Appendix D: Hydraulic Containment of Groundwater (PDF

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Appendix D: Hydraulic Containment of Groundwater (PDF
FINAL REPORT ON BEHALF OF
ACCESSUTS PTY LIMITED
OPTIMAL GROUNDWATER ABSTRACTION RATES
FOR HYDRAULIC CONTAINMENT OF
CONTAMINANT PLUMES AND SOURCE AREAS,
BOTANY NSW
FOR
ORICA AUSTRALIA PTY LTD
16-20 BEAUCHAMP ROAD
MATRAVILLE NSW 2036
By
Dr N. P. Merrick
National Centre for Groundwater Management
Project Number: C04/44/001
Date: 13 October 2004
This document was prepared on instructions by
Orica for specific purposes and should not be relied
upon by other parties for any other purposes. This
document may be superseded by a later document
based on more up-to-date data. The most up-todate documents should be sought.
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EXECUTIVE SUMMARY
Orica Australia Pty Ltd is required by the Department of Environment and
Conservation (DEC, formerly NSW EPA) to implement pump-and-treat remediation
in three areas on and downgradient of its premises at Botany NSW. Hydraulic
containment of the existing contaminant plumes and their source areas is to be
attained by means of groundwater interception bores along strategically placed
containment lines. This action is required under a Notice of Clean Up Action (NCUA)
issued by NSW EPA in September 2003 in response to higher than expected
concentrations of chlorinated hydrocarbons in the City of Botany Bay’s Herford Street
production bore and EPA’s concerns about the rate of movement of contamination in
groundwater. A Groundwater Cleanup Plan (GCP) devised by Orica in October 2003
was authorised for implementation in February 2004.
At that time, DEC issued a Variation Notice which included provision by 16th March
2004 of “Orica’s most recent groundwater extraction rate estimate for full
contaminant containment in the primary containment area, including full details and
supporting information”. This report updates the extraction rates provided in March
2004 and June 2004 for the Primary Containment Area (PCA), and provides revised
estimates of optimal abstraction rates for the Secondary Containment Area (SCA) and
for containment of dissolved phase contamination from inferred DNAPL source areas
A more detailed layered numerical model has been developed for simulating
groundwater flow. Good agreement has been achieved between simulated
groundwater levels and those measured between 2000 and 2002. Although more
recent water levels (March 2004) are available in the vicinity of the area of interest,
the 2000-2002 measurements remain the best dataset for regional coverage.
The flow model has been coupled with an optimisation model based on a nonlinear
programming algorithm. It is possible to optimise the number of bores, their locations,
and their pumping rates. Optimisation is achieved by guaranteeing compliance with
water level, hydraulic gradient, and pumping constraints.
Candidate interception bores have been placed along a number of containment lines:
Line A (south-western boundary of Southlands, to contain contamination in the PCA);
Line 1 (along McPherson Street east of Springvale Drain), Line 2 (Foreshore Road, to
provide containment for the SCA); Line 3 (extending Line 2 to the east, to capture the
Southern Plumes), Lines 5 and 6 (western boundary of the Botany Industrial Park, to
contain the dissolved phase contamination from inferred DNAPL areas for the
Northern and Central Plumes). In addition, candidate bores are placed within the core
of the Central Plume for rapid active removal of chemical mass as required by the
NCUA.
Hydraulic containment is achieved by designing an hydraulic barrier downgradient of
each interception line, where a flat or reversed hydraulic gradient is forced. The
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gradient is specified by the head difference between pairs of model cells (doublets),
and the optimisation software determines the optimal pumping rates that generate the
required gradient.
To achieve hydraulic containment of the Primary Containment Area, the Secondary
Containment Area, and the inferred DNAPL source areas, about 15 ML/day of
groundwater needs to be pumped and treated.
The water should be drawn from a maximum of 140 bores at 68 distinct drilling sites.
The actual number of bores will depend on whether a single screen can be used across
the sub-layers of Layer 2. The bore locations have been optimised spatially along each
line, and vertically across five stratigraphic layers. Model bores have been constrained
to pump at least 10 m3/day from Layer 1, and between 30 and 500 m3/day in the sublayers of Layer 2. A “model bore” is assumed to be screened across the full thickness
of a model layer. As it has not been necessary to pump from Layer 3, there can be up
to four model bores at the one location, associated with Layers 1, 2A, 2B and 2C. On
the ground, from one to four “field bores” could be drilled to realise four model bores,
depending on the choice and length of screened intervals, and the similarity of
recommended pumping rates. In practice, some rationalisation of “model bores” to
practical “well/pump” combinations is required, but such shifts in location or pump
depth should be undertaken in consultation with the modeller.
Regional impacts are expected to be minor. Pumping at the recommended rate will
reduce overall groundwater discharge to Botany Bay by about 15 percent but will
have more significant local effects in the shadow of the Secondary Containment Area
extraction line, where groundwater discharge will be significantly reduced or
eliminated. Groundwater with accompanying contamination will cease to discharge
into Springvale Drain and Floodvale Drain. Instead, interception pumping will induce
recharge from the drains and in dry weather conditions it would be expected that
drains would have very low levels or be dry..
The water table at the eastern end of the ponds in Sir Joseph Banks Park is expected to
drop by about 15 centimetres. The maximum drawdown at an external production
bore is 40 centimetres. Modelling has shown that subsidence is not a risk, with a
maximum likely subsidence of about 1 centimetre at Foreshore Road.
The predicted drawdown in the vicinity of Springvale Drain and Floodvale Drain is
generally 0.1–0.6 metre, and is buffered by water leaking from the drains. Typical
drawdowns along the other containment lines are from 0.2 metre to 3 metres.
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.TABLE OF CONTENTS
EXECUTIVE SUMMARY.........................................................................................II
LIST OF ILLUSTRATIONS ................................................................................. VI
LIST OF TABLES .................................................................................................. IX
1.0
INTRODUCTION........................................................................................1
2.0
MODELLING METHODOLOGY ............................................................2
2.1
2.2
2.3
2.4
3.0
3.1
3.2
3.3
3.4
3.5
4.0
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
5.0
5.1
5.2
5.3
5.4
5.5
5.6
5.7
6.0
6.1
6.2
7.0
PREVIOUS MODELLING............................................................................2
NEW SIMULATION MODEL......................................................................3
OPTIMISATION MODEL ............................................................................4
HYDRAULIC CONTAINMENT ..................................................................5
GROUNDWATER CONDITIONS ............................................................8
HYDROGEOLOGY ......................................................................................8
GROUNDWATER LEVELS.........................................................................8
VERTICAL HEAD DIFFERENCE...............................................................9
HYDRAULIC STRESSES ..........................................................................10
CONTAMINANT PLUMES .......................................................................11
SIMULATION MODEL............................................................................13
CONCEPTUAL MODEL ............................................................................13
MODEL GEOMETRY ................................................................................13
MODEL STRESSES....................................................................................15
CALIBRATION...........................................................................................16
AQUIFER PROPERTIES ............................................................................17
WATER BALANCE....................................................................................18
SENSITIVITY ANALYSIS.........................................................................19
LIMITATIONS ............................................................................................20
OPTIMISATION SCENARIOS ...............................................................21
CONSTRAINTS ..........................................................................................21
CHRONOLOGY..........................................................................................22
OPTIMAL BORE NETWORK ...................................................................28
VALIDATION OF CAPTURE ZONES......................................................30
REGIONAL IMPACTS ...............................................................................33
WATER BALANCE....................................................................................37
DRAIN SENSITIVITY................................................................................37
CONCLUSION...........................................................................................39
RECOMMENDATIONS .............................................................................39
MONITORING ............................................................................................40
REFERENCES ...........................................................................................42
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ILLUSTRATIONS - FIGURES 1 TO 41 ................................................................44
APPENDIX .................................................................................................................84
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LIST OF ILLUSTRATIONS
Figure
Title
Page
1
Model extents for the new model and prior models
45
2
Variable cell sizes for the new model
46
3
The principle of hydraulic containment
47
4
Hydraulic containment lines and candidate interception
bore locations
48
5
Locations of hydraulic barrier doublets
49
6
Locations of known groundwater bores
50
7
Representative groundwater levels recorded 2000-2002
51
8
Lowest groundwater levels recorded 1969
52
9
Groundwater levels recorded 1988
53
10
Likely distribution of active groundwater production
bores during 2000-2002
54
11
Conceptual model
55
12
Surface topography contours across the model area
56
13
Inferred topography at the interface between Layer 1 and
Layer 2
57
14
Inferred topography at the interface between Layer 2 and
Layer 3
58
15
Inferred bedrock topography at the base of Layer 3
59
16
Simulated water table contours in Layer 1
60
17
Simulated groundwater level contours in Layer 2,
compared with 2000-2002 interpolated measurements
61
18
Scattergram of simulated and observed groundwater
levels
62
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19
Simulated vertical head difference between Layer 1 and
Layer 2
63
20
Critical locations for monitoring groundwater drawdown
64
21
Optimal locations of all drilling sites on all containment
lines
65
22
Simulated groundwater levels in Layer 1 for optimal
hydraulic containment
66
23
Simulated groundwater levels in Layer 2A for optimal
hydraulic containment
67
24
Simulated groundwater levels in Layer 2B for optimal
hydraulic containment
68
25
Simulated groundwater levels in Layer 2C for optimal
hydraulic containment
69
26
Simulated groundwater levels in Layer 3 for optimal
hydraulic containment
70
27
Capture zones for (red) particles originating in Layer 1
71
28
Capture zones for (blue) particles originating in Layer 2A
71
29
Capture zones for (green) particles originating in Layer
2B
72
30
Capture zones for (silver) particles originating in Layer
2C
72
31
Capture zones for (magenta) particles originating in Layer
3
73
32
Simulated groundwater drawdowns in Layer 1 for optimal
hydraulic containment
74
33
Simulated groundwater drawdowns in Layer 2A for
optimal hydraulic containment
75
34
Simulated groundwater drawdowns in Layer 2B for
optimal hydraulic containment
76
35
Simulated groundwater drawdowns in Layer 2C for
optimal hydraulic containment
77
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36
Simulated groundwater drawdowns in Layer 3 for optimal
hydraulic containment
78
37
Anticipated subsidence for the Base Case, ignoring prior
consolidation
79
38
Anticipated subsidence for the Likely Case, taking
account of prior consolidation
80
39
Anticipated subsidence for the Worst Case, taking
account of prior consolidation
81
40
Simulated groundwater levels in Layer 1 for optimal
hydraulic containment (mAHD), and low water level in
drains
82
41
Simulated groundwater levels in Layer 2A for optimal
hydraulic containment (mAHD), and low water level in
drains
83
A1
Model grid and boundary conditions for Layer 1
85
A2
Model grid and boundary conditions for Layer 2
86
A3
Model grid and boundary conditions for Layer 3
87
A4
Land use pattern for rainfall recharge distribution
88
A5
Calibrated hydraulic conductivity pattern in Layer 2
89
A6
Sensitivity to hydraulic conductivity for Layer 1
90
A7
Sensitivity to hydraulic conductivity for Layer 2
91
A8
Sensitivity to leakance (Layer 1/2A and Layer 2C/3)
92
A9
Sensitivity to low rainfall recharge zone
93
A10
Sensitivity to medium rainfall recharge zone
94
A11
Sensitivity to high rainfall recharge zone
95
A12
Sensitivity to conductance, Springvale Drain north
96
A13
Sensitivity to conductance, Floodvale Drain north
97
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LIST OF TABLES
Table
Title
Page
1
Model column dimensions
14
2
Model row dimensions
14
3
Calibration statistics
17
4
Natural water balance with current groundwater abstraction
18
5
Drawdown constraints
21
6
Optimal abstraction rates
28
7
Optimal numbers of model bores
28
8
Average pumping rates
29
9
Comparison of natural flows and required capture flows for each
layer
32
10
Comparison of natural flows and required capture flows for each
line
33
11
Water balance with optimal hydraulic containment
37
A1
Calibration target groundwater levels
98
A2
Vertical head differences
101
A3
Locations of bores on all containment lines with optimal
pumping rates
102
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1.0 INTRODUCTION
Orica Australia Pty Ltd is required by the Department of Environment and Conservation
(DEC, formerly NSW EPA) to implement pump-and-treat remediation in three areas on and
downgradient of its premises at Botany NSW. Hydraulic containment of the existing
contaminant plumes and their source areas is to be attained by means of groundwater
interception bores along strategically placed containment lines. This action is required under
a Notice of Clean Up Action (NCUA) issued by NSW EPA in September 2003 in response
to higher than expected concentrations of chlorinated hydrocarbons in the City of Botany
Bay’s Herford Street production bore and EPA’s concerns about the rate of movement of
contamination in groundwater. A Groundwater Cleanup Plan (GCP) devised by Orica in
October 2003 was authorised for implementation in February 2004.
At that time, DEC issued a Variation Notice which included provision by 16th March 2004
of “Orica’s most recent groundwater extraction rate estimate for full contaminant
containment in the primary containment area, including full details and supporting
information”. This report updates the extraction rates provided in March 2004 and June
2004 for the Primary Containment Area (PCA), and provides revised estimates of optimal
abstraction rates for the Secondary Containment Area (SCA) and for containment of
dissolved phase contamination from inferred DNAPL source areas (Merrick, 2004a, 2004b).
The Primary Containment Area is defined as Block 2 of Southlands (west of Springvale
Drain). The Secondary Containment Area is the area hydraulically downgradient of the PCA
through which contamination has passed or will flow from the PCA.
The National Centre for Groundwater Management (NCGM) at the University of
Technology, Sydney (UTS) has undertaken simulation and optimisation modelling in order
to determine optimal locations and abstraction rates for interception bores placed along a
number of proposed containment lines. Possible regional impacts on surface water bodies
and other production bores, in terms of drawdowns and saltwater intrusion, are controlled by
specifying water level constraints during the optimisation phase. Sites that might be subject
to subsidence risks also constrain the optimisation results.
The objectives of this study are:
To determine the optimal volumes of water that need to be extracted from candidate
hydraulic containment lines in order to capture the contaminant plumes;
To determine the optimal spacings of bores along the containment lines;
To make an assessment of regional impacts in terms of drawdown, subsidence and
saltwater intrusion.
The objectives are accomplished by:
Developing a new calibrated site-specific layered numerical model;
Designing the model in such a way that it can be enhanced readily in the future (for
example: for simulation of solute transport, the unsaturated zone, or the saltwater
interface);
Running simulation scenarios for various containment layouts;
Linking the simulation model with an optimisation model to determine optimal abstraction
rates and optimal bore layouts, so as to comply with tolerable regional impacts.
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2.0 MODELLING METHODOLOGY
Modelling has been conducted according to the Australian groundwater flow modelling
guidelines recommended by Middlemis et al. (2000). According to the guidelines, the
appropriate model complexity for this project is “high”. A high-complexity model aims for a
reliable aquifer simulator that can be used to predict aquifer response to a range of
hydrologic conditions, and can be used for optimisation and management studies.
2.1
PREVIOUS MODELLING
Figure 1 shows the extents of prior models in the Botany area, two by UTS and two by
URS. None of the existing models is appropriate for current purposes. The model extent for
the new model in this study is also shown in Figure 1.
The whole-of-basin model (Merrick, 1994) using Aquifem-1 software has the advantage of
natural boundary conditions and variable spatial scale (due to finite element design), and
has been used successfully on all of the major infrastructure projects in the Botany Basin
(Third Runway, Airport Link, Eastern Distributor, Port Botany Expansion). Its weaknesses
are that it simulates one layer only, has coarse grid size in the Orica study area, cannot be
upgraded for solute transport, and would require new software to couple it with an
optimisation model.
The UTS analytical model (Merrick, 2003) using HotSpots software allows dense bore
networks, simulates two layers and has an in-built optimisation module. However, it cannot
accommodate spatial variability or drains, does not handle the bay boundary properly, and
cannot be extended to solute transport. This model investigated a containment line of 10
bores spaced 30 metres apart around the south-western corner of Southlands Block 2 (PCA),
and concluded (by optimisation) that a net abstraction of 1.3 ML/day would be required to
capture the plume without deleterious regional impacts.
The URS Stage 2 model (Woodward-Clyde, 1996) using MODFLOW (McDonald and
Harbaugh, 1988) and MT3D software covers an appropriate model extent and simulates
three layers. Its main shortcoming is the cell size range from 100 metres to 200 metres,
which is too coarse for investigating pump-and-treat bore networks and for accurate solute
transport modelling.
The URS Stage 3 model using MODFLOW and MT3DMS software has more accurate
solute transport modelling due to the cell size range from 20 metres to 100 metres.
Discretisation of Southlands Block 2 is suitably fine, but elsewhere the model cells are
relatively coarse. The main problem with this model is its limited spatial extent, and its
reliance on artificial boundary conditions which might overly constrain the simulation
results.
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2
2.2
NEW SIMULATION MODEL
A new model has been developed using MODFLOW software within the Groundwater
Vistas graphic interface. This choice of interface will allow subsequent use (beyond the
scope of the present project) of a more advanced version of MODFLOW, called Surfact,
that has integrated solute transport for multiple species, unsaturated zone simulation, and
simulation of density effects.
The model extent, shown in Figure 1, is designed to include the entire Lachlan Lakes
system, the full extent of the proposed Port Botany expansion, and extension to the east
towards the ocean where boundary conditions have been problematic in earlier models.
The cell sizes of the new model vary from 10 metres to 100 metres. The level of
discretisation is indicated in Figure 2. There are 236 rows and 234 columns. The design of
finite difference models, such as MODFLOW, requires that a column of 10 metres width
(for example) must propagate across the entire north-south extent of the model; similarly for
a row, across the east-west model extent. This means that Figure 2 indicates the maximum
cell size in a region. For example, in the region marked “100m CELL SIZE”, some cells
will be 100m x 100m, but others will be 100m x 25 m and 100m x 10m.
The inner core of 10m x 10m cells covers the area of candidate abstraction/injection bores.
The middle ring of 25m cells covers the analytical model extent (Merrick, 2003), where
regional impacts are likely. The outer ring of 100m cells extends the model to boundary
conditions.
Boundary conditions have been guided by the whole-of-basin model. They consist of
constant groundwater heads along the Lachlan Lakes, along the Mill Stream diversion
channel, and along the existing Botany Bay shoreline (prior to Port Botany expansion).
Boundaries that do not coincide with water bodies are set at constant heads provided by
measured groundwater levels, or by prescribed flow. Much of the eastern edge is a
prescribed flow boundary that tracks along a sandstone outcrop, in order to represent
infiltration of surface water runoff from sandstone hills. Some gaps along the boundary
permit groundwater outflow to Maroubra and Long Bay.
The new model includes interaction with Floodvale Drain, on the western edge of
Southlands, and Springvale Drain, passing through Botany Industrial Park and Southlands
(Figure 1).
The model has been calibrated against steady-state groundwater contours and measured
vertical hydraulic gradients between the upper and lower aquifers.
The original version of the model had three layers representing the shallow (Layer 1), deep
(Layer 2) and bottom (Layer 3) aquifers. In this report, all results are based on a five-layer
version of the model, in which Layer 2 has been subdivided into three sub-layers so that
interception bores could target the appropriate depth extent of contamination in Layer 2. The
layers are called Layer 1 (shallow), Layers 2A, 2B and 2C (deep), and Layer 3 (bottom).
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2.3
OPTIMISATION MODEL
An optimisation model has been developed with OPTIMAQ software created by Merrick
(2000, 2001). This software links directly with MODFLOW and uses third party generic
optimisation software called GAMS. OPTIMAQ can use either linear programming or
nonlinear programming algorithms.
Any problem that can be decomposed into components consisting of limited resources,
constraints, and an objective, can be called an optimisation problem. Pump-and-treat
remediation lends itself readily to an optimisation approach. It is possible to optimise the
number of bores, their locations (from a candidate list), and their pumping rates. By varying
the optimisation objective, it is possible to determine either the most hydraulically efficient
or the most economic way of operating the interception network.
Optimal interception of contaminated groundwater can be achieved by minimising total
continuous abstraction from a large number of candidate bores, placed across the
contaminant plumes, subject to attainment of specified reversed hydraulic gradient at
locations adjacent to and downgradient of the containment lines
The objective function can be formulated as:
min Z =
∑Q
j
j
where:
Qj
is the steady-state pumping rate at bore j.
OPTIMAQ has been applied successfully to a number of water allocation projects, and to
optimal design of a saltwater interception scheme on the Murray River. Practical
optimisation can be achieved for models with multiple layers and multiple planning periods.
Pre-processing software generates automatically the input files required for the many
MODFLOW simulations required by the response matrix approach used by OPTIMAQ, and
post-processing software automatically assembles the response matrix for import by the
optimisation routine. Optimisation is achieved by guaranteeing compliance with water level,
hydraulic gradient, and pumping constraints.
Some limited economic optimisation modelling also has been done in this study, in which
capital costs have been minimised. The best approach was found to be minimisation of a
penalty cost, so that high-yielding bores would be favoured and low-yielding bores would
be excised automatically:
Penalty cost = W1 * Qj * (maxuse – Qj) + W2 * Qj * max(minuse – Qj, 0)
where:
Maxuse = 500 m3/day
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4
Minuse = 50 m3/day
W1 = 100
W2 = 1005 (highly sensitive)
2.4
HYDRAULIC CONTAINMENT
Hydraulic controls are often used as surrogates for achieving a concentration-based
objective. The devices available for hydraulic control are pumping bores (wells), drains and
recharge pits. A contaminant plume can be confined by ensuring that the hydraulic gradient
is directed inwards everywhere. Velocity of migration can be controlled by specifying a
constraint on the horizontal hydraulic gradient. A contaminant can be prevented from
moving vertically to an uncontaminated layer by controlling the vertical hydraulic gradient.
The pump-and-treat optimisation problem can be extended to assess whether re-injection is
feasible, and if so, its optimal volume and location.
A zero lower bound on pumping rates is a simple device that enables identification of
unimportant candidate bores in a remediation network. Bores allocated low impractical rates
of pumping can be removed from the network, prior to repeating the optimisation with
fewer candidate bore locations.
The principle of hydraulic containment is illustrated in Figure 3. An hydraulic barrier can be
created downgradient of a bore by pumping at such a rate that the gradient is flat or reversed
at the target location. For outer barrier P, and inner barrier Q, the condition for an hydraulic
barrier is:
hP
≥ hQ
where hP and hQ are the steady-state groundwater levels at positions P and Q (Figure 3).
In the preliminary analytical modelling by Merrick (October 2003), the following
containment lines were investigated:
Line A – around the south-western corner of Southlands Block 2;
Lines B and C – on Southlands Block 2 within the core of the Central Plume;
Line 1 - on Southlands Block 1, along Springvale Drain, then along part of
McPherson Street;
Lines 2 and 3 – along Foreshore Road, straddling the extension of Floodvale Drain;
Line 4 – on Orica premises, at an inferred source area;
Line 5 – along the western boundary of Botany Industrial Park, across the Central
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5
Plume;
Line 6 - along the western boundary of Botany Industrial Park, across the Northern
Plumes.
In the previous study reported in June 2004, Lines 1 and 3 (being proposed reactive iron
barrier sites for contaminant containment) were not examined for hydraulic containment,
and Lines B and C were replaced by candidate bores dispersed throughout the core of the
Central Plume as defined by the 1000 mg/L EDC contour (at August 2003). Most lines were
longer than those in the earlier design, and Line 6 was subdivided into Lines 6A, 6B and 6C
to enable discretisation of this long containment line to match the contaminant profile.
For Line A, the Core, and Line 2, barrier doublets were placed in Layer 1 and Layer 2 of the
3-layer model at spacings of about 20 metres along a line that is 20 metres downgradient of
the containment line. Each doublet consisted of two cells spaced 10 metres apart usually
(sometimes 14 metres for diagonal cell pairs). The aim was to force the outer cell of each
doublet to have the same head or a higher head than the inner cell.
For Lines 4 to 6, barrier doublets were placed in various combinations of Layers 1, 2A, 2B,
2C and/or Layer 3 of the 5-layer model at spacings of about 20 metres along a line that is
generally 14 metres downgradient of the containment line. Doublet cells were generally 14
metres apart (sometimes 10 metres).
The current proposed containment lines with candidate bore locations are shown in Figure 4,
in relation to the EDC concentration contours at June 2004. All barrier cell locations are
shown in Figure 5. The candidate bores and barrier cells are not applied in every layer.
At the present time:
•
Lines 1 and 3 have been revived as Orica proposes to use hydraulic containment rather
than reactive iron barriers to provide contaminant containment for the Southern Plumes
at Southlands and Foreshore Road. This change to the Groundwater Cleanup Plan has
been presented to DEC.
•
Line 4 has been dropped off as it is effectively made redundant by Line 5.
•
Line 5 has been shifted eastwards to Second Street as drilling was not possible along
First Street.
•
Fewer candidate bores are designated in the Core and elsewhere in Layer 2, based on
experience with optimisation runs.
•
Bores along Floodvale Drain have been shifted eastwards to avoid an easement for a
new road.
•
Line 7 (candidate bores along Floodvale Drain’s alignment) was introduced for some
optimisation experiments in an attempt to reduce the stagnant zone downgradient of the
Primary Containment Area, but is not used in the final design.
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6
Following the latest optimisation run, some bores proved again to be in positions where
drilling was not possible. In that case, bores have been shifted a little and their pumping
rates fine-tuned by simulation to ensure that capture is still effective.
Optimal pumping rates are sensitive to the size and the location of the gradient constraint.
As the size of the constraint increases above zero, pumping rate must increase along with an
expansion of the downgradient capture zone. Similarly, pumping must increase as the
location of a specified-gradient constraint is moved away from the pumping site. Ahlfeld
and Mulligan (2000) report a brief investigation into the sensitivities of constraint strength
and position at the toe of a distinct plume, and conclude that constraint strength is more
significant. They warn that zero-gradient constraints might not guarantee capture at points
midway between candidate bores.
In this study, in order to minimise total pumping requirements, gradient strength has been
kept as low as possible (generally 0.05%, that is a head difference of 0.005 m when barrier
cells are 10 m apart, or 0.007 m for diagonal cells). Similarly, the distance between the
candidate bore and the nearest gradient cell is kept low, generally one model cell separation.
In Layer 2, gradient constraints are imposed generally adjacent to the candidate bore and
midway between neighbouring bores, to reduce the chance of particles slipping through the
gaps. It has been necessary to impose a flat gradient rather than a reversed gradient along
Foreshore Road to minimise saltwater intrusion risks.
It is not practical to investigate constraint placement sensitivity with a large optimisation
problem, as we have here, as any change to a constraint position requires repetition of
response matrix creation, which could involve running MODFLOW again in the order of
300-400 times. The approach taken here has been to fix the barrier cell locations,
experiment with gradient strengths, and verify capture by simulation of groundwater heads
and particle tracking.
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7
3.0 GROUNDWATER CONDITIONS
The Botany Sands aquifer is classified as a “high risk resource” by the Department of
Infrastructure, Planning and Natural Resources (DIPNR) in terms of groundwater quality,
due to the presence of a large number of contaminated sites. A groundwater protection zone
has been declared in the projected path of the Orica contaminant plumes. In this zone, bore
licences will be issued only for cleanup and control activities. The remainder of the northern
zone of the Botany Basin has been embargoed, which means that existing users may
continue to pump groundwater, but no new licences will be issued.
3.1
HYDROGEOLOGY
Groundwater in the Botany Bay district occurs in unconsolidated sediments of Quaternary
age which overlie a bedrock of Hawkesbury Sandstone. These sediments comprise the
Botany Sands aquifer and are made up of river, beach and dune sands interbedded with clay
and peat lenses. This sequence can be separated into three zones:
an upper, predominantly sandy section with occasional peat and silt stringers
(Layer 1);
a middle section of sand with interbedded peat layers (Layer 2);
a basal section of interbedded clays, peats and sands above the bedrock (Layer
3).
Discontinuous peat beds and indurated sand-rock layers, termed “Waterloo Rock” which
may be up to a few metres thick, can occur in the upper section. An extensive area of saline
peat (Veterans Swamp) underlies Banksmeadow to the north of the Botany Foreshore and
west of the Botany Industrial Park.
3.2
GROUNDWATER LEVELS
In the past, many bores have been drilled close to the northern shoreline of Botany Bay for
the purpose of monitoring groundwater levels, and for abstracting groundwater for industrial
or irrigation use. The locations of all known bores are shown in Figure 6. Not many bores
have survived, and there is no regular monitoring program in place apart from the Orica bore
network, which has been measured in full approximately once every two years with more
frequent monitoring for specific purposes.
The bores with the longest period of record are those of DIPNR (formerly DLWC), dating
back to 1974 for a few. The most comprehensive sets of water level measurements are for
April 1988 and April 2000, when DLWC conducted a census of their network. Orica
(through URS Australia) obtained a comprehensive set of water levels from their network in
May 2000. Hence, the April-May 2000 period provides the best set of water level data that is
available. In April 2002, Sydney Ports Corporation commenced monthly monitoring of
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water levels at 13 additional sites close to the foreshore.
In order to gain an appreciation of current groundwater conditions, given the spasmodic
sampling of water levels, the best that can be done is to combine water level measurements
over a 2-year period from April 2000 to April 2002. This gives the composite groundwater
level pattern shown in Figure 7, representative of the deep aquifer (Layer 2). (Lake and bay
levels have been used to constrain the contouring. Some older values near the airport define
the edges.) Groundwater flows in a general south-westerly direction towards Botany Bay.
Across Southlands, the water levels vary from about 2.2 to 4.8 mAHD. Table A1 in the
Appendix lists the coordinates and attributed layers of all bores that have been used in the
preparation of Figure 7; these water levels serve as calibration targets.
Although the 2000-2002 period has been drier than normal, groundwater levels in the
vicinity of the Botany Industrial Park and Southlands are higher than they have been in the
past. The lowest recorded levels were experienced in 1969, as shown in Figure 8. Water
levels dropped to several metres below sea level over the northern half of the Botany
Industrial Park, due to excessive groundwater abstraction to the north-west. Across
Southlands, the water levels varied from –2 to +1 mAHD. Water levels have been rising
since then, as the industrial demand for groundwater has reduced. The situation in April
1988, during a very wet period, is shown in Figure 9. Across Southlands, the water levels
varied from about 1.1 to 3.0 mAHD. In general, water levels on Southlands are 1-2 metres
higher now than they were in the late 1980s, despite lower rainfall.
Natural dynamic variations in groundwater levels over a decade are in the order of 1.5
metres east of Penrhyn Estuary and south of the Orica site, and 3 metres on the eastern
boundary of the Orica site. Fluctuations of 1 metre are common within a year due to rainfall
events. The drawdowns anticipated with interception pumping are of the same order, or less,
than the natural long-term variations in water level.
3.3
VERTICAL HEAD DIFFERENCE
The groundwater levels in the shallow and deep parts of the Botany Sands aquifer are not
identical, but in general they are similar to each other. The best representation of Layer 1
water levels has been prepared by URS Australia as Figure 4.2 in the Groundwater Cleanup
Plan (www.oricabotanygroundwater.com), for the May 2000 survey. This shows that there
is strong interaction between the water table and the two drains, Floodvale and Springvale,
that cross Southlands from north to south. Groundwater discharges to the drains along most
of the length of each drain. We can infer that groundwater discharge would have been much
lower in the past, when the water table was lower, and in some years (e.g. 1969) there would
have been no discharge at all, and the drains would have leaked water to the aquifer.
The magnitude of the vertical head difference has been investigated at sites where bores are
screened at multiple depths. There are 30 sites in the northern Botany Basin with
information on shallow and deep groundwater heads (see Table A2 in the Appendix). If the
shallow head exceeds the deep head, there is a potential for downwards flow. Conversely,
upwards flow is indicated if the deep head exceeds the shallow head. Of the 30 sites, 12
suggest upwards flow, 14 suggest downwards flow, and 4 sites have no head difference. At
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the sites where downwards flow is likely, the median head difference is 0.18 m and the
maximum is 1.0 m. At the sites where upwards flow is likely, the median head difference is
0.22 m and the maximum is 0.8 m.
The propensity for upwards flow is confined to a zone trending northeast from Penrhyn
Estuary through Southlands to a distance of 1.4 km from the shoreline. This is consistent
with strong groundwater discharge from Layer 1 to Springvale Drain and Floodvale Drain.
Elsewhere, downwards flow is indicated, even very close to the shoreline.
Due to insufficient data on Layer 3, water level contours cannot be drawn. We can infer that
they will be similar to the Layer 2 contours except where abstraction from Layer 2 occurs.
3.4
HYDRAULIC STRESSES
The most important dynamic stresses on the Botany Sands aquifer are rainfall and
groundwater abstraction. The main recharge area is in Centennial Park at the northern end of
the catchment. Substantial recharge also occurs in green space areas (parks and golf
courses). Groundwater levels are controlled by Alexandra Canal, the Lachlan Lakes and
Swamps, Cooks River and Botany Bay. In the vicinity of Southlands, the water table is
controlled by Springvale and Floodvale Drains.
Long term median rainfall is 1073 mm per annum at Sydney Airport (Mascot). There is a
strong correlation between rainfall and groundwater fluctuations. Merrick (1994), based on
calibration of an earlier groundwater model, estimated that rainfall infiltration varies from 6
percent on estuarine sediments to 37 percent on sand.
The Botany Sands aquifer has been an important source of water for more than a century.
Estimates of groundwater abstraction have varied from about 20 ML/day to about 55
ML/day in the last 50 years. In 1992, usage was reported as 30 ML/day. Since then, there
has been no official check on usage. In some instances, installed meters have been
vandalised and rendered inoperative. It is likely that usage has declined significantly over
the last decade, as industrial users close to the bay have shut down pumping operations (due
to pollution), have moved their businesses elsewhere or closed down their operations. The
likely distribution of production during the 2000-2002 period is presented in Figure 10, with
an estimate of the relative abstraction at each bore. The distribution is based on licensed
allocations, historical usage up to 1991, and local knowledge of active users (D. McKibbin,
DIPNR, pers. comm.). Total usage of groundwater during 2000-2002 in the northern part of
the Botany Basin is estimated to be about 7,000 ML/year (about 20 ML/day). It is
understood that the Solvay Interox Borefield closed down early in 2004 (D. McKibbin,
DIPNR, pers. comm.).
There are about 90 bores with current licences, but only about 60 percent would be in use.
About 70 percent of bores are used for irrigating parks and golf courses; the remainder are
used by industry. However, the industrial users account for about 60 percent of usage. Most
of the groundwater abstraction during the 2000-2002 period would have been due to three
industrial users:
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AMCOR
(about 34% of total usage)
Solvay Interox
(about 12% of total usage)
Orica
(about 11% of total usage)
The largest user at the time was AMCOR Packaging (Australia). AMCOR withdraws about
6 ML/day from a borefield at Snape Park (Figure 10), 3 km north of the Botany Mill site.
The water is discharged into a stormwater canal for transit to a dam adjacent to the Mill site.
Solvay Interox was withdrawing 2 to 2.9 ML/day on average from their borefield of five
bores close to the Lachlan Swamps (Figure 10). Water was piped to the company’s premises
in McPherson Street, due west of Southlands, for use as a coolant after which it was
transmitted to the dam at the AMCOR site. This borefield is included in model calibration
but is excluded for optimisation scenarios.
The Orica borefield (Figure 10) is comprised of four active bores in a borefield of five bores
that produce about 2 ML/day in winter, and 3 ML/day in summer (G. Fox and J. Stening,
pers. comm., July 2004).
3.5
CONTAMINANT PLUMES
Several chlorinated hydrocarbon plumes occur in groundwater flowing from the Botany
Industrial Park. Maps of the positions and concentrations of the plumes have been prepared
by URS Australia and are presented in the Groundwater Cleanup Plan
(www.oricabotanygroundwater.com), for August 2003 sampling. The outline of the EDC
plumes at June 2004 is shown in Figure 4.
For the southern-most plumes (the Southern Plumes), 1,2-dichloroethane (ethylene
dichloride or EDC) and trichloroethene (TCE) have reached Penrhyn Estuary in a zone
between Floodvale and Springvale Drains at the eastern end of the estuary. The plumes also
contain PCE (tetrachloroethene), CTC (carbon tetrachloride - present at Foreshore Road but
not at the estuary), 1,1,2,2-TeCA (tetrachloroethane), 1,1,2-TCA (trichloroethane) and a host
of degradation products including cis-1,2-DCE (dichloroethene), trans-1,2-DCE and VC
(vinyl chloride) (J. Duran, pers. comm., 2004). The representative concentration of EDC and
TCE is about 10 mg/L at the shoreline.
The Northern Plumes with core concentrations in the range 100 – 200 mg/L of EDC are
known to extend in a southwest direction from the Botany Industrial Park. The 10 mg/L
front is about 300 m wide but was well north of Foreshore Road at June 2004.
Another plume of EDC known as the Central Plume is moving towards the bay and more
specifically will probably enter Penrhyn Estuary. The plume extends upgradient across
Southlands to the site of former EDC storage tanks on Orica land (Figure 4). The core of
the plume has a concentration of greater than 5000 mg/L. At the southwest corner of
Southlands Block 2, its core is at a depth of about 15 m. Surrounding the core there are
concentration zones (100 – 1000 mg/L) that extend over about 13.5 m in the vertical
direction over the length of the plume.
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If the Central Plume should reach the shoreline, it will intersect the saltwater wedge and
move upwards to the seawater column of Penrhyn Estuary. This expected behaviour has
been confirmed for the Southern Plumes in a baseline study by URS (2004) on surface water
and groundwater discharge to Penrhyn Estuary. A bundle piezometer transect was installed
in the intertidal mudflats within Penrhyn Estuary to a depth of 2 metres below low tide. The
extensive conductivity and chemical evidence in the intertidal zone show trends that can be
explained only if there is active groundwater discharge in the intertidal zone. There is clear
evidence that the chemistry of the water on the downgradient side of the zone of diffusion is
due to seawater with little or no contribution from fresher groundwater. It can be concluded
with confidence that most groundwater discharges to Penrhyn Estuary and Botany Bay in
the zone between low water mark and high water mark.
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4.0 SIMULATION MODEL
4.1
CONCEPTUAL MODEL
Figure 11 shows the conceptual model for groundwater flow through the northern Botany
Basin. Rainfall infiltration is an important driver of groundwater dynamics, particularly in
the northern part of the aquifer near Centennial Park. The ponds in the Park are windows on
the water table. Groundwater discharges naturally at the ground surface at the upper end of
the Lachlan Lakes system. As the lakes are dammed, water discharges from the aquifer to
the upper reach of each dam, and water leaks from the lower reach of each dam to the
aquifer. The water table interacts significantly with the two stormwater drains (Floodvale
and Springvale), usually by discharging groundwater when groundwater levels are high. In
the past, when water levels have been much lower, water would have leaked from the drains
to the aquifer. Where the water table is close to the surface, and there is vegetative ground
cover, evapotranspiration can be expected as a mechanism for groundwater losses to the
atmosphere.
The destination for most groundwater is discharge to Alexandra Canal (formerly Shea’s
Creek), at the western edge of the Basin, and discharge to Botany Bay. Groundwater flow
under natural conditions is nearly horizontal until it arrives at a zone of diffusion roughly
between the low and high water marks. Due to the rapid change in salinity and density of
groundwater, groundwater will be driven upwards by the saltwater interface for discharge to
the Bay close to the shoreline.
There is active groundwater abstraction from bores for industrial and recreation purposes,
with minor domestic use through spearpoints. Some of this pumped water is returned to the
aquifer by deep drainage after irrigation of golf courses and parkland.
Along the elevated sandstone edges of the Basin, we anticipate surface water runoff that
becomes enhanced infiltration coincident with rainfall events.
4.2
MODEL GEOMETRY
The model extent is limited to an area that includes the entire Lachlan Lakes system, so that
the boundary conditions are well defined on the northern and western sides of the model.
The model area is 5400 m x 5000 m, defined by eastings 332500 – 337900 (MGA) and
northings 6239500 – 6244500 (MGA). The cell sizes vary from 10 metres to 100 metres, as
indicated in Figure 2 and detailed in Tables 1 and 2.
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Table 1. Model column dimensions
EASTING
(min)
332500
337000
334400
335900
336700
EASTING
(max)
337000
334400
335900
336700
337900
DISTANCE
(m)
1200
700
1500
800
1200
COLUMN
WIDTH (m)
NUMBER of
COLUMNS
100
25
10
25
100
12
28
150
32
12
DISTANCE
(m)
800
300
1600
1100
1200
ROW WIDTH
(m)
100
25
10
25
100
NUMBER of
ROWS
Table 2. Model row dimensions
NORTHING
(min)
6239500
6240300
6240600
6242200
6243300
NORTHING
(max)
6240300
6240600
6242200
6243300
6244500
8
12
160
44
12
The grid design is illustrated in the Appendix for each layer (Figures A1 to A3).
A range of sources has been used to define the surface topography of the area. Resolution is
limited by the 4 m contour interval on 1:10000 Orthophoto Maps (Maroubra U1837 and
Kogarah U0937). The contour data are supplemented by spot heights on the Orthophoto
maps, surveyed bore and ground levels by URS, and gravity station elevations (Tho, 2002).
All coordinates have been converted to the Map Grid of Australia (MGA) standard. The
surface topography contours are shown in Figure 12 at 2 m contour interval1.
Structure contours at the interface between Layer 1 and Layer 2 have been provided by URS
Australia as digitised contours from the Stage 2 ICI study by Woodward-Clyde (1996), at 2
m contour interval. The contours range from –6 mAHD to 20 mAHD, but there are no data
in Botany Bay and to the east of easting 337600.
URS Australia also provided digitised contours at 2 m contour interval for the Layer 2 –
Layer 3 interface, from the Stage 2 ICI study by Woodward-Clyde (1996). As detail on
Southlands was limited, the contour data have been supplemented with spot values at 39
CPT sites. The original contours range from –30 mAHD to -10 mAHD, but there are no data
to the east of easting 336500.
1
Default kriging interpolation with Surfer on 100 m grid.
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Figures 13 and 14 show the isopach (thickness) contours for Layer 1 and Layer 2. Layer 1
has median thickness 8.5 m (maximum 27 m). Layer 2 has median thickness 16.1 m
(maximum 32 m). Layer 3 has median thickness 6.6 m (maximum 34 m).
The data provided by URS Australia for bedrock topography (bottom of Layer 3) has 5 m
resolution from –60 mAHD to 15 mAHD and extends only as far as easting 337000, with
little control above northing 6243500. Bedrock depths interpreted from the gravity survey of
Tho (2002) have been used to fill in the data gap to the east. The re-constructed contours are
shown in Figure 15, after conversion to MGA coordinates. Due to limited resolution in the
Pagewood area (Figure 15), a known palaeochannel through this area is not properly
captured by interpolation. This channel passes through Snape Park where AMCOR has a
number of production bores.
The elevation arrays for each interface were imported by Groundwater Vistas, and cell
values were adjusted locally for negative thicknesses and smoothness. In places to the east
and northeast of Botany Industrial Park, Layer 1 had to be thickened at the expense of Layer
2 in order to reduce the number of dry cells during simulation, to improve model
convergence and stability.
4.3
MODEL STRESSES
The boundary conditions are depicted in the Appendix for each layer (Figures A1 to A3). In
each layer, the boundary between active and inactive cells on the eastern side is guided by
the bedrock elevation of Figure 15. The area to the north-west of the Lachlan Lakes is also
declared inactive in the model. Constant groundwater heads are assigned (in each layer) to
the cells coincident with the Lachlan Lakes and Botany Bay. Another line of constant heads
is assigned to the cells on the eastern boundary that are adjacent to the Maroubra Bay inlet.
Prescribed flows are assigned to cells adjacent to sandstone hills along the eastern outcrops,
to simulate enhanced infiltration due to surface runoff. Their locations and strengths have
been varied during calibration. Generally, runoff cells are limited to Layer 1, but calibration
suggests some enhanced infiltration in Layer 2A for the north-eastern part of the model
boundary.
Simulation has been limited to steady-state with the current model. However, earlier models
have achieved transient calibration (Merrick, 1994), and stresses and model
parameterisation from those models have guided the corresponding values in the current
model.
Rainfall recharge has been estimated as a percentage of the annual rainfall of 1100 mm
recorded at Sydney Airport. In earlier modelling, Merrick (1994) estimated 37% rain
recharge on parkland, 19% on urban or industrial land (on sand), and 6% on estuarine
sediments and on parkland adjacent to lakes. The Woodward-Clyde (1996) model used two
categories: parkland (35% recharge), other land use (15% recharge). In the current model,
three land use categories are maintained: parkland on sand (37% recharge), urban/industrial
on sand (22% recharge), urban/industrial on estuarine sediments and parks adjacent to lakes
(10% recharge). The land use distribution is illustrated in the Appendix (Figure A4).
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Evapotranspiration is specified uniformly with a maximum evapotranspiration rate of
6 x 10-4 m/d (20% of rainfall) and extinction depth 3 metres.
Floodvale Drain and Springvale Drain are simulated with MODFLOW’s RIV (river)
package. A conductance value of 160 m2/d is used for all drain cells. The water level (stage)
in Springvale Drain is varied from 2.1 mAHD to 7.0 mAHD in six linear segments. The
stage in Floodvale Drain is varied from 1.5 mAHD to 2.9 mAHD in two linear segments at
Southlands, with a northern extension in one segment from 3.0 mAHD to 3.1 mAHD. The
depth of water in the drain is taken to be 1 m on average.
All known production bores that are likely to be active are assigned to Layer 2B of the
model, in the absence of information on their screen depths. The exception is the Orica
borefield, where screen depths are known. Pumping from these bores is assigned evenly to
Layers 2B and 2C for four of these bores, and to Layer 2B for the fifth bore. Production
bore locations are shown in Figure 10 and in the Appendix (Figure A2). The volume of
water pumped from each bore is uncertain, as few bores are metered, and meter readings are
not reported to DIPNR (see Section 3.4).
4.4
CALIBRATION
Model calibration has been limited to steady-state, given that the main purpose of the model
is to use it as a basis for deriving long-term pump-and-treat abstraction rates for achieving
hydraulic containment. The calibration target is the 2000-2002 groundwater level contours
(Figure 7; Table A1). Subsidiary targets are the shape of water table contours in the vicinity
of the two drains (see Section 3.2), and the recorded vertical head differences (see Section
3.3; Table A2).
The simulated groundwater level contours are shown in Figures 16 and 17. The water table
contours (Figure 16) agree very well with those of URS in the Groundwater Cleanup Plan
(Figure 4.2), and show similar inflections across the two drains. The Layer 2A water levels
(Figure 17) agree well with interpolated measured values (see Figure 7), particularly across
the Botany Industrial Park and Southlands. The apparent disagreement to the east of the
Botany Industrial Park is more likely due to false extrapolation of sparse measurements.
There are nuances in the observed contours that are not well matched. It might be possible
to match better by allowing fine-scale variations in hydraulic conductivity in these areas.
However, there is considerable uncertainty in the observed values, as they are combined
across a long period of time. It could be that the nuances are “noise”, given that the aquifer
system is known to have significant dynamic fluctuations. The simulated hydraulic gradients
at the Orica site, where containment is required, are generally steeper than observed, but
generally within 15 percent of observed gradients. An overestimation of gradient will have
the effect of overestimating pumping requirements, so that there may be some conservatism
in the optimised total extraction rate.
Quantitative calibration statistics are presented in Table 3.
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Table 3. Calibration Statistics
STATISTIC
VALUE
UNIT
150
-
Range in head values
16.84
m
Residual mean
-0.18
m
Residual standard deviation
0.55
m
Absolute residual mean
0.42
m
Minimum residual
-1.69
m
Maximum residual
1.79
m
Sum of squares
49.7
m2
Standard deviation / Range
3.2
%
Number of target values
The last statistic in Table 3 is independent of sample size and independent of measurement
range; it gives the best intuitive measure of the calibration performance of the model. The
Groundwater Vistas manual suggests that this statistic should be less than 10-15 % for a
good calibration.
Comparison of simulated and observed heads at the 150 target sites is shown in the
scattergram of Figure 18.
The vertical head difference between Layer 1 and Layer 2A (Figure 19) is in the range 0.2 to
0.6 m near Springvale Drain, as observed, with Layer 2A heads being higher. Elsewhere,
Layer 1 heads are higher by 0 to 0.2 m, except at production bores and over runoff cells.
This is consistent with the magnitude of reported differences.
4.5
AQUIFER PROPERTIES
Merrick (1994) reports hydraulic conductivity values ranging from 12 to 29 m/d for
laboratory measurements, 20 to 85 m/d for pumping test analyses, and 20 to 28 m/d for
model calibration. Woodward-Clyde (1996) report mean values of 18 m/d (Layer 1), 23 m/d
(Layer 2), and 1.2 m/d (Layer 3) from recovery tests on 44 bores, but their calibrated model
estimates are 30 m/d (Layer 1), 35 m/d (Layer 2), and 1 m/d (Layer 3).
In this study, the calibrated values are 20 m/d (Layer 1), 30 m/d (Layer 2), and 1 m/d (Layer
3). Some spatial variation is inferred for Layer 2, as shown in the Appendix (Figure A5).
Slightly higher hydraulic conductivity (32 m/d) is assumed close to the bay. A zone of
higher hydraulic conductivity (40 m/d) is placed along the palaeochannel passing through
Snape Park, to counteract the underestimation in bedrock depths that has resulted from
interpolation of contoured bedrock elevations (see Section 4.2). Layer 2 thickness is about
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10 metres less in the model than is observed at the Snape Park bores.
Leakage coefficient is set at 0.05 d-1 at the interface between Layer 1 and Layer 2A, and
between Layer 2C and Layer 3. High leakance (5 d-1) is maintained between the sub-layers
of Layer 2, to simulate strong hydraulic connection within Layer 2 as a whole.
4.6
WATER BALANCE
Steady-state simulation results in the water balance listed in Table 4. The most important
sources of recharge are: runoff from sandstone hills (51% of total recharge), rainfall (27%),
and leakage from lakes (22%). For groundwater pumping estimated at 10.5 ML/d (29% of
total discharge), the most important destination for groundwater discharge is Botany Bay
(52%). Water is also lost to the drains (12%) and to evapotranspiration (7%).
Table 4. Natural water balance with current groundwater abstraction
COMPONENT
Rain Infiltration
Runoff Infiltration
Lachlan Lakes
Drains
Botany Bay
Production Bores
Evapotranspiration
TOTAL
RECHARGE
[ML/day]
9.7
18.94
7.68
0.12
0
0
0
36.31
DISCHARGE
[ML/day]
0
0
0
4.03
19.50
10.45
2.54
36.42
Groundwater discharge to the two drains is estimated at 4.3 ML/d. This is higher than was
measured by Woodward-Clyde (1996) when weirs were placed at the entry and exit points
of Springvale Drain and Southlands. Estimates were said to be difficult, and ranged from 40
to 140 m3/d. Given that this reach is one-sixth of the total length of both drains in the model,
we can extrapolate (pro rata) to get an estimate of about 0.8 ML/day maximum. However,
discharge to the drains will be highly dynamic and very sensitive to ambient groundwater
levels. For example, with projected pumping of 2.5 ML/d from Southlands Block 2, the
simulated groundwater discharge to the drains reduces to 2.8 ML/d. The Woodward-Clyde
(1996) model obtained drain discharge of 0.2 ML/d with groundwater abstraction at 22.4
ML/d, at a time when groundwater levels were very low (1988; see Figure 9).
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4.7
SENSITIVITY ANALYSIS
A systematic sensitivity analysis has been conducted on the following model parameters:
Hydraulic conductivity - Layer 1 (base 20 m/d)
Hydraulic conductivity - Layer 2 (2A, 2B & 2C) (base 30 m/d)
Leakance - Layer 1 / Layer 2A and Layer 2C / Layer 3 (base 0.05 d-1)
Rainfall recharge - urban/industrial on estuarine sediments and parks adjacent to
lakes (base 10%)
Rainfall recharge - urban/industrial on sand (base 22%)
Rainfall recharge - parkland on sand (base 37%)
Drain conductance – Springvale Drain north of Southlands (base 160 m2/d)
Drain conductance – Floodvale Drain north of Southlands (base 160 m2/d).
For each case, three performance measures have been examined:
Sum of squared residuals (m2)
Absolute residual mean (m)
Average head change (m).
The full results are presented in the Appendix as Figures A6 to A13. The findings from this
analysis are:
Calibration would benefit marginally (~2% in residuals) by increasing Layer 1
hydraulic conductivity from 20 m/d towards 30 m/d, the value adopted for Layer 2
The adopted Layer 2 hydraulic conductivity (30 m/d) seems optimal; it could be
increased to 40 m/d without any impact on the performance of the model, but cannot
be decreased below 25 m/d
Calibration would benefit (~7% in residuals) by increasing inter-layer leakance by an
order of magnitude (from 0.05 to 0.5 d-1); this suggests that pumping requirements
would be overestimated (with the adopted leakance), as a bore in a particular layer
would receive less drawdown assistance from pumping in underlying or overlying
layers, and would have to pump harder to achieve gradient reversal in the screened
layer
There would be a mild benefit (~1% in residuals) in reducing low rainfall recharge
from 10% towards 6%
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There would be a marginal benefit (~2% in residuals) in reducing medium rainfall
recharge from 22% towards 13%
There is very little sensitivity to the value chosen for high rainfall recharge across a
wide range, from 22% to 44%
Calibration would benefit marginally (~2% in residuals) by increasing the
conductance of the northern Springvale Drain by a factor of 3 (to about 500 m2/d);
however, it cannot be reduced much below its adopted value (160 m2/d) before
calibration performance is degraded
The model shows no sensitivity to values for the Floodvale Drain conductance
ranging from 48 to 480 m2/d.
The sensitivity to assumed average drain water levels is examined in Section 5.7.
4.8
LIMITATIONS
The underestimation of initial transmissivity in the Snape Park palaeochannel led to severe
problems with dewatered cells in Layer 1 and Layer 2A, in response to heavy abstraction
from the Snape Park bores. With increased transmissivity, the extent of dry cells has
reduced but the problem has not disappeared completely. It is likely, as reported by
Woodward-Clyde (1996; Figure 8.4), that Layer 1 is often naturally dry, particularly in the
eastern half of the Botany Industrial Park and to the east and north-east of the Botany
Industrial Park.
Surfact could have been used to avoid this simulation problem. However, the optimisation
software is not yet linked to Surfact, but only to standard Modflow 88. To get a stable
steady-state solution suitable as a baseline for optimisation, it was necessary to recycle the
steady-state solution heads as the initial heads for repeated steady-state runs until the initial
and final heads were identical.
It would be possible to get closer calibration between simulated and observed heads by
using automated calibration software (e.g. PEST) to infer a detailed hydraulic conductivity
distribution. Given the composite nature of the calibration target water levels, stretching
from 2000 to 2002, it is doubtful whether the resulting distribution would be realistic, as the
process might be fitting to noise due to measurements taken at different times.
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5.0 OPTIMISATION SCENARIOS
5.1
CONSTRAINTS
The OPTIMAQ software used in this study enables the determination of optimal abstraction
rates subject to compliance with constraints on water levels and individual bore pumping
rates. Critical water levels have been allocated to each drawdown monitoring site and each
subsidence monitoring site, as listed in Table 5, to guide the optimisation. These constraints
are in addition to the gradient constraints imposed at the hydraulic barriers. The locations of
critical sites are shown in Figure 20.
The tolerable drawdowns in Table 5 proved to be superfluous in nearly all optimisation
runs. Only the gradient constraints at the hydraulic barriers were found to be binding.
One of the potential impacts from substantial groundwater abstraction is subsidence. The
susceptibility of an aquifer system to compaction is determined by the presence and
thickness of fine-grained sediments such as clays and peats that are distributed throughout
the Botany Sands aquifer. The reduction of pressure in the lower aquifer will have more of
an effect than pumping from the water table.
Table 5. Drawdown constraints
MONITORING SITE
LAYER
TOLERABLE
DRAWDOWN
(m)
BAY1, BAY2, BAY3,
BAY4,
BAY5, POND
DYES, SOLVAY, GOLF, SNAPE,
HEFFRON
DRAIN1, DRAIN2, DRAIN3
1
0.2
2
1
1
2
0.5
13
ORICA3
2
2
2
2
2
2
2
2
2
2
12
1
0.9
2.4
3.2
3
2.4
5.5
7
10
CATEGORY
Surface Water
Industrial Bores
Springvale Drain*
Orica Production Bores ORICA1, ORICA2, HENSLEY
(Available Drawdown)
Subsidence
S1
S2
S3
S4
S5
S6, S7
S8
S9
S10, S11
* Many constraints were applied initially along Floodvale Drain, but were removed from later optimisation runs because
they were not controlling the optimal solution
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Compaction will have occurred in the Botany area in the past, given the long history of
significant groundwater use. The lowest recorded water levels occurred around 1969 (Figure
8). Comparison with recent higher water levels (2000-2002; Figure 7) shows that water
levels have been from 5 to 13 metres lower over the Botany Industrial Park, and 2 to 6
metres lower over Southlands. In the industrial area between Southlands and Botany Road /
Foreshore Road, levels have been at least 1 metre lower in the past. The subsidence
constraints in Table 5 have been derived from the difference between Figures 7 and 8.
5.2
CHRONOLOGY
A large number of optimisation scenarios has been run for various containment lines,
various lengths and depths of containment lines, and different degrees of hydraulic gradient
reversal.
The earliest optimisation work (Merrick, 2003) was done with a simple 3-layer analytical
model. This model showed that optimal groundwater abstraction of 1.3 ML/day would be
required from containment Line A consisting of 10 bores spaced 30 metres apart around the
south-western corner of Southlands Block 2 (PCA). Simulation modelling was done also for
fixed pumping rates along Lines B and C in the core of the central plume, and for fixed
pumping from all of Lines 1 to 6. At that time, total abstraction was estimated at 11 ML/day
from 72 bores, but there was no attempt to optimise any line other than Line A. The
possibility of re-injection of treated water along Denison Street was simulated also, using 22
bores spaced 50 metres apart.
Phase 1
The first optimisation with the 3-layer numerical model was reported by Merrick (2004a).
Preliminary results were reported for optimal abstraction from Line A around the southwestern corner of Southlands Block 2 (PCA), at a time when dewatering problems were
being experienced with modelling of the shallow aquifer. The optimisation showed that a
minimum network abstraction rate of 0.6 ML/day is required to give a flat gradient at the
hydraulic barrier. Higher rates of pumping are required to force a reversed gradient. For
example, a 0.1 percent gradient can be achieved by pumping 0.8 ML/day, and 0.2 percent
gradient with 1.1 ML/day. About 13 bores would be required in the network, roughly 20
metres apart.
Phase 2
After Layer 1 was activated in the model, optimisation was repeated for Line A by
minimising total pumping to achieve a flat hydraulic gradient in Layer 2 at the barrier
outside Floodvale Drain and along McPherson Street as far as Springvale Drain. Individual
pumping rates were constrained between 50 and 500 m3/day. The required abstraction was
found to be 2.1 ML/day from 11 bores in Layer 2.
The first optimisation of pumping from the Core of the central plume sought to maximise
pumping from 133 candidate bore sites subject to non-infringement of drawdown
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constraints imposed along the drains, at water bodies, at subsidence monitoring sites, and at
industrial production bores. This resulted in a huge required abstraction of 5.7 ML/day from
16 bores (5 in the core, 11 on Line A), when 0.5 m drawdown was allowed along the drains.
The first optimisation of simultaneous pumping from Lines 2, 4, 5 and 6 resulted in required
abstraction from Layer 2 of 9.1 ML/day from 47 bores, to achieve a flat barrier gradient. At
this time, there was a 120 m gap between Lines 5 and 6, and Line 2 was 280 m long.
(Subsequently, Lines 2 and 6 were extended.)
Phase 3
The objective for Core pumping was changed from maximised pumping to minimised
pumping, subject to pumping at least 1.1 ML/day from the core. This is the estimate of the
abstraction rate required to pump out two pore volumes in one year, based on the following
parameters:
Land area of core projection (1000 mg/L):
47,500 m2
Thickness of plume (1000 mg/L):
12 m (maximum)
Porosity:
0.35
One pore volume = (0.35) (47500) (12) = 200 ML
Rate for two pore volumes in one year = (2) (200) / 365 = 1.1 ML/day
The optimisation was further constrained by insisting that a third come from each of the
northern, central and southern portions of the plume, with the northern and central portion
bores forced to be on the plume axis. This resulted in a required abstraction of 2.24 ML/day
from 15 bores (6 in the core, 9 on Line A), with 0.26 m maximum drawdown at Floodvale
Drain, and 0.19 m maximum drawdown at Springvale Drain.
When Line 2 was activated, the optimal pumping from Line A plus the Core was found to
increase by 0.05 ML/day (to 2.29 ML/day) because pumping from Line 2 makes it more
difficult to reverse the hydraulic gradient along McPherson Street (Line A). The Line 2
requirement would be 1.0 ML/day from 10 bores in Layer 2, to achieve a flat barrier
gradient in Layer 2. The maximum drawdowns at the drains would increase to 0.28 m
(Floodvale) and 0.20 m (Springvale).
Phase 4
Optimisation scenarios were run for Line A plus the Core, for flat or reversed hydraulic
gradient at the barrier in Layer 2 only. For 0.05% reversed gradient, the required abstraction
would increase from 2.24 ML/day to 2.52 ML/day (an increase of 12.5%), with an increase
of 3-4 cm in maximum drawdown along the drains. For 0.1% reversed gradient, the required
abstraction would increase to 2.80 ML/day (an increase of 25%), with an increase of 6-8 cm
in maximum drawdown along the drains.
The first economic optimisation was performed on Line A plus the Core, assuming a flat
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barrier gradient. The objective was to minimise a penalty cost (see Section 2.3), which
essentially minimised capital costs by reducing the number of bores at the expense of higher
pumping rate and higher operational costs. This scenario reduced the number of bores from
15 to 8, saving about $500,000 in capital costs for the PCA only. However, the required
abstraction would increase from 2.24 ML/day to 3.0 ML/day (an increase of 34%). No
further economic runs were done, as it was considered that the operational costs would
exceed the capital cost savings.
Phase 5
Optimisation scenarios were repeated for Line A plus the Core, for flat or reversed hydraulic
gradient at the barrier in both Layer 1 and Layer 2. Pumping was allowed from either layer
to achieve hydraulic containment. For a flat gradient barrier, the required abstraction would
be 2.47 ML/day (an increase of 10% over Layer 2 protection only). This should be taken
from 5 bores in the Core (Layer 2), 9 bores in Layer 1 (Line A), and 8 bores in Layer 2
(Line A). The maximum drawdown at each drain would be 0.35 m, with an average of 0.20
m along Floodvale Drain and 0.16 m along Springvale Drain. For reversed gradient in each
layer, the required abstractions would be 2.79 ML/day (0.05% gradient) and 3.12 ML/day
(0.1% gradient).
With Line 2 extended 200 m farther west, to ensure capture of the easternmost plume of the
northern plumes, its activation causes the Line A plus Core pumping to increase from 2.47
ML/day to 2.53 ML/day (an increase of 2%) for flat gradient control. The required pumping
from the extended Line 2 would be 1.68 ML/day from 31 bores to achieve a flat gradient
barrier. This should be taken from 11 bores in Layer 2, and from a system of 20 spearpoints
spaced 20 m apart. Similarly, the Layer 1 abstraction from Line A could be achieved with
one bore and a line of 8 spearpoints spaced 20 m apart.
Phase 6
The simulation model was converted from three layers to five layers at this stage, to permit
targeted capture of plumes at different depths in the inferred DNAPL source areas (Lines 4,
5, 6). Layer 2 was divided equally into three sub-layers: Layers 2A, 2B, and 2C. Line 6 was
also divided into three segments (6A, 6B, and 6C), with Line 6C joining Line 5.
Candidate bore locations and corresponding hydraulic barriers were placed initially as
follows:
Line 4:
Layers 1, 2A, 2B
Line 5:
Layers 1, 2A, 2B, 2C
Line 6A:
Layers 2B, 2C, 3
Line 6B:
Layers 1, 2A, 2B, 2C, 3
Line 6C:
Layers 1, 2A
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The required abstraction from Lines 4-6 would be 8.8 ML/day, where flat gradient barriers
are specified in each pumped layer. Line 4 would pump the most (3.6 ML/day), followed by
Line 6A (1.8 ML/day), Line 6B (1.8 ML/day), Line 5 (1.4 ML/day), and Line 6C (0.3
ML/day).
With both Line 4 and Line 5 containment limited to Layers 1 and 2A, pumping would
reduce to 8.1 ML/day for a flat gradient, and to 8.6 ML/day for 0.05% reversed gradient.
With no containment of Line 4 (given that this material will be captured downgradient at
Line 5), pumping would reduce to 6.9 ML/day for reversed gradient (0.05%). Line 6A
would pump the most (2.2 ML/day), followed by Line 6B (2.1 ML/day), Line 5 (2.0
ML/day), and Line 6C (0.6 ML/day).
As Line 6B crosses Springvale Drain, there is no need to pump from Layer 1 to achieve
containment. The drawdowns along the drain on the Botany Industrial Park, caused by
overall pumping, are sufficient to induce leakage from the drain into Layer 1. This sets up a
groundwater mound along the drain, which serves as an hydraulic barrier by deflecting
groundwater flow to the south, parallel to the drain. With pumping removed from Layer 1
on Line 6B, the total required abstraction would be 6.3 ML/day for reversed gradient
(0.05%).
Phase 7
As pumping from Layer 3 would be very small (0.04 ML/day from Lines 6A and 6B), the
next run deactivated pumping from Layer 3, but still insisted on reversed gradient in Layer 3
by pumping Layer 2 harder. In addition, one bore was placed in Layer 1 on Line 6B to
protect a wedge of land (owned by State Rail) between the drain and the site boundary. The
pumping requirement would increase from 6.3 ML/day to 7.1 ML/day, to be taken from 55
bores at 27 drilling sites at an average rate of 129 m3/day. Line 6A would pump the most
(2.4 ML/day), followed by Line 6B (1.9 ML/day), Line 5 (1.9 ML/day), and Line 6C (0.9
ML/day).
Phase 8
Two further optimisation runs were conducted. For the inferred source areas, pumping was
limited to:
Line 4:
NIL (based on downgradient coverage by Line 5)
Line 5:
Layers 1, 2A
Line 6A:
Layers 2B, 2C
Line 6B:
Layers 1, 2A, 2B, 2C
Line 6C:
NIL (based on the main constituent being low concentrations of
carbon tetrachloride which could be remediated by a reactive iron
barrier if required at all).
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Reversed gradient (0.05%) was imposed in all pumped layers in addition to Layer 3 on
Lines 6A and 6B. Optimisation using the 5-layer model resulted in a pumping requirement
of 6.2 ML/day, to be taken from 49 bores at 27 drilling sites.
For the PCA and Line 2, optimisation was repeated using the 3-layer model for reversed
gradient containment around Line A, and flat gradient containment at Line 2. There would
be a risk of saltwater intrusion between Foreshore Road and Botany Bay, if 0.05% reversed
gradient is forced at Line 2. The optimal abstraction would be 2.8 ML/day for the PCA and
1.7 ML/day for the SCA.
The total pumping requirement from all lines is 10.7 ML/day. This was the situation at the
time of the Progress Report in June 2004 (Merrick, 2004b).
Phase 9
When it became known that the Solvay-Interox borefield was to be shut down, simulation
experiments were conducted to assess what impact this would have on groundwater levels at
the containment lines. Water levels would rise by 10-15 cm at Line 6A, 5 cm at Line 6B, 12 cm at PCA, and <1 cm at Line 2. However, hydraulic gradients would be affected little,
and hence the optimisation results should hold. The pumping rates and screen levels at the
Orica production bores were also reassessed at this time.
Phase 10
Seven candidate bores were placed along a new Line 7 (Figure 4) along the Central Plume
axis south of Southlands, in an effort to keep the plume moving and prevent its stagnation to
the south of Line A. Simulation experiments were conducted with additional pumping of
0.35 ML/day to 1.4 ML/day to demonstrate plume migration and to guide the specification
of gradient constraints around the perimeter of the plume to force water to flow inwards to
the plume axis.
Phase 11
Optimisation was repeated using the 5-layer model for all containment lines. Previously, the
optimisation of PCA and SCA was based on a 3-layer model. The inter-layer leakance in
Layer 2 was increased at this time, along with more accurate background pumping.
Line 1 was added along McPherson Street east of Springvale Drain to hydraulically capture
the Southern Plumes contamination from Block 1 of Southlands in lieu of a reactive iron
barrier.
Line 3 was added on Foreshore Road adjoining Line 2 at its eastern end for capture of the
Southern Plumes at Foreshore Road to protect Penrhyn Estuary.
Line 6A was extended to Layers 1 and 2A to capture low contamination levels for long term
reduction of contamination levels in shallow groundwater flowing beneath industrial and
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26
residential areas.
Line 6C was reinstated due to discovery of a new source zone from DNAPL source area
investigations,
Candidate bore locations were reduced in number, based on experience with preceding
optimisation. Code was written to allow mixed strength gradient control in the one run.
For conditions closest to Phase 8, the corresponding optimal production was found to be 0.5
ML/day higher (now 11.2 ML/day), due to re-distributed background pumping, more
detailed sub-layer constraints at PCA/SCA, and a greater separation between bores and
barriers along Floodvale Drain.
With new Lines 1, 3 and 6C activated, the optimal production rises to 13.6 ML/day. With
Line 7 included, the optimal pumping is 14.5 ML/day.
Phase 12
At this stage, Line 5 had to be shifted away from the BIP boundary from First Street to
Second Street, due to interference with buried infrastructure. This adds to the pumping
requirements, as there is a break in the containment “curtain” along the BIP boundary. The
optimal pumping is 15.0 ML/day.
The shift in Line 5 created other problems. The containment line is now positioned on the
flank of a bedrock ridge, which means that local transmissivities vary significantly. The line
has also moved closer to a region in the model which suffers from dry cells and numerical
instability. The response matrix approach becomes less accurate in this area. This means
that the drawdowns generated by the response matrix are no longer sufficiently accurate to
give reliable drawdowns and gradients in the vicinity of Line 5. Layer 1 pumping at Line 5
is underestimated, while Layer 2A pumping is overestimated. Some simulation fine-tuning
is required to ensure capture at this line.
Phase 13
Optimisation experiments were conducted to reduce the extent of the stagnation zone to the
south of McPherson Street, by varying the pumping split between the three segments of the
Core on Southlands Block 2, and by imposing drawdown constraints near Floodvale Drain
on Line A. This was successful, and showed that Line 7 should be deactivated. Pumping
requirements are 14.8 ML/day.
Phase 14
Floodvale Drain was extended to the north, to give an improvement in the calibration of the
simulation model. Springvale Drain was also segmented by deactivating piped sections. The
length of Line 3 was reduced by 20 metres to comply with access restrictions along the
median strip of Foreshore Road. Finally, the out-of-line bore on Line 6B was returned to the
BIP boundary, due to infrastructure interference.
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The optimisation results of Phase 13 were adopted in the main. However, trial-and-error
simulation was used to finalise the pumping rates along an extended Line 5, and at the new
boundary bore on Line 6B. After each trial, the simulated groundwater levels in the two
cells immediately downgradient of each pumped cell were examined to check that hydraulic
gradient was reversed or at least flat (at 1 cm precision).
5.3
OPTIMAL BORE NETWORK
The optimal abstractions of groundwater from each layer, on each line, are summarised in
Table 6.
Table 6. Optimal abstraction rates (ML/day)
LAYER LINE CORE LINE LINE LINE LINE LINE LINE LINE TOTAL
A
1
2
3
5
6A
6B
6C
1
0
0
0
0.21
0.21
0.37
0.65
0
0.05
1.48
2A
0.85
0.69
0.43
0.50
0.35
2.85
1.317
0.49
0.10
7.42
2B
0.25
0.45
0.09
0.51
0.26
0
1.67
0.29
0.28
3.81
2C
0.09
0.36
0.18
0.19
0.23
0
0.33
0.51
0.41
2.29
3
0
0
0
0
0
0
0
0
0
0
TOTAL
1.19
1.49
0.70
1.41
1.04
3.22
3.81
1.29
0.84
15.00
A “model bore” is assumed to be screened across the full thickness of a model layer. As it
has not been necessary to pump from Layer 3, there can be up to four model bores at the one
location, associated with Layers 1, 2A, 2B and 2C. On the ground, from one to four “field
bores” could be drilled to realise four model bores, depending on the choice and length of
screened intervals, and the similarity of recommended pumping rates. The optimal numbers
of model bores in each layer, on each line, are summarised in Table 7.
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Table 7. Optimal numbers of model bores
LAYER LINE CORE LINE LINE LINE LINE LINE LINE LINE TOTAL
A
1
2
3
5
6A
6B
6C
1
0
0
0
19
8
10
8
0
5
50
2A
3
2
2
6
3
10
8
4
3
41
2B
3
2
1
5
3
0
6
3
3
26
2C
1
2
2
4
2
0
3
5
4
23
3
0
0
0
0
0
0
0
0
0
0
Bores
7
6
5
34
16
20
25
12
15
140
The average pumping rates per bore in each layer, on each line, are summarised in Table 8.
The overall weighted average pumping rate is 107 m3/day.
Table 8. Average pumping rates (m3/day)
LAYER LINE CORE LINE LINE LINE LINE LINE LINE LINE
A
1
2
3
5
6A
6B
6C
1
0
0
0
11
26
37
81
0
10
2A
283
343
217
83
115
285
146
123
32
2B
82
223
92
102
88
0
278
98
95
2C
92
180
88
47
114
0
109
102
103
3
0
0
0
0
0
0
0
0
0
The 140 model bores occupy 68 distinct drilling locations, as shown in Figure 21 in relation
to the EDC plumes at June 2004. Their coordinates are listed in the Appendix (Tables A1,
A2, A3). As the model has a spatial resolution of 10 metres, it might be necessary to adjust
the locations of bores by a few metres to ensure they are on Orica property, or do not
interfere with infrastructure. This will not affect the results.
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5.4
VALIDATION OF CAPTURE ZONES
It is important to check that the proposed pumping rates in the bore network do achieve
hydraulic containment. This is done by running the 5-layer model in simulation mode. Other
industrial and irrigation production bores within the study area are assumed active at their
licensed entitlements.
The simulated groundwater levels in each layer are shown in Figures 22 to 26. In each
figure, the locations of the active bores are shown for the current layer.
Figure 22 (contrasted with Figure 16) shows a change in the aquifer-drain interaction due to
general lowering of the water table (Layer 1 head). Floodvale Drain now loses water along
most of its length, except in the far north. Springvale Drain loses water along its entire
length. Groundwater mounds, established beneath the drains, serve to focus groundwater
towards points of capture. The blocking efficiency of the mounds will depend on the actual
depth of water in the drains during prolonged interception pumping. Section 5.7 presents
results for simulation of a nearly dry drain system, and shows that groundwater mounds are
still likely.
Particle Tracking
The capture effectiveness of the designed bore network can be assessed by tracing flowpaths
perpendicular to the groundwater elevation contours in Figures 22 to 26. However, capture
is easier to visualise with particle tracking. This consists of placing tracer particles along a
number of lines, upgradient of containment lines and around the edge of the contaminant
plumes, and watching their progress as they are advected with groundwater flow. Figures 27
to 31 show the destinations of the tracer particles that originate in each layer.
Colour coding is used to show the layer in which a particle resides. The resident layers are:
Layer 1:
Layer 2A:
Layer 2B:
Layer 2C:
Layer 3:
Red
Blue
Lime Green
Silver
Magenta
On the whole, the interception network is successful in meeting DEC capture requirements.
Escapes are observed in a few places:
o Layers 1 & 2A: for 40 m along the eastern edge of the EDC central plume for
half the distance between Line 5 and the BIP boundary; however this
material is subsequently captured in the PCA
o The western lobe of the Northern Plumes is not captured – contaminants will
eventually discharge to the bay through Layer 1 and Layer 2A. As the
Northern Plumes are farther away from the receiving environment and are
moving less quickly, their capture was not intended with defined extraction
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arrangements and was outside the scope of the present project.
Everywhere else, there is complete capture.
Layer 1 (Figure 27):
o Particles starting in Layer 1 on BIP descend to Layer 2 (blue) and pass under
Springvale Drain to be captured at Lines 6A, 6B & 6C;
o Particles in the northern half of Southlands Block 1 pass under Springvale
Drain – that is, there is no discharge of contaminants to the drain;
o Some existing contamination in the Northern Plumes is captured by the
northern extension of Floodvale Drain;
o All particles on Southlands Block 2 are captured by deeper bores in the core
and on Line A;
o Particles along the eastern boundary of Southlands are completely captured
by Line 1, Line A and Line 3;
o The eastern edge of the Southern Plume where it crosses Foreshore Road is
captured by Line 3.
Layer 2A (Figure 28):
o In the northern part of BIP, many particles that start in Layer 2A descend to
Layer 2B for capture at Line 6A;
o Offsite in the industrial area, some existing contamination rises to Layer 1 for
discharge to the northern extension of Floodvale Drain;
o Most particles that start in Layer 2A on the northern and eastern boundaries
of Southlands are captured by bores in Layer 2B (green).
Layer 2B (Figure 29):
o There is no attempt to capture material passing through Line 5 – hence
particle traces are not shown there;
o Particles starting in Layer 2B on BIP remain in Layer 2B until they are
captured by Line 6A, 6B or 6C;
o On Southlands, some particles descend to Layer 2C (silver) for capture by
bores in the Core bores or on Line A;
o Some existing contamination in the residential area rises to Layer 2 and then
to Layer 1 for discharge to the northern extension of Floodvale Drain.
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Layer 2C (Figure 30):
o The drains cease to pull particles up towards the ground surface;
o Generally, particles that start in this layer remain in this layer until captured.
Layer 3 (Figure 31):
o Although there is no pumping from Layer 3, and containment is not required
as a rule, there is complete capture achieved by pumping from higher layers.
Darcy’s Law
A reality check on the recommended volumes of water to be pumped to ensure containment
can be made using Darcy’s Law to estimate the natural flow of water across each
containment line:
Qn
= K n L bn
∆hn
cos(θ )
∆x
where:
Q is the rate of flow [L3T-1];
n is the layer number;
K is hydraulic conductivity [LT-1];
L is the length of a containment line [L];
b is layer thickness [L];
∆h is the drop in groundwater level over distance ∆x;
ϑ is the acute angle between a containment line and a groundwater contour.
The cos(ϑ) term allows for flow that is not perpendicular to a containment line. This can be
dropped out, as the act of pumping will change natural flow directions to be perpendicular to
the line.
The results at the end of Phase 8 (Progress Report in June 2004) are reported on a layer-bylayer basis in Table 9. It appears that about 60% more water must be pumped than flows
naturally through each layer across all containment lines. We would expect a ratio greater
than unity, as pumping must draw in water from the sides, and from above and below.
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Table 9. Comparison of natural flows and required capture flows (ML/day) for each layer
LAYER
1
2
3
TOTAL
DARCY FLOW
[ML/day]
1.2
5.4
0.1
6.7
OPTIMAL FLOW
[ML/day]
1.9
8.8
10.7
RATIO
1.5
1.6
1.6
The results on a line-by-line basis (at the end of Phase 8) are shown in Table 10. Again,
about 60% more water must be pumped than flows naturally across each containment line
through all layers. Exceptions are Line A, where the optimal flow includes extra pumping
from the Core to remove mass from the Central Plume; and Line 6B, which straddles
Springvale Drain, and induces leakage from the drain.
Table 10. Comparison of natural flows and required capture flows (ML/day) for each line
LINE
A
2
4
5
6A
6B
6C
TOTAL
5.5
DARCY FLOW
[ML/day]
0.8
1.0
1.0
1.1
1.5
0.7
0.6
6.7
OPTIMAL FLOW
[ML/day]
2.8
1.7
1.9
2.4
1.9
10.7
RATIO
3.8
1.6
1.7
1.6
2.6
1.6
REGIONAL IMPACTS
Water Level Contours
The post-pumping simulated groundwater level contours in Figures 22-26 should be
compared with pre-pumping simulated groundwater level contours in Figures 16-17.
In Layer 1, water levels along Foreshore Road are at sea level (0.0 mAHD) generally, with
the lowest point at –0.04 mAHD. As water levels are higher than sea level between
Foreshore Road and the bay, saltwater intrusion is not a risk. The lowest water level along
the BIP boundary is about 3.4 mAHD (compared with about 5.5 mAHD pre-pumping). The
lowest water level along McPherson Street is about 1.3 mAHD (compared with about 2.5
mAHD pre-pumping). A strong feature in Layer 1 is the distortion of contours along the
Botany Primary Containment
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33
drains. This indicates that there will be no groundwater discharge to the drains, except at the
northern end of Floodvale Drain. The degree of predicted recharge from the drains to the
aquifer depends on the average water level in the drains after interception pumping
commences. The assumption here is 1 metre depth of water, but Section 5.7 assesses the
extreme case where the drain is assumed to be almost dry (0.1 metre depth of water).
The water levels in Layers 2 and 3 are similar. Along Foreshore Road, water levels are
generally below sea level by about 0.03 m, with the lowest level at –0.1 mAHD. The water
level along McPherson Street across the core of the Central Plume is about 1.2 mAHD
(compared with about 2.5 mAHD pre-pumping). The lowest water level along the BIP
boundary is about 3.3 mAHD (compared with about 5.5 mAHD pre-pumping). The natural
(pre-pumping) south-westerly direction of groundwater flow is changed to southerly and
south-easterly near Line 6.
Drawdown
The predicted drawdowns in each layer, in response to optimal pumping, are shown in
Figures 32 to 36. Subsidence monitoring points, labelled with their drawdown tolerances,
are shown in each figure. The maximum drawdown in each layer is about 3 metres.
Figure 32 (Layer 1) shows that drawdown in the vicinity of the two drains is buffered by
water leaking from the drains. The drawdown along the drains is generally 0.1 – 0.2 m along
Floodvale Drain, and 0.4 – 0.6 m along Springvale Drain. Typical drawdowns are: 1.2 – 1.4
m in the core on Block 2 and along McPherson Street between the drains; 3 m at line 5 on
BIP; 2 m along the BIP boundary at Line 6A; 0.2 – 0.5 m along Line 2; 0.9 m maximum on
Line 3. In Layers 2B, 2C and 3, the far-field drawdowns are much the same as for Layer 2A.
The water table at the eastern end of the ponds in Sir Joseph Banks Park is expected to drop
by about 0.15 m. The maximum drawdown at an external production bore is 0.4 m.
No subsidence constraints are breached. The locations that come closest to historically low
water levels are Botany Road (0.65 m vs 1.0 m drawdown), and at the southern end of
Springvale Drain (0.4 m vs 0.9 m drawdown).
Subsidence
MODFLOW includes an option for a first-order assessment of subsidence. This module is
capable of reliable predictions if fine-grained sediments are thin (as is the case at Botany), as
it is assumed that all drainage from soil pores occurs in a short time.
This package requires specification of the following parameters on a cell-by-cell basis
within a model layer that contains fine-grained interbeds:
Elastic storage coefficient;
Inelastic storage coefficient;
Botany Primary Containment
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34
Initial preconsolidation head;
Initial compaction.
The modeller has to aggregate interbed thicknesses spatially, and multiply by estimates for
specific storage. Given the lack of data on inelastic values, the inelastic storage coefficient is
usually estimated as a multiple of the elastic storage coefficient.
The term 'interbed', where subsidence in aquifers occurs in response to groundwater
abstraction, is assumed to be:
Of significantly lower hydraulic conductivity than the surrounding
sediments;
Of insufficient lateral extent to be considered a confining bed that separates
adjacent aquifers; and
Of relatively small thickness in comparison to lateral extent.
Compaction is computed in each cell in each layer at the end of a time step, by multiplying
the head change by the appropriate storage coefficient. If the current head is higher than the
preconsolidation head, then the elastic value is used. If the current head is lower than the
preconsolidation head, then the inelastic value is used and the preconsolidation head is set at
the new head value. Land subsidence is computed at a cell by summing the compaction
simulated in each of the model layers, and is reported for the model cell at the uppermost
layer.
Three scenarios have been simulated in this study:
Base Case, ignoring prior consolidation;
Likely Case, accounting for prior consolidation;
Worst Case, using parameters an order of magnitude larger.
Reports of modelling subsidence with MODFLOW are very rare. The only known example
where subsidence computations were calibrated against measured values is for the Lower
Namoi Valley NSW (Ali et al., 2004). The base case, here, uses values close to the Namoi
calibrated parameters:
Elastic specific storage:
1 x 10-5 m-1
Inelastic specific storage:
1 x 10-3 m-1
Specific storage must be multiplied by the aggregate thickness of fine-grained sediments
across the area. Six bore logs close to Foreshore Road (which could be at risk of subsidence
due to reclamation in the late 1970s) were examined. This revealed that fine-grained
sediments (peat, silt, clay) occupied 18% on average of the total thickness of Layers 1 and 2.
The maximum proportion was 32%. The Base Case assumes 20% as the thickness of fine-
Botany Primary Containment
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35
grained sediments.
Subsidence risk should be minimal in areas that have experienced low groundwater levels in
the past, as it is at this time that fine-grained sediments would have released water and
suffered irreversible compaction. The Base Case assumes that no prior consolidation has
taken place, in order to give an upper limit on the likely subsidence, and to handle newly
filled areas. Pre-pumping simulated water levels are used as the benchmark. This means that
the inelastic storage coefficient will be used exclusively.
The Base Case subsidence prediction is shown in Figure 37. The maximum anticipated
subsidence is 1.7 cm, associated with the pumping at Botany Industrial Park. Foreshore
Road has 1-2 mm subsidence in this case.
The Likely Case scenario modifies the Base Case by allowing for prior consolidation. The
July 1969 observed water levels (Figure 8) are used as the benchmark at which the inelastic
storage coefficient will be triggered. The Likely Case subsidence prediction is shown in
Figure 38. The maximum likely subsidence is 0.9 mm, associated with the pumping at
Foreshore Road. Botany Industrial Park has 0.1 mm subsidence in this case.
The Worst Case scenario modifies the Likely Case by assuming 30% as the proportion of
fine-grained sediments in a layer, and that the specific storages are an order of magnitude
greater:
Elastic specific storage:
1 x 10-4 m-1
Inelastic specific storage:
1 x 10-2 m-1
Prior consolidation is taken into account. The Worst Case subsidence prediction is shown in
Figure 39. The maximum subsidence is 1.3 cm, associated with the pumping at Foreshore
Road. Botany Industrial Park has 1-2 mm subsidence in this case.
Saltwater Intrusion
The risk of saltwater intrusion is low according to Figure 22, which shows that there is still a
positive hydraulic gradient towards the bay from a point midway between Foreshore Road
and the bay. However, the gradient is almost flat. Slight differences between the behaviour
of the real aquifer and the model’s representation of the aquifer could easily reverse the
gradient, and permit some saltwater intrusion. Tidal oscillations will superimpose a pushpull force on the average hydraulic gradient. Without further modelling of tidal dynamics, it
is not known at this stage if periodic reversals of gradient will be sufficient to allow
saltwater to penetrate the aquifer for other than a short distance.
Further modelling in Section 5.7 for a nearly dry drain system, during prolonged
interception pumping, suggests that saltwater intrusion is likely, as the hydraulic gradient is
reversed all the way from Foreshore Road to the bay. However, when the drains are nearly
dry, the interception pumping can be reduced accordingly because some of the water
pumped is induced from the drains. Lower pumping will reduce the risk of saltwater
intrusion.
Botany Primary Containment
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36
5.6
WATER BALANCE
Optimal pumping of 15.0 ML/day from the containment lines is somewhat greater than the
background pumping from existing bores in the model area (10.5 ML/day) at the time when
the Solvay-Interox borefield was active (to 2004). Much of this extra water is derived from
the interaction with the drains, by negating groundwater discharge to the drains (currently 4
ML/day), and inducing new recharge from the drains (about 5 ML/day). As groundwater
levels are generally lower, overall discharge to Botany Bay must decrease (by 15%) –
although localised impacts in the shadow of the secondary containment area extraction line
will significantly reduce or eliminate groundwater discharge to the estuary - and
evapotranspiration losses must decrease (by 8%). Less water leaks from the Lachlan Lakes
(3%) due to the cessation of Solvay-Interox pumping. The new water balance is itemised in
Table 11 (for drain water depth of 1 m).
Table 11. Water balance with optimal hydraulic containment
COMPONENT
Rain Infiltration
Runoff Infiltration
Lachlan Lakes
Drains
Botany Bay
Production Bores**
Evapotranspiration
TOTAL*
*
**
RECHARGE
[ML/day]
9.7
18.4
7.6 (down 3%)
5.1 (up from 0.2)
0
0
0
40.8 (up 13%)
DISCHARGE
[ML/day]
0
0
0
0.3 (down 93%)
16.2 (down 15%)
23.5 (up 124%)
2.2 (down 8%)
42.2 (up 17%)
The difference between recharge and discharge is the finite difference mass balance error
Excluding Solvay-Interox borefield
Merrick (1994) has demonstrated that the exchange of water between the aquifer and the
lakes is quite dynamic, with fluctuations from +8.6 ML/day (recharge) to –8.6 ML/day
(discharge). Similarly, groundwater discharge to the bay can vary by over 30% between dry
and wet periods (about 8 to 16 ML/day). The predicted changes in lake recharge and bay
discharge are within the ranges of natural fluctuation.
5.7
DRAIN SENSITIVITY
In all optimisation and simulation runs, the water depth in the drains has been assumed to be
1 m, both before and after interception pumping. Unfortunately, MODFLOW does not
adjust the water level in a leaking drain. A simulation experiment has been conducted for
Botany Primary Containment
C04/44/001
37
10 cm depth of water in the drains, as the depth of water should be reduced significantly due
to interception pumping.
The volume of water leaking from the drains is found to be roughly halved (2.65 ML/day vs
5.13 ML/day). This suggests that the designed network could pump less, perhaps by the
differential in drain leakage. This could reduce the required pumping from 15.0 to 12.5
ML/day (a drop of 16%). It would be expected that the higher rate is needed initially until
the drain water level settles at its new equilibrium position, after which less pumping would
be possible.
Contours of groundwater level are shown in Figures 40 and 41 for Layers 1 and 2A. Water
level is much lower, by as much as the reduction in drain water depth (that is, 0.9 m). The
water levels caused by pumping Line 2 and Line 3 suggest that saline intrusion from the bay
is a risk, as hydraulic gradients seem to be reversed all the way from Foreshore Road to the
bay. However, it should be possible to reduce pumping from Line 2 and Line 3 bores so that
plume capture still occurs with low risk of saltwater intrusion.
Drawdowns are greater. The maximum drawdown in Layer 1 increases from 2.9 m to 3.9 m.
For Layer 2, the increase is from 2.9 m to 3.7 m. The drawdowns are uniformly 1 m along
Floodvale Drain, and 1.2 – 1.4 m along Springvale Drain south. Along Springvale Drain
north, the drawdown is 1.8 – 2.2 m. The subsidence constraints are breached at Botany Road
and at the southern tip of Springvale Drain. However, Section 5.5 shows that there is no
serious risk of subsidence even when water levels become lower than previous levels.
Capture is easier to achieve with lower water levels in the drains. Hence, complete capture
can be demonstrated with design pumping of 15.0 ML/day.
The reduced pumping requirements for a nearly dry drain system will be distributed across
the bore network. Further optimisation modelling is recommended to assess the pattern of
re-distribution between nominated network bores, and to determine range requirements for
pumps and lower limits on pumping rates.
Botany Primary Containment
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6.0 CONCLUSION
To achieve hydraulic containment of the Primary Containment Area, the Secondary
Containment Area, and the inferred DNAPL source areas, about 15 ML/day of groundwater
needs to be pumped and treated.
The water should be drawn from a maximum of 140 bores at 68 distinct drilling sites. The
actual number of bores will depend on whether a single screen can be used across the sublayers of Layer 2. The bore locations have been optimised spatially along each line, and
vertically across five stratigraphic layers. Model bores have been constrained to pump at
least 10 m3/day from Layer 1, and between 30 and 500 m3/day in the sub-layers of Layer 2.
The optimal abstraction rates are about 60 percent higher than the natural groundwater flow
across each containment line, due to capture of extra water from side flow and vertical flow,
and the need to create permanent drawdown to maintain a reversed hydraulic gradient
beyond each containment line.
The predicted drawdown in the vicinity of Springvale Drain and Floodvale Drain is
generally 0.1–0.6 m, and is buffered by water leaking from the drains. Typical drawdowns
along the other containment lines are from 0.2 m to 3 m maximum. The water table at the
eastern end of the ponds in Sir Joseph Banks Park is expected to drop by about 0.15 m. The
maximum drawdown at an external production bore is 0.4 m. There is no area where the
predicted drawdowns come close to the subsidence limits, except when the drains carry very
little water. Subsidence modelling suggests that subsidence is not a risk, even in areas that
have been filled and built upon since the lowest water levels were experienced in the 1960s
and 1970s. The maximum likely subsidence is in the order of 1 cm at Foreshore Road. In
most other areas, subsidence should be less than 1 mm.
Pumping at the recommended rate will reduce overall groundwater discharge to Botany Bay
by about 15 percent; however, there will be more significant localised effects in the shadow
of the extraction lines at Foreshore Road where groundwater discharge will be significantly
reduced or eliminated. Some groundwater will continue to discharge into Penrhyn Estuary
along the eastern arm of the Floodvale Drain inlet to the estuary. Groundwater will also
cease to discharge into Springvale Drain and Floodvale Drain, and instead will induce
recharge to the aquifer from them. The amount of recharge will depend on the average depth
of water in the drains during prolonged interception pumping. This is not known in advance.
A nearly dry drain system is likely to reduce interception pumping requirements by 2 to 3
ML/day, but further modelling is required to confirm this figure.
6.1
RECOMMENDATIONS
An amount of 2.7 ML/day should be pumped from Line A and the Core to
protect the Primary Containment Area; no pumping is required from Layer 1, as
the induced groundwater mounds beneath Springvale Drain and Floodvale Drain
will act as effective hydraulic barriers (which are evident even for a nearly dry
drain system);
Botany Primary Containment
C04/44/001
39
An amount of 0.7 ML/day should be pumped from Line 1, all from Layer 2;
An amount of 1.4 ML/day should be pumped from Line 2 on Foreshore Road to
protect the Secondary Containment Area and most of the Northern Plumes; this
is composed of 0.2 ML/day from Layer 1 and 1.2 ML/day from Layer 2;
An amount of 1.0 ML/day should be pumped from Line 3 to capture all of the
existing Southern Plumes north of Foreshore Road; this is composed of 0.2
ML/day from Layer 1 and 0.8 ML/day from Layer 2;
An amount of 3.2 ML/day should be pumped from Line 5 to protect the inferred
DNAPL source areas for the Central Plume; this is composed of 0.4 ML/day
from Layer 1 and 2.8 ML/day from the upper third of Layer 2;
An amount of 3.8 ML/day should be pumped from Line 6A to protect the
inferred source areas for the Northern Plumes; this is composed of 0.7 ML/day
from Layer 1, 0.3 ML/day from the lowest third of Layer 2, and 2.8 ML/day
from the upper two thirds of Layer 2;
An amount of 1.3 ML/day should be pumped from Line 6B to protect the
inferred source areas for the Northern Plumes; this is composed of 0.5 ML/day
from the upper third of Layer 2, 0.3 ML/day from the middle third of Layer 2
and 0.5 ML/day from the lower third of Layer 2;
An amount of 0.8 ML/day should be pumped from Line 6C, distributed across all
of Layer 1 and Layer 2; this is composed of 0.05 ML/day from Layer 1, 0.1
ML/day from the upper third of Layer 2, 0.3 ML/day from the middle third of
Layer 2 and 0.4 ML/day from the lower third of Layer 2.
The total pumping requirement of 15 ML/day will lessen after the drain waters settle to new
levels in response to interception pumping. This should happen quite quickly. At this time,
it is anticipated that pumps can be scaled back in the vicinity of 10-15%. It is recommended
that further optimisation modelling be done to determine the reduced pumping requirements,
lower pumping rates, and range requirements for pumps for the nominated bore network.
6.2
MONITORING
After the interception network is in place, it will be necessary to monitor its performance.
The spatial pattern of predicted drawdowns can be checked by routine monitoring with the
existing observation bore network, supplemented with monitoring bores placed between
some (not all) of the interception bores.
For Line 2 and Line 3, where the predicted water levels are below sea level, it will be
sufficient to measure a sub-zero water level along the containment lines. This will prove
capture, as the downgradient groundwater level at the shoreline is constrained by nature to
match sea level on average. Hence the hydraulic gradient between the containment lines and
the shoreline must be reversed somewhere near the bores. Tidal influences will be most
pronounced at the junction of Lines 2 and 3 near the Floodvale Drain outlet into Penrhyn
Botany Primary Containment
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Estuary and at the western end of Line 2 where the distance to the shoreline is reduced.
Preferential monitoring near these locations will be required to determine if plume capture is
compromised during the periodic intervals of low tide, and whether saltwater intrusion
occurs at high tide.
It should be noted that all predictions are for equilibrium steady-state conditions, without
climate variations. The natural variation in groundwater levels at Foreshore Road is likely to
be a maximum of 0.05 m to 0.1 m, due to rainfall variability. The climatic variation in
hydraulic gradient is minor, and should have little effect on optimal pumping rates for
average conditions.
Botany Primary Containment
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41
7.0 REFERENCES
Ahlfeld, D. P. and Mulligan, A. E., 2000, Optimal Management of Flow in Groundwater
Systems. Academic Press, San Diego, 185p.
Ali, A., Merrick, N. P., Williams, R. M., Mampitiya, D., d’Hautefeuille, F. and Sinclair, P.,
2004, Land Settlement due to Groundwater Pumping in the Lower Namoi Valley of NSW.
CD Proceedings, Ninth Murray-Darling Basin Groundwater Workshop, Bendigo, 17-19
February, 2004.
McDonald, M. G. and Harbaugh, A. W., 1988, MODFLOW: A modular three-dimensional
finite-difference ground-water flow model. U.S.G.S., Scientific Publications Co.,
Washington.
Merrick, N. P., 1994, A groundwater flow model of the Botany Basin. IAH/IEA Water
Down Under ‘94 Conference, Adelaide, 21-25 Nov., Proceedings Vol. 2A, 113-118.
Merrick, N. P., 2000, Optimisation techniques for groundwater management. PhD
Dissertation, University of Technology, Sydney. Unpublished, 551p .
Merrick, N. P., 2001, How best to handle competition for a scarce resource. In: Seiler, K-P.
and Wohnlich, S. (eds.), New Approaches Characterising Groundwater Flow, Proceedings
of the XXXI IAH Congress, Munich, Germany, 10-14 September, 2001. Balkema, Lisse,
ISBN 90 2651 849 8, 569-572.
Merrick, N. P., 2003, Modelling of Hydraulic Containment Abstraction Rates and Regional
Impacts, Botany NSW. accessUTS Pty Ltd Report for Orica Australia Pty Ltd, Project No.
C93/44/004, October 2003, 30p.
Merrick, N. P., 2004a, Groundwater Abstraction Rates for the Primary Containment Area,
Botany NSW. accessUTS Pty Ltd Report for Orica Australia Pty Ltd, Project No.
C04/44/001, March 2004, 18p.
Merrick, N. P., 2004b, Optimal Groundwater Abstraction Rates for Hydraulic Containment
of Contaminant Plumes and Source Areas, Botany NSW. accessUTS Pty Ltd Progress
Report for Orica Australia Pty Ltd, Project No. C04/44/001, June 2004, 69p.
Middlemis, H., Merrick, N. P, and Ross, J. B., 2000, Groundwater Modelling Guidelines.
Aquaterra Report for Murray Darling Basin Commission, October 2000, 125p.
NSW EPA, 2003, Notice of Clean Up Action.
Orica Engineering Pty Ltd, 2003, Groundwater Cleanup Plan. Document No: EN1591-0010-001, http://www.oricabotanygroundwater.com
Botany Primary Containment
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Tho, L. K., 2002, Gravity Investigations in the Botany Basin. MSc Thesis, University of
New South Wales, 181p.
URS Australia, 2004, Penrhyn Estuary Baseline Survey – Surface Water and groundwater
Discharge. Report 46160-005/R009_A, www.oricabotanygroundwater.com, 13 February
2004.
Woodward-Clyde, 1996, ICI Botany Groundwater Stage 2 Survey. Contract S2/C3 Water /
Soil Phase 2. Final Report 3390R1-D for ICI Engineering Australia Pty Ltd. August 1996.
Botany Primary Containment
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ILLUSTRATIONS FIGURES 1 TO 41
Botany Primary Containment
C04/44/001
44
6249000
6248000
Centennial Park
ALEXANDRIA
Moore Park
6247000
WHOLE-of-BASIN
MODEL
KENSINGTON
Racecourse
BEACONSFIELD
6246000
RANDWICK
Alexandra Canal
KINGSFORD
6245000
NORTHING (m MGA)
MASCOT
DACEYVILLE
EASTLAKES
NEW 2004 MODEL
6244000
URS STAGE 2
1995 MODEL
PAGEWOOD
Airport
ANALYTICAL
2003 MODEL
6243000
BOTANY
EAST BOTANY
Cooks River
BOTANY
INDUSTRIAL
PARK
6242000
HILLSDALE
URS STAGE 3
2001 MODEL
ORICA
BANKSMEADOW
Southla
nds
6241000
6240000
BOTANY BAY
6239000
BOTANY
BAY
6238000
330000
331000
332000
333000
334000
EASTING (m MGA)
335000
336000
337000
338000
[Botany][Orica] AllGrids.SRF
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew, Border12.bln
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, mga12C.bln, Lakes.bln
HSmodel, URS1model, URS2model.bln
Figure 1. Model extents for the new model and prior models
Botany Hydraulic Containment
C04/44/001
45
6249000
6248000
Centennial Park
ALEXANDRIA
Moore Park
6247000
KENSINGTON
Racecourse
BEACONSFIELD
6246000
RANDWICK
Alexandra Canal
KINGSFORD
6245000
SI
ZE
CE
L
L
6244000
La
6243000
ch
lan
SI
ZE
CE
LL
HILLSDALE
Third
10
m
BANKSMEADOW
6241000
s
EAST BOTANY
25
m
6242000
ke
PAGEWOOD
CE
LL
BOTANY
Cooks River
La
SI
ZE
Airport
DACEYVILLE
EASTLAKES
10
0m
NORTHING (m MGA)
MASCOT
ay
Runw
6240000
BOTANY
BAY
BOTANY BAY
6239000
Each grid square is 100 metres
6238000
330000
331000
332000
333000
334000
EASTING (m MGA)
335000
336000
337000
338000
[Botany][Orica] CellSize1.SRF
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew,
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, GeolBound.bln, Lakes.bln
Figure 2. Variable cell sizes for the new model
Botany Hydraulic Containment
C04/44/001
46
HYDRAULIC
BARRIER
BLE
TER TA
A
W
L
A
NATUR
SHALLOW
AQUIFER
LAYER 1
GRADIENT
REVERSAL
DEEP
AQUIFER
LAYER 2
BOTTOM
AQUIFER
LAYER 3
P Q
[FirstOPTIM] BARRIER.SRF
Figure 3. The principle of hydraulic containment
Botany Hydraulic Containment
C04/44/001
47
6242400
EAST BOTANY
10
Stephen Rd
1
Brighton St
ks
P
6241000
10
00
10
00
10
0
Block 2
10 100
CORE
1
St
Bo
tan
ark
ORICA
Southla
nds
yR
LINE A
oa
d
Block 1
LINE 1
LINE
7
De
nt
Ban
5
ph
NE
LI
6C
BANKSMEADOW
6241200
4
NE
LI
6B
Floodvale Drain
6241400
Sir
Jos
e
NE
LI
NE
LI
6241600
St
rd
rfo
He
NORTHING (m MGA)
6A
6241800
BOTANY
INDUSTRIAL
PARK
10
0
NE
LI
6242000
Springvale Drain
10
0
6242200
6240800
LINE 2
LINE 3
6240600
BOTANY
BAY
6240400
334000
334200
Fo
re
Penrhyn ry
Estua
334400
334600
334800
335000
335200
EASTING (m MGA)
10
0
Candidate Interception Bore
EDC Concentration June 2004 (mg/L)
335400
sh
ore
Ro
335600
ad
335800
336000
[Botany][Orica2004] [Optim5E] CANDIDATE.SRF
[Grid12] ShoreOld, Roads, Orica.bln
[Orica] Border8MGA.bln, Stephens.bln
Penrhyn, MStream, FSdrain.bln, Towns.xy
[Botany] PondMGA.bln, DamMGA.Bln
[Optim5E] Candidate.csv
Figure 4. Hydraulic containment lines and candidate interception
bore locations
Botany Hydraulic Containment
C04/44/001
48
6242400
EAST BOTANY
6242200
Brighton St
6B
NE
LI
NE
LI
6241600
5
6C
rd
rfo
He
St
NORTHING (m MGA)
NE
LI
Stephen Rd
6A
6241800
Springvale Drain
NE
LI
6242000
BOTANY
INDUSTRIAL
PARK
6241400
Block 2
ORICA
CORE
BANKSMEADOW
6241200
Sir
J
ose
ph
De
Ban
nt S
Bo
tan
yR
oa
d
6240800
LINE 2
6240600
BOTANY
BAY
6240400
334000
ds
t
ark
Floodvale Drain
6241000
ks
P
Southla
n
Block 1
LINE A
LINE 1
LINE 3
Fo
re
Penrhyn ry
Estua
334200
334400
334600
334800
335000
335200
EASTING (m MGA)
Candidate Interception Bore
Inner Barrier Cell
Outer Barrier Cell
335400
sh
o
re
R
oa
d
335600
335800
Figure 5. Locations of hydraulic barrier doublets
Botany Hydraulic Containment
C04/44/001
336000
[Botany][Orica2004] [OptimSplit] BARRIER.SRF
[Grid12] ShoreOld, Roads, Orica.bln
[Orica] Border8MGA.bln, Stephens.bln
Penrhyn, MStream, FSdrain.bln, Towns.xy
[Botany] PondMGA.bln, DamMGA.Bln
[OptimSplit] Candidate.csv
Inner.csv, Outer.csv
49
6243500
riv
e
Wentw
orth R
oad
er n
40222
Cr
os
sD
1
uth
R1
NS
1
1 2
MWMW
1013
W
MMW
42165
So
6244000
Lachla
25543
4
18
EIS
SA
7
1
2
16SA
SA
13 SA 5
11SA SA1 4
1
SA
2
A
1S
5
ond
SA A6SA
i ll P
8 A7 S
3M
A
S A S S1
6242500
S
EI MSB22
ve
s Dri
40776
olme
H
l
ra
Gene
MSB20
MSB21
Lakes
n
PAGEWOOD
42161
6243000
75022
BOTANY
42174
WG51
WG50
75021
WG46 S20
75023
WG43
GJWC42163
WG49
WG47
42164
GJMB
UDMB
40777
AWC
42175
42168
B&T
42166
WG48
HILLSDALE
42167
WG45
WG40
JJMB
MSB18
JJWC
40775
S13
WG39
AR.P
40779
MSB19MSB4 MSB17
S15
BAYER
WG44
S16
WG38
SCOTTS
WG41
Bo
ta n
MSB3
yR
WG42
42162
oa
MSB16 MSB15
WG37
WG35
WG25
d
40778
PSWC
PSMB
MSB14
WG36
WG29
WG28
WG13
WG14
42176
SECO
WG15
APM1 WG27
SJB3
MSB13
WG60
SJB2 BANKSMEADOW
WG34
WG20
SJB1
WG33
ICI2
MSB12MSB11 MSB2
WG31
40774
WG17
WG21
WG18
WG26
WG16
APM3
ICI1
WG19
MSB10 MSB1
WG32
MSB6
GC8
WG30
40782
De
42177
APM2
APM4
GC9
nt
MSB5
MSB8A GC10
MSB10A
40773 St
GC7
WG24
APM5
MSB8
MSB6A GC6 GC1
APM6
GC2
42178
WG23
40772
GC5
WG22
GC4 GC3
42171
MSB9
MSB7
APM7
4217242170
EAST BOTANY
tr e
am
Di v
ers
ion
6241000
Third
6240500
ay
Runw
6240000
Fo
res
Pe
Es nrhy
tu a
n
ry
40783
t
Con
al
rick
Pat Termin
r
aine
th
B ro
Bore Network
6239500
BOTANY
BAY
DLWC
Ports/Industry
ers
Doc
re
R
oa
d
k
O
al
P & ermin
er T
in
a
t
Con
R
hip
nds
Frie
Airport
ORICA
6239000
332000
on
ho
Rd
6241500
332500
333000
333500
334000
334500
335000
335500
oad
Bumborah Pointt
NORTHING (m MGA)
lS
Mil
6242000
336000
75019
336500
337000
EASTING (m MGA)
[Grid12][Figures] BOREPLAN1.SRF
[Grid12] ShoreOld, Roads, Orica.bln
Penrhyn, MStream, FSdrain.bln
Towns, DLWC-old, DLWC-net.xy
MSB, Other, ICInew.xy
GeolBound.bln, PondMGA.bln
Figure 6. Locations of known groundwater bores
Botany Hydraulic Containment
C04/44/001
50
6243500
Lachla
n
Lakes
PAGEWOOD
6243000
BOTANY
6242500
Springvale Drain
6241500
Sir
Jos
eph
HILLSDALE
BANKSMEADOW
ORICA
Southla
nd s
Road
6241000
g
eron
De
Bo
nt S
tan
t
yR
oa
d
Bunn
ark
Floodvale Drain
t
dS
Ban
ks
P
Stephen Rd
Brighton St
6242000
BOTANY
INDUSTRIAL
PARK
r
rfo
He
NORTHING (m MGA)
EAST BOTANY
BOTANY
BAY
Fo
res
ho
re
Ro
ad
6240500
Penrhyn
6240000
333000
333500
334000
ry
Estua
334500
335000
335500
336000
336500
337000
EASTING (m MGA)
Measurement Point
[Botany][Orica] [Hotspots] WL2002a.SRF
[Grid12] ShoreOld, Roads, Orica.bln
[Orica] GeolBound.bln, Stephens.bln
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln, DamMGA.Bln
Towns.xy, [Hotspots] WL2002.grd
[WaterLevel] WL-Port.xls
Figure 7. Representative groundwater levels recorded 2000-2002
(mAHD)
Botany Hydraulic Containment
C04/44/001
51
6243500
Lachla
n
Lakes
PAGEWOOD
6243000
BOTANY
6242500
Springvale Drain
6241500
Sir
Jos
eph
HILLSDALE
BANKSMEADOW
ORICA
Southla
nd s
Road
6241000
g
eron
De
Bo
nt S
tan
t
yR
oa
d
Bunn
ark
Floodvale Drain
t
dS
Ban
ks
P
Stephen Rd
Brighton St
6242000
BOTANY
INDUSTRIAL
PARK
r
rfo
He
NORTHING (m MGA)
EAST BOTANY
BOTANY
BAY
Fo
res
ho
re
Ro
ad
6240500
Penrhyn
6240000
333000
333500
334000
ry
Estua
334500
335000
335500
336000
336500
337000
EASTING (m MGA)
Measurement Point
[Botany] July69MGA.SRF
[Grid12] ShoreOld, Roads, Orica.bln
[Orica] GeolBound.bln, Stephens.bln
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln, DamMGA.Bln
Towns.xy, [Hotspots] WL2002.grd
[Botany] Jul69MGA.dat
Figure 8. Lowest groundwater levels recorded 1969 (mAHD)
Botany Hydraulic Containment
C04/44/001
52
6243500
Lachla
n
Lakes
PAGEWOOD
6243000
BOTANY
6242500
Springvale Drain
6241500
Sir
Jos
eph
HILLSDALE
BANKSMEADOW
ORICA
Southla
nd s
Road
6241000
g
eron
De
Bo
nt S
tan
t
yR
oa
d
Bunn
ark
Floodvale Drain
t
dS
Ban
ks
P
Stephen Rd
Brighton St
6242000
BOTANY
INDUSTRIAL
PARK
r
rfo
He
NORTHING (m MGA)
EAST BOTANY
BOTANY
BAY
Fo
res
ho
re
Ro
ad
6240500
Penrhyn
6240000
333000
333500
334000
ry
Estua
334500
335000
335500
336000
336500
337000
EASTING (m MGA)
Measurement Point
[Botany] Apr88MGA.SRF
[Grid12] ShoreOld, Roads, Orica.bln
[Orica] GeolBound.bln, Stephens.bln
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln, DamMGA.Bln
Towns.xy, [Hotspots] WL2002.grd
[Botany] Apr88MGA.csv
Figure 9. Groundwater levels recorded 1988 (mAHD)
Botany Hydraulic Containment
C04/44/001
53
6244000
6243500
Lachla
n
Snape Park
Borefield
Lakes
PAGEWOOD
Solvay Interox
Borefield
6243000
BOTANY
EAST BOTANY
Jos
eph
B
Stephen Rd
Brighton St
Sir
Par
k
Orica
Borefield
HILLSDALE
BANKSMEADOW
nd s
Ro
ad
ad
BOTANY
BAY
Southla
g Ro
6241000
Bo
tan
y
Fo
res
ho
re
Ro
ad
6240500
Penrhyn
eron
De
nt
St
ORICA
Bunn
Floodvale Drain
ank
s
t
dS
6241500
Springvale Drain
6242000
BOTANY
INDUSTRIAL
PARK
r
rfo
He
NORTHING (m MGA)
6242500
ry
Estua
100 ML/year
6240000
333000
333500
334000
334500
335000
335500
EASTING (m MGA)
336000
336500
337000
[Botany][Orica2004] [FEMdata] Usage.SRF
[Grid12] ShoreOld, Roads, Orica.bln
[Orica] GeolBound.bln, Stephens.bln
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln, DamMGA.Bln
Towns.xy, [Hotspots] WL2002.grd
[WaterLevel] WL-Port.xls
[FEMdata] Usage.dat, Legend.use
Figure 10. Likely distribution of active groundwater production bores
during 2000-2002
[Background: groundwater levels 2000-2002 (mAHD)]
Botany Hydraulic Containment
C04/44/001
54
NORTH
SOUTH
RAIN
IRRIGATION
GROUNDWATER
ABSTRACTION
PONDS
LAKES
EVAPOTRANSPIRATION
RAIN
DRAINS
LAYER 1
BOTANY BAY
VERTICAL
FLOW
LAYER 2
TER
NDWA
GROU ARGE
H
C
IS
D
T
NDWA
GROU OW
FL
ER
LAYER 3
SANDSTONE
BEDROCK
ZONE OF
DIFFUSION
Figure 11. Conceptual model
Botany Hydraulic Containment
C04/44/001
55
RUNOFF
0
5
10
6244500
15
20
25
30
35
40
45
50 mAHD
DACEYVILLE
EASTLAKES
6244000
6243500
PAGEWOOD
6243000
NORTHING (m MGA)
BOTANY
6242500
EAST BOTANY
HILLSDALE
6242000
6241500
BANKSMEADOW
6241000
6240500
BOTANY
BAY
6240000
6239500
332500
333000
333500
334000
334500
335000
335500
336000
336500
337000
337500
EASTING (m MGA)
Each grid square is 100 metres
0m
1000m
2000m
3000m
4000m
[Botany][Orica2004] [Maps] GROUND.SRF
ALLtopo.csv, .grd, WL.clr
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln
HSmodell.bln, BlankBAY.bln, BAY.bln
Default Kriging @ 100m grid
Figure 12. Surface topography contours across the model area (mAHD)
[Modified after Woodward-Clyde, 1996]
Botany Hydraulic Containment
C04/44/001
56
1
3
5
7
6244500
9
11
13
15
17
19
21
23
25
27 metres
DACEYVILLE
EASTLAKES
6244000
6243500
PAGEWOOD
6243000
NORTHING (m MGA)
BOTANY
6242500
EAST BOTANY
HILLSDALE
6242000
6241500
BANKSMEADOW
6241000
BOTANY
BAY
6240500
6240000
6239500
332500
333000
333500
334000
334500
335000
335500
336000
336500
337000
337500
EASTING (m MGA)
0m
1000m
2000m
3000m
4000m
[Botany][Orica2004] [Maps] GVTHICK1.SRF
[Data] GVTHICK2.grd, WL.clr
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew, Bay.bln
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln
Figure 13. Inferred thickness of Layer 1 (m)
[Modified after Woodward-Clyde, 1996]
Botany Hydraulic Containment
C04/44/001
57
2
4
6
8
6244500
10
12
14
16
18
20
22
24
26 28
30
metres
DACEYVILLE
EASTLAKES
6244000
6243500
PAGEWOOD
6243000
NORTHING (m MGA)
BOTANY
6242500
EAST BOTANY
HILLSDALE
6242000
6241500
BANKSMEADOW
6241000
BOTANY
BAY
6240500
6240000
6239500
332500
333000
333500
334000
334500
335000
335500
336000
336500
337000
337500
EASTING (m MGA)
0m
1000m
2000m
3000m
4000m
[Botany][Orica2004] [Maps] GVTHICK2.SRF
[Data] GVTHICK2.grd, WL.clr
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew, Bay.bln
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln
Figure 14. Inferred thickness of Layer 2 (m)
[Modified after Woodward-Clyde, 1996]
Botany Hydraulic Containment
C04/44/001
58
-55 -50 -45 -40 -35 -30 -25 -20 -15 -10
6244500
-5
0
5
10
mAHD
DACEYVILLE
EASTLAKES
6244000
6243500
PAGEWOOD
6243000
NORTHING (m MGA)
BOTANY
6242500
EAST BOTANY
HILLSDALE
6242000
6241500
BANKSMEADOW
6241000
BOTANY
BAY
6240500
6240000
6239500
332500
333000
333500
334000
334500
335000
335500
336000
336500
337000
337500
EASTING (m MGA)
0m
1000m
2000m
3000m
4000m
[Botany][Orica2004] [Maps] GVbedrock.SRF
GVthick3.csv, GVbedrock.grd, WL.clr
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew, Bay.bln
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln
Figure 15. Inferred bedrock topography at the base of Layer 3 (mAHD)
[Modified after Woodward-Clyde, 1996]
Botany Hydraulic Containment
C04/44/001
59
0
5
10
6244500
15
20
25
30
35
40
45
50
mAHD
DACEYVILLE
EASTLAKES
6244000
6243500
PAGEWOOD
6243000
NORTHING (m MGA)
BOTANY
6242500
EAST BOTANY
HILLSDALE
6242000
6241500
BANKSMEADOW
6241000
6240500
BOTANY
BAY
6240000
6239500
332500
333000
333500
334000
334500
335000
335500
336000
336500
337000
337500
EASTING (m MGA)
Each grid square is 100 metres
0m
1000m
2000m
3000m
4000m
[Botany][Orica2004] [Optim5E] [RunS4CAL]
STEADY1.SRF
ALLtopo.csv, .grd, WL.clr
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln
[Maps] BlankBAY.bln, BAY.bln, FSdrain.bln
[Optim5E][RunS4CAL] ST1.grd
Figure 16. Simulated water table contours in Layer 1 (mAHD),
superposed on surface topography
Botany Hydraulic Containment
C04/44/001
60
0
5
10
6244500
15
20
25
30
35
40
50 mAHD
45
DACEYVILLE
EASTLAKES
6244000
6243500
PAGEWOOD
6243000
NORTHING (m MGA)
BOTANY
6242500
EAST BOTANY
HILLSDALE
6242000
6241500
BANKSMEADOW
6241000
6240500
BOTANY
BAY
6240000
6239500
332500
333000
333500
334000
334500
335000
335500
336000
336500
337000
337500
EASTING (m MGA)
Each grid square is 100 metres
Water Level Measurement
0m
1000m
2000m
3000m
4000m
[Botany][Orica2004] [Optim5E] [RunS4CAL]
STEADY2.SRF, ST2.grd
ALLtopo.csv, .grd, WL.clr
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln
[Maps] BlankBAY.bln, BAY.bln, FSdrain.bln
WL-PORT.grd, .xls
Figure 17. Simulated groundwater level contours in Layer 2A (mAHD),
compared with 2000-2002 interpolated measurements (dashed contours),
superposed on surface topography
Botany Hydraulic Containment
C04/44/001
61
18
16
Simulated Head (mAHD)
14
12
10
8
6
4
2
0
0
2
4
6
8
10
12
Observed Head (mAHD)
14
16
18
[Botany][Orica2004][Optim5E]
[runS4CAL] scatter.grf
target.out
Figure 18. Scattergram of simulated and observed groundwater levels
Botany Hydraulic Containment
C04/44/001
62
6244500
DACEYVILLE
EASTLAKES
6244000
6243500
PAGEWOOD
6243000
NORTHING (m MGA)
BOTANY
6242500
EAST BOTANY
HILLSDALE
6242000
6241500
BANKSMEADOW
6241000
6240500
BOTANY
BAY
6240000
6239500
332500
333000
333500
334000
334500
335000
335500
336000
336500
337000
337500
EASTING (m MGA)
Each grid square is 100 metres
0m
1000m
-0.8
-0.6
2000m
-0.4
-0.2
3000m
-0.0
0.2
[Botany][Orica2004] [Optim5E] [RunS4CAL]
H1-H2.SRF, H1-H2.grd, DEL.clr
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln
BlankBAY.bln, BAY.bln
4000m
0.4
0.6
0.8
1.0
1.2
Figure 19. Simulated vertical head difference between Layer 1 and Layer 2A (m).
[Negative values imply upwards flow; Positive values imply downwards flow.]
Botany Hydraulic Containment
C04/44/001
63
Snape Park
Borefield
Lachla
Swamp
n
s
PAGEWOOD
SNAPE
GOLF
6243000
Solvay Interox
Borefield
SOLVAY
6242500
EAST BOTANYORICA1
Brighton St
Stephens Rd
DYES
S11
Springvale Drain
6242000
Orica
Borefield
BOTANY ORICA2
INDUSTRIAL
PARK
HEFFRON
HILLSDALE
ORICA3
S10
6241500
S7
B an
ks
P
BANKSMEADOW
POND
6241000
Bo
t
tan
yR
oa
d
DRAIN2
S4
Southla
nds
DRAIN3
S3
Road
De
nt S
ORICA
g
eron
ark
S9
DRAIN1
S8
Bunn
sep
h
St
Sir
Jo
Floodvale Drain
rd
rfo
He
NORTHING (m MGA)
HENSLEY
S6
S5
S2
6240500
S1
BAY1
BAY2
BOTANY
BAY
BAY4
BAY5
BAY3 Estuary
334000
Fo
re
Penrhyn
334500
335000
335500
EASTING (m MGA)
Production Bore
Drawdown Monitoring Site
Subsidence Monitoring Site
sh
ore
Ro
ad
336000
336500
[Botany][Orica] [Hotspots] CRITICAL.SRF
[Grid12] ShoreOld, Roads, Orica.bln
[Orica] Border8MGA.bln, Stephens.bln
Penrhyn, MStream, FSdrain.bln
Towns.xy, [Orica]Current.3, Legend.Use
[Botany] PondMGA.bln, DamMGA.Bln
[Hotspots] Critical.Dat, Subside.dat
Figure 20. Critical locations for monitoring groundwater drawdown
Botany Hydraulic Containment
C04/44/001
64
6242400
EAST BOTANY
6242200
6242000
NORTHING (m MGA)
6241800
6241600
6241400
BANKSMEADOW
6241200
6241000
6240800
6240600
BOTANY
BAY
6240400
334000
334200
334400
334600
334800
335000
335200
335400
EASTING (m MGA)
Interception Bore
Each grid square is 200 metres
0m
250m
500m
750m
EDC June 2004
1000m
335600
335800
336000
[Botany][Orica2004] [Optim5E] [RunS6] AllBores.SRF
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln, Stephen.bln
BlankBAY.bln, BAY.bln, Floodvale.bln
[Optim5E] [RunS6] S6.csv
[Plumes] EDC June04.bln
Figure 21. Optimal locations of all drilling sites on all containment lines, in
relation to the EDC plumes at June 2004
Botany Hydraulic Containment
C04/44/001
65
6242400
EAST BOTANY
6242200
6242000
NORTHING (m MGA)
6241800
6241600
6241400
BANKSMEADOW
6241200
6241000
6240800
0.03
6240600
BOTANY
BAY
6240400
334000
334200
0.01
334400
334600
334800
335000
335200
335400
EASTING (m MGA)
Interception Bore
Each grid square is 200 metres
0m
250m
500m
750m
EDC June 2004
1000m
335600
335800
336000
[Botany][Orica2004] [Optim5E] [RunS6] H1.SRF
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln, Stephen.bln
BlankBAY.bln, BAY.bln, Floodvale.bln
[Optim5E] [RunS6] S6L1.csv, H1.grd
[Plumes] EDC June04.bln
Figure 22. Simulated groundwater levels in Layer 1 for optimal hydraulic
containment (mAHD)
Botany Hydraulic Containment
C04/44/001
66
6242400
EAST BOTANY
6242200
6242000
NORTHING (m MGA)
6241800
6241600
6241400
BANKSMEADOW
6241200
6241000
6240800
-0.03
6240600
BOTANY
BAY
6240400
334000
334200
0.01
334400
334600
334800
335000
335200
335400
EASTING (m MGA)
Interception Bore
Each grid square is 200 metres
0m
250m
500m
750m
EDC June 2004
1000m
335600
335800
336000
[Botany][Orica2004] [Optim5E] [RunS6] H2.SRF
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln, Stephen.bln
BlankBAY.bln, BAY.bln, Floodvale.bln
[Optim5E] [RunS6] S6L2.csv, H2.grd
[Plumes] EDC June04.bln
Figure 23. Simulated groundwater levels in Layer 2A for optimal hydraulic
containment (mAHD)
Botany Hydraulic Containment
C04/44/001
67
6242400
EAST BOTANY
6242200
6242000
NORTHING (m MGA)
6241800
6241600
6241400
BANKSMEADOW
6241200
6241000
6240800
-0.03
6240600
BOTANY
BAY
6240400
334000
334200
0.01
334400
334600
334800
335000
335200
335400
EASTING (m MGA)
Interception Bore
Each grid square is 200 metres
0m
250m
500m
750m
EDC June 2004
1000m
335600
335800
336000
[Botany][Orica2004] [Optim5E] [RunS6] H3.SRF
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln, Stephen.bln
BlankBAY.bln, BAY.bln, Floodvale.bln
[Optim5E] [RunS6] S6L3.csv, H3.grd
[Plumes] EDC June04.bln
Figure 24. Simulated groundwater levels in Layer 2B for optimal hydraulic
containment (mAHD)
Botany Hydraulic Containment
C04/44/001
68
6242400
EAST BOTANY
6242200
6242000
NORTHING (m MGA)
6241800
6241600
6241400
BANKSMEADOW
6241200
6241000
6240800
-0.03
6240600
BOTANY
BAY
6240400
334000
334200
0.01
334400
334600
334800
335000
335200
335400
EASTING (m MGA)
Interception Bore
Each grid square is 200 metres
0m
250m
500m
750m
EDC June 2004
1000m
335600
335800
336000
[Botany][Orica2004] [Optim5E] [RunS6] H4.SRF
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln, Stephen.bln
BlankBAY.bln, BAY.bln, Floodvale.bln
[Optim5E] [RunS6] S6L4.csv, H4.grd
[Plumes] EDC June04.bln
Figure 25. Simulated groundwater levels in Layer 2C for optimal hydraulic
containment (mAHD)
Botany Hydraulic Containment
C04/44/001
69
6242400
EAST BOTANY
6242200
6242000
NORTHING (m MGA)
6241800
6241600
6241400
BANKSMEADOW
6241200
6241000
6240800
-0.03
6240600
BOTANY
BAY
6240400
334000
334200
0.01
334400
334600
334800
335000
335200
335400
EASTING (m MGA)
Interception Bore
Each grid square is 200 metres
0m
250m
500m
750m
EDC June 2004
1000m
335600
335800
336000
[Botany][Orica2004] [Optim5E] [RunS6] H5.SRF
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln, Stephen.bln
BlankBAY.bln, BAY.bln, Floodvale.bln
[Optim5E] [RunS6] H5.grd
[Plumes] EDC June04.bln
Figure 26. Simulated groundwater levels in Layer 3 for optimal hydraulic
containment (mAHD)
Botany Hydraulic Containment
C04/44/001
70
Figure 27. Capture zones for (red) particles originating in Layer 1.
Figure 28. Capture zones for (blue) particles originating in Layer 2A.
Botany Hydraulic Containment
C04/44/001
71
Figure 29. Capture zones for (green) particles originating in Layer 2B.
Figure 30. Capture zones for (silver) particles originating in Layer 2C.
Botany Hydraulic Containment
C04/44/001
72
Figure 31. Capture zones for (magenta) particles originating in Layer 3.
Botany Hydraulic Containment
C04/44/001
73
6242400
EAST BOTANY
6242200
6242000
10.0
NORTHING (m MGA)
6241800
6241600
10.0
2.4
7.0
6241400
5.5
BANKSMEADOW
6241200
3.2
2.4
6241000
2.4
3.0
6240800
0.9
1.0
6240600
BOTANY
BAY
6240400
334000
334200
334400
334600
Subsidence Constraint (m)
Drawdown Monitoring Site
334800
Each grid square is 200 metres
0m
250m
500m
335000
335200
335400
EASTING (m MGA)
750m
Interception Bore
EDC June 2004
1000m
335600
335800
336000
[Botany][Orica2004] [Optim5E] [RunS6] DD1.SRF
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln, Stephen.bln
BlankBAY.bln, BAY.bln, Floodvale.bln
[Optim5E] [RunS6] S6L1.csv, DD1.grd
Critical.dat, Subside.dat
[Plumes] EDC June04.bln
Figure 32. Simulated groundwater drawdowns in Layer 1 for optimal
hydraulic containment (m)
[Subsidence drawdown limits are posted.]
Botany Hydraulic Containment
C04/44/001
74
6242400
EAST BOTANY
6242200
6242000
10.0
NORTHING (m MGA)
6241800
6241600
10.0
2.4
7.0
6241400
5.5
BANKSMEADOW
6241200
3.2
2.4
6241000
2.4
3.0
6240800
0.9
1.0
6240600
BOTANY
BAY
6240400
334000
334200
334400
334600
Subsidence Constraint (m)
Drawdown Monitoring Site
334800
Each grid square is 200 metres
0m
250m
500m
335000
335200
335400
EASTING (m MGA)
750m
Interception Bore
EDC June 2004
1000m
335600
335800
336000
[Botany][Orica2004] [Optim5E] [RunS6] DD2.SRF
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln, Stephen.bln
BlankBAY.bln, BAY.bln, Floodvale.bln
[Optim5E] [RunS6] S6L2.csv, DD2.grd
Critical.dat, Subside.dat
[Plumes] EDC June04.bln
Figure 33. Simulated groundwater drawdowns in Layer 2A for optimal
hydraulic containment (m)
[Subsidence drawdown limits are posted.]
Botany Hydraulic Containment
C04/44/001
75
6242400
EAST BOTANY
6242200
6242000
10.0
NORTHING (m MGA)
6241800
6241600
10.0
2.4
7.0
6241400
5.5
BANKSMEADOW
6241200
3.2
2.4
6241000
2.4
3.0
6240800
0.9
1.0
6240600
BOTANY
BAY
6240400
334000
334200
334400
334600
Subsidence Constraint (m)
Drawdown Monitoring Site
334800
Each grid square is 200 metres
0m
250m
500m
335000
335200
335400
EASTING (m MGA)
750m
Interception Bore
EDC June 2004
1000m
335600
335800
336000
[Botany][Orica2004] [Optim5E] [RunS6] DD3.SRF
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln, Stephen.bln
BlankBAY.bln, BAY.bln, Floodvale.bln
[Optim5E] [RunS6] S6L3.csv, DD3.grd
Critical.dat, Subside.dat
[Plumes] EDC June04.bln
Figure 34. Simulated groundwater drawdowns in Layer 2B for optimal
hydraulic containment (m)
Botany Hydraulic Containment
C04/44/001
76
6242400
EAST BOTANY
6242200
6242000
10.0
NORTHING (m MGA)
6241800
6241600
10.0
2.4
7.0
6241400
5.5
BANKSMEADOW
6241200
3.2
2.4
6241000
2.4
3.0
6240800
0.9
1.0
6240600
BOTANY
BAY
6240400
334000
334200
334400
334600
Subsidence Constraint (m)
Drawdown Monitoring Site
334800
Each grid square is 200 metres
0m
250m
500m
335000
335200
335400
EASTING (m MGA)
750m
Interception Bore
EDC June 2004
1000m
335600
335800
336000
[Botany][Orica2004] [Optim5E] [RunS6] DD4.SRF
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln, Stephen.bln
BlankBAY.bln, BAY.bln, Floodvale.bln
[Optim5E] [RunS6] S6L4.csv, DD4.grd
Critical.dat, Subside.dat
[Plumes] EDC June04.bln
Figure 35. Simulated groundwater drawdowns in Layer 2C for optimal
hydraulic containment (m)
Botany Hydraulic Containment
C04/44/001
77
6242400
EAST BOTANY
6242200
6242000
10.0
NORTHING (m MGA)
6241800
6241600
10.0
2.4
7.0
6241400
5.5
BANKSMEADOW
6241200
3.2
2.4
6241000
2.4
3.0
6240800
0.9
1.0
6240600
BOTANY
BAY
6240400
334000
334200
334400
334600
Subsidence Constraint (m)
Drawdown Monitoring Site
334800
Each grid square is 200 metres
0m
250m
500m
335000
335200
335400
EASTING (m MGA)
750m
Interception Bore
EDC June 2004
1000m
335600
335800
336000
[Botany][Orica2004] [Optim5E] [RunS6] DD5.SRF
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln, Stephen.bln
BlankBAY.bln, BAY.bln, Floodvale.bln
[Optim5E] [RunS6] DD5.grd
Critical.dat, Subside.dat
[Plumes] EDC June04.bln
Figure 36. Simulated groundwater drawdowns in Layer 3 for optimal
hydraulic containment (m)
Botany Hydraulic Containment
C04/44/001
78
6244500
DACEYVILLE
EASTLAKES
6244000
6243500
PAGEWOOD
6243000
NORTHING (m MGA)
BOTANY
6242500
EAST BOTANY
HILLSDALE
6242000
6241500
BANKSMEADOW
6241000
6240500
BOTANY
BAY
6240000
6239500
332500
333000
333500
334000
334500
Interception Bore
0m
500m
1000m
335000
335500
EASTING (m MGA)
1500m
2000m
336000
336500
337000
337500
[Botany][Orica2004] [Model5E] [RunSUB3] SUBbase.grd, .srf
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln, Stephen.bln
BlankBAY.bln, BAY.bln, Floodvale.bln
[Optim5E] [RunS6] S6.csv
[Plumes] EDC June04.bln
Figure 37. Anticipated subsidence for the Base Case, ignoring prior
consolidation
Botany Hydraulic Containment
C04/44/001
79
6242400
EAST BOTANY
6242200
6242000
6241800
NORTHING (m MGA)
6241600
6241400
BANKSMEADOW
6241200
6241000
6240800
6240600
BOTANY
BAY
6240400
6240200
334000
334200
334400
334600
334800
Interception Bore
0m
200m
400m
335000
335200
EASTING (m MGA)
600m
800m
1000m
335400
335600
335800
336000
[Botany][Orica2004] [Model5E] [RunSUB5] SUBbase2.grd, .srf
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln, Stephen.bln
BlankBAY.bln, BAY.bln, Floodvale.bln
[Optim5E] [RunS6] S6.csv
[Plumes] EDC June04.bln
Figure 38. Anticipated subsidence for the Likely Case, taking account of
prior consolidation
Botany Hydraulic Containment
C04/44/001
80
6242600
6242400
EAST BOTANY
6242200
6242000
NORTHING (m MGA)
6241800
6241600
0.001
6241400
BANKSMEADOW
6241200
6241000
6240800
0.001
6240600
6240400
BOTANY
BAY
0.001
6240200
334000
334200
334400
334600
334800
Interception Bore
0m
200m
400m
335000
335200
EASTING (m MGA)
600m
800m
1000m
335400
335600
335800
336000
336200
[Botany][Orica2004] [Model5E] [RunSUB6] SUBworst2.grd, .srf
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln, Stephen.bln
BlankBAY.bln, BAY.bln, Floodvale.bln
[Optim5E] [RunS6] S6.csv
[Plumes] EDC June04.bln
Figure 39. Anticipated subsidence for the Worst Case, taking account of
prior consolidation
Botany Hydraulic Containment
C04/44/001
81
6242400
EAST BOTANY
6242200
6242000
NORTHING (m MGA)
6241800
6241600
6241400
BANKSMEADOW
6241200
6241000
6240800
6240600
-0.03
BOTANY
BAY
6240400
334000
334200
334400
334600
334800
335000
335200
335400
EASTING (m MGA)
Interception Bore
Each grid square is 200 metres
0m
250m
500m
750m
EDC June 2004
1000m
335600
335800
336000
[Botany][Orica2004] [Optim5E] [RunS8] H1.SRF
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln, Stephen.bln
BlankBAY.bln, BAY.bln, Floodvale.bln
[Optim5E] [RunS8] S6L1.csv, H1.grd
[Plumes] EDC June04.bln
Figure 40. Simulated groundwater levels in Layer 1 for optimal hydraulic
containment (mAHD), and low water level in drains
Botany Hydraulic Containment
C04/44/001
82
6242400
EAST BOTANY
6242200
6242000
NORTHING (m MGA)
6241800
6241600
6241400
BANKSMEADOW
6241200
6241000
6240800
6240600
-0.03
BOTANY
BAY
6240400
334000
334200
334400
334600
334800
335000
335200
335400
EASTING (m MGA)
Interception Bore
Each grid square is 200 metres
0m
250m
500m
750m
EDC June 2004
1000m
335600
335800
336000
[Botany][Orica2004] [Optim5E] [RunS8] H2.SRF
[Grid12] ShoreOld, Roads, Orica.bln
VNewport, ShoreNew
Penrhyn, MStream, FSdrain.bln
[Botany] PondMGA.bln,DamMGA.bln
Towns.xy, Lakes.bln, Stephen.bln
BlankBAY.bln, BAY.bln, Floodvale.bln
[Optim5E] [RunS8] S6L2.csv, H2.grd
[Plumes] EDC June04.bln
Figure 41. Simulated groundwater levels in Layer 2A for optimal hydraulic
containment (mAHD), and low water level in drains
Botany Hydraulic Containment
C04/44/001
83
APPENDIX
Botany Primary Containment
C04/44/001
84
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
125
130
135
140
145
150
155
160
165
170
175
180
185
190
195
200
205
210
215
220
225
230
Prescribed
Flow
Constant
Head
Inactive
Cells
Figure A1. Model grid and boundary conditions for Layer 1
Botany Hydraulic Containment
C04/44/001
85
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
125
130
135
140
145
150
155
160
165
170
175
180
185
190
195
200
205
210
215
220
225
230
Production
Bores
Figure A2. Model grid and boundary conditions for Layer 2
Botany Hydraulic Containment
C04/44/001
86
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
125
130
135
140
145
150
155
160
165
170
175
180
185
190
195
200
205
210
215
220
225
230
Figure A3. Model grid and boundary conditions for Layer 3
Botany Hydraulic Containment
C04/44/001
87
22% Rain
Recharge
10% Rain
Recharge
37% Rain
Recharge
Figure A4. Land use pattern for rainfall recharge distribution
Botany Hydraulic Containment
C04/44/001
88
30 m/d
40 m/d
32 m/d
Figure A5. Calibrated hydraulic conductivity pattern in Layer 2
Botany Hydraulic Containment
C04/44/001
89
Figure A6. Sensitivity to hydraulic conductivity for Layer 1: Base value 20 m/day
Botany Hydraulic Containment
C04/44/001
90
Figure A7. Sensitivity to hydraulic conductivity for Layer 2: Base value 30 m/day
Botany Hydraulic Containment
C04/44/001
91
Figure A8. Sensitivity to leakance (Layer 1/2A and Layer 2C/3): Base value 0.05/day
Botany Hydraulic Containment
C04/44/001
92
Figure A9. Sensitivity to low rainfall recharge zone: Base value 10% rain
Botany Hydraulic Containment
C04/44/001
93
Figure A10. Sensitivity to medium rainfall recharge zone: Base value 22% rain
Botany Hydraulic Containment
C04/44/001
94
Figure A11. Sensitivity to high rainfall recharge zone: Base value 37% rain
Botany Hydraulic Containment
C04/44/001
95
Figure A12. Sensitivity to conductance, Springvale Drain north: Base value 160 m2/day
Botany Hydraulic Containment
C04/44/001
96
Figure A13. Sensitivity to conductance, Floodvale Drain north: Base value 160 m2/day
Botany Hydraulic Containment
C04/44/001
97
Table A1. Calibration target groundwater levels
EAST(MGA)
333504
333226
334096
334054
334118
332736
332676
334046
333928
335159
335159
335159
335159
335151
335151
335151
335151
335201
335201
335201
335212
335212
335212
335111
335111
335111
335123
335123
335123
335125
335125
335125
335211
335205
335205
335202
335198
335487
335474
335353
335461
335422
335350
335422
335337
335275
335082
335155
335173
335189
335242
334935
335324
335141
335496
335108
335208
335248
335298
335359
NORTH(MGA)
6241208
6241689
6241118
6241017
6240958
6242205
6242421
6241144
6241235
6241406
6241406
6241406
6241406
6241405
6241405
6241405
6241405
6241282
6241282
6241282
6241290
6241290
6241290
6241852
6241852
6241852
6241853
6241853
6241853
6241856
6241856
6241856
6241282
6241290
6241278
6241282
6241286
6241759
6241773
6241788
6241642
6241565
6242207
6241990
6241702
6241946
6241839
6241912
6241878
6241856
6242204
6242030
6242206
6242097
6241308
6241967
6241286
6241245
6241205
6241154
Botany Hydraulic Containment
C04/44/001
SWL(mAHD)
0.539
0.867
0.81
0.693
0.6
0.55
0.268
0.895
1.229
3.32
3.83
3.8
3.3
3.19
3.79
3.77
3.22
3.87
3.71
3.65
3.94
3.84
3.83
4.95
4.74
4.72
4.76
4.76
4.77
4.79
4.8
4.81
3.81
3.78
3.75
3.73
3.73
6.99
6.92
6.43
6.69
6.18
9.04
8.11
6.13
7.26
4.72
5.95
5.89
5.86
8.23
5.39
8.88
6.53
5.35
6.14
3.975
3.92
3.95
4.18
BORE
MSB12
MSB17
GC13
GC14
GC15
MSB21
MSB22
POND
SJB4
SP028A
SP028D
SP028I
SP028S
SP029A
SP029D
SP029I
SP029S
SP21D
SP21I
SP21S
SP22D
SP22I
SP22S
SP24D
SP24I
SP24S
SP26D
SP26I
SP26S
SP27D
SP27I
SP27S
WG100S
WG102S
WG103S
WG104S
WG105S
WG107
WG108
WG110
WG111
WG113
WG114
WG115
WG116
WG117
WG118
WG119
WG120
WG121
WG122
WG123S
WG127
WG128
WG13
WG130
WG137
WG139
WG140
WG141
LAYER
1
1
1
1
1
1
1
1
1
3
3
2
1
3
3
2
1
3
2
1
3
2
1
3
2
1
3
2
1
3
2
1
1
1
1
1
1
3
3
3
3
3
3
3
3
3
3
3
3
3
3
1
3
3
3
3
3
3
3
3
DATE
2-May-02
2-May-02
1-May-02
1-May-02
1-May-02
1-May-02
1-May-02
1-May-02
1-May-02
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
98
334551
334382
335010
334725
334968
335663
335032
335120
335120
335182
335208
335284
335725
335850
335510
335215
335152
335164
335152
335318
334902
335559
335219
335255
335425
335565
334944
335486
335487
334798
335418
335403
335126
335126
334429
335349
335347
335131
335128
335124
334390
334386
334388
335263
334997
334996
334994
335049
335049
334011
334009
335160
335185
334872
334834
335242
335241
335588
335587
335587
334903
334902
334904
334905
334371
334371
335632
335628
6240697
6240752
6241244
6240663
6241185
6241750
6241352
6241058
6241058
6241131
6241336
6241341
6241030
6241401
6241441
6241641
6241725
6241838
6241609
6241524
6242109
6241879
6242074
6241963
6242106
6242247
6241337
6241321
6241319
6240654
6241366
6241381
6241639
6241641
6242388
6241230
6241230
6241341
6241341
6241342
6241489
6241483
6241485
6241033
6241088
6241088
6241088
6240689
6240689
6240956
6240958
6241405
6241266
6241360
6241118
6241316
6241317
6241688
6241687
6241687
6242104
6242103
6241558
6241560
6240964
6240963
6241616
6242222
Botany Hydraulic Containment
C04/44/001
0.77
0.58
3.15
0.74
2.88
7.81
3.23
2.63
2.49
2.325
3.08
3.6
5.85
8.15
6.62
4.24
4.41
5.25
6.78
5.14
5.7
7.36
7.03
6.1
8.09
10.26
3.61
5.03
6.85
1.24
4.68
5.51
4.39
4.6
6.45
4.1
4.06
3.74
3.73
3.42
2.51
3.1
3.3
3.07
2.66
2.48
2.45
1.27
1.36
0.32
0.37
3.78
3.4
2.865
2.25
4.16
4.005
7.48
7.13
7.59
5.75
6.15
3.62
3.53
1.02
0.84
8.77
10.35
WG144
WG145
WG146I
WG143
WG147I
WG148I
WG149S
WG16D
WG16I
WG20
WG28
WG29
WG32
WG35
WG37
WG38
WG39
WG40
WG41
WG42
WG43
WG45
WG47
WG48
WG49
WG50
WG61
WG62
WG65
WG66
WG67D
WG67S
WG68D
WG68I
WG69S
WG70D
WG70I
WG71D
WG71I
WG71S
WG72D
WG72I
WG72S
WG73D
WG74D
WG74I
WG74S
WG75D
WG75I
WG76D
WG76S
WG77S
WG78S
WG79S
WG80S
WG82D
WG82S
WG83D
WG83I
WG83S
WG84D
WG84I
WG86D
WG86I
WG88I
WG88S
WG90S
WG93S
3
3
2
3
2
2
1
3
2
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
1
3
2
1
3
2
3
2
1
3
2
1
3
3
2
1
3
2
3
1
1
1
1
1
3
1
3
2
1
3
2
3
2
2
1
1
1
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
99
335674
335560
335217
335684
335214
335211
333236
333595
334348
336391
334346
334891
335923
335841
333675
336601
333768
336314
335394
335313
334613
334533
334334
333194
332973
332574
332514
332534
332684
332954
333134
332784
332644
332554
6242306
6242294
6241287
6242245
6241291
6241295
6242244
6242020
6241420
6240127
6240150
6242964
6244146
6241290
6242160
6242211
6242778
6243993
6244375
6243695
6243405
6243385
6243465
6243125
6241905
6242615
6242685
6242745
6242795
6242915
6242765
6242435
6242555
6242535
Botany Hydraulic Containment
C04/44/001
10.61
9.83
3.85
10.41
3.86
3.85
1.54
2.71
1.7
3.6
0.06
9.316
15.852
6.523
3.73
16.9
4.45
16.55
14.26
14.25
10.09
9.94
8.25
3.53
0.4
0.96
1.14
1.59
1.78
1.79
1.76
0.41
0.81
0.48
WG95S
WG96S
WG97S
WG94S
WG98S
WG99S
40776
40777
40778
75019
40783
42161
42169
42176
75023
75021
75022
75025
LAKE
LAKE
LAKE
LAKE
LAKE
LAKE
MSB18
SA14
SA15
SA16
SA17
SA18
SA2
SA3
SA5
SA6
1
1
1
1
1
3
3
3
3
3
3
3
3
3
3
3
3
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
20-Apr-00
20-Apr-00
20-Apr-00
20-Apr-00
19-Apr-00
19-Apr-00
19-Apr-00
19-Apr-00
14-Mar-00
13-Mar-00
13-Mar-00
13-Mar-00
15-Mar-94
14-Mar-94
13-Mar-94
12-Mar-94
11-Mar-94
10-Mar-94
1-Jan-94
1-Jan-94
1-Jan-94
1-Jan-94
1-Jan-94
1-Jan-94
1-Jan-94
1-Jan-94
1-Jan-94
1-Jan-94
100
Table A2. Vertical head differences
EAST(MGA)
335159
335151
335201
335212
335111
335123
335125
334798
335403
335126
335347
335124
334388
334994
335049
334009
335241
335587
334902
334905
334371
335090
334348
334346
335923
335876
335801
335693
335841
335633
NORTH(MGA)
h1-h2(m)
6241406
6241405
6241282
6241290
6241852
6241853
6241856
6240654
6241381
6241641
6241230
6241342
6241485
6241088
6240689
6240958
6241317
6241687
6242103
6241560
6240963
6240650
6241420
6240150
6244146
6240580
6240604
6240548
6241290
6240937
Botany Hydraulic Containment
C04/44/001
-0.53
-0.57
-0.22
-0.11
-0.23
0.01
0.02
-0.76
0.83
0.21
-0.04
-0.32
0.79
-0.21
0.09
0.05
-0.16
0.11
0.40
-0.09
-0.18
0.15
1.00
0.00
0.00
0.10
0.40
0.20
0.00
0.00
SHALLOW(mAHD)
3.3
3.22
3.65
3.83
4.72
4.77
4.81
0.62
5.51
4.6
4.06
3.42
3.3
2.45
1.36
0.37
4.005
7.59
6.15
3.53
0.84
1
1.7
0.06
15.852
3.7
3.6
2.8
6.523
4.7
DEEP(mAHD)
3.83
3.79
3.87
3.94
4.95
4.76
4.79
1.38
4.68
4.39
4.1
3.74
2.51
2.66
1.27
0.32
4.16
7.48
5.75
3.62
1.02
0.85
0.70
0.06
15.85
3.60
3.20
2.60
6.52
4.70
BORE1
BORE2
SP028S
SP029S
SP21S
SP22S
SP24S
SP26S
SP27S
WG66
WG67S
WG68I
WG70I
WG71S
WG72S
WG74S
WG75I
WG76S
WG82S
WG83S
WG84I
WG86I
WG88S
40772/1
40778/1
40783/1
42169/1
42170/1
42171/1
42172/1
42176/1
42177/1
SP028D
SP029D
SP21D
SP22D
SP24D
SP26D
SP27D
WG63
WG67D
WG68D
WG70D
WG71D
WG72D
WG74D
WG75D
WG76D
WG82D
WG83D
WG84D
WG86D
WG88I
40772/2
40778/3
40783/2
42169/2
42170/2
42171/2
42172/2
42176/2
42177/2
DATE
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
16-Sep-94
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
30-May-00
2000
20-Apr-00
19-Apr-00
19-Apr-00
2000
2000
2000
19-Apr-00
2000
101
Table A3. Locations of bores on all containment lines with optimal pumping rates (m3/day)
EASTING NORTHING
335065
6241825
335115
6241835
335095
6241795
335125
6241765
ROW
94
93
97
100
COL NAME LINE LAYER LYR1 LYR 2A LYR 2B LYR 2C TOTAL
107 G20A LINE 6B
1
0
150
130
85
365
112
G21 LINE 6B
1
0
0
0
0
0
110
G22 LINE 6B
1
0
150
130
85
365
113
G23 LINE 6B
1
0
57.9
174.6 232.5
0
335135
6241745 102
114
G24
LINE 6B
1
335145
6241725 104
115
335165
6241705 106
117
G25
LINE 6B
1
G26
LINE 6C
1
335185
6241685 108
119
G27
LINE 6C
1
335205
6241665 110
121
G28
LINE 6C
335215
6241635 113
122
G29
335235
335275
335295
6241615 115
6241715 105
6241695 107
124
128
130
335315
6241675 109
335335
335355
335375
335395
6241655
6241625
6241605
6241575
133.2
0
104.6
0
0
34.3
58.4
92.7
10
35.1
45.6
88.1
178.8
10
30
0
129.9
169.9
1
10
30
181.8
0
221.8
LINE 6C
1
10
0
57.5
42.4
109.9
G30
F-1
FO
LINE 6C
LINE 5
LINE 5
1
1
1
10
0
100
0
0
500
0
150
160
0
600
132
F1
LINE 5
1
30
300
330
111
114
116
119
134
136
138
140
F2
F3
F4
F5
LINE 5
LINE 5
LINE 5
LINE 5
1
1
1
1
30
30
30
30
300
300
300
250
330
330
330
280
335395
6241515 125
140
F6
LINE 5
1
0
0
0
335415
335415
335435
335275
335455
335465
335485
6241495
6241545
6241515
6241645
6241495
6241475
6241455
127
122
125
112
127
129
131
142
142
144
128
146
147
149
F7
F8
F9
F10
F11
F12
F13
LINE 5
LINE 5
LINE 5
LINE 5
LINE 5
LINE 5
LINE 5
1
1
1
1
1
1
1
0
30
30
0
30
30
0
0
250
250
0
250
150
0
0
280
280
0
280
180
0
334935
6242155 61
94
G4
LINE 6A
2B
37.8
99.5
131.3
0
268.6
334935
334935
6242115 65
6242075 69
94
94
G6
G8
LINE 6A
LINE 6A
2B
2B
32.6
18.9
71.8
45.2
0
0
113.9
44.5
218.3
108.6
334935
6242015 75
94
G11
LINE 6A
2B
92.7
209.9
376.8
0
679.4
334945
334965
6241995 77
6241975 79
95
97
G12
G13
LINE 6A
LINE 6A
2B
2B
0
112.8
0
217.4
0
387.1
0
0
0
717.3
334975
334995
6241955 81
6241935 83
98
100
G14
G15
LINE 6A
LINE 6A
2B
2B
0
79.6
0
147.7
0
288.5
0
0
0
515.8
335005
335025
6241915 85
6241895 87
101
103
G16
G17
LINE 6A
LINE 6A
2B
2B
0
172.5
0
200
0
395.4
0
0
0
767.9
335035
335055
6241875 89
6241855 91
104
106
G18
G19
LINE 6A
LINE 6A
2B
2B
0
99.4
0
175
0
90.8
0
170
0
535.2
334855
334855
6241215 155
6241195 157
86
86
AA1
AA2
LINE A
LINE A
2A
2A
0
0
0
0
0
0
0
0
334845
334845
6241135 163
6241095 167
85
85
AA3
AA4
LINE A
LINE A
2A
2A
0
223.6
0
0
0
92.2
0
315.8
334885
335005
6241085 168
6241065 170
89
101
A19
A25
LINE A
LINE A
1
1
Botany Hydraulic Containment
C04/44/001
0
0
0
237.8
0
0
102
335025
335045
335065
335085
6241055
6241055
6241055
6241045
171
171
171
172
103
105
107
109
A26
A27
A28
A29
LINE A
LINE A
LINE A
LINE A
1
1
1
1
0
0
0
0
0
0
0
335105
335125
6241045 172
6241035 173
111
113
A30
A31
LINE A
LINE A
1
1
335145
335175
6241035 173
6241035 173
115
118
A32
H1
LINE A
LINE 1
335195
335215
335235
335255
6241025
6241025
6241025
6241015
174
174
174
175
120
122
124
126
H2
H3
H4
H5
335275
335295
6241015 175
6241005 176
128
130
335315
334263
6241005 176
6240785 198
334288
334313
334338
329
112.1
0
0
0
0
50.7
0
50.7
0
1
1
0
0
296.4
83.6
0
380
0
LINE 1
LINE 1
LINE 1
LINE 1
1
1
1
1
0
0
0
0
0
0
86.8
351.9
0
89.8
86.8
0
441.7
0
H6
H7
LINE 1
LINE 1
1
1
0
0
82
91.6
0
173.6
0
132
35
H8
D-6
LINE 1
LINE 2
1
1
0
0
0
0
0
91.5
0
0
0
91.5
6240775 199
6240765 200
6240755 201
36
37
38
D-5
D-4
D-3
LINE 2
LINE 2
LINE 2
1
1
1
24.4
10
10
0
198.6
0
116.3
0
0
24.4
324.9
10
334363
334405
6240745 202
6240735 203
39
41
D-2
D-1
LINE 2
LINE 2
1
1
11.6
10
0
0
30
41.6
10
334425
334445
6240725 204
6240715 205
43
45
D0
D1
LINE 2
LINE 2
1
1
10
10
44
79.1
0
133.1
10
334465
334485
334505
6240715 205
6240715 205
6240705 206
47
49
51
D2
D3
D4
LINE 2
LINE 2
LINE 2
1
1
1
10
10
10
30
0
71.8
111.8
10
10
334525
334545
6240705 206
6240695 207
53
55
D5
D6
LINE 2
LINE 2
1
1
10
10
120.1
0
57.2
187.3
10
334565
334585
6240695 207
6240695 207
57
59
D7
D8
LINE 2
LINE 2
1
1
10
11.6
0
0
30
40
11.6
334605
334625
6240685 208
6240685 208
61
63
D9
D10
LINE 2
LINE 2
1
1
10
10
31.7
177.6
0
219.3
10
334645
334665
6240685 208
6240675 209
65
67
D11
D12
LINE 2
LINE 2
1
1
10.6
10
75.5
0
0
86.1
10
334685
334705
6240675 209
6240665 210
69
71
D13
J1
LINE 2
LINE 3
1
1
10
21.2
0
47.9
0
57.9
21.2
334725
334745
6240665 210
6240655 211
73
75
J2
J3
LINE 3
LINE 3
1
1
14.4
10
112.3
0
77.9
204.6
10
334765
334785
6240655 211
6240655 211
77
79
J4
J5
LINE 3
LINE 3
1
1
11.2
11.6
0
30
0
41.2
11.6
334805
334825
6240655 211
6240655 211
81
83
J6
J7
LINE 3
LINE 3
1
1
10
29.1
83
82.8
0
175.8
29.1
334845
334865
334885
6240655 211
6240645 212
6240645 212
85
87
89
J8
J9
J10
LINE 3
LINE 3
LINE 3
1
1
1
0
100
0
0
150
0
150
0
150
0
550
0
335035
6241265 150
104
CC1
CORE
2A
Botany Hydraulic Containment
C04/44/001
0
0
0
0
441.1
0
0
0
103
334965
334885
334935
6241165 160
6241105 166
6241075 169
97
89
94
CC2
EWB6
EWB5
CORE
CORE
CORE
2A
2A
2A
500
0
0
0
237.3
0
0
0
30
500
237.3
30
334985
334985
334925
6241085 168
6241205 156
6241145 162
99
99
93
CC5
EWB1
IWB1
CORE
CORE
CORE
2A
2B
2B
185
207.8
0
0
0
392.8
330
0
334975
335095
6241115 165
6241065 170
98
110
IWB2
EWB2
CORE
LINE A
2B
2B
Botany Hydraulic Containment
C04/44/001
0
0
330
0
0
0
0
0
104
Alan D. Laase
Hydrologist
2471 H Road
Grand Junction, Colorado 81505
(970) 270-3218
[email protected]
October 25, 2004
James Fairweather
Manager, Environmental Projects
Engineering Shared Services
Orica Australia Pty Ltd
Dear Mr. Fairweather,
I have completed my review of OPTIMAL GROUNDWATER ABSTRACTION RATES
FOR HYDRAULIC CONTAINMENT OF CONTAMINANT PLUMES AND SOURCE
AREAS, BOTANY NSW by Dr. Noel P. Merrick of the National Centre for Groundwater
Management. As directed by Orica Australia Pty Ltd, the scope of the review includes,
but is not limited, to the following:
Appropriateness and verification of:
Conceptualization of the model
Model design - lithologic/stratigraphical data inputs
- groundwater level data
- grid size
- boundary conditions
- reverse gradient conditions
Consistency between the conceptual model and the electronic model
Optimization model predictions
Correctness of data entry
Consistency between model output and results presented in the report
Conclusions regarding extraction requirements for subsidence impacts
First, before proceeding with a review of the report, Dr. Merrick needs to be commended
for producing such a well written report. In the scientific community, where dull and dry
are the norm, reviewing this report was a treat.
Modeling is initiated with a conceptual model formulation, which is nothing more than
tying together all the hydrologic components of a flow system in a logical manner, such
as where water enters and exits the system and how geology influences groundwater
flow. This report does a good job of presenting the various components of the conceptual
model and summarizing them into an easily understood description.
The next step in the modeling process is to translate the conceptual model into a
groundwater model starting with discretization of the model domain into grid cells. For
large regional models grid cells are typically hundreds to thousands square meters in size
while models used for remedial design have cells in the tens square meter size. This
model has a variable spaced grid with grid cells ranging from 10m x 10m to 100m x
100m. The smaller size cells are located within the remedial design study area and are
sized appropriately for remedial design.
For this model, external model boundaries, those on the edge of the model, are
represented by constant heads and prescribed flows representing the Lachlan Lakes,
Botany Bay, Maroubra Bay inlets and runoff from sandstone hills, respectively. The
bottom of the model is defined by the bedrock surface. Infiltration from rainfall is
applied to the upper layer of the model in varying amounts depending on land usage and
geology. Internal model boundaries are the Floodvale and Springvale Drains which are
represented using MODFLOW River Package (RIV). Water can either enter or leave
RIV cells depending on the relationship of the water levels in the drain to those of the
surrounding groundwater. Additionally, water supply wells are represented in the model
using analytical elements, which functionally are the same as MODLOW Well Cells
(WEL) but are advantageous in that discharge is automatically partitioned between model
layers. The external and internal model boundaries types described above and selected
for the model are appropriate. It should also be noted that the boundary conditions
applied to this model have also been used in previous peer reviewed modeling efforts,
some specific to the Orica Site and others for regional studies, and thus are not unique to
this model.
After assigning boundary conditions, aquifer properties such as hydraulic conductivity
and leakance (which represents resistance to flow between model layers), are located
within the model domain. For this model hydraulic conductivities are based on pumping
tests and previous calibrated model values. The distribution and values of hydraulic
conductivity within the model domain is reasonable based on descriptions provided
within the report.
Following model configuration a model is calibrated by adjusting boundary conditions
and hydraulic properties until a reasonable match is obtained between observed and
modeled water levels. This model was calibrated to 150 individual water- level elevations
and a potentiometric surface. Calibration statistics show that the model reasonably
matches the target values and the shape of the potentiometric surface and thus can be
used to simulate groundwater flow at the Orica Site.
A sensitivity analysis was performed on the calibrated model parameters and showed
while the calibrated values were perhaps not necessarily optimal values, defined as those
parameter values that produce the minimal difference between model predicted and
observed water levels, the values used produced results not significantly different than
2
those that would have been obtained had the optimal values been used. Based on the
sensitivity analysis results, the model is robust and can be used for remedial design.
The containment design presented in this report was optimized using an algorithm
developed by Dr. Noel Merrick. The algorithm is based on maintaining an inward
hydraulic gradient a specified distance downgradient of the pumping well. Algorithms
based on similar gradient specifications (MODMAN and MODOFC) are accepted by the
United States regulatory community and are used by modelers to optimize remedial well
fields. Additionally, a recent study commissioned by the United States Naval Facilities
Engineering Command (http://www.frtr.gov/estcp/index.htm) showed that optimization
produces designs at a minimum 25% more efficient than those produced using trial-anderror techniques further justifying the use of optimization techniques. Finally, to provide
verification that the design was adequate, the containment design was checked using
forward particle tracking and found to contain contamination along the specified
containment lines. In summary, the technique implemented is based on sound and
accepted principles and as shown by forward particle tracking yields a design that is
capable of containing groundwater contamination.
Fill was used to level land in the vicinity of the Orica Site prior to construction of many
buildings and infrastructure. Fill has the potential for irreversible compaction when
dewatered thus subsidence is a concern. Subsidence was evaluated using the
MODFLOW subsidence package for a base, likely and worst case and results show that
subsidence is not a concern. The subsidence analysis is as robust of an analysis as this
reviewer has ever seen and Dr. Merrick is commended for his thoroughness.
I have loaded the Groundwater Vistas (GWV) pre-processor file into GWV and viewed
the boundary conditions and hydraulic parameters and found them to be as reported. In
addition I have run the model and achieved the same potentiometric surface reported by
Dr. Merrick. Lastly, the model converged with an acceptable mass balance difference of
less than 1%.
In summary, this is a professional modeling effort and follows the protocols used by
experienced groundwater modelers. Dr. Merrick’s optimization methodology is
technically defensible and the presented design is capable of containing groundwater
contamination as described.
Regards,
Alan D. Laase
Hydrologist
Attachment: Laase Curriculum Vitae
3
Alan D. Laase
Hydrologist
2471 H Road
Grand Junction, Colorado 81505
970-270-3218
[email protected]
Experience
A. D. Laase Hydrologic Consulting, Grand Junction, Colorado
Hydrologist, September 2001 to present
Groundwater Transport Modeling
Calibrated groundwater transport models for three explosive derived contaminants (RDX, perchlorate and
TNT) and used the models to predict the fate of contamination under ambient and various remedial
scenarios.
Model Calibration
Calibrated a regional groundwater flow model of lower Cape Cod using parameter estimation and pilot
point techniques . Parameter estimation is an automated technique for determining the “best” parameter
values for a model as configured. Pilot points is an automated technique for determining the “best”
parameter configurations based on site observations such as water levels, fluxes and horizontal and vertical
gradients.
Extraction Well Field Performance Evaluation
Principle investigator of an extraction well field performance evaluation that determined the effectiveness
of the system and provided recommendations on how to improve mass capture rates. Recommendations
included reducing the number of extraction wells, shortening screen lengths, and modifying pumping
schedules.
Groundwater Quality Statistical Comparison
Principle investigator of a statistical comparison study tasked with determining whether low level inorganic
concentrations detected in deep monitoring wells were the result of site activities or consistent with
background concentrations.
Well Field Design, Optimization and Evaluation
Principal investigator of a well field design project tasked with determining the optimal extraction and
injection well configurations to contain and remove dissolved RDX, perchlorate and TNT within 10 and 30
years. Brute Force, a unique particle-track optimization algorithm was used to determine well locations
(both extraction and injection) and extraction rates required to satisfy the design objectives. Partitioning
theory was used to concurrently optimize , in a single Brute Force run, extraction well fields the three
primary contaminants of concern having different transport properties.
Model Comparison and Evaluation
Co-investigator of a model comparison study that used parameter estimation modeling to determine which
of two groundwater flow and transport models of the former Moab Mill Site in Utah was most
representative of the site groundwater flow system. Based on available calibration targets, neither model
A.D. Laase Page 2
was representative. Data gaps were identified and recommendations on how to improve future site
groundwater flow and transport models were provided.
Surface Water/Groundwater Interaction
Determined the contaminant mass loading rate to a river and the resultant river contaminant concentrations
as a result of contaminated groundwater discharge for a variety of climatic conditions at a former uranium
processing plant.
Phytoremediation Design and Evaluation
Co-investigator of a modeling study used to determine the viability of various plant combinations in
removing nitrate contamination from a former uranium mill site. Activities included calibrating the flow
model, using parameter estimation and simulating contaminant removal by transpiration.
Oak Ridge National Laboratory/AIMTech, Grand Junction, Colorado
Hydrologist, August 1990 to August 2001
Computer Code Development
Co-developer of Brute Force, a well field optimization computer code that determines optimum well
locations and pumping rates for vertical and horizontal wells and patterns of injections and pumping wells
using a unique particle-tracking algorithm. The advantages of particle tracking over gradient-based
optimization algorithms are particle travel times and capture availability are used as optimization criteria.
By doing so, pumping systems can be designed for combinations of specified plume pore volume removal
rates while excluding capture of groundwater from other portions of the aquifer.
Co-developer of a computer code consisting of master and slave programs that allows Brute Force to run in
parallel on a network of PC computers. The master program, residing on a single computer, parcels out
tasks (model runs) via the network to multiple slave computers. The slave computers execute the specified
tasks and transfer results to the master computer for compilation. Performance statistics are kept on all
slave computers so that non-parallel portions of the code can be assigned to the fastest slave computer.
Co-developer of Visual Three-Point Plus (V3PP), a computer code, that determines groundwater flow
direction and rate and temporal contaminant concentrations using three-point analysis and contaminant
partitioning theory. V3PP can be operated either deterministically or stochastically modes and was
developed to evaluate groundwater flow fields in the vicinity of reactive permeable barriers and determine
the viability of natural attenuation/flushing as remedial alternatives.
Site Conceptual Model Evaluation
Principal investigator of a parameter estimation modeling study that calibrated a number of conceptual
model representations of the Monument Valley, Arizona groundwater flow system. The conceptual models
differed in the number and distribution of hydraulic conductivity, recharge and evapotranspiration zones
within the modeling domain. The “best” conceptual model was that having the smallest sum of squares
residual, greatest parameter sensitivities and tightest 95% prediction confidence intervals.
Well Field Design, Optimization and Evaluation
Principal investigator of a well field design study that determined the optimum design and pumping
schedule for an interceptor system using parameter estimation, optimization and Monte Carlo modeling
coupled with economic-risk analysis. The most cost-effective design was chosen from combinations of
vertical and horizontal wells.
A.D. Laase Page 3
Senior advisor for an interceptor system design project devised to determine the optimal pumping and
injection well configuration for maximum contaminant removal at a former uranium mill site. The optimal
design was determined using parameter estimation and optimization modeling.
Principal investigator of an optimization and evaluation study of an existing interceptor system located at a
DOE uranium enrichment facility. Optimal parameter values and associated 95% confidence intervals
were determined using parameter estimation modeling. The affect of parameter uncertainty on capture
zone configuration was evaluated by simulating the interceptor system at the confidence interval extremes.
Principal investigator of a study that determined the effectiveness of a pumping well network in containing
three contaminant plumes at a DOE manufacturing facility using groundwater modeling.
Designed an interceptor system using groundwater modeling for a Corrective Measures Study (CMS).
Natural Attenuation/Flushing Studies
Groundwater modeling was used to evaluate the viability of natural flushing as a remedial strategy at a
former Uranium Mill site.
Principal investigator of a groundwater flow and contaminant transport modeling study that evaluated the
likelihood that natural attenuation would sufficiently degrading hydrocarbon and chlorinated solvent
contamination such that an adjacent surface water body would not be adversely impacted.
Principal investigator of a natural attenuation contaminant transport modeling study that evaluated the
potential for natural attenuation to reduce dissolved chlorinated solvent contamination to below drinking
water standards prior to discharge to a nearby creek.
Model Comparison and Evaluation
Principal investigator of a modeling study for DOE that compared MODFLOW and Groundwater Analysis
and Network Design Tool (GANDT) modeling results. GANDT, a computer code developed by Sandia
National Laboratory, uses Monte Carlo techniques to determine the range of hydraulic and contaminant
transport parameters that replicate known plume geometries. These parameter ranges are then used to
determine the probability that natural flushing of contamination will occur within one hundred years of
source removal. The reliability of GANDT was determined by comparing MODFLOW and GANDT
predictions.
Recirculation System Design for Oxidant Delivery
Groundwater modeling was used to design an injection and extraction for the delivery of oxidants to the
subsurface for treatment of DNAPL. Design considerations were available drawdown, injection pressure,
travel times, heterogeneity, containment, and pumping rates.
Reactive Permeable Barrier Design and Evaluation
Groundwater modeling was used to determine the optimal funnel and gate for passive treatment of
dissolved chlorinated solvents. Design considerations included the number and size of treatment gates,
residence times within the treatment gates, and orientation and length of the funnel sections.
Groundwater modeling was used to evaluate the hydraulic and chemical performance of an iron wall.
Design parameters were collected for extending the iron wall.
Invited participant to an EPA sponsored reactive permeable barrier work shop tasked with providing
recommendations concerning the design, installation and evaluation of reactive permeable barriers.
A.D. Laase Page 4
Alternate Concentration Limit Petition
Co-principal investigator of an Alternate Concentration Limit (ACL) Petition which evaluated the impact
of contaminated groundwater discharge to a nearby river on human health and the environment.
Subsidence Study
Principal investigator of a modeling study designed to determine the potential magnitude of building
subsidence as a result of the operation of an interceptor well field. Optimized pumping schedules were
determined to minimize the potential for subsidence.
PCB Colloidal Transport Study
Principle investigator of a study to evaluated the potential for subsurface PCB contamination to migrate
with groundwater via colloidal transport to a nearby creek.
Short Course Instructor
Instructor for a one-day short course on applied parameter estimation modeling sponsored by the
International Groundwater Modeling Center.
Thesis Advisor
Thesis advisor to a New Mexico State University Masters student who evaluated the viability of natural
flushing of dissolved uranium from groundwater at a former uranium mill site using groundwater modeling.
Modeling demonstrated that after source removal natural flushing would reduce contaminant levels to
below drinking water standards within 100 years and active remediation was not required.
Exit Pathway Analysis
Principal investigator of a study tasked with identifying and evaluating exit pathways for groundwater
contamination at the DOE Oak Ridge Reservation.
Industrial Hydrology Study
Principal investigator of a groundwater study to characterize the influence of man-made industrial features,
such as tile drain systems and leaking underground water supply and fire protection lines, on groundwater
flow and contaminant distribution at a DOE enrichment facility.
Seepage Study
A network of seepage meters and mini-piezometers were installed and sampled to ascertain the
quantity and quality of groundwater discharge from a contaminant plume to a river before and
after implementation of remedial measures.
Recharge Study
Groundwater samples were collected at multiple depths within the aquifer and age dated using tritium and
helium-3. Recharge rates from precipitation to the aquifer were calculated using the depth below the water
table from which the samples were collected and the age of the samples.
Fracturing Study
Co-investigator of a study designed to evaluate the effectiveness of pneumatic fracturing as a remedial
technique in low permeability saturated soils. The study evaluated the effect of fracturing on fluid flow,
A.D. Laase Page 5
the spatial distribution and longevity of the fractures and the relationship between advective and diffusive
transport before and after fracturing.
Colloidal Borescope Study
Principal investigator of a colloidal borescope study that characterized the effects of anthropogenic features
such as underground water supply and sanitary sewer lines on groundwater flow system at an industrial
facility. The colloidal borescope, developed by Oak Ridge National Laboratory, is a downhole camera that
views the advective transport of naturally occurring colloids through the well screen. A computer program,
coupled with a frame grabbing system that captures images of the colloids in the well bore, is used to
determine both groundwater flow direction and rate. Colloidal borescope data showed that a combination
of recharge from leaking underground water supply and fire protection lines and discharge to building
foundation drains contained groundwater contamination at the facility and prevented the contamination
from reaching a nearby creek.
ASTM Groundwater Modeling Committee Member
Former member of the American Society for Testing and Materials (ASTM) committee tasked
with developing consensus standards for all aspects of groundwater flow and contaminant
transport modeling.
Conference Session Chairman
Session chairman for both the Model Calibration and Model Validation sessions at the Symposium on
Subsurface Fluid-Flow (Groundwater) Modeling conducted June 1995, at Denver, Colorado.
Technical Reviewer
Ad hoc reviewer for Soil Science Society of America Journal and Health Physics Journal.
Geraghty & Miller, Inc., Raleigh, North Carolina
Office Discipline Manager Hydrocarbon Services, February 1989 to March 1990
Responsibilities included: communication with corporate hydrocarbon representatives,
development of marketing strategy, identification of potential clients, client liaison, proposal
preparation, and supervision of office hydrocarbon projects.
Project Manager, February 1989 to July 1990
RCRA Projects
Managed the environmental assessment of a large chemical and pharmaceutical manufacturing
plant. Activities included: identification of potential Solid Waste Management Units, work plan
preparation, design of monitoring well network, coordination of field program, hydrogeologic
analysis, report preparation, and client liaison.
Project manager of an RFI for a large pharmaceutical and pesticide manufacturing plant. Duties
involved preparation of the RFI work plan and client liaison.
CERCLA Projects
Project manager of an environmental assessment at a large abandoned wood preserving facility.
Activities included: work plan preparation, locating abandoned waste settling ponds, conducting
geophysical surveys, stream sediment sampling, design of monitoring well network, well
installation, coordination of field program, and client liaison.
A.D. Laase Page 6
EPA Work Assignments
Project manager and principal investigator of an EPA work assignment that examined various
methods of quantifying non-point-source contamination of surface water as a result of
groundwater discharge. Duties included preparation of a draft report reviewing and critiquing
existing methods used to assess groundwater discharge and loading to surface water in different
hydrogeologic settings in the United States and participation in a panel discussion concerning the
draft report.
Hydrocarbon Projects
Project manager of a contamination investigation at a residential neighborhood service station.
Approximately 4,000 gallons of gasoline were released to the subsurface in a catastrophic event.
Duties encompassed liaison with state regulatory personnel, design of monitoring well network,
contamination assessment report (CAR) preparation, and coordinating with staff engineers in the
preparation of a remedial action plan (RAP).
Project manager of a joint effort between three major petroleum companies to characterize
groundwater quality at the companies' adjacent petroleum terminals. Responsibilities included
contract preparation, liaison with group members, and report preparation.
Environmental Audits
Project manager and principal investigator for numerous environmental audits of small tracts of
land for law firms, banks, and private concerns.
Fate and Transport
Evaluated the fate and transport of inorganic and organic constituents in groundwater in both the
unsaturated and saturated zones for Geraghty & Miller's Risk Evaluation Group.
New Mexico Institute of Mining and Technology, Socorro, New Mexico
Teaching Assistant, January 1988 to December 1988
Teaching Assistant for introductory groundwater and surface water classes.
Geraghty & Miller, Inc., Oak Ridge, Tennessee
Field Operations Manager, September 1985 to August 1986
Managed field operations at two hazardous-waste facility investigations involving various organic
and inorganic constituents from multiple sources. Responsibilities included: supervision of field
personnel, project budgeting, preparation of drilling specifications, oversight of subcontractor
agreements, QA/QC of data and procedures, implementation of the health and safety program, and
report preparation.
Field Geologist, October 1984 to August 1985
Supervised the installation of numerous water-table and bedrock aquifer monitoring wells,
performed soil sampling, and conducted aquifer tests at two hazardous-waste facilities.
A.D. Laase Page 7
Geraghty & Miller, Inc., Palm Beach Gardens, Florida
Field Geologist, October 1983 to September 1984
Conducted a groundwater resource exploration program that determined locations of production
well fields using lithologic logs, aquifer tests, and electrical resistivity. Supervised the installation
and testing of a high-capacity wastewater injection well.
Education
M.S. Hydrology
New Mexico Institute of Mining and Technology, 1989
B.S. Geology
Michigan State University, 1983
Selected Publications/Reports
Tuba City UMTRA Site Semi-Annual Performance Evaluation, U.S. Department of Energy, Grand Junction
Colorado Office, May 2003.
Tuba City UMTRA Site Baseline Performance Evaluation, U.S. Department of Energy, Grand Junction
Colorado Office, May 2003.
Rapid Response Action/Release Abatement Measure Plan, Demo 1 Groundwater Operable Unit, U. S.
Army Corps of Engineers, New England District, Concord, Massachusetts, January 2003.
Evaluation of Natural Flushing Using Three-Point and Partitioning Theory Analysis, In Proceedings for
The Third International Conference on Remediation of Chlorinated and Recalcitrant Compounds, May
2002.
Lower Northeast Area Characterization and Iron Wall Evaluation Report, U.S. Department of Energy,
Kansas City Plant, Kansas City, Missouri, 2000.
Evaluation of the Kansas City Plant Iron Wall, In Proceedings for The Second International Conference on
Remediation of Chlorinated and Recalcitrant Compounds, May 2000.
Design, Optimization and Evaluation of Interceptor Systems for the Kansas City Plant Using Groundwater
Modeling and Economic-Risk Analysis, In Proceedings for the 26th Environmental Symposium and
Exhibition, National Defense Industrial Association, March 2000.
Application of Economic-Risk Analysis for Design and Optimization of the Kansas City Plant Interceptor
System, ModelCare 99: Calibration and Reliability in Groundwater Modelling. A. D. Laase et al.
Design and Optimization of the Kansas City Plant Interceptor System, U.S. Department of Energy, Kansas
City Plant, Kansas City, Missouri, 1999.
95 th Terrace RCRA Facilities Investigation Report, U.S. Department of Energy, Kansas City Plant, Kansas
City, Missouri, 1999.
Comparison of GANDT and MODFLOW Groundwater Flow Predictions for the UMTRA Site at Riverton,
Wyoming, U.S. Department of Energy, Grand Junction, Colorado, 1998.
Paducah Gaseous Diffusion Plant Northwest Plume Interceptor System Evaluation, A. D. Laase and
A.D. Laase Page 8
J. L. Clausen, ORNL/TM-13333, 1997.
Standard Guide for Calibrating a Groundwater Flow Model Application, ASTM Standard,
D. M. Brown and A. D. Laase, 1996.
Mirror Figure of Merit (MFM): An Alternative Measure of Model Error, A. D. Laase and J. R. Davidson,
in the proceedings from the Symposium on Subsurface Fluid-Flow (Groundwater) Modeling, June 1995,
Denver, Colorado.
Innovation and Regulation at the Department of Energy’s Kansas City Plant : Coupling Innovative
Technology with a Petition for Alternative Concentration Limits, N. E. Korte, M. T. Muck, A. D. Laase,
and J. L. Baker, and D. Brown, Air and Waste Management Conference Proceedings, 1995.
Review of Methods For Assessing Non-point Source Contaminated Ground-Water Discharge To Surface
Water, EPA 570/9-91-010, United States Environmental Protection Agency.
Potential Effect of Natural Gas Wells on Alluvial Groundwater Contamination at the Kansas City Plant ,
D. A. Pickering, A. D. Laase, and D. A. Locke , ORNL/TM-12226.
Alternative Concentration Limit Demonstration for the Kansas City Plant, U.S. Department of Energy,
Kansas City Plant, Kansas City, Missouri, 1995.
TCE Still Area RCRA Facilities Investigation Report, U.S. Department of Energy, Kansas City Plant,
Kansas City, Missouri, 1994.
Northeast Area RCRA Facilities Investigation Report, U.S. Department of Energy, Kansas City Plant,
Kansas City, Missouri, 1994.
Northeast Area Corrective Measures Study, U.S. Department of Energy, Kansas City Plant,
Kansas City, Missouri, 1994.
Annual Groundwater Monitoring Report for Calendar Year 1993, U.S. Department of Energy,
Kansas City Plant, Kansas City, Missouri, 1994.
Annual Groundwater Monitoring Report for Calendar Year 1992, U.S. Department of Energy,
Kansas City Plant, Kansas City, Missouri, 1993.
Interceptor System Evaluation Report, U.S. Department of Energy, Kansas City Plant, Kansas
City, Missouri, 1992.
Annual Groundwater Monitoring Report for Calendar Year 1991, U.S. Department of Energy,
Kansas City Plant, Kansas City, Missouri, 1992.
Annual Groundwater Monitoring Report for Calendar Year 1990, U.S. Department of Energy, Kansas City
Plant, Kansas City, Missouri, 1991.
TCE Still Area RCRA Facilities Investigation Work Plan, U.S. Department of Energy, Kansas City
Plant, Kansas City, Missouri, 1990.
Selected Presentations
Evaluation of Natural Flushing Using Three-Point and Partitioning Theory Analysis, In Proceedings for
The Third International Conference on Remediation of Chlorinated and Recalcitrant Compounds, May
2002, Monterey, California.
A.D. Laase Page 9
Evaluation of the Kansas City Iron Wall, The Second International Conference on Remediation of
Chlorinated and Recalcitrant Compounds, May 2000, Monterey, California.
Design, Optimization and Evaluation of Interceptor Systems for the Kansas City Plant Using Groundwater
Modeling and Economic-Risk Analysis, 26th Environmental Symposium and Exhibition, National Defense
Industrial Association, March 2000, Long Beach, California.
Application of Economic-Risk Analysis for Design and Optimization of the Kansas City Plant Interceptor
System, ModelCare 99, International Conference on Calibration and Reliability in Groundwater Modelling,
September 1999, Zurich, Switzerland.
Economic-Risk Analysis for Design and Optimization of the KCP Interceptor System, Technical
Information Exchange Conference, October 1995, Chicago, Illinois.
Capture Zone Analysis using Parameter Estimation Techniques, Geological Society of America Meeting
November 1996, Denver, Colorado.
Improved Modeling Report Comprehension Through Use of Visual Aids, Technical Information Exchange
Conference, April 1996, Sante Fe, New Mexico.
The Influence of Industrial Features on Groundwater Flow and Contaminant Distribution at the Kansas
City DOE Plant, Paducah Gaseous Diffusion Plant, June 1995, Paducah, Kentucky.
The Influence of Industrial Features on Groundwater Flow and Contaminant Distribution at the Kansas
City DOE Plant, United States Environmental Protection Agency, June 1995, Nashville, Tennessee.
Mirror Figure of Merit (MFM) : An Alternative Measure of Model Error, Symposium on Subsurface FluidFlow (Groundwater) Modeling, June 1995, Denver, Colorado.
Improved Modeling Report Comprehension Through Use of Visual Aids, Symposium on
Subsurface Fluid-Flow (Groundwater) Modeling, June 1995, Denver, Colorado.
The Groundwater Modeling Process : From Beginning to End, May 1995, Kansas City Plant, Kansas City,
Missouri.
Influence of Leaky Underground Utilities and Tile Drain Systems on Groundwater Flow and Contaminant
Distribution at the DOE Kansas City Plant, Technical Information Exchange Conference, April 1995,
Cincinatti, Ohio.
Site Characterization using the Colloidal Borescope, Technical Information Exchange Conference,
November 1993, Denver, Colorado.
Use of Seepage Meters and Mini-Piezometers to Characterize the Quantity and Quality of Groundwater
Discharge to Surface Water, Technical Information Exchange Conference, May 1993, Knoxville,
Tennessee.