major enabling works to construct a new pier (for the Thames
clippers) and relocate vessels to facilitate construction of
Thames Water’s ‘super sewer’
Tubular piling for
Courtesy of Tideway
sewerage system was designed by Sir Joseph Bazalgette in the
1850s, for a population of four million people. Whilst the
Victorian sewers are still in excellent working condition, they
are struggling to cope with the demands of the city’s growth.
Every year, tens of millions of tonnes of raw sewage pour into
the River Thames from combined sewage overflow (CSO) discharge
points all along the river. In 2014, 62 million tonnes of
untreated sewage entered the river from Chiswick in the west
through to Greenwich in the east. The solution to this
unacceptable, unsustainable situation is a tripartite one.
Thames Water has already delivered the first two components of
the overall London Tideway Improvement Programmes; the Lee
Tunnel, tackling the single largest overflow point near the
Olympic Stadium in Stratford and the expansion of the five
sewage treatment works on the tidal River Thames. The final
piece of the puzzle is the Thames Tideway Tunnel.
Thames Tideway Tunnel
The Thames Tideway Tunnel
is a planned 25km long 7.2m diameter interception, storage and
transfer tunnel running across London. The tunnel will intercept
and collect sewerage from thirty four of the most polluting CSO
discharge points along the River Thames.
appointed by Tideway to carry out enabling works in advance of
construction of the tunnel.
The project has been
split geographically into three main construction contracts,
which correspond to the anticipated tunnelling conditions in the
central, east and west of the capital. Each section of the
tunnel will be under construction at the same time to ensure
that the Thames Tideway Tunnel can be completed effectively.
This paper looks at the technical challenges of the enabling
works for the Blackfriars and Victoria sites in the Central
Sheet piling for Blackfriars Pier - Courtesy of Tideway
Tideway Central scope for
work on the early contractor involvement (ECI) phase in December
2014, followed by the start of construction in November 2015 and
is due for completion in June 2017. The scheme was required to
allow access for the main tunnelling works for the creation of
the new ‘super sewer’ beneath the river.
The construction works
Construction of the new
floating Blackfriars Millennium Pier for the Thames Clippers
A new lift and staircase
and associated landscaping to serve the new pier.
Decommissioning of the
existing Blackfriars Millennium Pier pontoon and access brow.
A new slipway for an
outdoor activity centre in Shadwell.
The relocation of the PS
Tattershall Castle, a floating pub and restaurant, to newly
constructed berthing facilities.
Removal of the old
moorings for the Tattershall Castle and HMS President.
This was the first
project undertaken by Tideway and tested the consenting
processes established, including the four‐way legal agreement
between Tideway and the river regulators which includes; the
Environment Agency (EA), Marine Management Organisation (MMO)
and the Port of London Authority (PLA).
Installation of scour protection for Blackfriars Pier -
Courtesy of Tideway
The contract consisted of
Phase one was an extended
ECI phase to assist with the finalisation of the design and
development of methodology.
Phase two was an NEC ECC
Option C construction contract.
Phase one was awarded in
December 2014 and undertaken to procure long lead items, to
commence preparing for and obtaining consents for the works, and
to finalise design and construction methodologies for the works.
Tideway’s approach was
that early integration of the delivery contractor within the
team would provide significant benefit to the scheme. Having
been awarded the contract in the summer of 2015, VolkerStevin
co‐located a team of ten personnel to work with Tideway and
their designer Arup, to develop work methods and commence
preparation of over 170 consent applications.
Construction on the new
pier commenced with a 92m long row of sheet piles, to stabilise
the toe of the river wall to enable a berthing pocket to be
dredged for the pier and clipper ferries it serves. The piles
were cut off at bed level by a team of divers. The bed was also
protected with a layer of geotextile and rock armour scour
The new pier was
constructed by Ravestein in Holland, along with the associated
walkways and bankseat. The 84 metre long pontoon was transported
across the North Sea on a submersible jack up barge and floated
off once it reached the relatively calm waters of the Thames.
Once towed up the Thames,
the pontoon was moored against two piles, each 1500mm in
diameter, 32m long and weighing 46 tonnes. Four similar tubular
piles were driven to support a bankseat structure along with two
smaller hospital piles to hang the 60 metre long and 140 tonne
canting brow from. The piles were driven with a vibratory
hammer, followed by a 60 tonne impact hammer and noise shroud.
Blackfriars Pier pontoon en route from
- Courtesy of Tideway
the new pier up the Thames
Courtesy of Tideway
Andy Alder, Tideway
delivery manager, said:
“The opening of the new
pier on schedule is a testament to the dedication and hard work
of the team, and the many stakeholders we have worked with.”
Due to the less
accessible location of the new pier versus the old, a new
staircase and lift were installed from Blackfriars Bridge down
to the towpath. Once the existing stairs and landscaping were
demolished, the poor ground conditions dictated that 51 (No.)
225mm diameter concrete piles had to be driven to support the
concrete slab foundations for the new stairs and lift plant
Due to the challenging
access constraints, all plant and materials were delivered via
river and removed using a jack up barge (JUB) and telescopic
crane. Access between the JUB and river was via a bespoke set of
steps and canting brow, as well as a spudleg linkflote barge.
Eagle eyed members of the
public will notice that the lighting for the landscaping stairs
and copper nickel clad lift is syncronised with the ebb and flow
of the tide.
Tattershall Castle involved the following operations:
A sheet piled wall and
dredging, similar to that carried out for the pier.
Dredging to form a
berthing pocket, in which an unexploded ordnance (UXO) was
Two pairs of mooring
dolphins and associated tubular piles along with grouted collars
with bolted connections to guide beams for the vessel to float
up and down on.
A secondary mooring
arrangement comprising of chains anchored to two additional
tubular piles and screw anchors.
15 tonnes of additional
ballasting in the engine room to off-set the additional weight
from the new heavier brows.
New utility connections.
Removal and disposal of
the old brows and access steps along with the supply and
installation of news ones.
Removal of the old
stairs open to the public
Lifting one of
the new Tattershall brows into position - Courtesy of
closely with Tideway to keep the local authorities, business
owners, residents, pedestrians and road users informed about the
works, listen to views and feedback and help minimise disruption
to the community.
The ECI phase allowed
VolkerStevin to establish a good working relationship with all
stakeholders, including organisations impacted due to their
vicinity to the works. Potential issues arising from noise
pollution were mitigated through adapted working hours to suit
performances at the Globe Theatre and avoid exams at the
prestigious City of London Boys School.
Bespoke noise shrouds
were installed around piling hammers and around the piles
beneath the water level to reduce the impact on fish.
VolkerStevin provided input regarding design change impacts to
the construction methodology, cost and programme. This gave
Tideway better clarity regarding the implications of forthcoming
changes prior to entering into a contract.
berthing pocket for the Tattershall Castle - Courtesy of
and publishers would like to thank VolkerStevin for
providing the above article for publication.