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Grimsby gears up to grow

Once famous for its fishing fleet, Grimsby is now the UK’s busiest car-handling port. Declan Lynch takes a look at its latest expansion plans.

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Grimsby will long be associated with its famous fish docks which once supplied most of the UK with fresh fish, but the reduced Atlantic fishing rights following the Cod War in the 1970s, declining fish stocks and strict European Union quotas have all but ended a once thriving industry.

Although the port still retains a strong connection with fishing and the food industry, its major focus now is on handling imported cars. More than 600,000 vehicles are imported through Grimsby each year, but scope for further growth has been limited by the size of the lock used by specialist car carrying vessels.

The existing lock dates from 1852, and limits ships using it to those with a maximum 800-car capacity. Car transporter ships can only pass through the lock twice a day, at high tide. They must then travel the length of the Royal Dock, before manoeuvring into the designated berths at the west end of the adjoining Alexandra Dock.

This is set to change soon as a result of a £25M investment by port owner Associated British Ports (ABP). It is building a new jetty out into the Humber, connecting to a floating pontoon onto which ships will unload. Ships will moor either side of a finger pier, which runs at right angles to the pontoon (see diagram).
The new Grimsby River Terminal, as it is known, will be able to handle two vessels each carrying up to 3,000 vehicles, significantly increasing the port’s capacity.

“The works are required to ensure the future profitability of the port,” says ABP Humber engineering manager Sean Blissett.

The terminal is being built in the Humber estuary to the east of Grimsby docks, avoiding shipping lanes.

“The biggest challenges are the weather and the sea conditions”

Contractor Graham is constructing the new terminal under an £18.8M fixed price design and build contract. Graham is working with Mouchel as its consultant.

The project splits into two areas - piling and manufacturing the precast deck units for the approach and finger jetties.

Piling for the project was restricted to a three month window between May and July so migrating wading birds could feed on the mud-banks. If the piling was not completed in this window then the contractor would have to wait until the following year before finishing it.

“We spoke to contractors at tender stage and Graham assured us they could pile within that timeframe,” says Blissett.

“The biggest challenges are the weather and the sea conditions,” says Graham project manager Gareth McLaverty. The site overlooks the Humber estuary and is prone to sudden weather changes.

Work began on site in February and one of the first jobs was to dredge the area under the pontoon - called a dolphin - and along the line of the finger jetty where the vessels will berth.

Marine subcontractor Westminster Dredging removed 160,000m3 of seabed, lowering the level by 6m to accommodate larger vessels. Dredging took place in March and April ready for piling to start in May.

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“It’s a live channel so we needed to liaise with the dock master to ensure we weren’t blocking traffic,” says McLaverty.

The water depth across the site ranged from zero at low tide to 11.9m and the tidal range is 9m. Below the water, the ground conditions consisted of a 7m layer of alluvium deposits, a 13m layer of glacial deposits and an 11m layer of chalk.

To create the 9.5m wide 250m long approach jetty from the shore to the link-span bridge, Graham had to install 62 piles. Each pile is a 762mm diameter, 32m long tubular steel tube.

Starting from the shore, a 9t crane drove the first four piles. Graham then used a “navvies’ mat” - a steel platform designed in-house to sit on four piles - to provide a platform for the crane to install the remaining piles. As piling progressed, the crane slid the navvies’ mat along the installed pile moving out into the water. The piles were delivered to site by barge.

“We did consider using a stone causeway,” recalls McLaverty. “But difficulties transporting all that stone to site meant we ruled it out.”

Along with the 62 vertical piles, Graham is installing six, 1.2m diameter raker piles to form the bankseat for the 70m long steel linkspan bridge.

This bridge, fixed at the shore end, connects the approach span with the floating dolphin where the vessels berth.

“The car trade wants to use bigger vessels and we’re offering what the customer wants.”

The bridge is being manufactured in China and will be delivered to site in November.

Graham is manufacturing the 80m by 30m, 6m deep dolphin in a Newcastle shipyard and will tow it to the site at the end of this month.

“We first thought we would use a steel pontoon,” says Laverty. “But the biggest thing is cost, and steel is more expensive [than concrete].”

Surrounding the pontoon are restraint piles. Using a 20t crane barge-mounted crane, engineers are installing two sets of 16, 1.42m diameter piles on the north and east sides of the pontoon to hold the dolphin in position.

The final piece of piling is for the finger pier, stretching 195m from the dolphin out into the River Humber, to provide mooring facilities for the car vessels. It comprises 22, 762mm diameter vertical piles, 18, 1.067m diameter piles and 15, 965mm diameter raking piles. The 1.067m diameter piles support the jetty’s fenders - a big shock absorber to help the jetty withstand the impact of ships.

Graham managed to squeeze in complete installation of all piles within the three month window. With the piles in position, engineers then cut them to size using a specially-fabricated platform which sits on the pile.

A mini precast yard adjacent to the site was set up to create the decks for the approach and finger jetties. There are two production lines on site to make the 225 precast units that form the platform for the approach jetty and finger pier. “We considered using precast yards, but we wanted more control,” says McLaverty.

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On the approach jetty, engineers will install a 1.515mm diameter inverted circular top hat to sit on each pile. On top sits a 1.5m wide, 900mm deep and 10m long trough beam which spans between the two piles. A total of 123, 2m long, 8.17m wide precast deck slabs will be placed across the trough units to form the roadway.

A 9t crane will install the top hats, trough beams and deck slabs from the sea working back towards the land.

Once all the precast sections are in place then the roadway will be cast in-situ working from the land back out to sea.

When the new terminal is complete next March, vessels as large as 165m long and 28m wide will be able to berth at the new facility - far larger than current capacity.

Along with the terminal, Graham is creating a 12,000m2 car parking space to store new vehicles when they are unloaded. “It gives a better service to our customers,” says Blissett.

“The car trade wants to use bigger vessels and we’re offering what the customer wants.”

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