Project Building seven glasshouses and ponds on a 92 ha site in Kent Project cost £80 million
Main contractor and civils contractorFitzpatrick
Substation contractor Provian
In the grocery world, Thanet is well known for its cabbages and potatoes. But when Fitzpatrick’s latest project is completed it will also be identified for its tomatoes, cucumbers and peppers.
The company is 12 months into a project as main contractor to turn a 92 ha site into seven huge glasshouses (up to 9 hectares each), holding ponds, a pack house and a substation.
This site will harvest rainwater and condensation, recycling as much as possible through the network of reservoirs. The development will not only produce enough gas fuelled power by combined heat and power generation (CHP) to supply the greenhouse complex called Thanet Earth but will put enough electricity back into the National Grid for half the Thanet peninsular.
Three of the glasshouses are already standing tall, the bones of the pack house are up, the substation is recognisable and the ponds are dug – even if some are still unlined.
Two-thirds of an access road linking the site to the main road is in and the hope is that tomato planting will begin in one of the glasshouses in December.
Although Fresca, a UK fresh produce supplier, is the main client, three other vegetable-growing firms from the Netherlands each own a glasshouse and have taken responsibility for hiring in their own contractors.
These Dutch contractors have in turn hired their own teams of piling, framework, glazing and mechanical and electrical subcontractors to build them.
The four other glasshouses are expected to be built once the first three have proved successful, but the groundworks for them have already begun.
Fitzpatrick project manager Deon Scholtz says the subcontracting firms came over from the Netherlands, where projects like this are common.
But because European Union health and safety regulations are different from those in the UK, Fitzpatrick had taken on the role of main contractor.
For Fitzpatrick, that meant making sure the Dutch contractors had health and safety plans, that supervisors had been through the necessary courses such as those on UK construction, complied with design and management regulations as well as doing inductions, sometimes in Dutch.
“We put up the temporary welfare facilities and helped with health and safety so they could operate here,” Mr Scholtz says.
He adds: “It also meant going onto site occasionally and reminding contractors that they had to wear their helmets and don high-visibility vests.
“We are not here to play policeman, we are here to work beside them,” he says.
Site workers from Fitzpatrick are building the access road, Fitzpatrick Construction employees are working on the pack house while Provian is busy building the substation.
But with up to 300 people working on the site each day, Fitzpatrick has also had to manage the needs of the different teams and how they interact with each other.
Before the Dutch subcontractors could build anything, the site had to be prepared – a mammoth task.
“We’ve moved a million tones of muck around the site,” says Mr Scholtz.
First the topsoil had to be removed and then 700,000 cu m of chalk had to be moved to create the seven massive platforms for the glasshouses and the 10 m-deep ponds for rainwater harvesting and overflow areas.
The stock-piled topsoil was then put down again on top of the chalk to create the bases of the glasshouses and rolled to be
Mr Scholtz says: “It was a major operation to move that amount of muck around a site and balance it so that we didn’t need to send any to landfill. We had to continually measure it and then move the platforms up or down as needed.”
At times, moving the very porous chalk in the middle of winter was “diabolical”. But because of the size of the site, the
contractors could move it and then work elsewhere until it settled, before returning to it.
He says: “[The material] has a compression rate of 90 per cent, which is what the engineers recommend.”
But before any chalk could be moved, the topsoil had to be stripped so archaeologists from the Canterbury Trust could map areas of interest and do further digging where necessary. Only when Kent Heritage gave the go-ahead could work begin.
Mr Scholtz says: “The dig has been going on for a year now and it has delayed the project by about six months. But it was part of the agreement to preserve archaeological areas.”
He estimates the investigative dig has cost the client about £1 million – considerably more than was budgeted for. But for Fitzpatrick, as civils contractor, it has caused a headache – when small pockets of land on site were made available by Kent Heritage, they were often not side by side.
Mr Scholtz says: “It was all about planning for where we could start work next.”
Southern Water also had to divert a main water line running under the positions of the new greenhouses. But it didn’t want the excavation for the new pipe to be backfilled until after the diversion was completed.
Mr Scholtz says the water company had finally been persuaded to allow part of the new pipe to be buried so contractors could get on with work on the site.
The construction of the glasshouses, which measure between seven and 9 ha, are relatively easy to build compared with the groundworks. “The glasshouses took 11 or 12 weeks to construct,” says Mr Scholtz.
First the Dutch contractors came in and drilled 1.5 m-deep, 500 mm-wide holes for the piling. They then drove in a specially modified truck with a shoot on the back that pours concrete into each of the holes before adding a precast concrete pile-cap.
Finally, a 0.5 m-high concrete beam was built around the footprint of each greenhouse to tie in piles installed around this perimeter.
A second set of workers arrived with prefabricated aluminium frames imported from the Netherlands. The workers bolted these to the pile caps and then constructed the frame.
In the frame
Mr Scholtz says the concrete pile caps mean that if parts of the frame need to be replaced at a later stage they can just be unbolted and new pieces put in. Finally, glaziers brought in 1 m by 2 m non-reflective glass sheets that are inserted from the inside by contractors on scissor lifts.
The welfare facilities, mechanical and electrical, and CHP generators, which are in each glasshouse, are being hooked up at present.
Mr Scholtz says: “Contractors are lining the ponds, which are first covered in a carpet and then HDPE [high density polyethylene] sheets. The carpet is used to stop the flint, which is found in the chalk, from cutting through the polyethylene.”
The ponds are linked by pipe to the glasshouse roofs so rainwater can be harvested and reused in the glasshouse irrigation system.
These reservoirs will hold almost 300 million litres of water, and it is anticipated Thanet Earth will be self-sufficient from May to September.
Developers of the Thanet site always knew it would be of archaeological importance because of its proximity to other areas of significance, but had no idea the extent of it.
When contractors had widened the nearby A253 road, they found a historical treasure-trove. This included Bronze Age burial sites, an Iron Age hut, a unique Romano-British village, a small Anglo-Saxon cemetery and a medieval farmstead.
Archaeologists for the Canterbury Trust have been on site since the beginning and have not been disappointed. Mr Scholtz says they seem to have found items from the Bronze, Iron and more recent ages. So far, early Bronze and Roman age burial sites, hundreds of domestic storage pits, medieval timber buildings and World War Two memorabilia have all been discovered on the site.
A skeleton found in one of the Bronze Age burial pits is thought to be 4,000 years old and has been described by archaeologists as a significant find.
POWERING THE SITE
Kent-based Provian Construction won the £870,000 contract to build a 132/11kV substation on the site to provide power for the site once it’s up and running.
However, this substation may not be needed and could be used instead to feed surplus power generated by the Combined Heat
and Power (CHP) system back through the substation and transformers into the national grid.
It is expected that the gaspowered CHP will produce enough electricity to supply half of Thanet.
The substation will include an 11kV switch-house and two concrete transformer foundations with red brick blast walls. Provian is also responsible for building internal access roads, a drainage system, palisade fencing and hard landscaping works.