case study – quarrying
Ref: W02a

A quarrying company caused a serious pollution incident when a pipe burst. Over time the pipe had become worn out with the material being continually pumped through it, and under pressure the weakest link had failed. The content of the pipe was a thick liquid mixture of clay minerals and water from the quarry. As a result the mixture entered the watercourse at its source (refer to B03 River System).

A quarry

The clay mixture entering the river meant that there was an increased amount of particles in the water being carried by the river. Mineral particles can clog the gills of fish such as trout and salmon and when the particles settle on to the river bed they smother the invertebrates that live in and on the river bed. Fortunately, the particles were so fine that they were easily carried down the river and flushed through with the next flood, but bigger particles can clog up all the gravel that lies on the river bed. Moving down river the pollution was also diluted as other tributaries joined the river and river inhabitants (refer to minibeasts B09a) were able to survive.

Lavrean stream, Cornwall after china clay spill

The quarry operators responded immediately to the accident by pumping the polluted water into an old pit. Here it was allowed to stand for a few days. During this time the particles in the water sank out of the water down to the bottom.

Sensors are now put in all rivers where there might be a risk of a similar problem happening. These sensors monitor the particles that the river is carrying and an alarm is triggered when a certain level of particles in the water is reached. Then pollution is investigated.

Quarry water channels

A system of valves, channels and catch pits have also been installed at the quarry to stop spillages from sections of pipe that are at high risk from causing pollution of the river. These incidents result in the company being prosecuted and having bad publicity for causing pollution.

To find out more about how rivers are monitored in this way look at the Environment Agency’s website www.swenvo.org.uk/environment.