Peel Ports - Alfred Passage Gates Cill & Bracket Repairs
Hughes Subsea were contracted to install brackets onto the cill, carrying out cill repairs where required to provide a new mating face for the lock gates.
The new mating face designed to prevent the loss of impounded water when pressure differentials existed across the closed gates.
With the Alfred River Entrance Gates failing earlier in the year(2020), Peel Ports had to manage operations for the dock system through the Alfred Passage Gates. This put further pressure on the Passage Gates which led Peel Ports to undertake refurbishments to prolong the operational life expectancy of the Passage Gates whilst the business awaited new Inner Gates.
Alfred River Entrance (ARE) is the only marine access link between the Birkenhead Dock Estate and the River Mersey and as such in its designed condition is to be continually operational. ARE is located between Twelve Quays Ferry Terminal (Birkenhead) to the south and East Street industrial estate (Wallasey) to the north and is included within the Port of Liverpool. The river entrance comprises two sets of gates (Outer and Inner), with the third set of gates (which this project was concerned with) situated in the passage between the east and west floats within the dock estate.
Due to failure of the North Inner gate in April 2020, vessel movements into and out of Alfred River Entrance remained limited to restrictions. Relying solely on the Passage Gates results in increased operations and stress being place on these gates which meant immediate refurbishment was required to ensure the gates remained sustainable and in operation during the Inner Gate replacement.
The sill had suffered degradation over the years resulting in the loss of the original 90 degree face and timber sealing face. Design works were undertaken by the client and a design produced for a temporary repair which would provide a new sealing face for the gates to mate against.
Hughes Subsea were contracted to install brackets onto the cill, carrying out cill repairs where required (illustrated as green on the below images) to provide a new mating face for the lock gates. The new mating face designed to prevent the loss of impounded water when pressure differentials existed across the closed gates.
Following the preliminary as found dive inspection it was clear that the existing cill was significantly more deteriorated than expected. The originally proposed grout seal (green area above) had to be increased to the full length of the cill over a height of some 250mm and a depth in places reaching 1.5m.
Hughes Subsea mobilized surface supplied equipment onto the multi-role vessel – Vital including hydraulic tooling. The vessel mounted hiab was used to lift in individual brackets into place; circa 800kg each.
Hughes Subsea designed and installed formwork to repair the cill such that the new brackets could be installed. This called for temporary formwork to be installed along the length of the cill and all gaps sealed to allow a self-leveling underwater grout to be pumped from the surface.
Once set brackets were lowered into position and adjusted to ensure they did not interfere with the natural mitering of the gates; which varied on each mating due to the age of the gates and the fact they “rode” up onto the cill due to material loss on the mating facing. The brackets were installed by coring into the underlying granite blockwork and pumping resin into the void; each bracket requiring 10 No. bolts evenly spaced along the 3m length.
Following completion of the remedial works Hughes returned after approximately 6 months to inspect the system. All brackets remained in place and no flow was observed across the gate when a pressure head was applied. The system was therefore observed to be satisfactory and provided the client with the end result they required.