The Quarry Process
Unless you’ve visited or toured a quarry, chances are you don’t know much about what goes on inside one. In the simplest terms, a quarry is a place where little stones are made from big stones. Although the basic process is the same, each quarry is different and some of the things in this quarry article may not apply to all operations. Geography, geology and the type of stone mined, how close a quarry is to neighbours, the size of the operation and the main transportation method used to get the stone products to customers, all have an impact on how each quarry is designed and operated.
At Fulton Hogan we take big stones out of quarries and make smaller stones and sand by crushing them. We sell the crushed stone and sand to builders and contractors who use them to build roads, highways, bridges, houses, shopping malls, schools, churches and other buildings and structures.
Finding, Preparing and Designing a Site
Before we can start operating a quarry many preparations must be made. First, our geologists must find a place where there is a large supply of rocks beneath the earth’s surface. A quarry is frequently located near a community where our products are needed because if it isn’t, it will cost our customers too much to haul the crushed stone, which is very heavy, over long distances.
After we find a good place to put a quarry, our geologists survey the land, and we develop a design that will make our quarry safe and efficient. Then, we have to get a variety of operating permits from local councils. For instance, to obtain the environmental permits, it is necessary to provide a plan that shows we can and will obey the environmental rules of the local, regional councils and where applicable New Zealand Petroleum And Minerals (NZPAM). Once we obtain the proper permits, equipment is purchased, roads are built to the facility and we begin building the processing plant.
Being A Good Neighbour
It is very important to us that we operate as a good neighbour in the communities where we build quarries. For example, at many sites we create landscape bunds and upgrade roads around the quarry so noise is kept to a minimum. We landscape the entrance to the quarry so that it blends with the surrounding area. Where needed, depending on teh type of quarry, we install special water systems so we can recycle the water we use in processing, and we put in many other features to protect the health and safety of our employees and our neighbours.
Being Good Environmental Guardians
Great care is also taken to protect the environment and the animals that live on our quarry lands. A quarry site might be as big as 100 hectares, but, only a small part of that land is actually used for the quarry and processing plant. We often establish wildlife habitats in the rehabilitated areas to attract and protect animals that might live around our quarries. Our quarries are full of so many interesting things that they are often seen as huge outdoor classrooms where students can come to see what we do and learn about earth science and nature.
Preparing the Site
In order to get to the stone beneath the surface of the earth, we have to clear a portion of the land we are going to quarry. Once we have the land prepared we are ready to begin quarrying stone. At many sites, the material that is removed is used to begin construction of berms/bunds, or donated for landscaping or construction projects in the community.
Loading and Hauling Stones From the Face
The area that begins to form out of the earth when we dig out or extract stone becomes the quarry or pit. We prefer to use field conveyers and loaders over large haul trucks to load and move the stones out of the face and to the processing plant where they are crushed and divided into different sizes. We do not use a lot of trucks to move back and forth between the face and the processing plant.
Now that we have the stones out of the ground and moved over to the processing plant, we begin turning big stones into little stones.
Once the stones reach the processing plant, the rocks are put into a primary crusher that will break them into smaller pieces.. Depending on what size we want to make the stones, they may be put through different kinds and smaller sizes of crushers one or two more times. As the stones pass through the crushers, they are moved around the processing plant on more conveyor belts.
Separating Stones Into Different Sizes
After crushing, comes screening. As the stones are broken down to smaller sizes, we use screens to separate them into piles that are the same size. Stones may be crushed and screened many times before they are put in a stockpile with other stones the same size.
Moving Stones Around the Processing Plant
For stones to get from one place to another at our plant, they travel on long, continuously moving conveyor belts. The conveyors help move stones in an economical way, saving money and time and avoiding the use of trucks and making dust.
Taking Care of Our Employees and Our Neighbours
During the entire quarrying process, we make sure that we protect the health and safety of our employees and neighbours. Quarrying stones and moving stones around a processing plant can create fine particles of dust. We control dust by using water sprays and mists on the stones as they are processed, and by having sealed roads within our quarries and using spraying equipment to wet quarry roads and trucks as they leave the site.
To protect the environment, we monitor our water use and where possible, due to quarry type, recycle and reuse our processing water. Where large amounts of water are used, we store it in ponds where the sediment is allowed to accumulate and settle out. If we have to discharge water from a recycling pond, we test the water to make sure that it is safe and that it meets environmental water quality regulations.
Stockpiles are large piles of stone, sand, gravel and other materials, and we do mean large. Some of our stockpiles are as much as 6 metres high and 24 metres around. They are so big that we have to keep them outside. Because they are exposed to the weather, they have to be carefully maintained so heavy rain doesn't wash the fine particles away. We also have to be careful not to let other materials get mixed in with them. We use front-end loaders to keep the stockpiles in place. When customers come to our facility for a load of crushed stone, they go to the stockpile. We use a loader to fill their trucks with the stones and other aggregate.
Delivering Stones to Where They are Needed
Most of the time customers come to our facilities and we load the materials they need onto their trucks for transport to where they need to use them. Sometimes though, the materials have to be moved over greater distances, which requires other modes of transport such as rail.
Weighing Stones and Trucks
Our stones are sold by the tonne. Before we can bill a customer for the materials they buy from us, we have to know the weight of each load. When trucks come to our facility, they will have been previously weighed before loading. This data is stored in our system. Once they are loaded they are weighed again. Then, we subtract the weight of the empty truck from the weight of the full truck and we know how much the load weighs. This is the way we calculate how much the company has to pay for the load. Weighing is also important because it helps to make sure that the trucks leaving our quarry are not too heavy for the roads they will travel on, as well as carrying their loads safely. Weighing of loads and product sold also helps us know what aggregate product our customers are using so we can make more to keep up with their needs.