Te Kuha Opencast Mine Review - S92 Additional … Coast Regional Council Te Kuha Opencast Mine...
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Te Kuha Opencast Mine Review - S92 Additional
Information 8 August 2017
Te Kuha Opencast Mine Review - S92 Additional Information
1014-02-1
August 2017
Prepared for the:
West Coast Regional Council 338 Main South Road
Paroa, Greymouth, 7805
Prepared by:
Paul Weber
Principal Geochemist
O'Kane Consultants (NZ) Ltd
PO Box 8257
Riccarton, Christchurch 8440
New Zealand
Telephone: (027) 294 5181
Web: www.okc-sk.com
Rev. # Rev. Date Author Reviewer PM Sign-off
(1) Draft 1-8-17 Dr Paul Weber William Olds Paul Weber
(2) Final Draft 8-8-17 Dr Paul Weber
DISCLAIMER
This document has been provided by O'Kane Consultants (NZ) Ltd (OKC) subject to the following limitations: 1. This document has been prepared for the client and for the particular purpose outlined in the
OKC proposal and no responsibility is accepted for the use of this document, in whole or in part, in any other contexts or for any other purposes.
2. The scope and the period of operation of the OKC services are described in the OKC proposal and are subject to certain restrictions and limitations set out in the OKC proposal.
3. OKC did not perform a complete assessment of all possible conditions or circumstances that may exist at the site referred to in the OKC proposal. If a service is not expressly indicated, the client should not assume it has been provided. If a matter is not addressed, the client should not assume that any determination has been made by OKC in regards to that matter.
4. Variations in conditions may occur between investigatory locations, and there may be special conditions pertaining to the site which have not been revealed by the investigation, or information provided by the client or a third party and which have not therefore been taken into account in this document..
5. The passage of time will affect the information and assessment provided in this document. The opinions expressed in this document are based on information that existed at the time of the production of this document.
6. The investigations undertaken and services provided by OKC allowed OKC to form no more than an opinion of the actual conditions of the site at the time the site referred to in the OKC proposal was visited and the proposal developed and those investigations and services cannot be used to assess the effect of any subsequent changes in the conditions at the site, or its surroundings, or any subsequent changes in the relevant laws or regulations.
7. The assessments made in this document are based on the conditions indicated from published sources and the investigation and information provided. No warranty is included, either express or implied that the actual conditions will conform exactly to the assessments contained in this document.
8. Where data supplied by the client or third parties, including previous site investigation data, has been used, it has been assumed that the information is correct. No responsibility is accepted by OKC for the completeness or accuracy of the data supplied by the client or third parties.
9. This document is provided solely for use by the client and must be considered to be confidential information. The client agrees not to use, copy, disclose reproduce or make public this document, its contents, or the OKC proposal without the written consent of OKC.
10. OKC accepts no responsibility whatsoever to any party, other than the client, for the use of this document or the information or assessments contained in this document. Any use which a third party makes of this document or the information or assessments contained therein, or any reliance on or decisions made based on this document or the information or assessments contained therein, is the responsibility of that third party.
11. No section or element of this document may be removed from this document, extracted, reproduced, electronically stored or transmitted in any form without the prior written permission of OKC.
West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information iv
O’Kane Consultants 8 August 2017 1014-02-1
EXECUTIVE SUMMARY
This report is provided by O’Kane Consultants (NZ) Limited (OKC) at the request of the West Coast
Regional Council (WCRC) in regards to whether sufficient information has been provided for the
proposed Te Kuha Mine by the applicant (Stevenson Mining Ltd) in relation to the Section 92(1) of
the Resource Management Act 1991 request for further information by the WCRC (dated 12
December 2016).
This report presents OKCs assessment of whether sufficient information has been provided by the
Applicant to address our original concerns (OKC, 2016) and any others that may arise as a result
of the additional information supplied. In this regard OKC have focused on those issues that had
significant uncertainty where the recommended action by OKC (2016) was that further data was
required to explain potential effects on the receiving environment and / or management options
before any resource consents are granted.
EXPLANATION
Previously OKC (2016) developed a matrix to consider the work completed to date and the risks for
the proposed project from a geochemistry perspective. Three classifications were developed for
that review:
Geochemistry Risk Classification
Recommended Action
Suitable Approach No further assessment required or recommended action appears reasonable.
Adaptive Management Regime Based on current data the identified risks can be managed from an adaptive management process and/or proposed site management plans.
Significant Uncertainty Further data required to explain potential effects on the receiving environment and / or management options before any resource consents are granted.
A number of issues were identified by OKC (2016) that have Significant Uncertainty as per the
above geochemistry risk classification system and it was recommended that further data are
required to explain potential effects on the receiving environment and / or management
options before any resource consents are granted. These were:
Further consideration is required for Cd in AMD impacted waterways as no data have been
presented.
Further consideration is required for Cu in AMD impacted waterways. In four instances,
Cu concentration data for upland streams was greater than the ANZECC (2000) 95%
West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information v
O’Kane Consultants 8 August 2017 1014-02-1
protection trigger value of 0.0014 mg/L threshold. These data should be considered for
establishing baseline conditions and that the rocks may contribute to elevated Cu
concentrations in site drainage waters. Consent conditions are required for Cu.
Further consideration is required for Pb as this element has been identified as being greater
than the 95% protection trigger value of 0.0034 mg/L in site groundwaters. Consent
conditions are required for Pb.
Further supporting information is required to justify the proposed consent conditions for Ni
and Zn.
The waste rock model needs to be presented and the mining schedule (stage plans) to
understand the timing of waste rock removal and ensure sufficient NAF waste rock is
available for the construction of the base of the ELFs and the final NAF cover layer. If the
required quantity of NAF is not available then an alternative management option needs to
be considered.
No data has been provided on the basal drainage contaminant load from the proposed
Engineered Landforms (ELFs). Flow rate and water quality are required for these basal
seeps including optimistic and conservative estimates for planning and adaptive
management purposes. This will require understanding net percolation rates into the ELF,
oxygen flux, and any concentrating effects on percolating waters through the ELFs.
ELF basal flow rate and water quality needs to be included in the GoldSIM water model
and effects determined, particularly during relatively dry periods when effects are likely to
be greatest.
The proposed monitoring locations are too low in the catchment and should be located on
the upper stretch of the haul road to preserve the downstream high ecological habitat.
SECTION 92 REQUEST FOR FURTHER INFORMATION
The WCRC reviewed the OKC (2016) report and presented the S92 request for further information
to the Applicant in regards to geochemistry. Besides the issues stated above, a number of other
issues were also raised by the WCRC based on the OKC (2016) report. These are presented in
the table below. A response by the applicant to these requests was also provided (dated 27 March
2017).
OKC has reviewed the additional information supplied by the Applicant and findings are presented
in the table below. Subsequent discussions were held on the 4th August, 2014 between OKC and
CRL Energy Limited (CRL), the Applicants consultants in regards to geochemistry, and any final
resolution of current uncertainties are discussed in the following table.
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O’Kane Consultants 8 August 2017 1014-02-1
Request
(WCRC to
Applicant)
Information Required Applicants Response
OKC Assessment of
Section 92
Response
OKC Analysis of Data Resolution
No data has been
presented on Cd in
the waterways.
Present data detailing the
levels of Cd in background
water samples and detail the
potential effect on Cd with the
addition of mine generated
runoff to the waterways, the
potential environmental effects
and therefore mitigation
methods.
Cadmium (Cd) levels in background water
samples are presented in the Appendix to the
report Te Kuha Mine – Water Management
Plan – Information Report (Update to Dec 15).
This report was provided as part of the AEE
(Appendix 4), however this report’s
appendices were originally not included as part
of the AEE. This report and its appendices
have been appended as Attachment G.
Cd was below detection limits in background
water samples. Cd was detected, however, in
leachate from the lysimeter columns. Potential
Cd levels from overburden ELFs is presented
in Section 2.3.1.2 and in Table 2 of the Mine
Drainage Management and Treatment
Contingency Plan (TCP) appended as
Attachment H. The management and
treatment of Cd is presented in the TCP in
Section 2.4.
The Applicant
indicates they have
provided such data.
The Applicant also
indicates how Cd will
be managed and
treated.
Data presented
indicates Cd could be
0.0008 – 0.007 mg/L
from ELF toe drainage,
which is higher than
the ANZECC
guidelines for 95%
level of protection of
0.0002 mg/L.
Treatment is proposed
using NaOH or
Ca(OH)2 during
operations and by
passive technologies
after operation.
A monitoring plan
needs to be developed
to confirm Cd is not an
issue. If it is not an
issue then monitoring
intensity can decrease;
if it is an issue then
appropriate
management is
required.
Following a meeting between
OKC and CRL Energy on the 4th
August, 2017, the Applicant
indicates a monitoring
programme will be established
immediately downstream of the
site for this contaminant of
concern as a resource consent
requirement. A compliance limit
is not proposed but any effects
will be considered under an
adaptive management process.
It was agreed that such data and
any effects would then be
discussed as required with the
regulatory authority.
Any proposed resource consent
should include a condition
relating to the requirement to
monitor this contaminant.
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O’Kane Consultants 8 August 2017 1014-02-1
Request
(WCRC to
Applicant)
Information Required Applicants Response
OKC Assessment of
Section 92
Response
OKC Analysis of Data Resolution
Cu values in some
background water
samples have been
above ANZECC
guidelines with no
discussion on the
potential effects of
adding mine
impacted water.
Details of the potential for the
addition of mine impacted
waters to further raise Cu
levels in background water, the
impacts on setting compliance
limits and any potential
environmental effects and
therefore mitigation measures.
Potential copper (Cu) levels from overburden
ELFs is presented in the TCP in Section
2.3.1.2 and in Table 2 and management and
treatment of Cu is presented in the TCP in
Section 2.4 (Attachment H).
The Applicant
indicates they have
provided such data.
The Applicant also
indicates how Cu will
be managed and
treated.
Data presented
indicates Cu could be
0.028 – 0.4 mg/L from
ELF toe drainage,
which is higher than
the ANZECC
guidelines for 95%
level of protection of
0.0014 mg/L.
Treatment is proposed
using NaOH or
Ca(OH)2 during
operations and by
passive technologies
after operation.
A monitoring plan
needs to be developed
to confirm Cu is not an
issue. If it is not an
issue then monitoring
intensity can decrease;
if it is an issue then
appropriate
management is
required.
Following a meeting between
OKC and CRL Energy on the 4th
August, 2017, the Applicant
indicates a monitoring
programme will be established
immediately downstream of the
site for this contaminant of
concern as a resource consent
requirement. A compliance limit
is not proposed but any effects
will be considered under an
adaptive management process.
It was agreed that such data and
any effects would then be
discussed as required with the
regulatory authority.
Any proposed resource consent
should include a condition
relating to the requirement to
monitor this contaminant.
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O’Kane Consultants 8 August 2017 1014-02-1
Request
(WCRC to
Applicant)
Information Required Applicants Response
OKC Assessment of
Section 92
Response
OKC Analysis of Data Resolution
Pb values in some
background water
samples have been
above ANZECC
guidelines with no
discussion on the
potential effects of
adding mine
impacted water.
Details of the potential for the
addition of mine impacted
waters to further raise Pb
levels in background water that
enters surface water, the
impacts on settling compliance
limits and any potential
environmental effects and
therefore mitigation measures.
Potential lead (Pb) levels from waste rock
dumps is presented in the TCP in Section
2.3.1.2 and in Table 2 and management and
treatment of Pb is presented in the TCP in
Section 2.4 (Attachment H).
The Applicant
indicates they have
provided such data.
The Applicant also
indicates how Pb will
be managed and
treated.
Data presented
indicates Pb could be
0.0018 – 0.034 mg/L
from ELF toe drainage,
which is higher than
the ANZECC
guidelines for 95%
level of protection of
0.0034 mg/L.
Treatment is proposed
using NaOH or
Ca(OH)2 during
operations and by
passive technologies
after operation.
A monitoring plan
needs to be developed
to confirm Pb is not an
issue. If it is not an
issue then monitoring
intensity can decrease;
if it is an issue then
appropriate
management is
required.
Following a meeting between
OKC and CRL Energy on the 4th
August, 2017, the Applicant
indicates a monitoring
programme will be established
immediately downstream of the
site for this contaminant of
concern as a resource consent
requirement. A compliance limit
is not proposed but any effects
will be considered under an
adaptive management process.
It was agreed that such data and
any effects would then be
discussed as required with the
regulatory authority.
Any proposed resource consent
should include a condition
relating to the requirement to
monitor this contaminant.
Elevated levels of AI
have been recorded
in baseline water
samples. This AI
may be in a non-
toxic form and
bound to dissolved
organic carbon.
Provide information detailing if
the AI is bound to dissolved
organic carbon and the
potential effects on the
environment of the results.
A conservative approach assumes that none
of the aluminium (Al) is in a non-toxic form.
Potential Al levels from overburden ELFs is
presented in the TCP in Section 2.3.1.2 and in
Table 2 and management and treatment of Al
is presented in the TCP in Section 2.4
(Attachment H).
The Applicant
indicates they have
provided such data.
The Applicant also
indicates how Al will
be managed and
treated.
The Applicant provides
a conservative
explanation of how
total dissolved Al will
be used as an
indication of toxic Al
species.
No further discussion required.
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O’Kane Consultants 8 August 2017 1014-02-1
Request
(WCRC to
Applicant)
Information Required Applicants Response
OKC Assessment of
Section 92
Response
OKC Analysis of Data Resolution
Zn and Ni levels for
compliance limits
have been
suggested to be set
above the ANZECC
guidelines.
Provide further supporting
information on why these limits
should be set above ANZECC
guideline limits.
It is acknowledged that the suggested zinc
(Zn) and nickel (Ni) compliance limits are set
above the ANZECC trigger levels. This is not
unusual and consent limits for other mine
treated wastewater discharges in the area are
also set above ANZECC trigger levels. It is
also acknowledged that the suggested Zn and
Ni compliance limits are well above the
existing Zn and Ni levels recorded from water
quality sampling within the upper and lower
catchments at Te Kuha.
The suggested Zn and Ni limits have been set
as a balance of:
water treatment at the site;
low flow to high rainfall events;
the range of water quality limits previously
included in resource consents for existing
mines on the West Coast of New Zealand;
monitoring (periphyton biomass and diversity,
macroinvertebrates, fish, sediments and
habitat) at a frequency of twice-yearly for a
period of five years (and then review) to
assess the biological health of the waterways;
and
level for the biological components of
monitoring that will require further investigation
if breached. This is discussed further in
Section C of our response and will need
further consideration following the collection of
baseline data.
The Applicant has
provided a response.
Proposed water quality
standards based on
predicted treatment
capabilities, or
scenarios based on
modelling of expected
water quality generated
from the proposed
mine should not be
used as justification for
water quality
standards.
Explanation of previous
resource consents
standards being
suitable need to be put
into context as to
whether they are
pristine/undisturbed
catchments, or whether
they were historically
affected by mining
operations, etc.
The Applicant needs to
confirm that the effects
of the proposed
resource consent
conditions for Zn and
Ni are less than minor.
It is noted that
biological monitoring is
proposed. This should
be confirmed by an
appropriately qualified
person including
consideration of any
required ecotox trials.
OKC and CRL Energy note that
any deviation from ANZECC
guidelines requires site specific
assessment by a competent
ecotoxicologist.
The Applicant notes that the
proposed limits are based on
predicted water quality from the
water treatment process. OKC
notes that the current GoldSIM
model does not include the new
water quality assigned to ELF
basal seepage and this model
needs to be rerun.
OKC notes that if there is
uncertainty about potential ecotox
effects then a conservative
approach should be undertaken.
West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information x
O’Kane Consultants 8 August 2017 1014-02-1
Request
(WCRC to
Applicant)
Information Required Applicants Response
OKC Assessment of
Section 92
Response
OKC Analysis of Data Resolution
Potential
contaminants of
concern have not
been adequately
considered.
Provide data and further
information considering levels
of nitrogen, Fe, AI, and SO4
and the potential for theme
elements to be released to the
environment.
Potential iron (Fe), Al, and sulphate (SO4)
levels from overburden ELFs is presented in
the TCP in Section 2.3.1.2 and in Table 2 and
management and treatment of Fe, Al, and SO4
is presented in the TCP in Section 2.4
(Attachment H). No information is available on
the potential nitrogen concentrations. Nitrogen
concentrations will be monitored during mining
and managed appropriately.
The Applicant
indicates they have
provided such data
for Fe, Al, and SO4
and management and
treatment options.
No data has been
provided on Nitrogen
concentrations.
The Applicant
indicates that nitrogen
will be monitored and
managed
appropriately,
although no further
references are
provided.
Proposed Fe and Al
concentrations have
been provided from
ELF basal seepage,
which may require
some form of treatment
(aeration,
neutralisation, etc).
Treatment should thus
be an expected part of
the project operational
activities during and
after closure. This
appears to be
acknowledged by the
Applicant.
Forecast sulfate
concentrations are
elevated against
drinking water
standards. Monitoring
is required to confirm
this is not an issue and
acceptable to
stakeholders and
regulators.
No data have been
presented on nitrates
after mining
commences.
Monitoring is
recommended to
confirm this is not a
concern
Following a meeting between
OKC and CRL Energy on the 4th
August, 2017, the Applicant
indicates a monitoring
programme will be established
immediately downstream of the
site for this contaminant of
concern as a resource consent
requirement. This includes
sulfate and nitrate. A compliance
limit is not proposed but any
effects will be considered under
an adaptive management
process. It was agreed that such
data and any effects would then
be discussed as required with the
regulatory authority.
Any proposed resource consent
should include a condition
relating to the requirement to
monitor these contaminants.
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O’Kane Consultants 8 August 2017 1014-02-1
Request
(WCRC to
Applicant)
Information Required Applicants Response
OKC Assessment of
Section 92
Response
OKC Analysis of Data Resolution
The timing of waste
rock removal needs
to be understood to
ensure sufficient
NAF waste rock is
available for the
construction of the
base and final cover
layer of the
engineered
landforms.
Provide a waste rock model
and mining schedule (stage
plans) and alternative plans if
there is not sufficient NAF rock
available.
Information on the volumes of non-acid
forming (NAF) material needed for the basal
layer and final cover system is presented in
Appendix 2 of the Waste Rock Management
Plan (WRMP), which is appended as
Attachment I. A waste rock block model for this
site is not warranted; an alternative
methodology is presented in Section 3.2.3 of
the WRMP.
The Applicant
indicates they have
provided such data
using an alternative
methodology.
Data has been
provided that suggests
sufficient NAF Paparoa
Coal Measures waste
rock is available for the
2 m basal layer and the
3 m cover layer of the
ELF.
It is recommended that
a detailed mining
schedule of materials
is created prior to
mining commencing as
part of the Construction
and Earthworks
Management Plan and
be updated annually as
more data becomes
available.
The Applicant has indicated that
a detailed annual mining
schedule will be developed prior
to mining and be in the
appropriate management plan.
The applicant indicates that the
general materials balance is
about 50:50 for the project life in
regards to BCM and PCM.
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Details of the basal
drainage
containment load of
the ELF’s needs to
be provided to
understand its
potential effect on
water quality.
Provide information on the flow
rate and water quality for basal
seeps from the ELF’s including
optimistic and conservative
estimates and potential
contaminant loads estimated.
These basal flow rates also
need to be incorporated into
GoldSIM water model with
details provided on the effects
determined, particularly during
dry periods. Explain how basal
ELF drainage will be collected
and managed within the mine
water treatment system and
after mine closure.
Estimated flow rates and water quality for
basal seeps are presented in the TCP in
Section 2.2.4 and Section 2.3.1, respectively
(Attachment H). Contaminant loads can be
calculated from the data in Table 3 in the TCP.
The collection of basal seeps is addressed in
Section 3.3.1 and Appendix 2 of the WRMP
(Attachment I). The management and
treatment of basal seeps is addressed in
Section 2.4 of the TCP (Attachment H).
The Applicant
indicates they have
provided such data
and management
methodologies.
New water quality and
flow data have been
provided for the ELF
basal drains. It
appears that based on
the data provided by
the Applicant that
acidity loads could vary
from 56 - 536 tonnes of
acidity (as CaCO3) per
year (or 153 – 1470
kg/day).
It does not appear that
these new data for the
basal seeps have been
included in any new
GoldSim Model, rather
the Applicant has
simply represented
Scenario 1 water from
the CRL (2017b) report
(Table 3).
GoldSim modelling
needs to be
undertaken to confirm
effects on the
downstream
environment during low
flow conditions when
basal seepage will
have maximum
impacts.
Information has been
provided on conceptual
plans to capture ELF
basal seepage.
Conceptual treatment
designs have been
proposed. Further
design detailed will be
required as part of the
CRL has noted that no alkalinity
has been provided in the
predicted water quality model (as
presented in Table 3 of the CRL
(2017b) report. CRL has
indicated this data will be
included in the evidence for the
hearing.
CRL has indicated that a new
GoldSim model will be included in
the evidence for the hearing,
which will include the current
predicted ELF basal seepage.
CRL will provide the new
GoldSim data to other
consultants to determine
discharge quantity/quality under
lower flow conditions. This will be
presented as evidence at the
hearing by the Applicant.
It was agreed that detailed water
treatment system designs will be
provided as part of the
appropriate management plan.
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O’Kane Consultants 8 August 2017 1014-02-1
Request
(WCRC to
Applicant)
Information Required Applicants Response
OKC Assessment of
Section 92
Response
OKC Analysis of Data Resolution
Water Management
Plan.
The potential
monitoring locations
identified in the
application provide
for a large mixing
zone which may not
be appropriate.
Proved further information on
alternative locations that could
be considered and why the
locations you have chosen are
justified in the regard to the
size of the mixing zone.
The points were selected for convenience and
the current GoldsimTM model includes dilution
from unimpacted catchments. Additional tracks
can be cut to reduce the mixing zone. The final
monitoring locations can be discussed with the
Council.
Limited comment on
this matter. Further
consideration
required.
Compliance monitoring
points further up the
catchment on the
access road would also
be a convenient
location and provide
greater protection for
the upper catchment,
which has been
indicated as being high
ecological value by the
Applicant.
CRL note this requires
consideration by a qualified
ecotoxocologist including
hydrology and the practical
issues of measurements during
low flow.
The peer reviewer
believes that an
acid mine drainage
management plan
should be
developed as there
is sufficient doubt
regarding the
generation of AMD.
Please indicate that an AMD
management plan will be
prepared for submission and
review by the Consent
Authority prior to any works
commencing.
The TCP, which is appended as Attachment H,
addresses any potential acid mine drainage
(AMD) generation.
The Applicant
indicates they have
provided such
information
The AMD Management
Plan presented by the
Applicant is a
conceptual plan and
will need updating prior
to any mining
commencing together
with site specific
operational protocols.
It was agreed that more details
would be provided as part of
management plans prior to
mining and that specific
operational protocols would also
be developed.
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O’Kane Consultants 8 August 2017 1014-02-1
Request
(WCRC to
Applicant)
Information Required Applicants Response
OKC Assessment of
Section 92
Response
OKC Analysis of Data Resolution
Coal samples may
have the potential to
produce AMD as do
the road cuttings.
Detail the acid base accounting
for the coal and road cuttings
and any risks associated with
stockpiling coal for any period
of time.
No acid base accounting (ABA) data has been
obtained for coal from Te Kuha or from road
cuttings (no road exist). However, a
conservative estimate of ABA values for coal
are presented in Section 4.0 of the WRMP
(Attachment I), prediction of potential water
quality in coal stockpile drainage is addressed
in Section 2.3.2 of the TCP, and management
and treatment of drainage from coal stockpiles
is addressed in Section 2.4 of the TCP
(Attachment H).
The Applicant
indicates no ABA data
for coal or road
cuttings is provided
and that management
and treatment options
have been provided
Estimates for MPA
have been provided for
coal stockpiles;
forecast low pH acidic
waters are expected
from such stockpiles.
Management and
treatment of drainage
from such stockpiles
should be part of the
AMD management
plan.
No ABA data provided
for road cuttings or fill
material for roads. A
conservative approach
is recommended and
methods should be
discussed in the
Construction and
Earthworks
Management Plan.
It was agreed that monitoring is
required and treatment may be
necessary for coal stockpiles.
This will be considered in the
appropriate management plan.
Any proposed resource consent
should include a condition
relating to the requirement to
monitor these areas.
In regards to the road cutting the
Applicant indicates that basic
data are available from geological
maps and more detailed
assessment (e.g., ABA testing as
required) will be undertaken
during construction as part of the
appropriate management plan.
West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information xv
O’Kane Consultants 8 August 2017 1014-02-1
Request
(WCRC to
Applicant)
Information Required Applicants Response
OKC Assessment of
Section 92
Response
OKC Analysis of Data Resolution
Additional samples
(100) are required
to produce accurate
acid base
accounting.
Please provide a new report on
the acid base accounting
incorporating the additional
100 samples recommended by
the peer review or detail why
that additional sampling is not
required and why the
information supplied in the
application is of sufficient
accuracy for consenting
purposes.
The results of additional ABA analyses are
presented in Appendix 1 of the WRMP, which
is appended as Attachment I.
The Applicant
indicates they have
provided additional
ABA data.
Additional information
has been provided.
Data indicates some
samples of the
Paparoa Coal
Measures (PCM) are
potentially acid forming
(PAF). Additional
classification criteria is
required for PCM PAF.
The current classification system
will be updated to include PAF
PCM. This new classification
system will be provided as part of
the management plans and any
updated waste rock block model.
Additional ABA data may be
required to confirm the waste
rock block model. Such a
requirement will be considered
during the preparation of the
management plans.
In OKC’s opinion it is better to
have the waste rock classification
scheme as a component of the
management plan rather than a
consent condition to enable
adaptive management. The
consent conditions should be that
there is an appropriate
classification system.
Potential for
inaccuracies in the
amount of various
rock types
produced.
Provide a rock block model for
this site. Also provide stage
drawings showing areas of
disturbance, volumes of
material disturbed each year
reported by class of waste rock
and progressive rehabilitation
areas and aligned with the
waste rock schedule.
Information on the volumes of NAF material,
Low acid neutralising capacity (ANC) NAF
material, potentially acid forming (PAF)
material, and Low PAF material is presented in
3.3.2.1.2 of the WRMP (Attachment I). A waste
rock block model for this site is not warranted;
an alternative methodology is presented in
Section 3.2.3 of the WRMP (Attachment I).
The Applicant
indicates they have
provided such data
using an alternative
methodology.
Volumes of various
rock types have been
determined. No cross-
sectional data has
been provided; such
data needs to be
provided as part of the
Construction and
Earthworks
Management Plan
including an annual
schedule of materials.
The Applicant has indicated that
a detailed annual mining
schedule will be developed prior
to mining and be in the
appropriate management plan.
The applicant indicates that the
general materials balance is
about 50:50 for the project life in
regards to BCM and PCM.
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Request
(WCRC to
Applicant)
Information Required Applicants Response
OKC Assessment of
Section 92
Response
OKC Analysis of Data Resolution
Lack of information
regarding potential
water quality from
waste rock
stockpiles.
Provide data and quantification
of oxygen ingress rates and
net percolation rates for ELF’s
and temporary rock dumps and
further discussion on methods
to prevent oxidation of
sulphides.
Potential oxygen ingress rates are presented
in Section 3.3.4.1 of the WRMP and potential
net percolation rates are presented in Section
3.3.4.2 of the WRMP. Methods to prevent
oxidation of sulphides are presented in
Sections 3.3.2.1.1 and 3.3.4.1 of the WRMP,
which is appended as Attachment I.
The Applicant
indicates they have
provided such data
and management
methodologies.
Oxygen ingress rates
for diffusion have been
provided although
consideration of
advective ingress of
oxygen is missing.
Data presented for
oxygen flux does not
consider extremes and
drier periods so is not
conservative.
The Applicant indicates that a
sensitivity analysis will be
undertaken and that a dry year
scenario will be run to determine
the potential effects. This will be
presented as evidence at the
hearing.
Insufficient
information on water
quality in the pit
lakes and
stockpiles.
Further discussion on the
expected water quality for the
proposed pit lakes and detail
how it was considered in the
water model for the site. Detail
the water management
techniques and potential
effects and mitigation methods
of drainage and resulting water
quality associated with coal
stockpiles.
There will be no pit lakes at the end of mining
life, however a pond will be created. A
discussion on water flow rates water quality,
and management of water from the pond is
presented in Section 2.2.6 of the TCP
(Attachment H). Prediction of potential water
quality in coal stockpile drainage is addressed
in Section 2.3.2 of the TCP, and management
and treatment of drainage from coal stockpiles
is addressed in Section 2.4 of the TCP
(Attachment H).
The Applicant
provides clarification
on this matter and
indicates further
information is
presented. The OKC
review sought
information on water
quality during mining.
The management of
poorer water quality
from highwalls / pit
area needs
consideration in the
Mine Water
Management Plan.
Poor water quality from
coal stockpiles has
been identified.
Management of such
drainage will be
required as part of the
Mine Water
Management Plan.
The Applicant will include
management of pit area water
and coal stockpile water in the
appropriate management plan
and explain any management
processes in the appropriate
management plans.
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Request
(WCRC to
Applicant)
Information Required Applicants Response
OKC Assessment of
Section 92
Response
OKC Analysis of Data Resolution
Insufficient detail on
the long term effects
of AMD should it be
identified.
Detail what on-going water
treatment will occur long term
upon closure of the site should
AMD be identified as an issue.
Discussion of water management and
treatment post-closure is presented in Section
2.4.2 of the TCP (Attachment H).
The Applicant
indicates they have
provided additional
information
Based on the water
quality data provided
by the Applicant for
ELF basal seeps and
the uncertainty of these
models it is
recommended that
water treatment be
expected for these
sites. Such treatment
should be presented as
part of the AMD
Management Plan or
Water Management
Plan.
The Applicant has provided plans
for the management and
treatment of poor water quality
from ELF basal seepage. It is
proposed that monitoring will
confirm when such treatment may
be required.
Source: WRCR letter dated 12 December 2016 to Stevenson Mining Ltd;
Section 92 Response by the Applicant dated 27 March 2017
Note: Information highlighted in red is summarised by the WCRC from the OKC (2016) report where the matter has Significant Uncertainty as per the Geochemistry Risk Classification.
Information highlighted in orange is summarised by the WCRC from the OKC (2016) report where the matter could be managed from an adaptive management regime
Information highlighted in yellow is summarised by the WCRC from the OKC (2016) report based on the executive summary and bullet points
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SUMMARY
Two key documents were provided by the applicant that provided additional information on waste rock
management and mine drainage management and treatment. These documents have been reviewed
to consider how initial uncertainties were addressed and identify any new issues. These documents
were:
CRL Energy Ltd, 2017. Te Kuha Mine – Waste Rock Management Plan. 14 March 2017.
Authors Dave Trumm and James Pope; for Stevenson Mining Ltd. 39 pp.
CRL Energy Ltd, 2017. Te Kuha Mine – Mine Drainage Management and Treatment
Contingency Plan. 14 March 2017. Authors Dave Trumm and James Pope; for Stevenson
Mining Ltd. 21 pp.
OKC has taken the approach that the management plans provided above are conceptual in nature,
developed with the data available prior to mining operations commencing. It is expected that before
mining operations start, updated management plans will be provided that include specific operational
protocols for the management of AMD related issues. This logic is presented in the figure below:
RECOMMENDATIONS
The current site is considered of high ecological value by the Applicant, unaffected by historical mining
activities or poor-water quality. As such any mining activities are likely to have greater impact on the
receiving environment compared to other recently consented mining operations within areas of
historical mining activity that already have legacy AMD issues.
Based on the data provided it is likely that some form of water treatment will be required during
operations and post closure for ELF basal seepage and coal stockpiles. This could be a function of
elevated Fe, elevated acidity, low pH, or elevated trace metals and significant uncertainty exists around
this. Treatment options should be considered upfront as part of the Water Management Plan and / or
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any AMD Management Plan. Adaptive management processes should be developed to consider
bounds for contaminant load and thus treatment options. Planning for treatment need to commence
prior to project start-up. Monitoring needs to commence at the inception of the project and should be
undertaken to confirm the contaminant load model. This contaminant load model should be reviewed
on an annual basis.
Previous recommendations as per OKC (2016) remain. A number of issues identified in that report
require consideration and resolution prior to mining commencing. In this regard, if the project gets
approval and resource consents are granted then they should be addressed as part of the appropriate
management plans prior to mining commencing.
Based on the review of the two new documents provided by the applicant a number of action items
have been recommended through this review with discussion provided in this report.
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TABLE OF CONTENTS
1 OVERVIEW ................................................................................................................. 3
1.1 Introduction ..................................................................................................................... 3
1.1.1 Waste Rock Management Plan ...................................................................................... 3
1.1.2 Mine Drainage Management and Treatment Contingency Plan .................................... 3
1.2 OKC Review Approach .................................................................................................. 3
1.3 Management Plans ........................................................................................................ 4
2 PREDICTION ............................................................................................................... 5
2.1 Acid Base Accounting .................................................................................................... 5
2.2 Waste Rock Model ......................................................................................................... 6
2.3 Geochemical Testing Programme .................................................................................. 6
2.4 Alkaline Addition ............................................................................................................. 8
3 ELF CONSTRUCTION METHODOLOGIES .............................................................. 10
3.1 Underdrain .................................................................................................................... 10
3.2 Material Placement ....................................................................................................... 10
4 OXYGEN FLUX ......................................................................................................... 12
4.1 Oxygen Diffusion .......................................................................................................... 12
5 NET PERCOLATION (NP) ........................................................................................ 13
5.1 Water Balance Modelling ............................................................................................. 13
5.1.1 GoldSimTM Model – 10% Infiltration ............................................................................. 13
5.1.2 Escarpment Barren Valley ELF Analogy – 21% infiltration .......................................... 13
5.2 Net Percolation Variability ............................................................................................ 14
5.3 Contaminated Coal Stockpiles ..................................................................................... 15
6 ELF WATER QUALITY ............................................................................................. 16
6.1 Introduction ................................................................................................................... 16
6.2 Water Quality ................................................................................................................ 16
6.3 Total Acidity Loads ....................................................................................................... 18
6.4 Coal Stockpiles ............................................................................................................. 18
6.5 Other Contaminants of Concern .................................................................................. 18
6.5.1 Nitrate (NO3) ................................................................................................................. 18
6.5.2 Sulfate (SO4) ................................................................................................................ 19
6.5.3 Other Contaminants ..................................................................................................... 19
7 TREATMENT ............................................................................................................. 20
7.1 Introduction ................................................................................................................... 20
7.2 Review .......................................................................................................................... 20
7.2.1 Flow .............................................................................................................................. 20
7.2.2 Quality .......................................................................................................................... 21
7.2.3 Monitoring Programme ................................................................................................. 21
7.3 Treatment ..................................................................................................................... 21
7.3.1 Treatment during Operations ....................................................................................... 21
7.3.2 Treatment at Closure.................................................................................................... 22
8 CLOSURE ................................................................................................................. 23
8.1 Closure Objectives ....................................................................................................... 23
8.2 Closure Objectives and Adaptive Management ........................................................... 23
8.2.1 Introduction ................................................................................................................... 23
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8.2.2 Adaptive Management Contingency Planning – AMD Treatment ............................... 24
8.3 Performance Monitoring ............................................................................................... 25
9 REFERENCES .......................................................................................................... 27
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1 OVERVIEW
1.1 Introduction
In response to the Section 92 Request for further information the Applicant has supplied two key
additional documents:
CRL Energy Ltd, 2017. Te Kuha Mine – Waste Rock Management Plan. 14 March 2017.
Authors Dave Trumm and James Pope; for Stevenson Mining Ltd. 39 pp.
CRL Energy Ltd, 2017. Te Kuha Mine – Mine Drainage Management and Treatment
Contingency Plan. 14 March 2017. Authors Dave Trumm and James Pope; for Stevenson
Mining Ltd. 21 pp.
In additional to these two documents there was additional information supplied, which was also
reviewed.
1.1.1 Waste Rock Management Plan
The report provides a summary of the proposed:
Geochemical classification scheme including QA/QC processes during mining;
Construction methodologies for the Engineered Landform;
Management of contaminated coal; and
Monitoring Programme.
1.1.2 Mine Drainage Management and Treatment Contingency Plan
The report provides a summary of the proposed:
Sources of mine water;
Predictions of mine drainage flow rates;
Prediction of mine drainage chemistry; and
Contingency management.
1.2 OKC Review Approach
The new data and information provided by the Applicant have been reviewed to consider how initial
uncertainties were addressed as discussed by OKC (2016). In addition any new issues have been
identified. As a guide, this review was based on the six step hierarchical approach to the prediction,
prevention, minimisation, control, and treatment of AMD and the closure of AMD impacted sites.
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1.3 Management Plans
It was indicated by the Applicant that a Site Environmental Management Plan (SEMP) will be prepared,
which will include a number of smaller plans focused on particular activities. In regards to geochemistry
and the management of mine impacted waters the following plans are important and should be reviewed
to confirm they address and manage the effects and risks of AMD:
Construction and Earthworks Management Plan;
Overburden Management Plan;
Water Management Plan;
Rehabilitation Management Plan; and,
Mine Closure Management Plan.
It is recommended that the respective plans are supported by operational procedures such that
operational staff have a clear understanding of protocols required to manage the effects of AMD. These
protocols should include detailed design specifications and need to be completed prior to operations
commencing at the site. These protocols should be approved by the regulatory authorities to ensure
they will achieve the expected outcomes of the Site Environmental Management Plan.
OKC have referred to these proposed plans as part of this review. OKC has suggested that an AMD
Management Plan could be prepared, but the avoidance of duplication across plans is needed.
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2 PREDICTION
2.1 Acid Base Accounting
The Applicant has provided further acid base accounting (ABA) data and methodologies to undertake
classification of waste rock in regards to geochemistry.
A number of assumptions have been presented, which are often necessary for subsequent calculations.
However, the effect of this is reduced certainty and thus consideration needs to be provided in regards
to adaptive management if the proposed data set is erroneous (e.g., mean data for MPA and ANC).
CRL (2017a) propose a process flow classification approach to determine the geochemical
characteristics of the waste rock based on:
1. Lithology being either Paparoa coal measures (PCM) or Brunner Coal Measures (BCM); the
risk being considered less for PCM; and then
2. Total S for BCM where:
PAF > 0.33 wt% S or an MPA of >10 kg H2SO4/tonne; and
Low PAF < 0.33 wt% S or an MPA of <10 kg H2SO4/tonne.
3. Total S and ANC for the PCM where:
NAF has an ANC:MPA ratio of > 5; and
Low ANC NAF has an ANC:MPA ratio < 5.
It is noted that consideration that all BCM is PAF is possibly conservative, but a simple and logical
operation approach. OKC notes that if the ANC:MPA ratio is less than 2:1 it should be considered PAF
as a conservative approach for long-term neutral mine drainage. This is due to the loss of alkalinity
from the waste rock stack where CO2 cannot exsolve from drainage waters within the confines of the
ELF.
Review of the additional ABA data provided by the Applicant indicates that some PCM samples had an
ANC:MPA ratio less than 2:1 (e.g., 103/342) and some samples were PAF (e.g., 103/343, 103/344,
103/246). Such low ANC samples and these PAF samples are not covered by the classification
process. Further consideration is required of this matter.
Action: An ANC:MPA ratio of > 2:1 and < 5:1 should be considered to define Low ANC NAF; anything
less than this ratio should be managed appropriately after such identification.
Outcome: This will be considered in a new waste rock classification scheme that will be developed as
part of the appropriate management plan. Any resource consent granted to the Applicant should
contain the condition that an appropriate waste rock classification scheme should be developed as part
of the appropriate management plan.
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Action: A PAF classification criteria is required for PCM waste rock and how such rock will be managed;
and a suitable waste rock block model that demonstrates the risk associated with PAF PCM (e.g.,
quantity).
Outcome: The Applicant agrees that a PAF PCM classification will be required. This will be reflected
in any new waste rock classification scheme that needs to be developed as part of the appropriate
management plan. Any resource consent granted to the Applicant should contain the condition that an
appropriate waste rock classification scheme should be developed as part of the appropriate
management plan and this should include PAF PCM as a classification.
2.2 Waste Rock Model
ABA data can be used to develop a waste rock block model, which can be based on geological and
geochemical interpretations. Such models can be quite difficult for coal measures where there can be
significant variations in rock types associated with lenses/channel deposits and discontinuous
lithological units.
CRL (2017a) has separated the deposit stratigraphically into Paparoa- and Brunner- coal measures
and indicate that a detailed geological map will be used to separate PCM and BCM rock and where
there is uncertainty more detailed ABA testing will be undertaken. It is noted additional work is
necessary.
No cross sections, or block models have been provided to demonstrate the representativeness of the
ABA sampling programme or whether the proposed waste rock blocks can be mined.
CRL (2017a) discuss quantities of waste rock in Appendix 2 that will be available to construct the basal
layer of the ELFs. It is estimated that 727,000 m3 of NAF waste rock is required in year 1 and that
1,545,000 m3 will be moved in year 1. It is indicated that 2,360,000 m3 of NAF PCM is required for the
3 m thick cover layer and that depending on mine scheduling some NAF PCM may require stockpiling.
Action: A clear mining schedule is required to understand the availability of NAF and PAF materials
and any requirements for stockpiling of NAF as this may require consideration in the mine plan and will
result in additional cost through double handling. The mining schedule should present estimated annual
volumes of waste rock as per the geochemical classification.
Outcome: The Applicant notes that a mining schedule for PCM and BCM is available. It was agreed,
that a more detailed annual schedule will be provided before mining commences as part of the
appropriate management plan.
2.3 Geochemical Testing Programme
The Applicant proposed that a geochemical testing programme will occur during mining to confirm the
geochemical classification of waste rock including:
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Paste pH testing of each 500 bcm of waste rock mined, or up to 4 samples per day.
o OKC note this has limited value unless the rocks are oxidised
ABA testing – One sample per 4,000 bcm mined, or up to one sample every other day
o Further context is required
Sulfur speciation – 10% of ABA samples
o No explanation is provided as to how this will be incorporated into the proposed
classification process.
In Section 5.0 of the CRL Report (2017a) it is noted that ABA results will be available after the waste
rock is placed in the ELF. It is noted these data will be used to refine the geochemical model. However,
in Appendix 2 of the CRL (2017a) report it discusses that blast holes will be sampled and that ABA data
(Total S and ANC) will be obtained from composite holes so that every 1,000 tonnes of waste rock is
characterised. Similar is also discussed for BCM and PCM waste rock going into the ELF
Action: The Applicant indicates that further work is required on the geological / geochemical model
and that a detailed mining schedule cannot be produced until such data are obtained. The Applicant
needs to provide such data in the proposed Construction and Earthworks Management Plan prior to
mining commencing or explain how the separation of waste rock will be managed without such data.
Outcome: It was agreed that this will be provided by the Applicant as part of the appropriate
management plan prior to mining commencing.
Action: The limited ABA sampling programme proposed (paste pH, ABA, sulfur speciation) does not
address the possible uncertainties presented or how this will be done. It appears this will be a QA/QC
check of the waste rock block model. Further explanation is required prior to mining of how this
sampling will be undertaken (e.g., on blast holes) and how appropriate is the proposed sampling
programme from a QA/QC perspective in regards to validating any waste rock block model. It is
recommended that a concise operational protocol is developed before mining commences.
Outcome: The Applicant indicates that all resource development holes / blast holes will be sampled as
part of the ABA sampling programme, which will involve a QA/QC process. The operational protocols
for this sampling, analysis, block model update, and QA/QC will be reflected in the appropriate
management plan.
Action: The Applicant needs to explain how limestone will be added if rock is placed in the ELF before
ABA data is available.
Outcome: The Applicant has clarified that ABA data will be available before any waste rock is placed
in the ELF. The operational protocol for how this limestone will be applied will be explained in the
appropriate management plan.
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2.4 Alkaline Addition
It is proposed by the Applicant (CRL, 2017a) that limestone will be added to PAF and Low PAF waste
rock to achieve an ANC:MPA ratio of 1.5 in addition to the current ANC already present. It is proposed
that:
36 kg limestone be added to each tonne of PAF waste rock; and
0.9 kg limestone be added to each tonne of Low PAF material.
The following data in Table 2.1 are provided by Applicant (CRL, 2017a) on page v of that report. OKC
has provided some analysis of these data and note the following issues:
Action: The tonnes of waste rock presented by CRL (44,400,000 tonnes) does not represent the tonnes
of waste rock presented on page iii of the executive summary (15,200,000 tonnes); and on page 22 of
18,250,000 m3. Explanation is required.
Outcome: CRL has indicated that 44,400,000 tonnes is the total quantity of rock to be disturbed for the
project.
Any PCM material classified as Low ANC NAF that has an ANC/MPA ratio of less than 2 could result
in acidic drainage with time.
Action: Alkaline amendment to a minimum of 2:1 is recommended due to the loss of alkalinity from the
waste rock stack where CO2 cannot exsolve from drainage waters within the confines of the ELF.
Outcome: The Applicant believes a ratio of 1.5:1 is appropriate for ANC:MPA. This is based on the
expectation that with an overall ANC:MPA ratio of 4.2:1 within the greater ELF that there is sufficient
ANC available to generate alkaline drainage.
CRL (2017a) suggest that this ANC:MPA ratio is sufficient to prevent the formation of acidic drainage,
which may be correct, but preferential flow needs to be considered and also the fact that trace metals
associated with pyrite oxidation may still remain in solution (e.g., Zn, Ni, Cu). A conservative approach
is thus recommended to ensure all drainage from ELFs is captured and directed to appropriate locations
if treatment is required (OKC note this has been proposed by the Applicant).
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Table 2.1: Bulk ABA accounting data and OKC analysis
Unit Tonnes of
rock
Total MPA as Tonnes
of CaCO3
MPA (kg/t)
ANC (tonnes)
Total ANC (kg/t)
ANC/MPA Ratio
Data source CRL
(2017a) CRL
(2017a) OKC Calc.
CRL (2017a)
OKC Calc.
OKC Calc.
BCM PAF 2,400,000 61,000 25.4 9,000 3.8 0.15
BCM Low PAF 22,000,000 27,000 1.2 21,000 1.0 0.78
PCM NAF 14,000,000 9,000 0.6 355,000 25.4 39.44
PCM Low ANC NAF 6,000,000 26,000 4.3 32,000 5.3 1.23
Limestone addition to PAF rock 82,000
Limestone addition to Low PAF Rock 19,000
Total 44,400,000 123,000 518,000 4.21
The Applicant suggests that limestone will be mixed with the waste rock by using a hopper which will
dispense limestone to each truck load of waste rock as required. Other options are also proposed that
may also be suitable.
Action: No annual materials balance is presented to confirm the amount of NAF waste rock needed
for the proposed ELF design. This needs to be presented at a current conceptual level, which should
be refined prior to mining and on an annual basis.
Outcome: It was agreed that this will be provided by the Applicant as part of the appropriate
management plan prior to mining commencing.
Action: The Applicant should confirm that all waste rock, including waste rock placed in temporary ex-
pit landforms will have the limestone added.
Outcome: The Applicant confirms that all ex-pit placement of waste rock that requires additional ANC
will also have limestone added at the proposed rate.
Action: Alkalinity loss from the ELFs need to be considered in mass balance calculations (as presented
in Table 6.1), as a sensitivity check and to acknowledge such loss with time.
Outcome: These data will be presented as evidence at the hearing by the Applicant.
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3 ELF CONSTRUCTION METHODOLOGIES
3.1 Underdrain
OKC has reviewed data and information relating to the proposed underdrainage system, but notes that
any design needs to be signed off by a competent engineer and this is not OKC’s role. OKC has simply
provided comment on matters as they relate to AMD management.
The Applicant proposes that an underdrainage network will be constructed under each ELF that will
follow the natural contours and discharge to small sumps at the edge of the ELF via a swan-neck type
arrangement to prevent oxygen ingress. It is proposed that the underdrainage system will be perforated
piping sized to take 0.37 L/s/ha based on a maximum net percolation (NP) of 21% of rainfall. It is
proposed a factor of safety of 2 is applied to the maximum flow rates.
Action: It is proposed by CRL (2017a) that the underdrainage system is designed to 21% of rainfall
with a safety factor of 2. As explained by CRL (2017a), it was agreed that a factor of two should be
applied to maximum flow rates as well. It is recommended this factor of safety for the underdrains be
confirmed by a competent engineer.
Outcome: The factor of two is applied, in the conceptual plan, for the maximum expected flow rate of
42% for the underdrain capacity. CRL indicates that this will be designed by a competent engineer as
part of the appropriate management plan.
Action: It is recommended that a detailed design (plan view and cross section) of the underdrainage
system for the site be developed prior to mining. These plans should explain how a swan-neck type
arrangement will be built to prevent oxygen ingress along the cobble-filled trench. The plans should be
approved by a competent engineer.
Outcome: The applicant has recognised the issue and this will be addressed in the appropriate
management plan by a competent engineer.
3.2 Material Placement
It is proposed the ELFs at the project will be constructed with a 2 m basal layer of PCM NAF and an
overlying final cover layer of 3 m of PCM NAF over PAF BCM and low ANC PCM placed within the core
of the ELF.
The Applicant proposes a range of options to minimise the advective ingress of oxygen into the ELFs
and ways to reduce acid generation including:
2m basal NAF layer to prevent basal flow interacting with PAF waste rock.
Addition of limestone to PAF materials.
Construction of the ELF in 4 m high lifts.
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Use of a water trap to prevent oxygen ingress along the basal underdrain layer.
A 3 m NAF cover layer to be wheel-rolled to compact the surface to encourage runoff. Tests
will be undertaken during construction to determine the success of compaction in regards to
permeability on both flat surfaces and ELF slopes.
Action: Ensure this first layer is paddock dumped or short 2 m high tip heads are used. Consideration
is required on how this will be achieved on sloping ground from a mine operations perspective. Analysis
is required to ensure groundwater mounding is not greater than 2 m. Such explanations need to be
included in the AMD Management Plan or the Construction and Earthworks Management Plan.
Outcome: This will be explained in the appropriate management plan.
Action: Construction of the ELF in 4 m lifts needs to be included in the site specific operational
protocols for construction of the ELF including QA/QC.
Outcome: This will be explained in the appropriate management plan.
Action: “Wheel-rolled” does not provide a specification for compaction. Further explanation is required.
Outcome: This will be explained in the appropriate management plan.
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4 OXYGEN FLUX
4.1 Oxygen Diffusion
CRL (2017a) indicate that construction of the ELF in short lifts using adequate compaction will limit
oxygen diffusion into the ELF. Fick’s First Law is used to calculate oxygen flux and thus potential
contaminant load. The diffusion coefficient determined by Fick’s First Law is directly related to the
degree of saturation. CRL (2017a) indicate that the surfaces of the ELF will be 81.4% saturated on
average, quoting the work of Pope and Dutton (2016).
Fick’s First Law is used to determine diffusion of oxygen. It does not consider advective ingress of
oxygen. Advective ingress of oxygen can be the greatest contributor to oxygen ingress. Assuming that
the entire ELF cover system will remain at 81.4% saturated (average) is not conservative.
CRL (2017a) determine that the oxygen flux is 168 gO2/m2 per year (or 26 tonnes of O2 for all the ELFs
at closure) equating to an estimated annual acidity load of 212 tonnes of CaCO3 equivalent. CRL
(2017a) report in the Executive Summary that the annual acidity load is 225 tonnes of CaCO3
equivalent.
Action: The Pope and Dutton (2016) report does not provide an explanation of how the number of
81.4% saturated was determined. The use of average data does not consider extremes such as in
summer where significant O2 flux could occur. A more comprehensive approach to oxygen flux is
required (including consideration of advective ingress of oxygen) and explanation of seasonal
fluctuations in surface saturation is needed together with impact on oxygen flux.
Outcome: The Applicant indicates that a sensitivity analysis will be undertaken and that a dry year
scenario will be run to determine the potential effects, which will be considered in regards to potential
impacts on the receiving environment. This will be presented as evidence at the hearing.
Action: OKC requests that the different oxygen flux numbers presented in CRL (2017a) Executive
Summary and the body of the report be checked.
Outcome: CRL will review these calculations as part of the new water quality model for ELF basal
drainage.
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5 NET PERCOLATION (NP)
5.1 Water Balance Modelling
Net Percolation (NP) is fundamental component of determining contaminant loads for the project. NP
is the water that infiltrates through the waste rock dump and is therefore the transport medium for
contaminants of concern.
CRL (2017a) indicates that NP for Te Kuha ELFs is predicted to range from 10% to 21% infiltration of
rainfall. This is based on:
1. The GoldSimTM model (CRL, 2016) that estimates 10% of rainfall will report as infiltration (NP);
and
2. An analogy model, using flow rates derived from the Escarpment Coal Mine, Barren Valley ELF,
which indicated that infiltration was 21% of rainfall.
CRL (2017a) indicate that based on an annual rainfall of 5.6 m/yr, long term flow rates for the proposed
ELF’s at Te Kuha are estimated at 13 – 27 L/s. Data presented by CRL (2016) indicates that rainfall
can range from 4 – 7 m per year at the Te Kuha project site.
5.1.1 GoldSimTM Model – 10% Infiltration
CRL (2017a) report that “net percolation can be estimated using soil-plant-atmospheric (SPA) modelling
or VADOSE/W, a finite element CAD software product for analysing flow from the environment, across
the ground surface, through the unsaturated vadose zone and into the local groundwater regime.
However, approximations of net percolation can be made by assuming various infiltration rates of total
precipitation for the area.”
This quote suggests VADOSE/W modelling was not undertaken, which appears to be the case from the
data presented. It would be more appropriate for such modelling methodologies to be undertaken.
The GoldSimTM Model (CRL, 2016) assessed the current environment, prior to mining to determine
runoff coefficients of 90%. This was based on a thin shallow aquifer that would quickly become
saturated enabling, within a short time frame, elevated surface runoff. The calibration of the proposed
NP model is thus done to pre-mining conditions. However, a waste rock dump is a significantly different
system.
5.1.2 Escarpment Barren Valley ELF Analogy – 21% infiltration
The use of data from the Escarpment Barren Valley ELF provides a good data point, however no
workings or analysis are provided. Data presented by CRL (2017a) indicates that the flow rate derived
for the Barren Valley ELF is 0.37 L/s/ha, which equates to 21% of average annual rainfall reporting as
net percolation. Based on these data CRL (2017a) indicates this provides a conservative maximum
infiltration rate for ELFs at the Te Kuha Project and a calculated toe seepage rate of 27 L/s.
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CRL (2017a) indicates that a factor of 2 should be applied to maximum flow rates to account for flow
variations after heavy rainfall based on analysis of data from the Escarpment Mine. CRL (2017a) state
this is conservative as Escarpment mine does not have a capping layer in place and that a capping
layer will be constructed at Te Kuha.
OKC sees no significant difference between the current Barren Valley ELF at the Escarpment Mine,
which has been capped with NAF and the cover layer proposed for Te Kuha. The capping layer
proposed for Te Kuha involves 3 m of NAF PCM waste rock that will be wheel compacted (CRL, 2017a).
No design specifications are provided. Without design specifications there cannot be an argument that
the 3 m NAF cover layer at Te Kuha will perform better than the Barren Valley ELF at the Escarpment
Mine.
One issue with the data point obtained from Escarpment Mine is that it may not represent the long term
flow rate as the whole ELF may not have wetted up. Wetting up takes time and is a function of a number
of variables including, for instance, infiltration rate, waste rock particle size distribution, porosity, and
waste rock dump height. Typically the toe of a waste rock dump wets up first as this is usually
constructed first, and also is the thinnest part of the waste rock dump. An ELF can take decades to wet
up in some environments. Hence, the data point presented by CRL (2017a) for the Escarpment Mine
may not be representative of Te Kuha and the Applicant should confirm whether the Barren Valley ELF
has wetted up before such reliance is given to these data being used as the conservative maximum
infiltration rate. Furthermore, it is one data set and an argument that it is a conservative data set lacks
scientific argument. The safety factor of 2 applied to this data provides some needed conservatism,
although it may actually only create a more reasonable value.
5.2 Net Percolation Variability
As stated by CRL (2017a) a factor of 2 should be applied to the maximum flow rates, which therefore
suggests that NP could be 42% of rainfall. It was also indicated by CRL (2017a) that this factor should
be applied for design of the underdrainage system.
Action: Clarification is required to confirm whether the underdrainage design is based on a NP of 42%
of rainfall and then a factor of 2 for safety.
Outcome: The factor of two is applied, in the conceptual plan, for the maximum expected flow rate of
42% for the underdrain capacity. Maximum flow rates in the underdrain are therefore 54 L/s. CRL
indicates that this will be designed by a competent engineer as part of the appropriate management
plan.
Action: Flow rates from the ELFs are a critical component of the water model for the site. It is
recommended that Soil Plant Atmosphere (SPA) modelling or similar be undertaken prior to mining
commencing and such data be incorporated into the Water Management Plan. Furthermore, accurate
monitoring of flow rates from the ELF basal drainage system should be undertaken from the inception
of the project to confirm such models.
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Outcome: An updated model for net percolation will be provided as part of the appropriate
management plan, which will be validated by flow monitoring from the ELFs.
This detailed model should be completed such that the data can be used for mine planning and design
as the flow rates would have implications for:
Underdrainage capacity;
Treatment design and treatment capacity;
Contaminant loads; and
Effects on the downstream receiving environment.
5.3 Contaminated Coal Stockpiles
CRL (2017a) report that coal can contain up to 1.22 wt% sulfur. Assuming this is all pyritic this
represents a MPA of 37 kg H2SO4/tonne. CRL (2017a) suggest that the pyritic content of the
contaminated coal would be about 15 kg H2SO4/tonne and that 21 kg of limestone would be added to
each tonne of contaminated coal placed into the ELF.
Action: The management of such rock as PAF is appropriate. It is suggested that further testing of this
contaminated coal for ABA characteristics commence once such materials are developed to confirm
the limestone requirements. It is suggested that an ANC ratio of 2:1 be used rather than 1.5:1 as
proposed.
Outcome: This will be reviewed and considered as part of the appropriate management plan, once
ABA data are available.
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6 ELF WATER QUALITY
6.1 Introduction
Additional discussions have been provided by the Applicant as part of the S92 request for further
information on expected water quality for the project. Such data are discussed here.
The Applicant has used oxygen flux and subsequent assumptions around pyrite oxidation to develop
additional data to determine water quality for the project. Oxygen flux by diffusion was estimated with
an assumption of 81.4% saturation of the surface of the ELF and no advective ingress of oxygen. Water
quality data presented based on these stoichiometric and molar conversions are thus optimistic as it
does not consider climatic extremes (e.g., lower surface saturations in summer) where gas flux would
increase significantly or advection of oxygen due to temperature and pressure differentials etc.
6.2 Water Quality
It is noted by CRL (2017a) that “basal seepage from ELFs can be concentrated compared to the results
of field leachate trials”. This agrees with previous comments by OKC (2016) and it is good to note that
such a conservative approach is being considered. It is also noted (CRL, 2017a) that where oxygen
concentrations are lowered, reduced iron may be present in waste rock drainage and that seepage from
waste rock at this site could produce elevated concentrations of Ni, Zn, and Cu. CRL (2017b) note that
Fe concentrations could range from 77 – 158 mg/L.
Action: Such Fe concentrations represent a Lewis acidity of 138 – 283 mg/L, although CRL (2017b)
note that Fe concentrations of 15 – 25 mg/L are more likely. The Applicant needs to present expected
alkalinities from such drainage paths and whether they will be sufficient to neutralise the acidity load
associated with reduced Fe.
Outcome: The applicant indicates the model will be reviewed and will be presented as evidence at
the hearing.
On page 14 (CRL, 2017b) it is stated that concentrating up the lysimeter data yield unrealistic
concentrations and show that this technique is not suitable for predicting trace element concentrations.
For instance, it was noted Zn would be greater than 100 mg/L, which is higher than any other
documented AMD site in New Zealand (CRL, 2017b). CRL propose that a better approach to estimating
the trace element concentrations is using the summation method of first flush data and current years’
lysimeter data.
A key consideration for determining basal seepage water chemistry for waste rock stacks is the amount
of water interacting with a much larger volume of rock over a very long period and subsequent
geochemical reactions such as precipitation, adsorption, and dissolution. In one model CRL (2017b)
reduce the volume of water to represent NP values but do not increase the quality of rock keeping the
amount of rock constant. In another approach all the leachate concentration data is added together
and does not consider the contaminant load derived per unit of rock. Such data is generated from
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oxidising columns with high flushing rates and is unlikely to be comparable to waste rock with the centre
of the ELF (where it is proposed by the Applicant that no oxygen will be present).
The greatest effect of basal seepage from the ELFs is during dry periods when the basal seeps may
represent a significant risk to the downstream receiving environment due to elevated concentrations.
CRL (2017b) presents data of the predicted water quality from these basal drains as shown below in
Table 6.1.
Some data are anomalous in that concentrations are unlikely, e.g., Al concentrations of 5.8 mg/L at pH
7, which is a function of the simplistic numerical approach used to derive water quality. However, if
these data are used, then nearly all the parameters presented in Table 6.1 could cause elevated
concentrations in receiving streams at low flow, when the only source of flow in the catchment is likely
to be basal drainage from the ELFs.
Table 6.1: Predicted ELF Basal Seep Water Quality Data
Parameter
(assumed dissolved)
Predicted Water Quality
(mg/L except for pH)
ANZECC Guidelines (95% Protection Trigger Value – mg/L
except for pH)
pH 7 6 – 9
SO4 264 - 543 250 DWS
Fe2+ 77 – 158
Al 0.15 – 5.8 0.5*
Cd 0.0008 – 0.007 0.0002
Cu 0.028 – 0.4 0.0014
Mn 0.023 – 0.29 1.9
Ni 0.0094 – 0.32 0.011
Pb 0.0018 – 0.034 0.0034
Zn 0.067 – 2.2 0.008
Source: Water Quality Data from CRL (2017b), page 16;
DWS = Drinking Water Standard
* - Proposed resource consent compliance limit.
Action: The data presented in Table 6.1 and the optimistic and conservative flow rates (10% and 42%
NP respectively) should be used in the Goldsim model to understand the effects on the receiving
environment during low flow periods. As noted by the Applicant previously streams in the area dry up.
Due to storage of water within the ELFs the basal flow is not likely to diminish significantly and could
have significant environmental effects during low flow.
Outcome: The Goldsim model will be rerun including a scenario for oxygen flux under dryer conditions;
and the predicted water quality (including alkalinity) for the ELF basal seepage. This data will be
included in the greater site water model and will be presented by the Applicant as evidence at the
hearing.
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Action: It is recommended that a monitoring programme be established at the inception of the project
to monitor basal seepage from the ELFs, once the underdrainage system is installed. The data should
be used to validate water quality forecasts and update the water quality model for the project.
Outcome: It is agreed a monitoring programme will be developed for the contaminants of concern
identified by this review and OKC (2016). This monitoring plan should become a condition of any
consent.
6.3 Total Acidity Loads
Based on oxygen flux it is proposed by CRL (2017a) that 0.2% of the available MPA will be oxidised
each year and 0.04% of the ANC will be used to neutralise the resulting acidity. Analysis by CRL
(2017a) indicates that it will take 550 years for all the pyrite to be oxidised and 2,000 years for the
alkalinity to be removed.
OKC notes that this does not consider the loss of alkalinity from the ELFs in excess of any alkalinity
used to neutralise any acidity generated.
Action: Alkalinity loss from the ELFs should be considered and should be incorporated into the water
quality model.
Outcome: This will be included in the new model for ELF basal drainage and will be presented by the
Applicant as evidence at the hearing.
6.4 Coal Stockpiles
CRL (2017b) note that the water quality from the coal stockpiles could be pH 2.8 - 3.1 with elevated
sulfate and iron. In such a situation, trace metals are also likely to be elevated.
Action: A management protocol is required for how drainage from the coal stockpiles will be managed
and this needs to be developed prior to mining commencing. This needs to be presented in either an
AMD Management Plan of Water Management Plan.
Outcome: This will be managed in an appropriate management plan.
6.5 Other Contaminants of Concern
6.5.1 Nitrate (NO3)
CRL (2017a) note that one assumption is that nitrogen-based explosives may contribute nitrogen to
waste rock drainage (page 13). No further comment is provided on this. It is recommended that a
monitoring programme be established to either confirm the effects are less than minor and nothing
further needs to be undertaken, or an adaptive management process developed to manage these
nitrate loads.
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Action: Propose a suitable monitoring programme and also explain any management approach if
monitoring results indicate elevated nitrates.
Outcome: It is agreed a monitoring programme will be developed for this contaminant. This monitoring
plan should become a condition of any consent.
6.5.2 Sulfate (SO4)
As noted sulfate may be elevated in basal seepage from ELFs. Sulfate is becoming more regulated
worldwide and consideration should be given to the management of any elevated sulfate
concentrations. This is important in a catchment that is pristine and not affected by any mining activities.
Action: Establish a monitoring programme for sulfate from ELFs, which provides data on geochemical
reactions within the ELF and also provides guidance on whether sulfate concentrations are appropriate
for the downstream receiving environment.
Outcome: It is agreed a monitoring programme will be developed for this contaminant. This monitoring
plan should become a condition of any consent.
6.5.3 Other Contaminants
Action: It is recommended the AMD management plan provide comment on other contaminants such
as As, Co, Cr, and Mn, as being identified as potentially of concern (Pope et al., 2010) to demonstrate
these contaminants will be compliant with ANZECC guidelines. Basal seepage from the ELF should
be monitored to confirm the concentrations are acceptable.
Outcome: It is agreed a monitoring programme will be developed for this contaminant. This monitoring
plan should become a condition of any consent.
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7 TREATMENT
7.1 Introduction
CRL (2017b) present a section on contingency treatment. Given the uncertainty in both oxygen flux
into the ELF, flow rate associated with NP, and possible water quality concentrations, the appropriate
approach is to expect water treatment for ELF basal seepage may be required.
Treatment of low pH metal-rich drainage will also be required for the coal stockpiles based on the data
presented by the Applicant.
7.2 Review
This section reviews the treatment of AMD impacted waters. It is likely the key risks for AMD will be
associated with the ELF underdrainage system.
7.2.1 Flow
CRL (2017a) indicate that underdrainage will report to sumps, designed to have a minimum of 2 hours
residence time and that each sump will be able to be treated in accordance with the mine drainage
treatment contingency plan so that dosing could occur in the sump or through pumping to a centralised
water treatment system.
Action: Explanation is needed why 2 hours residence time was selected and whether this residence
capacity considers the factor of 2 safety.
Outcome: 2 hours was based on an expectation that a pump would operate on a semi-continuous
basis to pump water to the water treatment plant.
Action: A safety factor of 2 was applied to NP rates, meaning that NP rates could be 42% of rainfall or
equivalent to 54 L/s (for all ELFs) based on average rainfall data. It was indicated that a safety factor
of 2 was also applied to underdrains, but clarification is required on this matter.
Outcome: Treatment systems are designed for expected maximum flow rates. This information will be
presented as evidence at the hearing.
Action: It is recommended, due to the model uncertainty, that treatment systems be designed for 54
L/s for conceptual designs until site data are available, or the model is rebuilt to continue extremes in
NP and oxygen flux.
Outcome: Treatment systems are designed for expected maximum flow rates. This information will
be presented as evidence at the hearing.
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7.2.2 Quality
Data was supplied by CRL as presented in Table 6.1 for the predicted ELF basal seepage for the
project. Maximum flow rates of 27 L/s was allocated to the maximum water qualities presented in Table
6.1, which provides some conservatism. However, as discussed, the conservative approach presented
by CRL (2017a) was to double these flow rates. This is not observed in these data presented by CRL
(2017b).
CRL (2017b) note that the optimistic water quality for the basal seepage from the ELFs is better than
the current surface runoff as presented by the GoldSim Scenario 1 model. However, it was noted by
CRL (20176b) that if the water chemistry for the ELF basal seeps is more like the maximum
concentrations presented in Table 6.1 then water treatment will be required.
Action: OKC note that it is unlikely that surface waters for the site will be worse water quality than
basal seepage from the ELFs. From a management perspective it is recommended that as a
conservative approach, treatment should be expected for these basal seeps, particularly during low
flow conditions.
Outcome: The applicant indicates that the water quality model will be redone to include alkalinity and
these data will be presented as evidence at the hearing.
7.2.3 Monitoring Programme
Although poor water quality associated with pits and any future pit lakes may represent lesser risk to
the project compared to AMD impacted waters from the ELFs a monitoring programme should be
established to confirm any such effects.
Action: Develop a monitoring programme for the site to ensure all potential sources of AMD impacted
water is assessed.
Outcome: A water quality and quantity monitoring programme will be developed as part of the
appropriate management plan. This monitoring plan should become a condition of any consent.
Treatment
7.2.4 Treatment during Operations
CRL (2017b) suggest a number of options could be undertaken to treat water from the ELFs if required
including pumping affected water to the water treatment plant or treatment at the seep. It is proposed
that treatment reagents could include either Ca(OH)2 or NaOH and that target pH would be dependent
on the contaminants of concern and what pH would be required to achieve metal hydrolysis. It is
proposed sludge disposal will be within the NAF cover zone.
Action: No analysis has been provided on the amount of reagent required or the amount of sludge
produced. Such data needs to be calculated prior to mining for management purposes and should
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include, design of treatment plants and sludge disposal methodologies. This needs to be included in
the Water Management Plan.
Outcome: A sludge management plan needs to be prepared by the Applicant, which should be part of
the appropriate management plan.
7.2.5 Treatment at Closure
CRL (2017b) indicate that treatment may still be required after year 15. It appears that passive
treatment is proposed.
As indicated by CRL (2017b) the expected water quality from each ELF will be elevated in iron, which
will require removal to manage this contaminant. It is expected this will be ongoing, even after mining
has been completed.
Action: No data is presented to explain water quality at closure, treatment requirements, or the amount
of sludge that will be produced and where it will be disposed to. Such data and methodologies need to
be presented as part of the Mine Closure Plan and/or any Water Management Plan.
Outcome: A conceptual model for long term water quality and quantity will be presented as evidence
at the hearing together with expectations around any treatment requirements.
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8 CLOSURE
8.1 Closure Objectives
As previously discussed (OKC, 2016) a Closure Management Plan is required for the site. This plan
should be developed before mining commences aligned with agreed closure objectives.
The Applicant indicates a Site Environmental Management Plan (SEMP) will be prepared, which will
include a number of smaller plans focused on particular activities. It was indicated that a Mine Closure
Management Plan would be developed. This plan should be in alignment with resource consent
conditions in regards to the management of AMD and any associated impacts after closure of the site,
possibly in perpetuity.
Action: Develop a Mine Closure Management Plan for the site before mining operations / activities
commence that addresses closure objectives for the site. As part of the adaptive management process
and as more data becomes available, this plan should be updated on an annual basis.
Outcome: It was agreed the mine closure management plan would be developed prior to mining
operations commencing.
Action: It should be acknowledged that with the current uncertainty around flow rates, water quality,
and contaminant loads for the ELFs that there is the possibility of water treatment in perpetuity for the
project. As such, there is a high probability that site access will be needed after closure for the
management of water treatment systems. This needs to be considered in any closure objectives for the
site as a part of an organic adaptive management process.
Outcome: A conceptual model for long term water quality and quantity will be presented as evidence
at the hearing together with expectations around any treatment requirements. This will be used to
consider closure objectives for the site.
8.2 Closure Objectives and Adaptive Management
8.2.1 Introduction
As previously mentioned (OKC, 2016): Stevenson Mining Limited (2015) note that the mine plan “ is a
conceptual design as it is based on a relatively low level of exploration data and that further work is
recommended in order to develop a bankable mine design and schedule”. Often this is the nature of
such projects and the first hurdle, after project viability, is to obtain regulatory approval to mine.
However, because of the limited dataset and the conceptual nature of methodologies to manage the
effects of AMD, it is recommended that an adaptive management regime be developed if approvals are
given. The adaptive management process should be imbedded in Site Environmental Management
Plans, which should be organic documents, and should include a range of options to manage potential
effects to the receiving environment.
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Adaptive management for AMD needs to consider the all potential outcomes associated with the
expected range of water qualities, from optimistic models to conservative models, such that
management systems are available if required. It is acknowledged the some adaptive management
options may be conceptual in nature. However, the applicability of an adaptive management strategy
is predicated on the level of risk and the ability to respond quickly should the matter arise.
Understanding the potential risk is thus a key step in the development of an adaptive management plan.
In OKC’s opinion there is significant uncertainty in the current understanding of the project in regards
to the proposed ELFs including:
Oxygen flux;
Net percolation rates; and
Water quality.
This includes such matters during the operational period of the mine and post closure. CRL (2017a)
propose that one year prior to the rehandling of waste rock (which is towards the end of the project)
that the following activities are undertaken:
Assessment of the adequacy of the water treatment facilities on site and modifications were
required;
Long term prediction of the behaviour of final landforms with regard to leachate geochemistry;
and
Establishment and operation of passive water treatment systems if required.
OKC note that for appropriate and proactive adaptive management, such options should not be
reviewed in the waning stages of the project but should be reviewed on a regular basis as new data
become available. Leaving such assessments to the end of the project can result in additional project
costs and legacy issues that could have been addressed earlier if the adaptive management process
had been followed.
Action: It is recommended that water quality data are collected on a regular basis and that the mine
closure plan is updated annually with consideration of these to ensure closure objectives will be
achieved.
Outcome: A water quality and quantity monitoring programme will be developed as part of the
appropriate management plan, which will provide guidance on how to achieve closure objectives. This
monitoring plan should become a condition of any consent.
8.2.2 Adaptive Management Contingency Planning – AMD Treatment
Adaptive management for water treatment must address the expected bounds for optimistic and
conservative water quality and flow. CRL (2017b) have presented optimistic and maximum values for
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water quality and have indicated flow rates of 10% and 21% of NP. CRL (2017a) suggest that maximum
flow rates should be doubled. These data have been used to provide the bounds for the Applicants
Adaptive Management Process, which suggest that based on a range of ELF basal flow rates of 13 –
54 L/s and a water quality having an estimated acidity of 138 – 315 mg/L CaCO3 equivalent (see Table
2.1) that contaminant loads for the project could be 56 - 536 tonnes of acidity (as CaCO3) per year (or
153 – 1470 kg/day). Such loads are not within the accepted bounds of passive treatment technologies
(150 kg/day) and the Applicant should provide discussion on this matter. It is expected that other
contaminants (e.g., trace metals) can be manged accordingly by such similar passive treatment
methodologies.
Action: Passive treatment trials of ELF basal seepage must be undertaken to confirm the appropriate
technology for the site. Given the high forecast contaminant loads this work should be implemented in
the first few years of the project. It is noted that active treatment after closure is not likely as no power
will be available. The Applicant needs to confirm the requirements for water treatment as soon as
practical.
Outcome:
Action: The contaminant load model is a key tool for forecasting the requirements for water treatment
at the site. It needs to be updated each year as new data are obtained.
Outcome: This will be done on an annual basis.
8.3 Performance Monitoring
Performance monitoring is a key aspect of any AMD Management Plan to ensure that the proposed
goal posts for the project will be obtained as proposed in the Mine Closure Management Plan.
Action: A performance monitoring programme needs to be established to confirm that the conceptual
model proposed for the site remains correct. This needs to be developed as part of the Management
plans associated within mining operations and the mine closure management plan. Performance
monitoring for this project should include:
1. Water Quality Monitoring: In regards to AMD, the monitoring programme should be focused
on ELFs, pit areas, coal and contaminated coal stockpiles, and other areas of significant
disturbed overburden. Monitoring should include:
a. Water quality for contaminants of concern; and
b. Flow rates.
2. Oxygen Ingress Monitoring: As per the proposed ELF design it is suggested that only the outer
2 m of the ELF will be oxidising. Oxygen probes or similar electronic equipment need to be
installed into each ELF to confirm the model and also construction processes. Temperature
should also be considered and water quality measurements within the ELF.
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3. Quality Control / Quality Assurance (QA/QC): A number of QA/QC processes need to be
undertaken to confirm the agreed management plans are being adhered to, which are designed
to achieve closure objectives. QA/QC programmes should, for instance, include:
a. Waste rock geochemical characterisation;
b. Waste rock placement as per geochemical requirements;
c. Limestone addition;
d. Waste rock placement as per engineering design;
e. Compaction specifications for the NAF cover;
f. Permeability of final cover system; and
g. Flow rates from the basal drains and water quality.
4. Water Treatment: Confirmation that water treatment processes are appropriate including:
a. Design specifications are being achieved;
b. water quality targets are being achieved; and
c. Sludge management expectations and management processes are acceptable
Outcome: A performance monitoring programme will be developed to consider the above data
collection processes. This performance monitoring plan should become a condition of any consent.
West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information 27
O’Kane Consultants 8 August 2017 1014-02-1
9 REFERENCES
Australian and New Zealand Environment and Conservation Council (ANZECC) and Agriculture and
Resource Management Council of Australia and New Zealand (ARMCANZ) (2000). Australian and New
Zealand Guidelines for Fresh and Marine Water Quality. Canberra.
CRL Energy Ltd, 2017. Te Kuha Mine – Waste Rock Management Plan. 14 March 2017. Authors Dave
Trumm and James Pope; for Stevenson Mining Ltd. 39 pp.
CRL Energy Ltd, 2017. Te Kuha Mine – Mine Drainage Management and Treatment Contingency Plan.
14 March 2017. Authors Dave Trumm and James Pope; for Stevenson Mining Ltd. 21 pp.
CRL Energy, 2016. Te Kuha Mine Project GoldSim™ Drainage Model and Predicted Chemistry. CRL
Report No. 15-41101. 63 pp
Pope, J., Newman, N., Craw, D., Trumm, D., Rait, R., 2010. Factors that influence coal mine drainage
chemistry West Coast, South Island, New Zealand. New Zealand Journal of Geology and Geophysics
53 No. 2-3: 115 – 128.
Stevenson Mining Limited, 2015. Te Kuha Mine Design and Planning. September 2015 – V7.
PowerPoint Presentation, 63 slides.
For further information contact:
Paul Weber
Principal Geochemist
O'Kane Consultants (NZ) Ltd
PO Box 8257
Riccarton, Christchurch 8440
New Zealand
Telephone: (027) 294 5181
Web: www.okc-sk.com