Phase One: Grand Sluice

We are refurbishing the Grand Sluice in Boston, a project that will help with flood, navigation, water management and much more.

The Grand Sluice plays a vital role in managing water levels on the Lower Witham. For 250 years it has kept the tide out of the River Witham and managed water levels in the river from Boston to Bardney. It protects 9,000 homes and more than 25,000 hectares of farmland.

Downstream is the Boston Barrier which protects against extreme tidal surges. Grand Sluice takes care of the regular tides, protecting homes and businesses from flooding, allowing navigation for boaters, and supporting water supply for homes and 126 water abstractions for farms.

Since it was officially opened in 1766 Grand Sluice has been refurbished, repaired, and upgraded multiple times. To ensure the sluice can continue its vital job we are carrying out another refurbishment which is planned to take place over four years.

Grand Sluice in Boston 

The current pointing doors and guillotine gates were installed in the early 1980's and are nearing the end of their design life. The pointing doors stop the tide coming in from the sea and keep the Witham upstream as freshwater. They also open to let river water flow out. The guillotine gates control the river level upstream, keeping it safe for navigation and for water supply.

It is essential that Grand Sluice continues to work smoothly with no mechanical failure. We need to make sure it meets current demands and stays reliable for the future.

These refurbishment works will ensure the structure continues to meet its purpose:

1. To keep high tides out of the Lower Witham
2. To manage the water levels in the Lower Witham catchment.

Grand Sluice pointing doors

 

To ensure the sluice can continue its vital job the two main components, the pointing doors and guillotine gates will be replaced.

We will make changes to the sluice gates so aquatic weed can be flushed more effectively without losing as much water. We will also make improvements to the stop logs for safe maintenance and install new mechanical and electrical parts. We’ll also be carrying out repairs to the upstream channel floor.

The team are working to secure the relevant permissions. Because Grand Sluice is on the River Witham, holds Grade II listed status, and lies in a conservation area, heritage considerations are a key part of the planning process.

We are also working with a team of biodiversity experts who advise and help us adapt our work to select options and methods to manage the risk to the environment and meets relevant legislation.  

Construction is planned for 2025-2029.

For the latest project updates visit our Phase One: Grand Sluice newsfeed.