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LATEST:
MINE SUBSIDENCE CRACKs
AQUIFERS
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Ulan
Coal Mines recently released some of the findings
from monitoring of aquifer behaviour affected by mining
(from long wall mining).Their consultants Coffeys
& Assoc. concluded from groundwater monitoring
data that there was a 12 m drawdown observed close
to longwall panels within Triassic Sandstone aquifers
(decreasing to negligible approximately 1.5km - 2km
away). This represented around 30% of the 11-18Ml/day
of water being extracted from the mine (ie 4-6 Million
Litres per day). The balance was sourced from the
Permian coal aquifer ~ 8-12 ML/day. Where this water
normally exits to the surface (discharges) and how
these damaged aquifers will eventually recover is
unknown and highly speculative.
Studies
indicate that the diversion of the Goulburn River
in the 1980s is leaking - losing around 1-2 ML/day
of base flow some into the adjacent opencut pit.
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WATER
AND COAL MINING
Mining in the Ulan Wollar area raises
many questions concerning interference to the regional
groundwater system and long term viability and integrity
of the Goulburn River.
There
are clear indications that 25 years of coal mining,
mine subsidence and dewatering of the underground,
has significantly disrupted the groundwater system.
This has serious implications for the base flow of
the Goulburn River.
Ulan Coal Mine, (operating since
1982) is a 'wet mine' that produces excess water in
their underground mine -currently 13ML/day and predicted
to reach over 17ML/day of water by 2011. Mine subsidence
fractures and distorts the rock strata and associated
aquifers, the groundwater can become contaminated
by salts and other minerals posing a long term risk
to the health of the groundwater and river systems.
To dispose of some of this water Ulan Coal Mine is
applying to discharge its excess water into the Goulburn
River under license.
The amount of excess water being produced by Ulan
CM, and the ongoing difficulties they have experienced,
calls into question Moolarben Coal Mine's
water management plans and predicted ‘water
make’ of 6.9Ml/day and suggests the maximum
prediction of 27Ml/day may be closer to reality.
The proposed Moolarben underground mine extends beneath
the saturated Triassic aquifers that feed the river
and within 120m of the river banks. While the three
open cuts are along a major catchment tributary upstream,
also in a water rich area. The actual coal seam is
also a major aquifer.
The question of where the underground water is coming
from and where this water would normally discharge
to the surface is still to be addressed and requires
an INDEPENDENT REGIONAL WATER SURVEY before
any informed decision can be made about the environmental
impacts of this mine.
The million dollar question is what will happen over
the long term to the groundwater and river system
when mining ceases:
- will the groundwater reservoirs ever recover
- what will be the resulting water quality and salinity
levels of water from these ‘degraded’
areas
- what affect will this have on river flow, local
bores, soaks and springs and downstream irrigators.
Coal mines around Cessnock have a huge problem with
acid and saline water leakage from old coal shafts.
The combined total of 'water make' from
Ulan (17Ml), Wilpinjong (6.2Ml) and Moolarben Mines
(6.9Ml) is predicted to exceed 30 Million Litres per
day or
11 Gigalitres per year!
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Spring-fed
Cliffs - The Drip Gorge
Goulburn River Rock Pools
at Corner Gorge
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