The gates were initially installed in 1922 and due to their age and structural condition; care had to be taken to ensure no further damage would occur that could potentially de-stabilize the gates and affect their buoyancy during the un-stepping procedure.
A confined space/diving survey was carried out to determine the dimensions of the tidal and buoyancy chambers, which would assist in calculating the weight of each leaf and therefore the buoyancy conditions that would be required for the works operations.
Kaymac’s engineers carried out the calculations to determine the conditions required to achieve the necessary buoyancy to safely un-step and relocate each leaf. During the unstepping procedure, operatives continually monitored the volume of water within the tidal and buoyancy chambers, which was controlled using pumping equipment.
The control of the buoyancy conditions allowed each leaf to be floated from their holding pintle and then rotated into a horizontal position to ensure safe transportation of each leaf to within the adjacent operational dry dock. Kaymac then set and secured the position of the gates to correspond with the submerged setting down blocks on the invert of the docks.