KGAL Fluid SUMMER 2026 - Flipbook - Page 5
consulting engineers
Boston Grand Sluice Refurbishment
Where heritage engineering meets modern flood control
The 260 years old Grand Sluice on the River Witham, at the heart of Boston, Lincolnshire, has been managing
tidal flow for over two centuries. Originally constructed with three channels, each fitted with twin sets of mitre
gates to prevent seawater moving upstream, the structure has evolved over time. During a major upgrade in the
1980s, the upstream gates were replaced with vertical lift gates, along with new mitre gates on the downstream
side. Consequently, elements of the current installation are now reaching the end of their operational life.
A multi-million pound phased refurbishment programme, delivered for
The Environment Agency and Arup, is now underway to bring the structure
up to modern standards while maintaining its critical flood management role.
KGAL’s involvement sits at the core of that upgrade.
The scope covers both outline and detailed design for three new vertical lift gate
systems, complete with embedded parts and gantry-mounted electric actuators for
reliable operation, with additional capability to pass surface weed via an integral
tilting gate. Alongside these, new upstream and downstream stoplog systems are
being introduced across all three channels, including lifting beams and monorail
gantries to allow safe handling and maintenance.
The last timber mitre gates installed in 1980 are also being replaced. Three new
sets, designed with counterweight closing systems, will maintain the traditional
function while improving longevity.
Working collaboratively with Arup and the Environment Agency, KGAL has
developed an intelligent control philosophy that builds upon the existing control
Pointing door
View downstream
system with significant enhancements. A key feature is pre-emptive flood control
using early warning data from upstream monitoring stations. The design
incorporates multiple resilience layers including dual control modes (PLC automatic
with hard-wired backup), triple-redundant sensing, and a manual hand wind facility
that can accept a battery powered operating device. The design also includes a
smart fish and eels pass facility to support salmonids and other fish migration
during tidal events.
Following successful stakeholder engagement, the Control Philosophy is now under
final review before progressing to the detailed Performance Specification.
Work on site began in 2025, led by Jackson Civil Engineering, focusing initially on
downstream civil works, stoplog liners, and installation of a new electrical supply
and distribution kiosk. As expected with a tidal limit of a fluvial river flow control
structure, construction paused over the winter period and has now resumed.
Centregreat Ltd is fabricating the stoplogs and liners, while IMAC (Installation
Maintenance and Controls Ltd) handles the detailed design and manufacture of the
DNO kiosk.
Sluice gate
View of the pointing doors
View from upstream looking downstream at sluice gates
