Environmental Engineering Reference
In-Depth Information
leakage into the atmosphere, disturbance of sub-surface aquifers and geo-
logical structure, fragmentation of landscape and disruption of agricultural
production. 1,24,30-34 The magnitudes of these threats are not merely un-
certain in the statistical sense; in some cases they are driven by complex
systems that work in ways we do not fully understand, even conceptually. In
the face of these uncertainties and unknowns, the above-mentioned separ-
ation of surface and sub-surface rights limits the protections for landowners.
Their protection, like that of the general public, depends on the willingness
and capacity of governments to implement adequate regulatory regimes.
3.2.1 Water Issues. CSG extraction on the scale planned in Queensland
'produces' vast quantities of waste water contaminated by chemicals
found in and around the coal seams and sometimes introduced in the
fracking water. Because aquifer systems are multi-layered and inter-con-
nected, and groundwater and surface water are components of a single
hydro-system, dewatering has system-wide impacts. 1,23,33,34 Contaminated
waste water is 'produced' in vast quantities:
Groundwater is depleted and water tables fall, with volume and quality
implications for other users and groundwater-dependent ecosystems,
and unwanted surface water interactions with groundwater occur over
the short and long term;
Multiple projects in an inter-connected system will have cumulative
impacts;
Water from surface sources and other aquifers will eventually flow into
the depressurised aquifers around the coal seams to establish a new
hydraulic equilibrium;
Altered hydraulic gradients may produce mixing and cross-contamination
between different aquifers and between groundwater and surface waters
with different quality characteristics;
Gas may migrate into surrounding aquifers, wells and water bores, and
surface waters;
Reduced water pressure in sub-surface layers may lead to compression
of layers, alteration of hydraulic properties and subsidence at the
surface;
Surface and groundwater will be substantially less available in the new
equilibrium unless waste water is recycled effectively; and
Two kinds of recycling can be conceived: treated water is re-introduced
to surface steams and alluvial aquifers, and waste water (with minimal
treatment) is re-injected into the coal seam. Both would tend to re-
equilibrate the hydraulic system, but in very different ways and with very
different economic consequences.
This vast and complex system does not lend itself to compartmental-
isation, but a little bit of ad hoc labeling and grouping of impact categories
may help the exposition.
 
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