Major work on a listed bridge crossing from South Holland into Norfolk will see an upgrade of systems to keep the traffic flowing.
The Cross Keys Bridge, Sutton Bridge, is a swing bridge on the A17 and the only river crossing between the two counties.
A £30,000 project to complete a refurbishment of the four hydraulic jacks is nearing its end, with three of four due to be complete this week.
“The current hydraulic and operating systems are circa 40 years old and either obsolete or unsupported, meaning that replacement parts are scarcely available and the operating software requires an upgrade,” says a report to the county council.
There have been ‘numerous mechanical failures in recent years due to ageing worn equipment,’ it continues.
A separate £1.6m project to upgrade the electrical and mechanical systems on the bridge is the subject of a current planning application.
If Lincolnshire County Council failed to pursue the upgrade, the bridge operating systems would remain vulnerable, says a report.
“The worst case scenario is the bridge fails part way through an operating cycle so the bridge is neither open for marine traffic or for the traffic on the A17.”
The diversion is via Wisbech and a 32-mile detour and if the bridge failed, there would be serious economic consequences for the region.
Fairly regular ‘unforeseen’ failures and breakdowns are currently dealt with by ‘the skill of the bridge operators’ but the situation can become ‘stressful.’
The worn mechanical and electrical systems may also pose an environmental threat as the hydraulic jacks are fed via a tank of 1,500 litres of oil.
“The system has been designed to complete an operating cycle even if a leak is present, meaning a potentially large amount of hydraulic oil in the river,” says the report.
A detailed set of working schedules is the subject of a planning application with the county council as it is a Grade II listed building.
The bridge, built in 1897, is manned 24 hours a day by six staff on a three-shift work pattern.
It spans 94m in three sections and when open allows a 30m passage for ships using Wisbech port.
The turret on top of the bridge still has the original control levers which had been used to open and close it. In 1987 there was a major maintenance scheme which saw a computer-aided programme added. It has its own bespoke software system.
In 2021 the bridge was swung 550 times to service growing marine shipping demand. The river has priority over the road by an Act of Parliament.
The new mechanical, electrical, control and automation equipment is designed to minimise maintenance.
It has been designed for 550 operations a year with maximum of two per hour in daylight hour, once during the night and three an hour during maintenance.
An initial scheme for full electrification of the hydraulic system has been discounted due to the size of the units and challenges with the speed of operations.
The majority of changes will not be visible to the public.
The planning application has been submitted to the county council by itself and a separate listed building consent application has also been made.
