Wambo Coal AEMR 2011-2012 - Peabody Energy

2011-2012 AEMR
2.8.1 Water Supply and Use
Continuity of water supply to the CHPP, Open Cut
and Underground is important for the processing of
coal and the operation of the mine. During this
reporting period the site water balance for the
mining activities was recalculated. This water
balance is presented in Table 2.5.
WCPL manages its water supply through a number
of site water storage dams. The mine routinely
obtains water from the Hunter River Licence
(Number 20AL200631), Wollombi Brook Licence
(Number 20SL033872), the Wollemi and
Homestead goaf areas and from rainfall runoff.
WCPL’s annual water catchment generally matches
operational water requirements for CHPP and Open
Cut usage. In 2010-2011, minimal water was
extracted from the Hunter River catchment via the
Wollombi Brook pumps. Water extracted from
Wollombi Brook (and the Hunter River) is used to
supply the fire suppression system, underground
operations and open cut workshop.
2.8.2 Surface Water Management
To minimise the potential for water quality impacts
from mining operations, a network of water storages
has been established to separate the clean water
(runoff from undisturbed areas) and dirty water
(runoff from disturbed areas). Rainfall runoff from
undisturbed areas is diverted away from mining
areas. Runoff from areas disturbed by mining is
diverted into the onsite dams for use across the site.
West Cut Dam and Area C Dam have now been
dewatered and are only sumps.
South Wambo Dam, Chitter Dam, Homestead Pit
(North) decant dam and sumps across site are
pumped to the CHPP’s supply dam (Eagle’s Nest)
and to tank fill points in the Open Cut to allow water
carts to fill and assist in dust suppression.
The wash down and runoff water from the CHPP
and adjacent stockpiles is accumulated in
sedimentation ponds which feed into the Gordon
Below Franklin Dam network. The Gordon Below
Franklin Dam network is designed to slow the flow
of the water and encourage the precipitation of fine
sediment to drop out. The sediment ponds are
cleaned out on a regular basis using a variety of
methods including dredging and truck and
excavator. Water from these dams is returned to the
Eagles Nest Dam. A new dredging program was
carried out during the period to remove excess
sediment from the CHPP dam network.
Water stored in Eagles Nest Dam is used in the coal
washing process and for dust suppression at the
CHPP.
2.8.2.1 Water Balance & Modeling
In March 2010, WCPL completed a detailed review
of the operations water balance. The water balance
is based on monitoring data from numerous water
flow meters on site and information provided by
WCPL technical personnel.
In addition, a comprehensive predictive site water
and salt model was finalised in February 2011, in
accordance with recent development consent
requirements. The completed water model includes
a predictive accounting system for water and salt
budgets.
2.8.2.2 NWC Discharge Report
In April 2008, the North Wambo Creek (NWC)
Diversion Plan was approved by DP&I, DTIRIS and
NOW, subject to a number of approval conditions. In
accordance with the approval conditions for the
NWC Diversion Plan, WCPL must prepare and
submit a flow assessment report after each flow
event down the diversion.
Construction of Stage 2 of the North Wambo Creek
Diversion was completed in September 2008. The
original design was modified to incorporate a
temporary outlet from the proposed take-off point for
the Stage 3 diversion channel to North Wambo
Creek. The design profile near the downstream end
of the permanent diversion channel was also
modified from the design to incorporate a large hard
rock-outcrop exposed during the excavation of this
area. The rock outcrop was partially excavated to
form a local rock-bar.
Construction of Stage 3 of the diversion
commenced in late 2011 and remains scheduled for
completion in September 2012.
Since the Stage 2 diversion was commissioned a
series of small and medium intensity rainfall events
have been experienced over the upstream and
adjacent catchment areas, several of which
produced a measurable flow in the diversion
channel.
An initial review 5 and survey of the diversion
condition was undertaken in mid July 2009 following
moderate flood flows recorded in February and early
April 2009.
Inspections were also conducted along the upper
reaches of South Wambo Creek and the mid
reaches of Apple tree Creek which were selected as
5 Gilbert & Associates Pty Ltd “Review of North Wambo Creek
Diversion (Stage 2)”, September 2009
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