Coal is found in deeper layers of earth. To retrieve coal from those layers, underground tunnels need to build. These underground tunnels tend to fill with
ground water. To prevent this, steam pumps were installed to keep the tunnels dry. The groundwater pumped out of the mines is “comparatively clean” (Wilkinson 2011, 3).
Once the steam pump is shut off, the underground water is able to fill up the abandoned mine over years. After all tunnels are filled up, the water finds a way to release itself. This is called natural drainage water (Wilkinson 2011, 3). In case of the project, this happens through the outfall which is right above high water spring tide. The water that is released through the outfall is not as clean as the actively pumped out water.
But why does this happen?
The digging of underground tunnels resulted in weathering processes of different minerals that are found in rocks because they got exposed to oxygen. After abandoning the mine, the ground water filled the tunnels and the minerals got exposed to water as well.
Tides is the “regular rise and fall in the level of the sea” (Siedler 2001, 118) that is caused by the gravitational force of the moon and the sun as well as the motion of the earth. The influence of the moon on the movement of the water is stronger than the one of the sun since it is closer to earth (Charlier 2009, 65).
There are different types of tides, which have been called according to their repetition within a daily cycle.
One has to distinguish between ‘diurnal tides’ (one high and one low in a tidal day), ‘semidiurnal tides’ (two highs and lows in a tidal day) and a mixture of them (so called mixed diurnal and mixed semidiurnal tides) (Charlier, 2011, 66).
Tides occur on a regular basis but underlie a monthly spring-neap cycle, “which arises from the relative positions of the Sun, Moon and earth in the orbital plane” (Lyndon 2011, 1).
When gravitational attraction of sun and moon act together (sun, earth and moon are in a straight line) “tide raises forces are at a maximum” (Little, 2009, 8). This is the case during new moon and full moon and is called ‘spring tide’. During spring tide, the tidal amplitude is very large.
The opposite is called ‘neap tide’ and occurs when sun and moon are at right angles. The gravitational attractions act in opposition and the tidal amplitude is very low.
7.4 Rocky shore
These shores were shaped by different natural forces. Those forces include the rise and fall of tides, wind, intensity of waves and variation in temperature. They consist of rocky ledges, boulders and pebbles. Furthermore, pools with seawater can be found.
Rocky shores can be divided into different zones, according to vertical height. The zones vary in diversity (see Fig. 6) and most species are adapted to a specific zone (Little 2009, 17).
The top of the shore is bare rock and living organisms such as littorinid snails or lichens can be found there. This zone is called ‘splash zone’ as it above...