Making Waves

Clustering higher value services and utilising lower value aggregate products in-house for high-end materials is the direction the quarry industry in the UK has been moving for while. But nowhere is the ideal end of such planning realised better than in Tarmac’s Leeds-based Cross Green facility linked by rail with its flagship Swinden Quarry near Skipton in the Yorkshire Dales National Park. MQR paid both sites a visit to gain greater insight into their workings, the people that run them and the process of product creation from rock face to truck-loading and found two sides of the same coin busy making waves in the traditionally still world of quarrying.

Everyone seems to have an opinion on who will buy Tarmac. All the usual suspects get mentioned. But if your knowledge of the currently Anglo American-owned firm was restricted to its Skipton-based Swinden Quarry and Leeds-based Cross Green urban cluster site, you would probably come up with some interesting wagers.

Based on these sites, a retail giant such as Philip Green or M&S may enter the betting fray. Maybe even a few fast-moving consumer goods specialists. Why? Because all that is missing is the glass for the shop window. These are sites a long way from traditional quarrying. In fact, they are slightly ahead of contemporary quarrying!

The country gent quarry of Swinden and the urbanite future-savvy Cross Green are two sides of the same coin. Both technologically up-to-date, both environmentally sensitive, both aware of the power of communication and image, and both managed by young, career-driven, forward thinking men.

Joined by an arterial rail link, both sites open themselves right up to both the public and potential customers. In fact, this openness is part of the sales pitch. They are the industry’s equivalent of an open-plan high street fashion outlet. Except at these sites it is the industry itself as well as its new business model that is on display.

Once a local pariah, Swinden has undertaken a multi-million pound upgrade over the past decade to become a sensitive – as well as a dust and noise free – neighbour. Meanwhile, once a wasteland, the Cross Green site encompasses asphalt and concrete plants, DSM, wet mortar, recycling, cement storage and from January this year, national contracting. It is the ultimate clustered operation as well as the materials hub for other Tarmac operations.

And as project Trident works its way through Tarmac, reporting on potential efficiency savings and better ways of doing business, the two sites working as a unit must be seen as a model for other sites across the UK.

So how does it all work? Well, the best place to start is a sunny afternoon in the Yorkshire Dales National Park surrounded by 36 gaggling secondary school children. “I’ll be with you in a minute,” says zone and quarry manager Phil Dukes as he bobs up from a sea of young faces – around 300-400 children visit the site each year from as far afield as Sussex. Dukes is then swept away, not to be seen again for a couple of hours.

Local school governor Dukes is a busy man. He is the area zone manager for Tarmac’s Northern Aggregate Products division – a Tarmac uber-job title that raises people’s responsibility levels to encompass a range of sites. Dukes is top man at three operations across the Yorkshire: Swinden Quarry, Arcow Quarry and Skipton Rock coating plant.

“Have you seen Phil Dukes,” asks consultant George Gray. We reply: “briefly”. Someone else says that he thinks he is in the quarry and so Gray sits at the picnic tables outside the visitor centre with the rest of us, waiting for the elusive zone manager.

Dukes has asked for Gray’s advice on constructing a ramp in the quarry, the Scotsman explains as we sit watching oyster catchers bob along a limestone path cutting through manicured grassland and young indigenous woodland.

When the talking stops you suddenly realise you can’t hear any quarry type noises. This is an operation that last year extracted and processed around 2.2million tonnes of limestone. Yet the B6265, the bleating of sheep, and chirping birds – and occasionally the rumble of schoolchildren – appear to make up the local soundscape.

As for the landscape, even the road leading to the visitors’ centre – a multi-media educational experience more often found in tourist attractions – is a serpentine path walled by greenery.

It is broken only by an overhead conveyor feeding the rail head from the quarry’s processing area. The belt is the only outward sign – apart from a lump of limestone advertising Swinden at the entrance – that there is even a quarry here. It is easy to wonder if you are entering a quarry at all.

And this feeling continues as you round the hill into the quarry area away from the visitors’ centre and stand in the roofed ‘viewing gallery’. Complete with information boards and over-looking the full excavation and processing area, it is the shop window into the site allowing both the Yorkshire Dales National Park, in which the quarry sits, and potential customers to buy into the Swinden brand.

Of course, this also plays well given that Swinden has a planning application to extract a further 24million tonnes up to 2030 waiting to be heard by park planners in October. There are only 14 years of consented reserves left at the site so it wants the park on side.

But Tarmac is also offering to surrender its permission to extract 24million tonnes from nearby Threshfield Quarry in exchange for the extension at Swinden, with the former site being restored within two years of the proposal being granted.

Making a change
In short, Swinden is a good sign of how quarry firms have found better, win-win ways of doing business. After all, the quarry is currently excavated to 40m below the water table. There is a further 60m to go. This is the kind of work that makes national parks nervous.

One unchecked oil leak from a crusher could be disastrous. The open, partnership approach helps ease planners’ nerves and makes for a better working relationship. It was a lesson learned at Swinden over a decade ago.

Brian Lockey is unit manager for Swinden and Duke’s right-hand man. In the zone manager’s continued absence he shows us around. He has worked at the site for 26years and remembers the time of Tilcon when things were much different.
Lockey: “The investment in the site after the Anglo American buyout merged Tarmac and Tilcon made a huge difference. Before we were processing on top of the quarry, creating a lot of noise and dust. It had to change.”

The investment he refers to is a £15million injection in plant at the site made in 2000. Jobs were lost and some dead wood removed. At the time Tarmac predicted direct employment levels would still “exceed 50”. However, increasing use of computers and general outsourcing over the past eight years means the number currently stands at 28.

Many of these have been on site for years, explains Lockey. “There are people who have been here longer than me and are younger than me. Once they get into the environment they tend to stay. Retirement is our biggest drive to recruitment,” he says.

Focusing on the process
And leaving doesn’t mean that you don’t come back. Michael Howes is a good example, he transferred to Ritchies when Tilcon outsourced explosives duties at the site to the geotechnical specialist before the merger. We catch him as he puts the finishing touches to today’s bang.

He is checking the shock tube wiring connected to the detonators for the ammonium nitrate matrix explosive ready for the 3.00pm blast – it should have all happened at 1.00pm, he explains, but the explosives truck broke down, losing time and making things tight for the earlier blast.

Earlier an Atlas Copco ROC L8 drill rig finished drilling the 44 holes needed to lift the 53,181tonnes of limestone from the MDL laser profiled quarry face. The 23m holes all now hold an average of 200kg of emulsion explosive – as the site is well below the water table ANFO is not a possibility.

Howes needs to produce blocks of 1.5m3 and smaller to fit into the wide jaws of the Metso LT160 tracked crusher – the largest tracked model in Europe. To do this – as well as minimize noise, dust and vibration – timing of the blast needs to be millisecond perfect.

“There is a primer and detonator in the bottom of the hole with a 475millisecond delay on it,” explains Howes. “This goes off first. At the top of the hole is a 500millisecond delay detonator. If the bottom one fails then the top one will kick in with surface connectors holding them together.

“Blast holes in the front row have a 67millisecond delay between them, coming back to the back row where it increases to 109milliseconds. The face is peeled off from the front first. If they all fired at the same time it would be like a bomb going off,” he says.

As he talks, a Cat 5130B happily buckets blocks up to 1.5m3 into the LT160 below us. The primary crusher is now eight years old and processes around 2million tonnes of 1.5m3 blocks down to -300mm each year.

From the top of the face you can see the steel structure holding the belt and transfer points taking material from the crusher stretching to the far side of the quarry to the processing plant. Does Lockey know how long it is?

“A fair bloody distance,” he says with a smile. “I don’t know for sure but I know we are extending it by 60m every two-three months at the moment. We used to use dump trucks to move the material but the tonnage rate is much higher this way.”

The exact length of the main conveyor currently, Dukes says later, is 360metres. However, this will be taken to 480metres over the coming months. It was constructed by Continental Conveyor but is maintained by Ace Conveyor who do belt repairs and vulcanising. “We can clip joints into it for repairs but then we can’t scrape well so we tend to vulcanise where possible,” explains Lockey.

The belt carries the -300mm the current 360m to where it ends over a stockpile. Beneath the high cone of material is a tunnel. And on the ceiling of the tunnel there are three vibratory feeders capable of processing 500tonnes of material an hour each.

However, the 1,500tph capacity is rarely used, says Lockey. The normal setting is to use two feeders running off at 900tph. It is a constant process with material then falling on to a conveyor and moving to the secondary crusher. This time it is a US-made Pennsylvania rotary impact model sourced through project managers Fairport Engineering.

This crushes the -300mm to -90mm, which then all enters the screen house packed with two triple, two double and two single Don Valley screens. The belt splits at the top and feeds down either side of the screen house.

The poorer brown material or fines from the secondary crusher can be scalped out and is fed by conveyor to become primary fill or a 6N product. We will see more of this at Cross Green later.

The 40-90mm material gets screened into a rejects bin ready for reprocessing. This is drawn back down into a tertiary Pennsylvania crusher – the plant has the ability to re-crush everything above 10mm.

From the screen house the bunkers are filled with fine dust, coarse dust, 6mm, 10mm, 14mm, 20mm, 32mm, and 40mm. Local markets are fed directly from the bunkers.

Materials breakdown
Cross Green in Leeds is the biggest single recipient of material from the site and it all arrives by rail (for more on this see below). Almost a quarter of all material from Swinden went to Leeds last year. This year the figure should be higher.

In between trying to fire up schoolchildren into wanting to choose the industry as a future career, discussing ramps with Gray and general site activities, civil engineering graduate Dukes took his brief late afternoon lunch break to give an insight into business outlets.

“Leeds is demanding a lot of material,” he says. “Single size, dust and general fill material. They can’t seem to get enough currently. The maximum number of trains we can send in a week are making their way down.”

Around 16% of rail traffic goes to Hull, he continues. Here Tarmac has a baby brother to Cross Green with an asphalt plant, two concrete operations and a resale hub. The rest goes to Dewsbury, where there is a resale yard, and other operations such as Corus’ steelworks in Scunthorpe.

Overall, 67% of material from Swinden was used in-house by Tarmac last year. And as the afternoon train fills with type-one and 6N from the silos destined for developments in Leeds fed by either Cross Green or one of the other Tarmac facilities in the city, it is easy to see this percentage rising higher.

The train with its Tarmac livery NACORS trucks slowly moves out of the station southwards towards Cross Green. As it rattles out unit manager Lockey says that a few weeks ago Channel Five came to film a quarry blast.

“Everything was about huge explosions,” he says. “They wanted to emphasise how dangerous everything was. We had to explain to them that the industry is about making things safer not blowing things up.”

And anyone having visited the site would have to wonder how programme makers could have thought otherwise. From the visitor centre and viewing platform to the ubiquitous PPE, manicured surroundings and attention to detail of the staff, this is a site that is a long way from being dangerous (but just so you don’t lose out on a moment of danger, Brian, the picture on pages 18-19 is for you. Many thanks for your excellent guide duties – ed).

The same thing can be said of Cross Green. As well as being a site that tries to define the term “future-proof”, safety is again all around. After all, it is another Tarmac shop window that offers viewers an insight into how the industry is planning to develop. In fact, it is so forward looking that even the train delivering type-one that afternoon from Swinden arrives 30minutes early.

Tarmac rail operative Chris Lindley looks impressed. “Wasn’t expecting him yet. Better get started then,” he says, as he disappears to begin his task of ensuring all the rock leaving the train ends up at the right plant or is stockpiled.

Watching Lindley check the computer, site manager Steve Curtin explains that the aggregate goes mostly to the asphalt operation and the concrete plant. The type-one and 6N being delivered today, however, will be stockpiled ready for sale without processing.

The site can receive two trainloads of material from Swinden a day, five days a week. There is the night train that is scheduled to get in at 8.55pm and leave at 11.05pm and the day train that is supposed to get in at 2.10pm and leave at 4.10pm.

NACORS are the night trains in Tarmac colours (see picture page 20). They have 28 trucks in total each holding 66tonnes. The day train trucks are rented from National Power and run by EWS. There are 20 of these operating with capacities of 75tonnes each.

According to the fax sent from Swinden shortly after loading the trucks that morning, today’s daytime cargo is 11 carriages of type-one and 10 carriages of 6N fill material totalling 1,554tonnes.

Every Friday afternoon Curtin receives a programme of work from Tarmac’s national contracting arm. This lets him know the materials needed over the coming week. From this he estimates roughly the number of trains and carriages needed for the week, he explains.

Then it is a case of delivery amounts being determined by bay capacity and level. Curtin: “We keep 1,000tonnes at most in each bay and we have a stock-board in the office keeping track – sensors monitor bay levels. If we take 400tonnes from a bay, we know we need to fill it.

“Chris or one of the lads will phone Swinden the night or morning before the train is set to get in to order. A call would have been made this morning for tonight’s train and tomorrow morning’s train. Someone will phone tomorrow for tomorrow night’s train.”

As he is explaining, EWS train man Mick Brearley hops off and gets ready to signal driver Rob into the rail head. The train inches into the covered area. The driver is radioed to stop when the trucks are between two yellow lines.

The first two carriages stop over two separate grilled hoppers. The truck undercarriages open and 150tonnes of brownish Swinden limestone material thunders into the hoppers through the grill.

Moving through the hoppers the material lands on two separate conveyors, which feed on to a shuttle conveyor. Its actions are determined by the computer Lindley is using (see picture page 20).

The shuttle either stops above an asphalt bay in the toaster rack, links to a conveyor taking material to the concrete plant bins – more on this later – or links to a stockpiling conveyor outside of the covered bay area housing the shuttle and the bays.

Today’s delivery of 6N is routed outside while the type-one is stored in bays 16 and one – for H&S reasons, sirens sound each time the bays are filled. But different products take different routes through the process.

Asphalt
All bays making up the toast rack for feeding the Parker twin fixed Blackmix 2400F asphalt mixing plant have single sizes in them.

And at the bottom of each bay is a ground feeder, which allows the plant to pull off the material it needs.

In fact, the Cross Green asphalt set-up is two plants in one. And as such, there are two conveyors for each bay to feed plants A and B and the system pulls out the aggregates it needs just before the drying process.

For a limestone base this could be 20mm, 10mm and 6mm with percentages depending on end product. The conveyors spring into life feeding the desired mix of rock into one of two dryers – one for hardstone and the other for limestone.

The dryers take the moisture from the mixed product in a few seconds and pull off any excess filler or fine dust. The dust enters either a hardstone or a limestone filler silo. If these are full they can use a large silo outside as extra storage.

After the dryer, the mixed product falls down a chute and into elevators – essentially buckets inside a tube. It is then transported to the top of the plant where it is screened out into its constituent parts again and sent to separate aggregate bins for storage.

As soon as the mix is entered into the mixing room computer by mix-man and plant operative Pete Morton, the rock is weighed up and filler and bitumen added. It all goes into a mixer where it is churned for 45seconds before being dropped into a skip in 3tonne batches on each side.

The asphalt is then pulled up into storage bins. Bins one and four hold 40tonnes, bins two and five 60tonnes and bins three and six up to 90tonnes. The time from pulling off materials to asphalt entering a tipper for delivery depends on the product. But each plant will do anything between 120 and 220tonnes an hour.

Curtin explains further: “An SMA, which has fibres in it, or MasterFlex road topping will take the longest because of the materials. If we have to swap and change products and clean out the bins, tonnages shrink. Fibres can also take time to mix.

Many things can slow it down. But a 32mm base can be hammered out all day. Around 2,000tonnes on a 10hour shift could easily be reached.”

Asphalt orders are received the previous day from distribution. There are 256 different asphalt “recipes” on the mix computer, although 25 a day is the usual demand level. The more variety in the orders, the lower the tonnages processed. It’s a balancing act.

Curtin: “We have to plan for all eventualities. The customer calls the shots and we have to try and meet demand. We have hot storage bins and so we can start between 5.00-5.30 in the morning and get it mixed.

“If it were a base you could get away with eight hours in the storage bins. However, if hot roll or Masterflex then the bitumen runs off through the door at the bottom of the bin. There is no storage life with it.

“So if we do a 100tonne run of Masterflex we like to have four or five eight-wheelers lined up ready to go. There are a lot of swings and roundabouts involved. It is a difficult job making it all balance,” he told MQR.

And customers coming first also means they have the right to ask for material to be tested in the Cross Green lab should they want to. This is dealt with by senior technician Frank Lowe. His job is to unmake the mix.

Lowe: “I deal generally with the Yorkshire area covering asphalt, sand and gravel quarries and the on-site recycling operation here where I make sure the type-one is graded properly. Essentially, I get samples and break them down into parts.”

In terms of asphalt this means taking a sample, weighing it and then adding methylene chloride to remove the bitumen. This is left on for around half an hour.

The bitumen breaks down and releases the filler and aggregate, which is sieved and filtered into grades. Lowe then works out the rock percentages to check everything is OK. All bitumen tested is re-used. Methylene chloride dissolves at 40ºC so they boil it all up and drain off the binder.

For surface course material a sample is taken every 600tonnes. Base course samples are taken every 1,000tonnes. Each morning they tot up the tonnages and see how many they need and take it from there.

And as well as testing, a keen eye is needed. While the process is fully automated it is a long way from being perfect. Morton: “It seems easy because of the computer but you get your problems with it.

“For example, you might not get enough gear up so you will have to feed more in or you might get too much of a certain aggregate so you have to filter some off. It is not a case of just letting it get on with it. Unfortunately it just doesn’t work like that,” he says.

Load out man Craig Wassell nods his head. “You need to keep a close eye on things,” he says amid the bustle of the mixing room. Wassell’s job is to tell the others what to mix each day based on information sent from the Birtley office the previous afternoon.

This information includes job numbers, the customer’s name, site the material is going to, the material’s code for the mixing computer, and a description of the material. Scheduling is everything, he says, although they can accommodate last minute orders.

Wassell: “We have to be as flexible as possible. We can help out other Tarmac operations as well if they are struggling. We also have to back ourselves up sometimes. If there is a big night job with lane closures at night, for example, and we need to get on and off site quickly. Backing up means we can do this.”

With 11 asphalt trucks based at the site and an extra five hire trucks, Cross Green supplies asphalt as far as York although has even gone as far as Skegness and Scarborough, says Wassell. The concrete operation, however, stays a little closer to home.

Concrete
The introduction of the railhead in 1994 – facilitated in part by a £1.3million Section 8 rail grant from the Strategic Rail Authority – led the way to the Liebherr concrete plant being built in 2003, the same year the DSM plant was constructed.

Dust, 10mm and 20mm material delivered from Swinden follows the same route as the asphalt rock. However, rather than being shuttled into individual bays it carries on past the toast rack, out through the side of the enclosure at a 90º angle to the stockpiling conveyor and into a Skako silo where it is stored.

Next to the large silo is a smaller one for storage of sand for use in the concrete plant – this comes from Nosterfield Quarry near Rippon where Curtin used to be quarry manager – and for sand to feed the DSM operation.

As with the asphalt operation, the plant pulls the material it needs for the mix and there are storage bins at the top, which Curtin likes to keep full. On the side of the plant are four smaller silos. Two of these store cement while the others hold GGBS from Tarmac’s slag operation at Corus’ Scunthorpe iron works.

Again in common with the asphalt operation, there are two plants. This allows Cross Green to meet demand and serve different markets. A 2m3 plant for the smaller Busy Bees service with 2m3 capacities and the 2.7m3 plant for the 7.5m3 trucks.

Combined the plants can mix up to 1,200m3 of concrete a day, but the average mixed annually is lower than this, says Curtin. Concrete plant supervisor John Harding points out the volume sold so far that day was 460m3. “It’s a slow day,” he says. Plant operative Mark Wisniowski, nods in agreement.

The comment makes you wonder what a busy day would be like. A short drive through Leeds and every other concrete truck appears to sport a yellow and green livery. In reality, around 10 big trucks and three Busy Bees feed material into Leeds projects daily. But with a truck complement of three 6m3 belt models, three Busy Bees and 12 normal concrete mixers, this is almost a full capacity service.

And with all services now in one area it is difficult to see how Tarmac will not continue to build on its domination of construction materials supply and services in the Leeds area from the site. And the pressure is certainly being kept up to ensure it happens with the site itself becoming part of the marketing mix.

Cross Green could be operated under factory regulations. Instead Tarmac chooses to run it under quarry regulations. This increases the pressure to ensure compliance but helps offer spin-offs in terms of lower numbers of H&S incidents. Curtin says simply: “We like to demand a higher standard”

This higher standard is also shown in his decision to have pathways and green areas landscaped across the site. This adds to both employees’ enjoyment of their workspace.

And just as Tarmac has spruced itself up to woo potential buyers so Cross Green is becoming a much more attractive shop window for potential customers. It is something the site shares with the quarry that feeds it. As Curtin says: “It is a viewing gallery”.

Cross Green is the most clustered site Tarmac has and it is a model that appears to be working. Curtin: “It is good for tendering and reflects Tarmac’s desire to be seen as the single solution. Customers come down and we say this is what we have, all in one place. They see how it can work for them.

“Tarmac is about cross-selling within building and aggregate products. All of us from different divisions are managing the site and working together. We are saying we can do the asphalt, blocks, contracting, the whole lot, from the quarry to the contract.”

Swinden: 01756 731010
Cross Green: 0113 2350545