Quarrying, More than 23,000 work in the quarrying industry in some capacity Most work in rural areas

It is often impossible to see a quarry or pit. The industry takes care to ensure that very little of the operations are visible and it is only within the perimeter that the workings are revealed.

Quarries are screened by contoured banks that hide any buildings, or by trees planted at the quarry's edge. Good landscape treatment is most important.

In a crushed rock quarry controlled blasts produce a predetermined quantity of rock. These blasts, which are designed to minimise noise and vibration for nearby housing, are carried out at pre-planned times. An explosion occurs as a chemical reaction when a substance converts to gas producing an enormous pressure. This occurs very rapidly shattering the rock adjacent to the explosive exposing the surrounding rock area to stress. The explosion initiates a shock wave that passes through the rock fracturing it on the initial and reflected waves. The waves, together with the force of the expanding gases, raise the medium into a cupola. Material is then forced outwards producing a pattern of cracking and shattering of the rock.

The rock produced by the blast is then transported by truck and or conveyor to a crusher, and there begins the process of size reduction. The rock is moved through various stages of crushing and screening into a range of final sizes of aggregate. It may sometimes be washed before being carefully stored in segregated piles according to it's size or even colour. The quarry can become very deep over a period of years with steps or benches of many meters.

Some of the aggregates are mixed on site with bitumen or cement to make asphalt or ready-mix concrete. This reduces the loading and transportation operations.

Many of the production and ordering processes are computer controlled

This loading chute delivers the order at the press of a button

Cliffe hill quarry has taken advantage of the new technologies available today. Many production processes are computer controlled. When a order is received from a driver the information is fed straight into a terminal. When the driver stops his truck under a chute the correct size, colour and amount is immediately discharged at the press of a button.

200,000 tonnes of aggregate is used in every mile of motorway

today very strict rules govern the location, lifespan and workings. Quarry owners make every effort to be as unobtrusive as possible.

Minimising the nuisance factor

Prominent notices advise the public of blasting times, which are regulated and preceded by warning sirens. The industry has assisted instrument manufacturers in developing sophisticated equipment to help identify sources of environmental disturbance and research into explosive firing patterns, types and sizes of charge. This has resulted in improved methods of working quarry faces to minimise the disturbance in sensitive areas.

Dust

Cliffe hill quarry has wheel-cleaning facilities to ensure that mud and dust are not carried outside the quarry area. Within the quarry itself, areas particularly prone to dust are sprayed with water and the stone itself is sprayed as it enters the crusher.

When the aggregates are heated and dried to make asphalt, dust is eliminated by fan extraction and the dirty air is then put through filters before being discharged.

Pics - a dust extractor in operation, loads being sheeted and wheels cleaned before transport leaves the quarry

Re-instatement and aftercare

Rock quarries are difficult to restore because of their depth

Conclusion

Our life-style demands high quality building products and this means that quarries must work effectively and efficiently and economically while remaining environmentally aware.

There are many ways to restore a quarry - to lakes, for boating, fishing or nature conservation, as parks or woodland, for public enjoyment as well as for commerce and buildings such as houses, factories and shops.