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Clark's Bridge
Refurbishment Project |
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Project Team: British Waterways – East Midlands
(client & design), Galliford Try (construction)
The Clark’s Bridge refurbishment project was
carried out to strengthen and repair a Grade II Listed
structure on the Grantham Canal, a remainder canal in
Nottinghamshire. It was a joint project between British
Waterways East Midlands and Galliford Try Construction.
The structure is a masonry arch bridge, constructed
of handmade bricks with lime mortar bedding circa 1797
for farm access. Prior to repair it had a reduced capacity,
had been highlighted through British Waterways’
inspection programme as a structure in need of repair,
and was on the local council’s buildings at risk
register.
Saddling was the preferred strengthening option as
the works were relatively straightforward on the lightly
trafficked structure, and the saddle would be hidden
once works were complete. This option also significantly
prolonged life for a minimal additional present day
cost. Additional work included the repair of damaged
brickwork on the parapets and spandrel walls, replacement
of the arch ring face with blue engineering bricks and
the reintroduction of a continuous blue brick stringcourse
at the base of the parapets. The parapets themselves
were in such poor condition that they were taken down
and rebuilt in their entirety, to the original bond
pattern. The underside of the bridge was re-rendered
with hydraulic lime mortar as repair of this brickwork
would have been difficult to achieve
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Re-rendered underside
of the bridge
(showing bat box entrance) |
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The correct choice of materials was an important aspect
of the works. The aim was to maintain the heritage of
the structure and to minimise the volume of material
either taken off site or imported. Damaged bricks were
carefully removed, cleaned, turned and re-used. Where
this was not possible due to excessive damage, they
were replaced with reclaimed bricks selected to closely
match those in the existing structure. The damaged bricks
were crushed and re-used in the fill material; the remaining
fill was made of recycled material. FSC timber was used
for both temporary and permanent works.
Representative samples of the existing lime mortar
were sent for analysis to determine a matching mix.
As part of the Listed Building consent, the lime mix
and reclaimed brick type was agreed with the local planning
authority. The lime mortar was protected with sheeting
as the works were undertaken during the winter months.
During the coldest period the structure was protected
by tented scaffold and heating.
The props holding the intrados up during the works
were drilled and fixed to the abutments in order to
minimise disturbance to the waterway. Scaffold was close
boarded and covered with plywood sheeting to retain
debris. Debris netting was also installed to prevent
materials from falling into the waterway
The bridge was enclosed in a heated tent to protect
the lime mortar during a cold spell. Maintaining a free
waterway by keeping the propping out of the water minimised
disruption to canal wildlife.
The site lies within a county wildlife site, and the
adjacent (privately owned) farm is part of a countryside
stewardship scheme. Disturbance of the surrounding landscape,
including trees and hedges, was kept to a minimum. The
top of the bridge was covered with Suretrac, an environmentally
friendly material, and seeded with locally sourced grass
and wildflower species. A survey determined bats were
using the area, but not the bridge. A bat box has been
cast into the concrete saddle and is accessed from the
intrados via a small opening in the lime render. An
interpretation panel was installed to assist understanding
and appreciation of the structure
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