WJEC – Geology of the Human Environment (GL3) – Jan 2002
2.
Figure 2 is a schematic section through a limestone escarpment.
Figure 2
(a)
(i)
(ii)
Mark on Figure 2 the level of the water table above
the shale.
[1]
Account for the location and presence of the lake.
[2]
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(b)
Plans were made to extend the quarry as shown. This will require some
local interference with the hydrological system.
(i)
Describe how the level of the water table might be locally altered
to allow the quarry to be extended.
[2]
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(ii) Predict the possible consequences of such interference in this area.
[3]
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(c)
Disused quarries are sometimes used as landfill sites for domestic waste.
(i)
Give a geological explanation of two possible hazards associated
with landfill sites.
[2]
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(ii)
Explain how potential hazards may be overcome by engineering
practice.
[3]
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Total 13 marks
Notes for answers
These represent suggested answers and do not necessarily represent all the possible
acceptable alternatives of a mark scheme.
Question 2
(a)
(b)
(c)
(i)
Line linking lake level and wells.
[1]
(ii)
Natural depression at base of escarpment
Underlain by impermeable shale
Water table forced to surface
(2 max)
[2]
(i)
Boreholes drilled around quarry (Credit use of existing wells)
Over pumping of groundwater (greater than recharge)
Creating a cone of exhaustion.( (or drawn/annotated on Figure 2)
(other appropriate - e.g. providing sump at bottom of quarry)
(2 max)
[2]
(ii)
Lowering of WT may cause
wells (springs feeding lake) may dry up
lake may disappear/evaporate if WT does not reach surface
instability/subsidence owing to reduced pore pressure.
other sensible - e.g. extra surface runoff from pumped water
(3 max)
[3]
(i)
Accept general answer or specific to Figure 2.
One from any TWO of the following:
 Leachate pollution
- as limestone permeable
- groundwater flow to water supply (towards the lake (SSSI))
 Methane gas production
- migrates through permeable rock
- methane gas is explosive
 Subsidence/instability
- as waste decomposes and surface collapses
(2 max)
[2]
(ii)
Contained site - Impermeable HDP lining
Leachate management system
Boreholes around to monitor
Boreholes to vent methane
Sealing top to reduce leachate
Cells within to separate/confine reactive materials
(3 max)
[3]
Total 13 marks
ESTA would like to thank the WJEC for allowing this question to be published on GEOTREX. Any
comments should be directed to the Subject Officer for Geology at the WJEC. 15/04/2007