Bird in Hand Gold Project Woodside Community Consultative ...€¦ · 120 compliance criteria ... Pre-excavation grouting is used to stop or reduce groundwater inflow into the mine

TERRAMIN AUSTRALIA LIMITED

Bird in Hand Gold Project

Woodside Community Consultative Committee

Water Technical Reference Group Meeting

Wednesday 26th July 2017 Woodside Bowling Club

Welcome and agenda

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Description

Time

1 Welcome

7.00 pm

2 Orientation: how we came to be here

• Community engagement opportunities

• Progressing the WCCC

7. 05 pm

3 Review of water studies

7.20 pm

4 Thank you, next meeting and close

9.00pm

Community consultation

In the past, Terramin has conducted:

• public meetings

• one on one meetings and small group meetings

• drop in session

This community input has been used in Terramin’s work to date in putting together its mining proposal

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Opportunities for the local community to be involved

• The WCCC has been established to promote a community based approach to broad community engagement rather than a Terramin led process

• special focus groups will be held by Terramin to directly address particular

community groups and respect unique circumstances such as ‘some members of the community have more to lose / gain than others and this must be recognised and taken into account’ (comment made at the first WCCC meeting 3rd July 2017)

• drop in sessions may be held that could include presentations from the

mining regulator and other stakeholders

• community members will always have the right to contact Terramin or the

mining regulator directly as well as other stakeholders like their local elected members or relevant Ministers of government.

4

Moving forward

Handover • Christine Charles is MD of a company called Design for Growth and is working with

Terramin

• Christine along with Katy and Matt who you know, will be the ‘go to’ people within Terramin

WCCC governance working party • Terms of Reference

• Independent Chair and secretariat

WCCC meeting • Complete introduction to WCCC core group members

• Special item CSIRO survey

• Reports from WCCC governance working party

• Key issue (s) for consideration

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WCCC Water Technical Reference Group (TRG)

• Learn more about the ground water assessment report for the Bird in Hand Gold Project, and the independent review

• Understand the purpose of the report

• Ask questions

• Provide comments and other input

• Identify challenges, concerns and priorities

• Identify opportunities

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Water issues brought forward from last WCCC meeting

• A closer look at the data collected

• An understanding of the assumptions used in the Assessment Report

• An understanding of the modelling with a special focus on its reliability

• An understanding of the potential for salinity migration in the catchment

• An understanding of the likely volume of any water that may be released into the mine, plans for any reinjection for any of this water and methods of any proposed reinjection

• An understanding of water allocation requirements, water planning and / or water purchase that may be required

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TERRAMIN AUSTRALIA LIMITED SLIDE No. 8

Groundwater Technical Reference Group

Tonight’s format

Groundwater

Existing conditions and Modelling

– Jason van den Akker Hydrogeologist

Underground water management strategies

Grouting: what and how?

– Katy Fechner Terramin

Depressurisation and Reinjection

– Matt Daniel Terramin

Groundwater Monitoring Networks

– Matt Daniel Terramin

Question and Answer Session


Approach

Information gathering (>3 years)

Develop conceptual groundwater

model

Build computer model

History matching

Groundwater predictions

Independent review of conceptual &

computer models

Conceptual model

Computer model


Information gathering

Anecdotal evidence

(1930’s & 50’s)

Groundwater levels

(regional flow pattern)

Groundwater pumping

Groundwater recharge

(rainfall)

Groundwater & surface

water interactions

Drilling & aquifer testing to

understand aquifer

permeability


Conceptual groundwater model –

Regional scale

Groundwater flow direction

Project site


Conceptual groundwater model –

Local scale

Fractures

Marble

Historic BiH mine

Proposed mine decline

NW SE

Aquifer characterised based

on

>60 exploration holes

5 investigation bores

Several aquifer tests


Computer model

Groundwater models are computer models of groundwater flow

systems.

The model was developed to:

Represent the current state of groundwater

Predict the rate of groundwater inflows

Assess groundwater impacts

Evaluate water management options Project site


Computer model construction

900,000 model cells (5 to 50 m3 in size)

Assign aquifer (rock thickness, dip, faults)

Assign aquifer properties such as

permeability

Regional groundwater flow into & out of

model (catchments)

Add private bores (pumping)

Add rainfall recharge

Add Inverbrackie Creek


History matching

Model Calibration – matching historic observations to model

predictions

The model needs to replicate:

Current groundwater flow pattern – 35 observation bores

Seasonal groundwater level change due to pumping – 28

observation bores

The results of the 6 day pumping test – 20 observation

bores

Historic mine dewatering – Mine managers records &

Government reports used to validate model


History matching to observations at 28

bores

Project site


History Match – Simulation of regional

groundwater flow pattern

Project site


Model review process

Groundwater modelling guidelines

120 compliance criteria

Iterative process looking at

Planning

Conceptual model

Design and construction

Calibration & sensitivity analysis

Predictions of impacts

Model is fit for purpose

Government will conduct its own review


Model uncertainty

Robustness of the model is based on the amount of

information available to inform construction

Limited info = low confidence (need to make assumptions)

More info = higher confidence (less assumptions)

This model has evolved over 3 years

Sensitivity analysis:

What parameters is the model sensitive to?

How does altering these parameters influence the model

predictions of impacts?


Uncertainty

Worst case

Interception of water bearing fault (beyond 60 L/s)

Different grouting effectiveness (reduce inflows to 4 to

12 L/s)

Increase aquifer permeability (+7 L/s)

Reduce rainfall recharge


• Located in Western Mt Lofty Ranges Prescribed

Water Resource Area - September 2013. Unlimited

GW use prior to then. Now 940ML/year.

• The rules of the WAP are designed to protect the

groundwater system and the rights of existing users

to a sustainable groundwater supply.

• Terramin will protect the groundwater and existing

users through the same rules.

• Terramin have not started exploring options with the

department to clarify water licensing on inflows and

reinjection

• WAP binds Terramin to same “no impact” rules

Water

Allocation

Water Allocation Plan


Water Allocation Plan Principles


Law - Proposed Outcome Criteria

What we are proposing to be monitored

against

All aspects of the project have outcome

statements like these

Provide the basis for all design and

monitoring

WATER “No adverse impact to the supply or

quality of water by the mining operations to

existing users and water dependant

ecosystems”


1. UNDERSTAND – existing

geology and hydrogeology

2. DESIGN – mine plan to

avoid water bearing zones

3. PROBE – ground

conditions ahead of mining to

know what’s ahead

4. GROUT – Grouting for

groundwater control

5. REPLACE – reinject

groundwater back into the

aquifer around the mine

Groundwater Management Strategy

How can we manage groundwater impacts?


1. UNDERSTAND and 2. DESIGN to avoid

fracture zones

Fractures in the

“Hanging wall”

Marble

Historic BiH mine

Proposed mine decline

NW SW

>60 drillholes

Fracture

mapping

Targeted

investigation

bores

Several

aquifer tests

Creates a 3D

model of

geology


Pre-excavation grouting is used to stop or reduce groundwater inflow into the mine

Cement is pumped into the fractures approximately 2-5m around the mine void prior to progressing the tunnel

The need to grout is determined by the results of the probe drilling and conditions encountered during mining process

Constantly builds on info

from steps 1 and 2

3. PROBE and 4. GROUT process


Why?

Identify old mine shafts, geology check, rock strength for tunnel, water bearing fractures ahead of tunneling

3. PROBE drilling and 4. GROUT process


Why?




Why?




Probe hole diameter

40-63mm

Are inflows larger

than predicted?

Do we need more

probe holes to

explore or inject

grout?

Is the grout

working? Checking

from verification

probe holes

3. PROBE and 4. GROUT process

Continuous checking


Water Pressure Entering Through Probe

Hole and Engineering Formulas for

Grouting

Pressure gauges allow us to

understand the hydrogeology

and the fracture ahead

Grouting program designed in

response to the probe drilling

program at each face

Inflows determines how much

grout applied - equation

Holes drilled after grouting to

check grout is effective


The mining cycle with grouting

Drill initial Probe holes

Grout holes

Drill verification probe holes

Drill face charge holes

Develop the tunnel

Re-entry inspection

Geological/geotechnical

inspection and mapping

Install ground support

(bolts, mesh, shotcrete).

Inflows above specified levels?

Remove rock with gold

Y

N

Inflows above specified levels? Y

N




N

Y

Y

N

Inflows above specified levels? Y

N N

Y


Interest point - 1945 Government Report

on 381 day BIH pump test in 1934

Government pump test 9th June 1934 – 13th July 1935

381 days at 4.4ML/day

11th November 1934

“Shear filled with altered slate in crosscut 35 ft. west of the

shaft at the level responsible for increased flow. Shear

enters shaft at 389 ft. 80% of water making in mine is in

Victoria Shaft.”


Shotcrete

Shotcrete is a sprayable cement product, often including small fibres and

aggregate to improve strength properties, used to manage exposed ground

conditions (i.e. on the surface of the excavation).

Applied to bare rock face and/or over already installed mesh and bolts.

http://bestsupportunderground.com/fibre-reinforced-shotcrete/?lang=en

It does not

penetrate the

structure of the

rock.

Can help seal

minor

groundwater

inflows







What if – we developed the tunnel and

inflows are larger than expected?

Post-excavation grouting available to ‘seal off’ open

fractures

Used modelling to see impact on surrounding

bores of hitting fracture zone at both 130m below

surface and 300m below surface

Impact showed 1-2m groundwater drawdowns after

two weeks

Blue – 130m

Red – 300m

Reinjection

still operating


3. Depressurisation and Managed Aquifer

Recharge

Decreases pressure head above mine void

Increases effectiveness of grouting system

Reduces risk of grouting failure

Keeps water out of mine – take it out above mine

before it enters and reinject around mine (radial)

Reinjection allows for the “cone of depression” to

be very steep and narrow around mine

Together allows Terramin to operate without

impacting groundwater supply to existing users


Snapshot - Seasonal Summer Drawdown


Differences with and without Reinjection


Reinjection bore locations

Reinjection will be in a

radial pattern around

the mine workings

This makes the ‘cone’

very steep and narrow

Prevents impacts to

operational bores in the

area – reinjection

between mine and

receptors

Prevents drawing in salt

from Dawesley

Catchment


Depressurisation and Reinjection

Reinjection creates

a higher water level

outside the mine to

prevent impacts to

other uses

Over 40 MAR

systems in SA

Irrigation bores

Reinjection bore

Above mine


Water Quality of Receiving Environments

Reinjection water must be of same quality as

receiving environment

Salinity

Metals

Nutrients

Environment Protection (Water Quality) Policy 2015


Volumes from Modelling

Year 90% Grout 70% Grout

ML/y ML/d L/s ML/y ML/d L/s

1 70.8 0.2 2.2 212.4 0.6 6.7

2 109.4 0.3 3.5 328.1 0.9 10.4

3 137.8 0.4 4.4 413.3 1.1 13.1

4 160.4 0.4 5.1 481.1 1.3 15.3

5 143.3 0.4 4.5 430.0 1.2 13.6


Groundwater Management Summary

Built in capacity for water management contingencies

Strategies are designed to prevent water inflows from

the fracture zone and manage water inflows

Probe drilling allows active and adaptive management

Allows actions before inflows become an issue

Grout will be applied to limit the water inflows into the

underground workings – amount based on probe drilling

result

Reinjection creates a pressure barrier that prevents

impacts to other groundwater users


Groundwater Monitoring Network

Conceptual

Additional monitoring

wells to be placed

between receptors and

reinjection:

Private wells

Inverbrackie Creek

Dawesley Creek

catchment

High frequency

monitoring of :

Groundwater

seepage & quality

Groundwater levels

& quality

---- Reinjection bore network

---- Monitoring bore network


Responding to Monitoring

“Trigger Action Response Plans”

A TARP provides early warning triggers and response actions for

prevention of impacts to nearby water users

The monitoring program will be designed to:

detect changes to groundwater levels, groundwater salinity &

inflow rates,

indicate that an abnormal condition relating to mining has

developed

Trigger levels to be set for particular impacts at which a response is

needed

Baseline monitoring data provides guidelines for trigger levels

Action - repeat monitoring, investigate cause, notify

Response – Review and implement management strategies in order to

meet our obligations


Conceptual Groundwater model

Computer Groundwater model

Groundwater Impact Assessment

Independent review of conceptual and computer Groundwater models

Assessment of water management options

Assessment of Project against

Water Allocation Plan + Determination

Develop Plan for Management and Monitoring

What’s Next?

Modelling of 5 years of drought

5 years of above average rain

Additional monitoring bores

installation

Ongoing monitoring of existing

groundwater network

Approval from Government to drill

and test reinjection bores

Review and update model with

new information

Update with

new

information

We are

here

Next meetings and close

Next Water TRG meeting

WCCC governance working party

Next WCCC meeting

Great to meet you

My very best wishes to you all

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Documents

Bird in Hand Gold Project Woodside Community Consultative ...€¦ · 120 compliance criteria ... Pre-excavation grouting is used to stop or reduce groundwater inflow into the mine