£3m investment will see major overhaul for vital Plymouth flood defence barrier

Plymouth’s lock gates which form a key part of the city’s coastal defences, protecting hundreds of homes and businesses from flooding, and providing access to the marina and fish quays in the Sutton Harbour and Barbican area of the city, are to undergo a £3m repair and maintenance project in the autumn.

The work is being carried out by the Environment Agency, with funding from the UK Government, and will see the replacement of worn lock gate cills and other key maintenance items.

The work, which is scheduled to take place from mid-September 2022 until early April 2023, will ensure the effectiveness of the tidal barrage and its ability to maintain water levels in Sutton harbour for another decade.

Impact on usage of the lock system into the harbour will be from October 2022 through to the end of March 2023.

Sutton Harbour Company, which is the statutory harbour authority and operates the lock, Plymouth Fisheries and Sutton Harbour Marina, will be working in a collaborative partnership with the Environment Agency and selected contractors Kier, in the successful planning and operational aspects regarding the harbour access, taking into consideration the lessons learnt from the intervention works on the locks in over 10 years.

Mitigation measures will be in place to minimise disruption for harbour users during these essential works, working to support the continued operation of Plymouth’s fishing fleet. Continued access to landing, berthing, fuel and ice facilities have all been taken into account.

The works have been scheduled to take place throughout the later part of the year to avoid disruption to the leisure users of the harbour.

For the majority of the works the lock will still function on a freeflow basis (generally up to three hours either side of high tide), with a limited number of 24-hour closures. Access will be maintained for pedestrians using the swing bridge across the lock.

David Harker from the Environment Agency said: “We are pleased to be undertaking this major repair work, which will ensure the continued operation of the lock gates, to maintain the standard of protection from flooding that Sutton Harbour and the Barbican enjoy. It will also ensure that the fishing and leisure fleets will continue to have 24-hour access to the harbour into the future.

"The work is necessary as the bottom seals of the gates have worn out and are no longer reliable. There is a risk that they could fail and result in a loss of water from the harbour or not function when needed to prevent flooding. We are also taking this opportunity to also refurbish the structure which seals the old harbour entrance (the stoplog gate) to avoid another piece of work in the near future.

"We are working closely with Sutton Harbour Company, and our contractor Kier to ensure the project runs as smoothly as possible.”

Mark Veale, Sutton Harbour Harbourmaster, said: “It is welcome news that this vital flood defence for the harbour and the city is to receive such a significant investment to complete these necessary works.

“We will work closely with the Environment Agency and Kier to facilitate the project and with all harbour users to minimise disruption.

“We are already in discussion with fishing representatives and will work very closely with the local and visiting fishing fleet to put agreed mitigation plans in place. These are likely to include a pre-arranged alternative landing site with truck access to the Fish Quay for periods when access to the harbour is restricted, to ensure the ongoing operation of the industry.”

The project involves replacing the existing four gate seal assemblies which are fixed to the bed of the lock, below the tidal gates at Sutton Harbour. As well as this, the adjacent flood barriers (or stop logs) which were installed across the original harbour entrance will be replaced. The pedestrian walkway above the stop logs will also be replaced, but not until the end of the project and avoiding the busy Easter holidays. This work is only expected to take around a week.

Specialist divers will be carrying out the underwater works, where they will be assisted by a shore-based team providing the necessary support. Construction teams will carry out works accessible via the quaysides.

A new website www.lockgates.info has been created by the project partners as an information portal for the project and as a resource for all harbour users, local businesses, members of the public and anyone with an interest in the harbour. More detailed information will be added in advance of the start of work and will be regularly updated throughout the project on the timetable of work, daily access arrangements to the harbour and mitigation measures.