York’s ancient fortifications need some protection of their own right now.
One corner of York’s medieval city walls has been shored up by the Queen Street Bridge since it was built in 1877.
Now the bridge is being demolished. So a new structure needs to be put in place to ensure the city walls stay solidly upright.
That’s why one section of the bridge was left in place after the rest was demolished two weeks ago.
As YorkMix revealed last month, this will stay put until a retaining wall is to be built to support the city walls.
Only then will the last part of the bridge be removed.
A City of York Council spokesperson said: “While most of Queen Street Bridge has now been removed, some parts remain in place.
“The Queen Street approach ramp at the southern end has been left in position, which will act as a piling platform to allow the installation of a contiguous piled retaining wall.
“This wall will support the embankments and protect the city walls from any possible movement once the remaining parts of the bridge are removed.
“Construction of the piled retaining wall will begin in about two weeks’ time and is expected to take two months. At that stage the remainder of the bridge will be removed.”
Accurate measurements
While walking along the walls near to Queen Street, you may have noticed that they are dotted with little grey units.
These have been attached to the stonework with removable fixative, and they form part of a system to monitor the fortifications.
Laser signals are bounced off the units from stations found on top of the Railway Institute building and the Network Rail building behind.
These allow engineers to monitor any movements of the walls. It is accurate up to one millimetre, and a source told YorkMix that if a movement as large as 10mm was detected, all work on the demolition would have to stop.
The monitoring was put in place as part of meticulous work to ensure the walls are not put at risk.
As a Scheduled Ancient Monument, the York city walls are nationally important, and afforded special protection.
That means work that might impact on the medieval fortifications has to be granted Scheduled Monument Consent from the government.
Historic England has acted as an advisor to the government on the bridge demolition project to ensure York’s walls are safeguarded.
“A key part of this was the installation of a monitoring system, with monitoring targets being attached to the walls and embankments,” said the council spokesperson.
“This allows the council, Historic England and the contractor to monitor the behaviour of the walls before, during and after the works.
“Advance works has enabled the team to understand typical wall movement throughout the year and develop a plan to mitigate for any movement during or after the works.
“During the Queen Street Bridge demolition works, no movement has been recorded to date.”
While the retaining wall is built, other work on the new Station Gateway project will continue.
Contractor Sisk will begin to construct the permanent new road, with improvements to cycling and walking facilities, the new bus interchange and public realm areas.