Wambo Coal AEMR 2011-2012 - Peabody Energy

2011-2012 AEMR
assessed through review of the historical water level
and water quality data. For the depth to water level
and EC, the upper and lower trigger levels have
been assigned as two standard deviations greater
and less than the maximum and minimum observed
values. In terms of pH, the lower and upper trigger
levels have been specified as 6.0 and 9.5
respectively which encompass the normal range for
groundwater. To date, few pH values at either
WCPL or United Collieries have been measured
outside this range.
The groundwater quality criteria from the updated
GWMP which were applicable to groundwater
monitoring sites from December 2005 are
summarised in Table 3.2.
The depth to water monitoring results during the
reporting period are illustrated in Figures 3.13a-b to
3.17 and provided in Appendix 2D. All water levels
are measured from the top of the borehole casing.
3.5.2.1 Depth to Water
In general, water levels remained static for most of
the reporting period, with most groundwater
monitoring sites displaying slightly elevated water
levels through this period. Good rainfall events in
each of the months September through December
2011 of 72.4mm, 68.8mm, 119.6 mm and 77.8mm
respectively and again during February and March
2012 of 124.5mm and 85.9mm respectively
supported this trend.
Groundwater Wells
GW02 and GW11 located on the Brosi property
were monitored throughout 2011-2012. During this
time, the water levels showed slight increases,
peaking in February 2012 before showing a gradual
decline for the remainder of the reporting period.
levels at the end of the reporting period. As
recorded in the 2010-2011 reporting period, the
water level at GW09 again remained outside the
water level criterion during the 2011-2012 reporting
period.
100 and 200 Series Piezometers
The 100 and 200 series piezometers located
adjacent to the Wollombi Brook were monitored
throughout 2011-2012. The 100 series piezometers
standing water levels were generally higher than in
2010-2011 reporting period. Piezometers P106,
P111, P114 and P116 were periodically outside
their respective criteria “minimum” level at times. As
per other groundwater monitoring sites, standing
water levels appeared to be elevated in months
corresponding to good rainfall events.
The 200 series piezometers standing water levels
remained static during the reporting period and also
displayed similar characteristics to the 100 series
piezometers regarding increases in water levels in
February 2012 and April 2012.
300 Series Piezometers
The 300 series piezometers are located adjacent to
Stony Creek. During this reporting period P301 and
P315 water levels were maintained within their
respective depth to water level criteria. Due to
access issues, GW315 was not sampled in April
and June 2012.
Longwall Panel 5 moved adjacent to P301 during
January 2012, corresponding to a drop in measured
depth to water level in December 2011. However
further monitoring in February 2012 displayed a
substantial recovery of the standing water level.
While GW02 achieved the criteria values, GW11
was found to be periodically below the minimum
criterion level in 2011-2012. In contrast, both water
levels in GW02 and GW11 during 2010-2011
remained stable and within criterion for the period.
GW08 and GW09 are located on WCPL property
and were monitored throughout the 2011-2012
period. The water levels remained mostly static for
the period with a slight increase in water levels
noted after heavy rainfalls in March 2012.
Groundwater monitoring in 2011-2012 identified
only minor decreases and fluctuations of water
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