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Boston Barrier Vertical Sector Gate

The English city of Boston (UK) is located on the river The Haven with a direct, open connection to the North Sea, making the city susceptible to flooding during extreme tidal differences and storms. The river is also the entrance to Boston Harbor, among other things. After several major floods along the east coast of England, including in 2013, flood defenses are being built in various places. The new Boston Barrier was also constructed to protect the English hinterland of Boston against high water. Hollandia Infra has received an order from construction consortium Bam Nuttall-Mott MacDonald to design and build three steel segment doors for this new flood defense “Boston Barrier”. These 3 emergency barriers are part of the Boston Barrier Flood Protection Project, which aims to protect some 14,000 households in the Lincolnshire hinterland from flooding. It makes us proud that we can make an important contribution to this from the Netherlands, a country of “hydraulic engineers”!

In order to better protect Boston and the hinterland against high water, the English government has decided to build the tidal storm surge barrier “Boston Barrier”. Hollandia Infra has received an order from the main contractor, construction consortium BAM Nuttall-Mott MacDonald, to design and build three steel segment doors for this new storm surge barrier.

Water-retaining construction

The “Boston Barrier” is made up of 2 water-retaining structures. Hollandia Infra previously designed and built a vertically moving steel segment door. This “Radial Sector Gate” is 30 meters long and weighs 350 tons. The segment door is normally on the river bed and is only turned up within 20 minutes during storms to close off the river. The door is comparable in form and function to the steel emergency flood barrier that Hollandia Infra supplied for the Ipswich Barrier tidal barrier, also off the east coast of England. Secondly, the assignment for Hollandia Infra includes the design and delivery of two horizontally moving segment doors. These 2 “Vertical Segment Gates” turn from their recess in the quay into the waterway; the operation is comparable to the well-known storm surge barrier “Maeslantkering” near Hoek van Holland. The 2 segment doors for the Boston Barrier each weigh 100 tons, are 10 meters high and together close the 18 meter passage. The doors are located in front of the entrance to Boston Harbor and, on the one hand, protect the harbor against high water and, on the other, they serve to regulate the internal water level in the harbor, so that boats do not run dry at low tide.

Project approach

Commissioned by the Environment Agency (similar to Rijkswaterstaat in the Netherlands), the joint venture BAM Nuttall – Mott MacDonald has carried out the project for the “Boston Barrier Flood Protection Programme”. The work is split into three main phases; the storm surge barrier and flood walls on the right bank, a new left quay and flood walls, and the harbor entrance and flood walls. The project includes a 25m wide rising gate across the section of the River Witham (better known as the Haven) south of downtown Boston between Black Sluice and the landmark Maud Foster Sluice. A new control building will serve the barrier. There are flood defenses on both banks and replacement gates opposite the entrance to the existing Boston Harbor. Furthermore, the project includes the widening of the access to the dock, new quay walls for the port, accommodation works; temporary mooring facilities for the Boston fishing fleet and a turning basin for commercial shipping. To complete the project, two grain towers, a jetty and two large warehouses will also be demolished. The work was carried out in the immediate vicinity of residential houses. An important point of attention in this project is the good relationship with the local residents and thus avoiding nuisance for residents as much as possible. The central part of the storm surge barrier program is formed by a 30 meter long visor slide, which can be turned up within 20 minutes in the event of a storm and imminent high water, thus offering protection against high tides from the North Sea.

The Vertical Sector Gates (VSG)

The “Wet Dock Gates” also known as the two “Vertical Sector Gates (VSG)” are located in front of the entrance to the harbor to protect it during high water and to regulate the internal water level in the harbor. The Vertical Sector Gates are two quarter round retaining devices, consisting of open frame constructions with a closed retaining wall. When the doors are closed, the doors rotate horizontally around the vertical pivots on the quay wall and the two radial shapes touch each other in the middle of the passage. When the doors open, they pivot into niches in the concrete quay walls. The fully symmetrical convex shape of the doors ensures that all resulting forces from the water forces pass through the pivot point and no resulting rotating force remains. These segment doors therefore do not move under the influence of water pressure. These turning means together close off the passage, retaining water in 2 directions. This is because they also have to ensure that the ships in the harbor do not run dry during the low tide. These ‘Wet Dock Gates’ of approximately 100 tons each have been placed at the entrance of the harbor and thus form a secondary emergency barrier. The tidal difference in the river The Haven, which is in open connection with the North Sea, can be as much as 5.8 meters.

Please visit this website for more information: Boston Barrier – Hollandia

Photos: PortPictures