bird in hand gold project woodside community consultative ...€¦ · 120 compliance criteria ......
TRANSCRIPT
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TERRAMIN AUSTRALIA LIMITED
Bird in Hand Gold Project
Woodside Community Consultative Committee
Water Technical Reference Group Meeting
Wednesday 26th July 2017 Woodside Bowling Club
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Welcome and agenda
2
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
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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
3
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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
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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
5
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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
6
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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
7
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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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 9
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 10
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 11
Conceptual groundwater model –
Regional scale
Groundwater flow direction
Project site
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 12
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 13
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 14
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 15
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 16
History matching to observations at 28
bores
Project site
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 17
History Match – Simulation of regional
groundwater flow pattern
Project site
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 18
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 19
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?
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 20
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 21
• 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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 22
Water Allocation Plan Principles
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 23
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”
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 24
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?
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 25
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 26
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 27
Why?
Identify old mine shafts, geology check, rock strength for tunnel, water bearing fractures ahead of tunneling
3. PROBE drilling and 4. GROUT process
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 28
Why?
Identify old mine shafts, geology check, rock strength for tunnel, water bearing fractures ahead of tunneling
3. PROBE drilling and 4. GROUT process
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 29
Why?
Identify old mine shafts, geology check, rock strength for tunnel, water bearing fractures ahead of tunneling
3. PROBE drilling and 4. GROUT process
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 30
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 31
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 32
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
Inflows above specified levels?
Inflows above specified levels?
Inflows above specified levels?
N
Y
Y
N
Inflows above specified levels? Y
N N
Y
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 33
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.”
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 34
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 35
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 36
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 37
Snapshot - Seasonal Summer Drawdown
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 38
Differences with and without Reinjection
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 39
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 40
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 41
Water Quality of Receiving Environments
Reinjection water must be of same quality as
receiving environment
Salinity
Metals
Nutrients
Environment Protection (Water Quality) Policy 2015
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 42
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 43
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 44
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 45
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
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TERRAMIN AUSTRALIA LIMITED SLIDE No. 46
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
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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
47