te kuha opencast mine review - s92 additional … coast regional council te kuha opencast mine...

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

[email protected]

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


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.

West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information vi


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.

West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information vii


Request

(WCRC to

Applicant)


OKC Assessment of

Section 92

Response


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,


the ANZECC

guidelines for 95%


0.0014 mg/L.


using NaOH or

Ca(OH)2 during

operations and by


after operation.

A monitoring plan


to confirm Cu is not an





appropriate

management is

required.





















West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information viii


Request

(WCRC to

Applicant)


OKC Assessment of

Section 92

Response


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,


the ANZECC

guidelines for 95%


0.0034 mg/L.


using NaOH or

Ca(OH)2 during

operations and by


after operation.

A monitoring plan


to confirm Pb is not an





appropriate

management is

required.





















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.

West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information ix


Request

(WCRC to

Applicant)


OKC Assessment of

Section 92

Response


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


Request

(WCRC to

Applicant)


OKC Assessment of

Section 92

Response


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









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





monitor these contaminants.

West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information xi


Request

(WCRC to

Applicant)


OKC Assessment of

Section 92

Response


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.

West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information xii


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


West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information xiii


Request

(WCRC to

Applicant)


OKC Assessment of

Section 92

Response


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.

West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information xiv


Request

(WCRC to

Applicant)


OKC Assessment of

Section 92

Response


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





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


West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information xv


Request

(WCRC to

Applicant)


OKC Assessment of

Section 92

Response


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


The applicant indicates that the

general materials balance is

about 50:50 for the project life in

regards to BCM and PCM.

West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information xvi


Request

(WCRC to

Applicant)


OKC Assessment of

Section 92

Response


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.

West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information xvii


Request

(WCRC to

Applicant)


OKC Assessment of

Section 92

Response


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

West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information xviii


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

West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information xix


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.

West Coast Regional Council Te Kuha Opencast Mine Review - S92 Additional Information 1


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



8.2.2 Adaptive Management Contingency Planning – AMD Treatment ............................... 24

8.3 Performance Monitoring ............................................................................................... 25

9 REFERENCES .......................................................................................................... 27



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.



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.



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.



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


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:



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




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).



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.



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.



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.


Action: “Wheel-rolled” does not provide a specification for compaction. Further explanation is required.




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.



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.



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.



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.



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



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.



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.



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.



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.





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.



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



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.



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.



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



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.



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.



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

[email protected]

O'Kane Consultants (NZ) Ltd

PO Box 8257

Riccarton, Christchurch 8440

New Zealand

Telephone: (027) 294 5181

Web: www.okc-sk.com

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