Appendix D: Hydraulic Containment of Groundwater (PDF
Transcription
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 This document may be superseded by a later document based on more up-to-date data.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. i Botany Hydraulic Containment C04/44/001 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 ii Botany Hydraulic Containment C04/44/001 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. iii Botany Hydraulic Containment C04/44/001 .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 iv Botany Hydraulic Containment C04/44/001 ILLUSTRATIONS - FIGURES 1 TO 41 ................................................................44 APPENDIX .................................................................................................................84 v Botany Hydraulic Containment C04/44/001 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 vi Botany Hydraulic Containment C04/44/001 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 vii Botany Hydraulic Containment C04/44/001 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 viii Botany Hydraulic Containment C04/44/001 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 ix Botany Hydraulic Containment C04/44/001 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. Botany Primary Containment C04/44/001 1 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. Botany Primary Containment C04/44/001 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). Botany Primary Containment C04/44/001 3 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 Botany Primary Containment C04/44/001 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 Botany Primary Containment C04/44/001 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. Botany Primary Containment C04/44/001 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. Botany Primary Containment C04/44/001 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 Botany Primary Containment C04/44/001 8 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 Botany Primary Containment C04/44/001 9 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: Botany Primary Containment C04/44/001 10 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. Botany Primary Containment C04/44/001 11 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. Botany Primary Containment C04/44/001 12 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. Botany Primary Containment C04/44/001 13 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. Botany Primary Containment C04/44/001 14 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). Botany Primary Containment C04/44/001 15 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. Botany Primary Containment C04/44/001 16 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 Botany Primary Containment C04/44/001 17 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). Botany Primary Containment C04/44/001 18 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% Botany Primary Containment C04/44/001 19 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. Botany Primary Containment C04/44/001 20 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 Botany Primary Containment C04/44/001 21 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 Botany Primary Containment C04/44/001 22 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 Botany Primary Containment C04/44/001 23 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 Botany Primary Containment C04/44/001 24 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). Botany Primary Containment C04/44/001 25 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 Botany Primary Containment C04/44/001 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. Botany Primary Containment C04/44/001 27 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. Botany Primary Containment C04/44/001 28 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. Botany Primary Containment C04/44/001 29 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 Botany Primary Containment C04/44/001 30 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. Botany Primary Containment C04/44/001 31 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. Botany Primary Containment C04/44/001 32 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 C04/44/001 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 C04/44/001 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 C04/44/001 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 C04/44/001 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 C04/44/001 38 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 C04/44/001 40 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 C04/44/001 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 C04/44/001 42 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 C04/44/001 43 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.