Hunting Linear Quarry
The first site we look at in our Changing face of aggregates focus is a good example of one of the many smaller sites now starting up around the UK to feed the growing demand for more sustainable aggregates. The new Bristol-based company has taken its name from the sought after virgin material replacement. The Sustainable Aggregates operation is the smaller tonnage end of the supply business and it is seeking to exploit the growing pressure on roadworks and utilities firms to ensure the products they use are as green as possible. MQR caught up with MD Clive Holloway to find out more.
[img_assist|nid=12888|title=|desc=A lorry makes a delivery at the site behind the Komatsu PC210LC and the Dig-a-screen bucket, which are busy with spoil management.|link=none|align=left|width=266|height=200]
One area where traditional aggregates producers will see market share wane over the coming years will be in utilities, rail and roadworks. And one person who can verify this is Network Rail consultant Rick Elliott.
He has a haul road problem. These are used to move material for jobs such as embankment stabilisation without holding up movement on the busier rail routes. And they are an increasingly expensive luxury.
Elliott told MQR: “It is a three-phase process. We strip out material, then buy-in type-one to build a new bed. At the end we strip it out again and landfill it before making good. On my projects these roads are often 1000s of metres long.”
He is on the look out for new ideas and so has come to take a look at the new Sustainable Aggregates site in Avonmouth Docks in Bristol. He feels he may have found the solution in the operation’s stabilised material for reinstatement (SMR) product.
“Using a product like this,” he says, “rather than the current method of buying and dumping type-one, I could save 50% of my costs”. His message for quarry firms is simple: “Expect a lot less business from me in terms of type-one sales”.
He is not alone. And as the Waste Strategy keeps up the pressure on the sustainable sourcing of building materials and with the Highways And Utilities Committee (HAUC) having updated Advice Note One to make it easier to use recycled materials and SMR (see box opposite page), the number jumping the virgin type-one ship can only grow.
And this is what Sustainable Aggregates MD Clive Holloway is banking on.
We arrive at the Avonmouth site just off junction 18 of the M5 in early February. It is a clear, bright day. This is the first site and it has been open a week.
By early March there will be a second Sustainable Aggregates operation just off of junction 10 of the M23 in Copthorne. By the end of the year there will be a further four, probably in south London. And by the end of 2010 he plans to have 24 sites running. And this is not all.
Holloway also has 14 SMR dealerships running across the UK. By the end of 2010 he wants the combined number of Sustainable Aggregates sites and SMR dealerships to total 85 nationally. No-one can accuse him of having a lack of ambition.
However, his aspirations are a result of what he sees as a recent change in attitude from contractors and materials specifiers. While many people have been banging the recycling and sustainability drum for a number of years, the sound has been travelling slowly.
Holloway: “I’ve seen more change in the past five months than I have in the past nine and a half years. Attitudes are only just changing but the message is getting through. That’s why I feel our targets are easily achievable.
“I think the reason for this change is that bodies such as WRAP and NISP are finally starting to make some headway. They are pushing harder than they were and it is starting to show. So hats off to them,” he told MQR.
The Waste Strategy 2007 is also playing its part. It calls for the level of construction, demolition and excavation waste going to landfill to halve by 2012. Throw in a consultation on tightening the regulations on inert waste going to landfill, new pre-treatment of waste landfill regulations and site waste management plans and the ground looks set for business.
Holloway’s main hunting ground is the linear quarry, or streetworks. The solution is simple. Utilities firms or contractors tip their waste for a price. Then they leave. However, if they also picked his SMR product on the way out to reinstate the works then they pay the gate fee plus 50%.
“We are offering a WRAP quality protocol governed material that allows them to tip legally rather than illegally,” says Holloway. “It is all about pleasing the guys on the ground and giving them a good product and a good service.
“We are taking market share away from traditional quarrying by taking the arisings from roads or footpaths, improving them and sticking them back in. Across all the SMR sites in the UK we have recycled over 1million tonnes of spoil. It has been used on over 600,000 reinstatements and we are still waiting for our first failure.”
His reinstatement product demands good spoil management. The target is for a 100% waste recovery rate rather than the more common 50%. Key to this is the separation of –60mm and clean oversize. “We don’t want to take the traditional route of putting everything through the crusher,” he explains.
The process is simple. The site only allows certain coded waste. After it is delivered an excavator with a bucket screen (see page 20 for more on the plant) separates material between the –60mm and the oversize.
Oversized material is moved to another bay. What happens next depends on the moisture content of the –60mm. If low in moisture it will be moved to the processing bay. However, if it is wet and the day is fine then sunshine will be used to pre-process it using a loader to turn it over.
Another route to pre-processing is to add Holloway’s SMR powder, which dries the –63mm out. As compaction is the catalyst to the material binding, powder can be added to cure the material – it also means the end product can be supplied unbound.
In the pre-processing bay, crushed oversize can also be added. Holloway explains: “We seek to improve the particle interlock of the material in exactly the same way as you would a type-one GSB.
“If we consider we have insufficient aggregates to give a high-quality product we will crush some of our oversize material using a crusher bucket and put it into the material in the pre-blending bay so we have a good mix of soil, small stones and crushed aggregate in the finished product,” he says.
The screened, crushed, dry material then enters the Achiever blender, shredder and trommel. It has been specially adapted to meet the demands of the updated advice note one from HAUC covering the use of recycled and SMR materials in streetworks.
It states that the mixing and the production of alternative reinstatement materials (ARMs) is closely monitored. The update to appendix 9A (see MQR Nov/Dec) also places more pressure on authorities to specify ARMs if available.
Holloway has modified the plant by placing load cells under the SMR powder hopper and belt. They feed into a computerised system with control panel on the side of the machine. “Product mixing in the earlier Achiever was a bit hit and miss,” he says.
He continues: “All we have to do now is adjust the ratio – which is checked by the computer every second – so we know how much SMR is going in and how much material is going up the belt.”
[img_assist|nid=12889|title=|desc=The specially adapted Screen Machine with a potential 3-way split. See page 20 for more on this. |link=none|align=right|width=266|height=200]
There is also an eye on productivity. The UK is a wet country so a finger screen has been added to the main opening. If the weather stymies pre-treatment of material he can put it through still damp, although he points out this is not something he would do by choice.
Another key modification compared with the standard Achiever is the addition of another hydraulic circuit. This allows him to run a second conveyor. And as the trommel screen is split between –63mm at the back and –10mm at the front with the belt feed hopper also split, this augments the products he can sell.
“If I want pipe bedding I can have -63mm dropping in one conveyor, -10mm off the other and oversize on the other. This will give us 0-10mm, 10-63mm and +63mm. We won’t do it everyday but we wanted the flexibility to do so,” he says.
The 10-63mm reinstatement product then enters the bay for stockpiling to be picked up by contractors. It gets turned by a shovel before it goes out to keep the product equal in size.
According to site manager Tony Barnes, 150tonnes of the SMR product had been moved in the first week of being open. Around 200tonnes had been delivered with about 40tonnes being reprocessed back into product. This leaves only 10tonnes to be landfilled.
The site is licensed to hold 20,000tonnes at any one time, although naturally Holloway doesn’t want to have this level of arisings lying around: “That’s a lot of spoil to keep dry,” he says with a horrified grin.
Having previously worked for a rival SMR operation in the Bristol area, Barnes puts the success of the new operation down to investment in both plant and people. “At the last place it was one JCB, a tiny trommel and me. When someone came in over the weighbridge I had to stop processing. It was destined to fail from the beginning.
“Here there is the right kit along with me and John Williams the plant operator. We have the time and the machinery,” he says.
Network Rail consultant Elliott for one appeared suitably impressed. And by the mid-afternoon was considering other ways of using the SMR product.
“I’d be mad not to use it as a type-one replacement as long as it can be mixed on site which he says it can. After all, we can lay the turf on the compressed SMR when we are finished and it will be there if we need to use it again in future.
“There is also another benefit for us. We have a lot of old sidings with hydrocarbon contamination. A product like this would lock it in freeing the land up for development. I don’t know why it has taken us all so long to catch on to products like these. But that is definitely changing now,” he told MQR.
SA: 07500 104910
