New Plant In The Dove Valley
Bardon Aggregates’ Uttoxeter Quarry comes on stream
Earlier this year one of Bardon Aggregates’ newest sand and gravel operations finally came on stream some six months later than originally planned. After 12 years in the planning process, this final delay was not due to any last-minute technical problems with the plant, instead it was brought about by last year’s outbreak of foot-and-mouth disease, which effectively closed down of much of the British countryside.
Uttoxeter Quarry, operated by Bardon Aggregates, the aggregates and asphalt business of Aggregate Industries UK who own the site, is located in the heart of rural England, close to the Staffordshire/Derbyshire border. The site is being developed on 100ha of greenfield land in the Dove valley, approximately one mile north-east of the town of Uttoxeter, adjacent to the B5030 (Rocester road). The main extraction area is located on some 60ha of flat agricultural land bordered by the river Dove to the east and the river Tean to the south.
Geological investigations at the site have identified potential reserves of approximately 4.7 million tonnes of saleable sand and gravel. The deposit itself is fluvioglacial in origin with a depth ranging between 1.5m and 8.5m. Compositionally it comprises 6% silt, 30% sand and 64% gravel, the latter being predominantly quartzitic in nature. The sand and gravel is underlain by a layer of alluvium which overlies the Mercia mudstone group.
Bardon Aggregates plan to work the deposit in 12 phases over a period of 12 years, with each 12-month phase yielding around 400,000 tonnes of material. The quarry has been established primarily to supply concrete aggregates to outlets within the business in the Midlands region, in particular sharp sand and –20mm +5mm aggregate to the Bardon Concrete plants at Cheadle, Sandbach and Stoke, and 8mm single-size gravel to a new concrete block plant at Newbold.
Extraction and processing
Uttoxeter Quarry is a wet-dig operation with the sand and gravel being raised by a Sennebogen 640R/KB dragline supplied by E.H. Hassell & Sons Ltd. This machine was selected for this particular application because of its ability to extract the material at a rate of up to 250 tonnes/h throughout the full depth of the deposit. The as-raised material is deposited in a stockpile adjacent to the dig where it is left to dry out for a period of up to two weeks.
A Cat 966F wheel loader is used for the subsequent load-and-haul journey from the stockpile to the nearby field feed hopper. This 20-tonne capacity hopper discharges on to a fully refurbished second-hand field conveyor system, supplied by BB Conveyors Ltd, which delivers the as-raised material to the 200 tonnes/h processing plant where it is washed, screened, crushed and sized into three final products.
On arrival at the plant the material is discharged from the field conveyor into a 20-tonne capacity Finlay plant feed hopper equipped with a sloping reject grid with bars set at a spacing of 150mm. A reversible belt feeder mounted beneath the hopper allows the sand and gravel to be either sent on for further processing or fed to an adjacent as-raised stockpile which provides a supplementary raw material supply in the event of serious flooding in the working area.
From the plant feed hopper, a 27m long inclined static conveyor, fitted with a 750mm wide belt and equipped with a Beckford belt weigher at the tail end, delivers the material to the first screen. This comprises a 20ft x 5ft twin-deck Finlay washing screen fitted with polyurethane panels and rubber-lined chutework. The screen’s top deck removes any +75mm material, which is fed to an adjacent oversize stockpile by means of a short side conveyor, while –3.5mm material is washed through the lower deck and fed by a flume arrangement to a variable-speed electric/hydraulic Finlay 200E Hydrasander for dewatering. The –3.5mm sharp sand discharged from the Hydrasander is delivered to stockpile by a 24m long x 750mm wide Finlay 830 mobile stockpile conveyor with a powered hub for 120° radial movement.
The middle product from the first screen is discharged directly into a Finlay 206 log-washer which is powered by a 45kW electric motor and offers an adjustable angle of slope from 4° to 10°. Any sand liberated by the log-washer is once again flumed to the Hydrasander, while the coarser fraction is discharged directly on to a 17m long transfer conveyor for delivery to the second screen. This conveyor, like all others at the site, is fitted with a trip-wire safety system supplied by Davis Derby Ltd.
The second screen comprises a 20ft x 5ft twin-deck Finlay rinsing screen, the first 4ft of which is fitted with spray bars while the remainder of the unit is dry. Once again, any residual sand liberated by the rinsing action is flumed away to the Hydrasander. The Uttoxeter plant has a total water requirement (Hydrasander, spray bars etc) of 1,200 gal/min, which is met entirely by the recirculation of process water through two 100m x 90m lagoons.
The quarry’s remaining final products (–20mm +5mm and 8mm single size) are sized on this screen and delivered to stockpiles by a Finlay 830 mobile/radial stockpiler and a 24m long static conveyor respectively. Meanwhile, the –75mm +20mm oversize from the top deck of the second screen is fed on to a 24m long x 750mm wide chevron conveyor for delivery to a 20-tonne crusher surge hopper. A Locker vibratory feeder mounted beneath the hopper choke feeds a Nordberg HP200 cone crusher, which in turn feeds –20mm +5mm crushed material back on to the transfer conveyor to the second screen, in a closed-circuit arrangement, via a Finlay 430 mobile conveyor. Crusher settings are monitored and controlled by means of a Nordberg A2020 control unit located in the containerized switchgear/plant control room which overlooks the plant. Likewise, the crusher hopper level and crusher bowl level are monitored by a pair of MultiRanger Plus ultrasonic continuous level-measurement systems from Milltronics.
All three final products are rehandled and loaded out by a Cat 966F wheel loader. The site employs a full-time staff of eight and operates from 7.00am to 6.00pm Monday to Friday and from 7.00am to 1.00pm on Saturdays.
Supported by a comprehensive environmental statement, Bardon Aggregates’ planning application includes provision for the progressive restoration of the entire landholding. On cessation of extraction in around 12 years’ time, the processing plant and its ancillary buildings will be dismantled and the area restored. As the processing plant lies outside the flood plain, it is proposed that the majority of this land will be returned to agriculture. However, at the request of the ‰ Environment Agency, the clean-water pond and silt lagoon will be landscaped and restored as shallow-water features for nature conservation.
The majority of the main 60ha excavation area will be turned into two deeper-water lakes — a 42ha eastern lake and a smaller 5ha western lake. The lake margins will be formed using the overburden and soils stripped from the site and both lakes will be planted and maintained in accordance with an approved restoration and aftercare scheme.
Peripheral restoration to 5ha of water meadows that will link with undisturbed areas of the flood plain towards the river Dove will be carried out on the eastern boundary of the larger lake. Approximately 5ha of native woodland are also proposed in this area. In addition, a number of public footpaths which will be diverted during the mineral extraction operations will be reinstated to complement the restoration.
As well as the conservation areas mentioned earlier, two other specific areas for nature conservation will also be created, the first in the south-east corner of the smaller lake, and the second, larger (3ha) area along the eastern boundary and south-eastern part of the larger lake.
The editor wishes to thank Aggregate Industries UK, part of Aggregate Industries plc, for permission to visit Uttoxeter Quarry and, in particular, Keith Gray, quarry manager, and Michael Ward, sales manager with Finlay Hydrascreens (Omagh) Ltd, for their help in preparing this article.