It’s not often you find a quarry site with a stable of thoroughbred horses, a working farm, a network of public footpaths and a resident woodcutter. Joanna Booth went to Kent to discover how Gallagher Group is keeping England’s garden green - and investing £2 million in new plant to raise production
It's not often you find a quarry site with a stable of thoroughbred horses, a working farm, a network of public footpaths and a resident woodcutter. Joanna Booth went to Kent to discover how Gallagher Group is keeping England's garden green - and investing £2 million in new plant to raise production
INSIDE the Gallagher site office a 3D scale model of the entire Hermitage Quarry and the surrounding countryside sits in a glass case.
'At community meetings we found people had difficulty visualising how our plans would affect the area so we had this made, ' explains Martin Hobbs, managing director of Gallagher Aggregates.'If you crouch down and look across the model you can see that the quarry isn't visible from the adjacent land.'
Gallagher approaches site upkeep with the same thoroughness it does community liaison.The company has planted 60,000 trees and shrubs on the 275-ha estate and erected £7 million-worth of post and rail fencing.
Over 200 cattle graze the unquarried fields.
This commitment to making the quarry area environmentally sound is strengthened by the fact that it really is in company chairman Pat Gallagher's back yard.He bought the site in the mid-1980s and built himself a house within the estate.
Kent is ragstone country - a sandy limestone used in the Tower of London and St Paul's Cathedral. It is interspersed with hassock, a soft, sandy material with a high silt content. Ragstone is capable of producing quality products but, because it forms in thin beds and in equal ratios, some quarries process both rocks together to form lower-grade fills.Gallagher quarries around 600,000 tonnes a year and separates the ragstone and hassock using a trommel screen.
Before the introduction of the aggregates levy, the hassock was sold as fill but, like many, Gallagher has found the tax has made this uneconomical.
The ragstone is processed and sold as type 1 sub-base, rock armour, gabion stone, capping layers, drainage blankets, sand products, and is made into concrete by two on-site readymix batching plants.These produce 40,000 cu m a year.
Two years ago the company decided to explore ways to make the hassock saleable and found that, if the silt was washed out, good quality materials could be produced.Gallagher sells the hassock as two grades of sand and four sizes of aggregate.
'Washing is simple, ' explains Mr Hobbs.'If you add enough water and agitate it, you get it clean. It's what you do with the silt that comes off which is key.'
Gallagher worked with specialists Powerscreen to select the technology that suited them best.The company needed to induce the silt to thicken and then squeeze as much water out of it as possible.
The fully-automated system is designed to produce a manageable silt cake from the sludge. It is pumped into two 7 m-diameter deep cone thickeners. Flocculent, a chemical that coats the particles of silt and makes them stick together, is added to aid the separation of water and silt.Anionic flocculent is added as the mixture enters the cones to accelerate the settling of the silt.
The clarified water weirs over the top of the thickeners and is piped away. It is reused by the washing plant, which gets through 2,500 gallons a minute.
Cationic flocculent is then added to drive out as much water as possible before the silt goes through two multi-roll belt presses and emerges from the press in cake form.
Gallagher chose the Italian deep cone thickening system over a conventional method as it works purely by gravity, with no moving parts in the drum that could fail. But these had only been used in conjunction with expensive plate presses.Gallagher would have needed at least four of them.
'We had some concern because the deep cone thickeners had never been used with multi roll-belt presses, ' remembers Mr Hobbs.'The Italian technician who came to set up the system didn't speak much English and wasn't familiar with the action of a multi-roll press, so we had some headaches. But we needed the belt presses because of their capacity.We have two and they can deal with 80 tonnes of dry silt an hour.'
The system has reduced the amount of hassock waste Gallagher sends to landfill to 15 per cent of the total. Because the silt is pressed until solid, it also means that there are no pools of sludge scarring the countryside.
The company invested £2 m in the washing plant and silt management system.All civils works were completed by Gallagher Group's contracting arm, which began work on site in December last year. 5,000 cu m of Gallagher concrete went into the huge slab the plant sits on in the centre of the live quarrying area.To avoid crossing the site with miles of cable the company has ducted it all underground.
The Gallagher Aggregates team is small, with 12 workers in the quarry and only three sales staff in the office.Mr Hobbs joined the company four years ago, having worked for Hanson and ARC, and enjoys the freedom a smaller company allows him.
'It's great. I talk things over with Pat but that's it.Over the years I've written loads of projects trying to get capital for new plant but big companies take too long to decide.They stifle innovation because you can't get things off the ground quickly enough.'
Gallagher has quarried and backfilled two fields, and has planning permission for two more.These reserves should last for 15 years.After that Mr Gallagher is hoping to extend permission to cover more of his land.
An area of certified ancient woodland in the estate may present problems when it comes to getting planning permission. But the company is trialling ways to retain the seed bank in the soil so that trees could regrow.
Mr Hobbs argues that quarrying the site would actually be better for the area and the environment.
'If there were quarries like this all over Kent there would be no need to import limestone aggregates. From the country's point of view it is better to use our indigenous sources. If you haul aggregate a long way it's environmentally damaging. People don't think of that.'
He underlines that Gallagher would quarry as sympathetically as possible.
'We're thinking of tunnelling from a corner of the existing site and coming up in the middle of the wood.We could leave the trees round the perimeter.Unless you were in a plane or trespassing you wouldn't know we were quarrying. It won't minimise costs but this is Pat's garden, and he wants it looking nice, ' he says.
Adverse effect of the aggregates levy
BEFORE the introduction of the aggregates levy Gallagher used to sell hassock as a cheap constructional fill product but adding the £1.60-per-tonne charge to a product being sold at only £2 a tonne soon stopped that.
Initially Gallagher had to dump the hassock back into the quarry using void space which could have been used for inert landfill.
'We were quarrying more to sell less and producing more waste, ' says Mr Hobbs.'This wasn't what the levy was intended for.Our local customs and excise guy agreed but the central office wouldn't listen.'
Mr Hobbs' argument with customs and excise isn't over yet.
'All of the waste hassock that has gone to landfill can be reexcavated and reprocessed. In my mind that makes it recycled, and tax-exempt.They haven't accepted that yet though.We will re-excavate the hassock anyway but we're still fighting them on this one.'
He feels that the levy itself has had an adverse effect on the industry.'We gambled a lot of money on trying to deal with a problem created by the government. I can't believe they don't recognise the environmental damage they've caused with its introduction.The idea of it was to reduce the amount of primary aggregate excavated.We've had to almost double it. Somebody got that wrong, didn't they?'