining. A 450mm lateral
connection was reconnected with a 500kg,
20mm-thick reinforcing plate, site-welded to
distribute the load.
Stakeholder and environmental
management was a key factor on the project.
The site was therefore protected by Haki
temporary shelters and Soundex Acoustic
curtains to minimise odour and noise for local
residents.
Jon Hynes, utilities agent, DSJV, said, "To
install 50t of 50m-long duplex stainless steel
liner into a live sewer, 10m below ground, and
500mm above the Crossrail running tunnels
sums up the complex nature of the task that
faced DS JV and UKDN Waterflow nicely.
"However, it belies the extent of the
consultation, interface and design progression
that all partners embarked on a full 18 months
before the first liner sections arrived on site.
"From conception, it was clear that
numerous parties had a stake in this game;
from residents to asset owners, from the
project manager to various designers, and
from consultants to contractors.
"In addition, to keep us all on our toes,
we had the Drive Z TBM launching from the
Pudding Mill Lane portal, some 100m east of
us.
"In other words, no liner - no launch."
The first TBM successfully passed the
reinforced section in August 2013, without
incident. The second TBM is due to pass in
2014. With no injuries and a 100% safety
record, the UKDN team's work on this site
will continue until 2015 when the shafts
will be reinstated. Most recently the team
has inserted a UV-cured GRP liner into the
adjacent Wick Sewer to provide additional
protection.
As this 1.2m-diameter sewer is slightly
smaller, and that bit further away from the
tunnelling works, a GRP lining could be used.
UKDN Waterflow teams continue to deliver
agile and ground-breaking stabilisation
programmes at Crossrail sites throughout
London. nnn
wwtonline.co.uk
