The east coast of England can be a beguiling place. From its northernmost reaches around the Scottish border to its southern most stretch as it turns the corner into the English Channel the east coast has something to offer everyone.
It was on this coast that the great British seaside holiday was invented and vast quantities of fish were landed at its quaysides to feed workers during the industrial revolution.
And although huge stretches of the coast have been in decline over the past few years there are signs that the green shoots of recovery are starting to show.
At Great Yarmouth in Norfolk, the borough council has finally approved plans to build a new outer harbour at the entrance to its existing port which will provide the area with a much-needed commercial boost.
Things have been pretty tough in this part of the world since the decimation of the fishing fleet that used to call Great Yarmouth its home port. Most of the activity at the dockside now serves industries supporting the southern reaches of the North Sea Oil Field. But Great Yarmouth Borough Council and port operator Great Yarmouth Port Company, a subsidiary of International Port Holdings, are planning to change all that and bring some of the good times back to this corner of East Anglia.
By providing deeper facilities for longer, wider vessels than are currently able to use its inner harbour, Great Yarmouth hopes to capitalise on its closer proximity to the major ports in The Netherlands, particularly IJmuiden, and divert some of the existing container traffic away from its rival down the coast at Felixstowe.
Locally-based contractor Nuttall John Martin and dredging and marine specialist Van Oord are working under a joint venture partnership to help deliver the new harbour, the first significant new port development on the east coast for years.
“The port was first mentioned in council minutes about 25 years ago but it has only been in the past few years that the drivers have come together to help push the project forward,” says Nuttall John Martin site agent Bob Perry.
Attractive to shipping
These include a push to improve transport efficiency and the projected downturn in fortunes from the southern North Sea oil fields.
If the price of fuel continues to spiral at its current rate the likelihood will be that any transportation hub that enables bulk quantities of material to be handled will be of increasing interest.
Here at Great Yarmouth the new harbour will make the whole port more attractive to shipping companies and should help make entering the old harbour in the mouth of the River Yare easier - a strong north to south tidal flow can drag unsuspecting ship’s captains past its entrance.
Lack of depth in the existing port is also an issue but the new, deeper-water harbour could make the old port more accessible, according to Van Oord assistant project manager Angus Macdougall.
“The outer harbour will allow vessels of greater draught to use Great Yarmouth,” he says. “Loading in the existing port is very much tide-restricted. The new outer harbour, particularly the southern breakwater, will produce an eddy from the north-south flow, which should make getting in easier.”
The non-integrated joint -venture between the two companies is split into two sections of work.
Scope A is the offshore work - dredging, breakwater construction - which is being undertaken by Van Oord, while Scope B is the onshore work - construction of new quay walls and piling work - being carried out by Nuttall John Martin.
Scope A is taking the lion’s share of the £53.5 million total spend with the contract price running at around £40 million. Scope B soaks up the £13.5 million balance.
Currently part of the Van Oord fleet of vessels is standing offshore, dropping rock of various shapes and sizes into position as the breakwaters are crafted.
It is using more than 800,000 tonnes of Norwegian granite, shipped across the North Sea, to construct almost 1.5 km of breakwater at the development.
“It is actually easier and quicker to use Norwegian stone than UK-sourced material because we can load it straight into the boat at the quarry,” says Mr Macdougall.
The Frans, a side-dumping vessel, carries smaller stone across the North Sea and hydraulic rams discharge the cargo. By setting a predetermined rate of dispatch and carefully controlling the ship’s speed, Van Oord can accurately place layers of stone, slowly building them up until the required depth is reached.
At the waterside toe of the breakwater that first layer will be a minimum 400 mm-thick carpet of 25-100 mm sized material followed by an 800 mm-thick carpet of larger stone weighing between 60 and 300 kg. The main core of the breakwater is being built using 10-1,000 kg stone, or ‘quarry run’, which is protected on the seaward side with a 1 m-thick layer of 250 kg secondary armour before a final 2.1 m-thick layer of primary armour with rocks weighing 2.5 tonnes is placed. This primary armour layer is beefed up to a thickness of 2.5 m using rocks weighing as much as 4.5 tonnes at the crest of the breakwater.
“The first filter layers act as a scour apron in front of the breakwater,” says Mr Macdougall. “The larger rocks are placed individually using the Razonde Bol. She’s a pontoon-mounted backhoe dredger fitted with a rock grab to place the primary and secondary armour.”
The larger chunks of rock is actually waste product from the cutting of granite worktops to grace Norwegian kitchens. It is shipped over from Norway on pontoons capable of carrying some 20,000 tonnes of rock before being unloaded offshore onto smaller pontoons. These then ferry that material closer to shore, where the Razonde Bol places it precisely.
Anchored a small distance away and overseeing the transferral of the rock from the larger vessels to the smaller pontoons is an agent from the Department for Environment, Fisheries and Rural Affairs.
In what must amount to one of the dullest jobs in the world, Defra agents log the transferral, one by one, of every single rock from the larger vessel to the pontoons. The officers will note any rocks that are dropped to the so that they do not become a danger to fishing trawlers or other vessels.
After all, the last thing the UK’s latest port would need is a built-in hazard at its entrance.
Dredging down to depth
Material dredged from the internal pocket of the harbour to a depth of 11 m below chart datum is being used to backfill around the breakwaters.
The medium-to-fine sand is being placed in two stages, initially to a height of 3 m above chart datum before being topped up to 5.5 m above datum once the combi-wall has been completed.
“The material is pumped from the seabed at a mixture of five parts sea water to one part sand,” says Angus Macdougall. “The water compacts the sand as it is placed; there is no need for any further compaction.”
Any surplus material will be pumped to the ‘spending beach’ on the south side of the harbour entrance. A rock revetment placed at the back of the harbour will soak up the effects of south-easterly swells that bear down on Great Yarmouth through the Holm Channel – a gap in the huge Scroby Sands sandbank that protects this section of the Norfolk coast from all but the fiercest storms.
Nuttall John Martin on Scope B
The landside portion of the work at Great Yarmouth, referred to as Scope B, is equally as complex as anything the water-borne project team can throw up.
On the northern side of the harbour, a combi-pile wall is being built, which will eventually form the quayside. Defended by huge buffers to fend off damage from docking ships, the quayside wall is being installed using a line of 1,067 mm-diameter, 25 m-long steel tubes driven to about 20 m below chart datum.
Then three linked steel sheet piles will be driven to a similar depth to provide the infill between the tubular piles. Initially sourced as high grade steel pipes for the petrochemical industry, the piles are shipped from Rotterdam.
“The tubular piles are load-bearing but the wall can’t stand on its own,” says Nuttall John Martin site agent Bob Perry. “There is a retained height of 16 m and an anchor wall will be installed 30 m behind the combi-pile wall.”
Installed using 6 m-long sheet piles, the anchor wall will be tied to the combi-pile wall by 85 mm-diameter tie rods with articulated joints designed to allow some rotation. A capping beam will be cast along the length of the quay wall, which will act as a crane rail for unloading ships.