Engineering Design Consultants

Conwy Marina Cill Gate Replacement

M G Bennett and Associates Ltd were appointed to design a replacement ballast water pumping system for the replacement cill gate at Conwy Marina, as well as writing the PLC control software to operate it. Whilst employed by Bennetts, David Price was responsible for the detailed design of this system as well as helping to develop the control software.

This project involved replacing a 25m long, 3m high buoyant cill gate which impounds the marina at Conwy during low tides. The existing gate, which had been in place for the last 8 years, was leaking badly and had failed to operate on a number of occasions causing the marina to partially drain.

The design of the gate is a flap gate, which rotates about a horizontal axis using hinges fixed to the concrete structure below. There are two main longitudinal tube members on the gate which are connected together with rectangular hollow section ribs. This frame is then covered in a 5mm steel skin plate to retain the water.

The gate operates by utilising the top longitudinal tube member as a buoyancy tank. Ballast water is pumped in to the tank to sink the gate thus increasing the draft for vessels and increasing the window of opportunity for accessing the marina. As the tide drops to a predetermined level, the ballast water is pumped out of the gate to a storage tank on the land. The gate then rises to the closed position which prevents the marina from draining.

The whole system is automatically operated utilising a variety of actuated valves, pumps, field sensors and PLC control system.

Involvement in the project included detailed design and drawings of the ballast water pumping system and also developed the PLC control software. The project was carried out whilst working for M G Bennett & Associates Ltd.

For more information regarding our waterways & flood defence design services or to discuss your requirements, please telephone 0114 399 0400 or email us.

Key Facts
  • Location:
    Conwy, North Wales