Determination of Aquifer Properties and Heterogeneity in a Large Coastal Sand Mass: Bribie Island, Southeast Queensland

QUEENSLAND UNIVERSITY OF TECHNOLOGY School of Natural Resource Sciences

DETERMINATION OF AQUIFER PROPERTIES AND HETEROGENEITY IN A LARGE COASTAL SAND MASS: BRIBIE ISLAND, SOUTHEAST QUEENSLAND

Timothy J. Armstrong B. App. Sc

SUPERVISOR Dr. Malcolm Cox Queensland University of Technology

A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Applied Science.

March, 2006

School of Natural Resource Sciences, Queensland University of Technology Brisbane Queensland 4001 GPO Box 2423

Abstract

Aquifer heterogeneity within the large coastal sand island of Bribie Island, Queensland, Australia, has an affect on groundwater occurrence and migration. The stratigraphy of Bribie Island is complicated by the presence of low permeability humate-cemented indurated sand layers.

Occurrences of indurated sand layers have previously been identified within many unconsolidated profiles along the east coast of Australia and around the world. Indurated sand layers are often discontinuous resulting in localised aquifer heterogeneity. However, their regional significance is commonly underestimated.

The groundwater resource of Bribie Island is of commercial and environmental significance to the surrounding bay area. Recent development proposals for the groundwater resource necessitate an investigation into the nature of the water bearing properties of the island aquifer and in particular the presence of aquifer heterogeneity. Investigation of a “reference” transect across Bribie Island has involved the drilling and development of monitoring wells and the performance of hydraulic tests.

This study demonstrates how detailed measurement of stratigraphy, groundwater levels, rainfall, barometric pressure and hydraulic testing can be used in conjunction to identify and assess aquifer heterogeneity within a sand island environment.

Drill logs confirm the position of a palaeochannel within the sandstone bedrock that extends from the mainland continuing under Bribie Island. The overlying sediment profile is thickest within the palaeochannel. The Pleistocene and Holocene unconsolidated profile reflects a prograding barrier island/strandplain formation. The vertical sequence of sediments consists of units that range from offshore sandy silts to foreshore and beach medium-fine grained sands.

An extensive indurated sand layer exists throughout the centre of the island. The greatest thickness of indurated sand is located centrally on the island beneath the

main beach ridge system. The indurated layer at its thickest is approximately 5-8 m thick, but over much of the island the thickness is 1-3 m. The top of indurated sand layer is generally 1-3 m above mean sea level.

Hydrographs from a network of groundwater monitoring wells illustrate that the groundwater resources across the reference transect can be divided into a shallow unconfined water table aquifer and basal confined aquifers. These upper and lower aquifers are characterised by different hydrological processes, physico-chemical properties, and water chemistry.

The stratification of water levels across the reference transect and the relatively flat piezometric surface are in contrast with the classical “domed” water table aquifer expected of a barrier island. Stratified head gradients through the Bribie Island aquifers suggest groundwater migration to depth is impeded by the indurated sand layer. An elevated shallow water table results from the mounding of water above the indurated sand layer. The indurated sand layer is extensive across the reference transect.

The elevated unconfined groundwater is usually stained with organic matter (“black water”), where as groundwater sourced from beneath the indurated sand layer is colourless (“white water”). The unconfined groundwater is also distinguished by low pH, low bicarbonate concentrations and high concentrations of organic carbon. Interaction between unconfined groundwater and surface water are also evident.

Hydraulic tests indicate that each of the unconsolidated units across the reference transect has distinctive hydraulic characteristics. Estimates of vertical and horizontal hydraulic conductivity of the unconfined aquifer are two to three orders of magnitude greater than estimates for the indurated sand layer. Beneath the indurated sand layer hydraulic conductivities of the basal aquifers are also greater by two to three orders of magnitude than estimates for the indurated sand layer. The lower hydraulic conductivity within the indurated sand layer is responsible for the local semi- confinement of the basal aquifers.

Contents

Abstract

List of Figures

List of Appendices

Statement of Original Authorship

Acknowledgements

Glossary

1.0 INTRODUCTION 1 1.1 Aim 2 1.2 Objectives 2 1.3 Significance of Research 2

2.0 BACKGROUND TO MATERIALS AND EVOLUTION 3 2.1 Beaches, Strand Plains and Barrier Coasts 3 2.2 Barrier Coasts 5 2.2.1 Coast environments 5 2.3 Barrier types and facies 6 2.3.1 Prograded barriers 8 2.4 Barrier Coast Hydrology 9 2.4.1 Surface water 9 2.4.2 Groundwater occurrence 10 2.4.3 Porosity and aquifer storage 11 2.4.4 Hydraulic conductivity 13

2.4.5 Aquifer heterogeneity 15 2.4.6 Hydrochemistry 17 2.5 Nature of Indurated Sand 18

3.0 PHYSICAL SETTING OF BRIBIE ISLAND 21 3.1 Regional Setting 21 3.2 Geology 24 3.3 Geomorphology 26 3.3.1 Pleistocene beach ridge system 26 3.3.2 Holocene beach ridge system 29 3.3.3 Active foredune system 29 3.3.4 Estuarine tidal delta system 29 3.4 Drainage System 30 3.5 Climate 30 3.6 Evaporation 31 3.7 Groundwater Recharge 32 3.8 Vegetation 33 3.9 Land Use 33

4.0 HYDROGEOLOGICAL STUDIES OF BRIBIE ISLAND 35

5.0 METHODS 39 5.1 Drilling and Hydraulic Testing 40 5.1.1 Drilling program 40 5.1.2 Well construction 42 5.1.3 Water level monitoring 45 5.1.4 Bailer tests 46 5.1.5 Pumping tests 47 5.2 Hydraulic Tests Analysis 50 5.3 Water and Sediment Sampling 58 5.3.1 Sediment samples 58 5.3.2 Age dating samples 59 5.3.3 Age dating analysis 59 5.3.4 Water sampling 60 5.3.5 Elemental analysis 62

6.0 RESULTS 64 6.1 Island Stratigraphy 65 6.1.1 Aquifer description and distribution 65 6.2 Island Evolution and Age 69 6.3 Island Hydrology 70 6.3.1 Groundwater levels 72 6.4 Barometric Efficiencies 77 6.5 Water Geochemistry 82 6.5.1 Physico-chemical properties 82 6.5.2 Major ion chemistry 84 6.5.3 Water types 85 6.5.4 Organic carbon content 87 6.6 Aquifer Hydraulic Testing 88 6.6.1 Bailer tests 88 6.6.2 Pumping test 1 91 6.6.3 Pumping test 2 93 6.6.4 Pumping test 3 97

7.0 HYDRAULIC TEST ANALYSIS AND

INTERPRETATION 99 7.1 Bailer Tests 99 7.2 Pumping Tests 102 7.2.1 Pumping test 1 103 7.2.2 Pumping test 2 105 7.2.3 Pumping test 3 106

8.0 DISCUSSION 115 8.1 Comparison of Hydraulic Conductivities 115 8.2 Conceptual Hydrogeological Framework 117

9.0 CONCLUSION 121

REFERENCES

APPENDICES

List of Figures

Figure

1. Comparison of barrier island, strandplain and tidal flat morphologies 4 2. Geometry and morphological relationship of barrier types, Bribie Island (1a) 7 3. Cross section of a typical barrier island, and barrier facies model 9 4. Fresh groundwater water flow through a homogenous and isotropic barrier island 11 5. Range of hydraulic conductivity values of earth materials 14 6. Fresh groundwater flow through a heterogeneous barrier island 16 7. Location of Bribie Island in Moreton Bay, Queensland, Australia 21 8. Geographical map of Bribie Island 22 9. Bribie Island topographical map 23 10. Geological map of Bribie Island 24 11. Aquifer base contour map of Bribie Island 25 12. Lithological map of Bribie Island 27 13. Thickness of indurated sand layer for Bribie Island 28 14. Rainfall data for Bribie Island years 1993 to 2000 31 15. Previous monitoring well locations 38 16. Location of current groundwater monitoring wells 41 17. Typical construction method for monitoring wells 44 18. Manual electrified tape measure for the monitoring of water levels (photo) 45 19. Automatic groundwater level logging equipment and rainfall gauge (photo) 45 20. Schematic illustration of bailer hydraulic test 47 21. Schematic illustration of confined drawdown and cone of depression 48 22. Schematic illustration of cones of depression in pumping wells 49 23. Schematic illustration of the mechanics of a bailer test 52 24. Groundwater flow during a pumping test 53 25. Analysis of data from pumping test with the Theis method 56 26. Locations of surface water sampling points 61 27. Geological cross-section of Bribie Island across the reference transect D-D′ 67 28. Vertical sequence of progradational barrier sequence 68 29. Glacio-eustatic sea level curve for the last 340 000 years 71

30. Hydrographs of water levels from nested monitoring wells 74 31. Hydrographs from automatic loggers on monitoring wells 127 and 090 75 32. Water level contours across the reference transect 76 33. Flow net across the reference transect using averaged groundwater levels 71 34. Computation of barometric efficiency 81 35. Barometric response functions 82 36. Tri-linear diagram of major ion chemistry for groundwater and surface water 86 37. Summarised transect D-D' showing bailer test wells 88 38. Rising head plots derived from bailer testes of foredune and beach sand aquifer 89 39. Rising-head plots derived from bailer testes of swale deposits 90 40. Rising-head plots derived from bailer testes of indurated sand layer 91 41. Vertical cross section of transect D-D′ (pumping test 1) 92 42. Response of monitoring wells during pumping test 1 93 43. Vertical cross section of transect D-D′ (pumping test 2) 94 44. Response of monitoring wells during pumping test 2 95 45. Influence of barometric pressure during pumping test 2 96 46. Vertical cross section of transect D-D′ (pumping test 3) 97 47. Response of pumping well and monitoring well during pumping test 3 98 48. Plots of bailer test results based on lithological groupings 100 49. Analysis of recovery data from pumping test 1 103 50. Analysis of recovery data from pumping test 2 105 51. Theis analysis of drawdown data from pumping test 3 106 52. Cooper-Jacob analysis of drawdown data from pumping test 3 108 53. Schematic cross section and plan of an aquifer with a straight barrier boundary 109 54. Calculation of radius to image well from Cooper-Jacob plot 111 55. Schematic cross section including barrier boundary conditions 113 56. Stallman analysis of drawdown data from pumping test 3 114 57. Conceptual hydrogeology of Bribie Island including aquifer heterogeneity 120

List of Tables

Table

1. Porosity ranges for unconsolidated sediments 12 2. Specific yield in percent for unconsolidated sediments 12 3. Annual rainfall from registered stations located on Bribie Island 30 4. Mean monthly rainfall – Bongaree 31 5. Mean monthly evaporation – Brisbane 32 6. Well type and slotted casing lengths of monitoring wells across the reference transect 42 7. Details of pumping tests 50 8. Sediment sampled details for OSL analysis 59 9. Calculated burial ages of sediment samples from Bribie Island 69 10. Barometric efficiencies 79 11. Physico-chemical parameters for groundwater and surface water 83 12. Major ion concentrations for groundwater and surface water 85 13. Total dissolved organic carbon concentrations and charge balances 87 14. Hydraulic conductivity values determined from bailer tests 99 15. Vertical hydraulic conductivity estimates based on head gradients 101 16. Hydraulic conductivity and specific storage estimates 102 17. Previous estimates of hydraulic conductivity for Bribie Island 115 18. Comparative estimates of hydraulic conductivity 117

List of Appendices

Section A: Associated publications

A Chemical character of surface waters on Bribie Island: a preliminary assessment. (extended abstract)

B The relationship between groundwater and surface water character and wetland habitats, Bribie Island, Queensland (conference paper)

C Controls over aquifer heterogeneity within a large sand island and analysis by hydraulic testing, Bribie Island, Queensland, Australia (accepted manuscript - Hydrogeology Journal)

Section B: Data

D Stratigraphic Logs

E Sediment Age Dating

F Groundwater Level Data

G Physico-chemical Data

H Major and Minor Ion Chemistry

I Calculation of Organic Anion Concentration

Statement of Original Authorship

The work contained in this thesis has not been previously submitted for a degree or diploma at any other higher education institution. To the best of my knowledge and belief, the thesis contains no material previously published or written by another person except where due reference is made.

Signed: ……………………………………………………………………………...

Date: ………………………………………………………………………………..

Acknowledgements

I would like to take this opportunity to thank everyone who has helped with this project in any way. Successful completion of this study has been made possible through the practical and professional assistance of many people and institutions, in particular; • Dr Malcolm Cox (Principal supervisor) The expertise and guidance provided to me throughout the project has been invaluable. Thank you for your encouragement, I am greatly appreciative. • John Harbison Thank you for your support and encouragement throughout the project. Your contributions to fieldwork, hydrogeological discussion and to the writing process are greatly appreciated. • Queensland University of Technology Dr Micaela Preda, Dr Brendan Brooke, Sharron Price, Whathsala Kumar, Bill Kwiecien • Caloundra City Council Bill Haddrill • Department of Natural Resources, Mines and Energy Peter Cochrane, Robert Ellis and Bill Mead • Department of Primary Industries - Forestry Stan Ward and Dr. Ken Bubb • Queensland Parks and Wildlife Bribie Island National Park Rangers • PRCCA (Pumicestone Region Catchment Coordination Association) • Pacific Harbour • HLA Envirosciences Pty. Ltd. • The Natural Heritage Trust - funding under project (992417) • Collaborative funding Caboolture Shire Council and Department of Primary Industry Forestry – Beerburrum Office • Thank you to all my friends • Thank you to all my family

Glossary

• Aquifer A formation that contains sufficient saturated permeable material to yield significant quantities of water to wells or springs. • Aquitard A saturated unit of low hydraulic conductivity that can store and slowly transmit groundwater either upward or downward depending on the vertical hydraulic gradient. • Barrier boundary Boundaries that inhibit groundwater flow. Examples are faults, bedrock, or thinning of an aquifer. • Conceptual model A simplified representation of the groundwater system that indicates flow directions and boundary conditions affecting flow. • Cone of Depression A depression in the water table or piezometric surface surrounding a pumping well. The shape of this depression is similar to an inverted cone. • Confined Aquifer An aquifer whose upper and lower boundaries are impervious and in which the fluid pressure is greater than atmospheric pressure. The water level in a well penetrating a confined aquifer will rise above the base of the upper confining layer. • Darcy’s Law An equation that relates the volume of water per time moving through a given cross-sectional area of aquifer to a particular potentiometric head gradient. • Drawdown The amount of water level change from the static water level position during a pumping test.

• Flow Net A two-dimensional representation of steady-state groundwater flow. The flow net consists of intersecting lines of equal hydraulic head and associated flow lines. • Heterogeneity Relating to the physical properties of an aquifer from point A to point B, including packing, thickness and cementation. Heterogeneous units differ in physical properties from point A to point B. • Homogeneity Relating to the physical properties of an aquifer from point A to point B, including packing, thickness and cementation. Homogenous units have similar properties from point A to point B. • Hydraulic Conductivity A value representing the relative ability of water to move through a geologic material of a given permeability. • Indurated Sand Quartz sand grains cemented together by the infilling of pores by a variety of cements, predominately organic matter and clays. • Perched Water Unconfined groundwater separated from an underlying main body of groundwater by an unsaturated zone. • Permeability The ability of a porous medium to transmit fluid under a given gradient. • Piezometric Surface Imaginary surface that represents the static head. The surface is defined by the levels to which water will rise in a well when that well penetrates an aquifer. • Porosity The volume of void space within earth materials. • Specific Storage The amount of stored water released from a unit volume of aquifer per unit decline in head. • Storativity (= Storage Coefficient)

The volume of water released or taken into storage per unit plan area of aquifer per unit change of head. • Swale An extensive depression between series of beach ridges, representing a period of cessation of progradation. • Unconfined Aquifer An aquifer whose upper surface is at atmospheric pressure. • Water Table The top of the saturated zone of an unconfined aquifer where the pressure is at atmospheric pressure.

1.0 INTRODUCTION

Sand island formation by the dominant process of beach ridge progradation suggests that the associated groundwater aquifers may be relatively homogenous. However, the complex stratigraphic framework of many sand islands produce substantial aquifer heterogeneity. Heterogeneity of aquifers within sand islands can significantly affect groundwater occurrence and groundwater movement through the island (e.g. Harris 1967; Bolyard et al. 1979; Vacher 1988; Burkett 1996; Collins and Easley 1999; Anderson et al. 2000; Ruppel et al. 2000). Aquifers typical of sand islands can contain substantial reserves of freshwater that support environmental flow to wetland habitats, water supply for the island community and offshore discharge.

Important features of the southeast Queensland coastline are a series of large sand islands that contain freshwater hydrological systems that store vast quantities of groundwater. Bribie Island is currently used as a source of freshwater by local authorities and various land users. Excessive use of groundwater in such settings has the potential for inducing saltwater intrusion, desiccation of wetlands and degradation of groundwater quality.

Throughout coastal southeast Queensland the elevation of shallow groundwater across indurated sand profiles has been well documented (Laycock 1975; Thompson 1981; Reeve et al. 1985; Ward and Grimes 1987; Thompson et al. 1996). Additionally, Cox et al. (2002) and Ezzy et al. (2002) suggest that the indurated sand profiles within the coastal area not only produce a degree of separation of groundwater bodies, but that differences in the chemical composition of the waters is also quite evident. It is therefore apparent that due to the reduced porosity and permeability, extensive indurated sand profiles can play a dominant role in hydrological processes in coastal areas.

A conceptual model for groundwater occurrence on Bribie Island was developed by Harbison and Cox (1998) and a two-aquifer system proposed. It has been noted that even small-scale heterogeneities can be important in controlling groundwater flow

within sand island environments (Anderson et al. 2000). This current study investigates the heterogeneity of the Bribie Island aquifers and is designed to establish the water-bearing properties of aquifer material and presents new data of stratigraphy, groundwater levels, rainfall, barometric pressure and hydraulic testing.

1.1 Aim

The aim of this research is to quantify aquifer heterogeneity within the unconsolidated sands of Bribie Island by use of hydraulic testing and determine vertical and lateral flow of groundwater within a detailed transect of the island and relate this to groundwater chemistry.

1.2 Objectives

Several research objectives are proposed to achieve the aim of this study:

• Further define the geological framework of Bribie Island with particular reference to the spatial distribution of stratigraphic units across a reference transect. • Identify trends in groundwater levels that may reflect aquifer heterogeneity across the reference transect. • Identify spatial variation of groundwater and surface water chemistry that may highlight processes such as groundwater migration and flow. • Determine aquifer hydraulic properties of various stratigraphic units with reference to aquifer heterogeneity across the reference transect. • Develop a conceptual hydrogeological model including aquifer heterogeneity of the central section of Bribie Island. 1.3 Significance of Research

The outcomes of this research will have implications for:

• Greater understanding of causes and distribution of aquifer heterogeneity within coastal environments particularly sand islands. • Provide information on the role of aquifer heterogeneity and the recharge and movement of coastal groundwater. • Contribute hydrogeological information towards an effective groundwater management plan for Bribie Island.

2.0 BACKGROUND TO MATERIALS AND EVOLUTION

Accumulations of masses of sand are a common occurrence along the east coast of Australia (e.g. Stephens 1992; Thom 1984; Roy et al. 1994). These coastal sand bodies are usually related to the position of sea level and are often highly dynamic in form, and in cases where well developed, these sand masses can host major supplies of groundwater. The Bribie Island sand mass is described as a partially drowned extensive strandplain of prograded Pleistocene to Holocene beach ridges (Lang et al. 1998); a distinctive elongate sand spit forms the northern extension of the island.

To enable an understanding of the internal structure, and the occurrence of groundwater on Bribie Island, some understanding of the evolution and sedimentary composition of a prograded sand island is necessary. To provide this background a summary of the geology, morphology and hydrogeology of barrier coasts follows.

2.1 Beaches, Strand Plains and Barrier Coasts

Wave dominated sandy shorelines are often characterised by elongate, shore-parallel sand deposits. These can occur as single mainland-attached beaches, broader beach- ridge strandplains, or as barrier islands (Reinson 1984). The prime characteristics of beaches, strandplains and barrier islands are derived from marine inundation during rising sea level, and reworking of sediments, as distinct from direct fluvial influx. These systems are supplied by longshore transport of river-derived sediments, onshore transport of shelf sediments, erosion of local headlands, and by small coastal streams (Galloway and Hobday 1983). Migrating sediment is concentrated in barrier complexes, tidal flats, or may accrete directly on the mainland as strandplain beaches. The contrasting morphologies of barrier/lagoon and strandplain coasts are shown in Figure 1.

Barrier islands possess some features of strandplains and are transitional to them in character (McCubbin 1982; Reinson 1984). For example, barrier islands can consist of a single active barrier beach (transgressive barrier), or a series of parallel beach ridges and swales situated behind the active beach shoreline (prograded barrier).

Additionally, the prograding barrier typically encloses an extensive back barrier lagoon/estuary. This lagoonal or estuarine water body distinguishes the prograding barrier from a strandplain; otherwise the two systems are genetically very similar (Reinson 1984). An important variable between these systems is the position of sea level.

Figure 1. Comparison of contrasted morphologies of A) barrier/lagoon, B) strandplain coasts and C) tidal flats and their relation to different water bodies (after Galloway and Hobday 1983)

Strandplain systems are broad sheet-like, strike-elongate sand bodies that develop by successive seaward accretion of beach ridges (Galloway and Hobday 1983), and their multiple beach ridges are separated by narrow, marshy swales. The vertical

strandplain sequence is similar to that of a prograding barrier island, grading from shoreface sand, silt, and mud into quartzose beach sands. The morphological character of Bribie Island best fits the model of a “drowned” strandplain. Additionally, strandplains lack the extensive tidal channels associated with low-tidal and sub-tidal sand bodies (Figure 1).

2.2 Barrier Coasts

Often the term “barrier coast” is applied to coastal, unconsolidated sediment bodies (islands or drowned strandplains) that are elongate and parallel to the shoreline. Typically, these sand masses impede drainage from the mainland and are separated in whole or in part by an estuary or lagoon, swamp or marsh, and/or a sand or mud flat (McCubbin 1982; Reinson 1984; Thom 1984; Boyd et al. 1992; Davis 1994). Barrier coasts currently comprise approximately 10-15% of the world’s total coastline (Glaeser 1978; Summerfield 1991). Considering such a wide global distribution, this type of coastal setting is of particular importance in respect to environmental status and hydrological processes.

There is great variation in the type, shape, size, and age of these coastal barriers. However, there are three common primary requirements for the formation of all barriers (Davis 1994): 1. a significant sediment supply, 2. marine and wind processes that will develop and maintain the barrier, and 3. a geomorphic setting where barrier formation can take place.

2.2.1 Coast environments

A number of major geomorphic features are recognised as being common to barrier systems (Galloway and Hobday 1983; Reinson 1984; Thom 1984); a) the sandy barrier complex, b) the enclosed body of water behind the barrier (lagoon/estuary), and c) the channels that cut through the barrier and connect lagoon and sea.

Each environment is characterised by distinct lithofacies. Typically, the barrier (predominantly sand) is partially vegetated and consists of dune ridges landward of

the sub-aerial beach. These sub-aerial beaches may or may not be inundated during high magnitude storm surge conditions (Thom 1984). The enclosed or partly enclosed body of water (lagoon or estuary) and associated back barrier (sand or tidal flats) lie behind the barrier complex (Thom 1984). The lagoonal sedimentary sequences generally consist of interbedded and interfingering sand, silt and mud facies characteristic of a number of overlapping sub-environments (Reinson 1984). Channel inlets provide water movement between the back barrier and open ocean environments during each tidal cycle. Varying tidal ranges result in inlets of varying character, in particular the size of the inlet and the longshore migration rate (Galloway and Hobday 1983). The deepest parts of most channel inlets are dominated by ebb currents and typically have an erosional base marked by coarse lag deposits (Reinson 1984).

2.3 Barrier types and facies

Barrier coast development is favoured by relatively flat, low-gradient continental shelves, abundant sediment supply, and low to moderate tidal range (Glaeser 1978). The origin of barriers has been attributed to at least three distinct mechanisms: 1. the vertical growth and emergence of offshore bars (bar emergence) 2. down drift growth of spits (spit elongation) 3. detachment of beach ridges from the mainland by a rise in sea level (ridge engulfment)

The third mechanism is most likely to occur in coastal zones of low relief (Swift 1975), while barriers built by coastwise elongation may be more common along higher relief coastal zones (Glaeser 1978). Bar emergence is considered less influential in the development of barrier coastlines, a process which is discussed in detail by Otvos (2000). Clear distinction is often difficult among these various modes of origin, particularly as many barriers show evidence of composite development and modification.

To achieve some clarification, four primary modes of barrier formation exist (Roy and Thom 1981; Galloway and Hobday 1983; Reinson 1984; Thom 1984) and have been termed:

1. prograded barrier 2. stationary barrier 3. receded barrier 4. episodic transgressive barrier

Typically, the first three are recognised as the most significant modes of barrier development, however, the inclusion of the fourth mode of formation is necessary to account for the large sands islands of Fraser, Moreton, and North Stradbroke that occur on the high-energy east coast of Australia (Stephens 1992; Thom 1984). Figure 2 illustrates the sectional geometry and morphological relationship of these four types of barrier formation.

Figure 2. Generalised diagram illustrating the sectional geometry and morphological relationship of four barrier types (including some variants) that occur on the high-energy east Australian coast including Bribie Island (1a) and Moreton Is, Nth Stradbroke Is, and Fraser Is (4a) (after Thom 1984)

Strandplain deposits such as that of Bribie Island are common on the relatively low- relief coastline of Queensland (Stephens 1992; Jones 1993). The classification of a strandplain by Thom (1984) includes prograded barriers that contain the presence of a parallel ridge/swale pattern (Figure 2, 1a). This pattern can be seen on maps and aerial photographs of Bribie Island and is characteristic of the prograding evolution of the island.

2.3.1 Prograded barriers

Prograded barriers or strandplain complexes are characterised by multiple, coast parallel beach or foredune ridges (Figure 2) and require abundant supplies of near shore sand for this type of barrier formation (Thom 1984). Sand accumulation takes place on the beach face and is blown inland onto low-relief foredune ridges where it is bound by vegetation. Over time these dune sands are subjected to leaching and soil development. Further accumulation results in seaward migration of the beach face and the formation of either a beach ridge or strandplain (Thom 1984); narrow marshy swales typically develop between the ridges (Galloway and Hobday 1983). These ridges and swales characteristically have amplitude of 3-5 m, often reaching elevations of 7-10 m above sea level (Thom et al. 1978).

In respect to sediment type and grain size, the typical prograding sequence becomes coarser upwards from alternating sand and clay of the shelf and lower shoreface, to sand of the upper shoreface and beach (Galloway and Hobday 1983). Drilling data from barriers on the east coast of Australia show the beach sands to be uniformly fine to medium grained and moderately well sorted (Roy et al. 1994). As shown in Figure 3 the progradational origin of the barrier as well as the coarsening upward profile of the prograding stratigraphic model.

Figure 3. A) Cross-section of a typical barrier island, showing progradational origin of the main beach ridge system (after McCubbin 1982), B) barrier facies model of prograding barrier island stratigraphic sequence (after Reinson 1984)

2.4 Barrier Coast Hydrology

A major role of barrier coastlines is in habitat creation, such as sheltering fragile estuaries and marshlands that serve as incubators for marine organisms. Additionally, barriers contribute to the cycling of nutrients and other materials through the natural wetland habitats (Ruppel et al. 2000). A certain amount and quality of freshwater is therefore needed by all physical, chemical and biological systems associated with barriers.

All naturally occurring freshwater on these barriers originates from precipitation. Although rainfall is the most prevalent type of precipitation on barrier coastlines, precipitation can also take the form of snow, dew condensation and fog interception (Urish 1977). Freshwater occurrence on barriers can be considered as two forms (a) surface water, and (b) groundwater, although they may be connected.

2.4.1 Surface water

Surface water drainage patterns are typically little developed and may be diffuse in character along barrier coastlines due to the low-relief morphology and the highly transmissive surface sediments. However, despite the highly transmissive upper dune sands, surface water accumulation can occur throughout many parts of the

barrier system. Surface water often occurs within the marshy swales between the dune ridges. Additionally, if a swale is sufficiently deep it may intersect elevated groundwater resulting in a “window” into the water table. Open bodies of surface water are typically restricted to a narrow strip along the coastline behind the foredune ridges. These water bodies often occur as brackish lagoons which are tidally affected and are typically separated from the sea by small sand bars that are often breached during severe storm events.

2.4.2 Groundwater occurrence

Barrier islands contain variable reserves of freshwater, despite being surrounded by seawater. Precipitation continuously infiltrates permeable island sediments, and a freshwater body develops as saltwater is displaced (Collins and Easley 1999). Figure 4 illustrates the development of a typical freshwater lens beneath a homogenous and isotropic barrier island.

In barrier islands, groundwater flow is approximately normal to the long axis of the island, and the phreatic aquifer takes the form of a Dupuit-Ghyben-Herzberg (DGH) freshwater lens partially or wholly underlain by more dense saltwater (Urish 1977; Ruppel et al. 2000). These lenses typically occur under islands that are small, very permeable, and/or lightly recharged (Vacher 1988).

The DGH principle is a combination of the Dupuit assumption of horizontal flow and the Ghyben-Herzberg principle that states when a freshwater lens overlies saltwater water in homogenous and isotropic material, the freshwater lens will extend below mean sea level (MSL) at a ratio of 40:1 (Harris 1967; Vacher 1988). For an island characterised by homogenous and isotropic hydraulic properties and similar values for mean sea level on both the lagoon and ocean sides, the DGH lens should be symmetrical as illustrated in Figure 4 (Ruppel et al. 2000).

Figure 4. Fresh groundwater water flow through a barrier island of homogeneous and isotropic sedimentary composition, where hf = the head of freshwater above mean sea level and Z is the depth of the freshwater lens (after Harris 1967)

However, in most islands it is inappropriate to view the boundary between fresh and saline groundwater as the sharp interface that is generally inferred in respect to the DGH principle (Vacher 1988). The actual state of the lens is highly dynamic and influenced by many factors that lead to a transitional zone of finite thickness (Urish 1977; Vacher 1988). The size and position of the transitional zone can be affected by numerous factors such as higher mean sea level (MSL) on the ocean side of the island than the lagoon side, tidal action from both sides of the island, freshwater extraction via evapotranspiration and pumping, recharge amount and variability, and hydraulic properties of the island aquifer (Harris 1967; Urish 1977; Vacher 1988; Ruppel et al. 2000).

2.4.3 Porosity and aquifer storage

The amount of groundwater a barrier island aquifer can take in or release for a given change in head controls the amount of groundwater that can be stored. The amount of water an aquifer can hold in storage is determined by its porosity (Weight and Sonderegger 2000); the porosity (n) of a material is the percentage of the formation that is void of material (Fetter 1994). The general range of porosities that can be expected for some typical sediments is listed in Table 1.

Table 1. Porosity ranges for unconsolidated sediments (after Fetter 1994) Sediment type Percentage of void space Well sorted sand or gravel 25 – 50 Sand and gravel, mixed 20 – 35 Glacial till 10 – 20 Silt 35 – 50 Clay 33 – 60

Porosity within a barrier island is governed by the function of size, shape and arrangement of the sediment grains (Weight and Sonderegger 2000). The porous voids are typically filled with air or fluid. Primary porosity between the sediment grains forms during the formation of a barrier island. Secondary porosity is limited on a sand island and relates to features that occur after the deposit has formed such as pathways made by vegetation roots and animals burrows. The porosity of an aquifer can also be reduced; fine-grained material can be flushed into shallow aquifers where it fills void spaces.

The specific yield (Sy) of an aquifer is the ratio of the volume of water that drains from a saturated aquifer by gravity, to the total volume of the aquifer (Fetter 1994). Table 2 lists a number of sediment types and the typical specific yield as percent.

Table 2. Specific yield in percent for unconsolidated sediments (after Fetter 1994) Material Maximum Minimum Average Clay 5 0 2 Sandy clay 12 3 7 Silt 19 3 18 Fine sand 28 10 21 Medium sand 32 15 26 Coarse sand 35 20 27 Gravely sand 35 20 25

Since specific yield represents the volume of water that an aquifer will yield by gravity drainage, with specific retention (Sr) the remainder, the sum of the two is equal to porosity (Fetter 1994): n = Sy + Sr

Storativity (S) is a dimensionless value assigned to an aquifer and relates to the amount of water an aquifer can store. The storativity for an unconfined aquifer is typically taken to be equal to the specific yield, and has a range of 0.03 to 0.3 (Fetter 1994). In confined aquifers the water released from storage is a function of the compressibility of the aquifer materials and the compressibility of water and is expressed as specific storage (Ss) (Weight and Sonderegger 2000). Storativity values -3 -6 for confined aquifers (Ss x aquifer thickness) can range from 10 to 10 . Typically, aquifers that have a storativity value between 0.03 and 10-3 are described as leaky or semi-confined aquifers.

2.4.4 Hydraulic conductivity

Groundwater contained within the pore spaces of an aquifer is capable of moving from one void to another. Thus, it is the ability of an aquifer to transmit water that, together with its ability to hold water, constitute the most significant hydrogeologic properties (Fetter 1994). Darcy’s Law defines the quantity of groundwater movement through porous material:

Q = −KAi (1) Where; Q = Volumetric discharge rate (L3/t), and L = length or distance K = Hydraulic conductivity (L/t) A = b x w, the cross-sectional area perpendicular to flow (L2), [in horizontal flow, the saturated thickness of the aquifer (b) multiplied by the width of aquifer (w)] i = Hydraulic gradient (L/L) or slope to the potentiometric surface

Darcy’s law expresses that the volumetric rate (Q) of groundwater is proportional to the proportionality constant (hydraulic conductivity, K) of the porous media and the change in head over the length of the material (i.e. hydraulic gradient) (Fetter 1994; Weight and Sonderegger 2000). The negative sign indicates that the flow is in the direction of decreasing hydraulic head. Therefore, hydraulic conductivity is dependant upon the nature of the porous medium and is a measure of the rate at which water can move through the permeable medium. Hydraulic conductivity may also be referred to as the coefficient of permeability.

Hydraulic conductivity has the dimensions of length over time (L/t). Typical units of expression are m/day or cm/sec, and hydraulic conductivity values for earth materials can range over twelve orders of magnitude (Weight and Sonderegger 2000). The ranges of hydraulic conductivity values for various materials are illustrated in Figure 5.

Figure 5. Range of hydraulic conductivity values of earth materials (after Weight and Sonderegger 2000)

A barrier island typically composed of silty sands and clean sands will therefore have a relatively narrow range of hydraulic conductivity from 10-2 to 102 depending upon the lithology of the island (Figure 5). Due to the relatively high hydraulic conductivity of barrier islands, a decrease in permeability may have a substantial affect on the groundwater system.

Estimation of hydraulic conductivity can be made by a number of established methods. The hydraulic conductivity of unconsolidated sands can be estimated from the grain-size distribution of a sample by the Hazen method (1911). The effective grain-size is determined from a grain-size distribution plot, and together with a sorting coefficient is related to hydraulic conductivity (Fetter 1994; Weight and Sonderegger 2000). Additionally, the hydraulic conductivity of samples may be obtained from laboratory measurements via permeameters. Permeameters enable water to move through the sample and the flux is measured to estimate hydraulic

conductivity. However, both grain-size analysis and laboratory testing require the removal of samples from field conditions. Removal of a sample may disturb sediment packing leading to error within the estimated hydraulic conductivity. In situ hydraulic testing to determine aquifer properties therefore often results in more accurate estimates. In situ hydraulic testing is often performed via bailer or slug tests and pumping tests.

2.4.5 Aquifer heterogeneity

Very few, if any, coastal barriers are completely homogenous and isotropic (Harris 1967), and aquifer heterogeneity within sand islands has a profound affect on groundwater occurrence and movement through the island. Lateral or vertical variations in hydraulic properties and the presence of low permeability layers at depth have been shown to cause deviations of the freshwater lens from the idealised DGH morphology (Ruppel et al. 2000).

Layers of less permeable sediment can restrict or prohibit the infiltration of water through the unsaturated zone, and cause water to accumulate on top of these layers (Fetter 1994). Elevated groundwater tables that exist above layers of less permeable units are termed perched water tables (Driscoll 2003). The presence of low permeable material affecting the groundwater regime of barrier environments is not uncommon (e.g. Harris 1967; Bolyard et al. 1979; Vacher 1988; Burkett 1996; Harbison 1998; Collins and Easley 1999; Anderson et al. 2000; Ruppel et al. 2000). Perched groundwater moves laterally above the low permeability layer and may either seep downward toward the main water table at the layers margin or is discharged at the coastal boundary.

Additionally, where the lens is perched on shallow, low permeable material, water tables are often higher than they would be if the material were not present (Vacher 1988). Figure 6 illustrates the response of the freshwater lens to low permeability material at a shallow depth within the sedimentary profile of a sand island.

Figure 6. Fresh groundwater flow through a barrier island composed of stratified sediments of different permeability, where hf = the head of freshwater above mean sea level and Z is the depth of the truncated freshwater lens (after Harris 1967)

As a well studied example, Hatteras Island, North Carolina, USA, contains heterogeneous stratigraphy resulting in elevated water levels across the island (Harris 1967; Burkett 1996; Anderson et al. 2000). Field data consisting of cross-island water table trends indicate unusually high water table elevations that are related to a shallow low permeability unit (Anderson et al. 2000). The low permeability unit was interpreted as a former wetland that has been buried by a series of parabolic dunes.

Hydraulic tests on Hatteras Island by Burkett (1996) consisted of several multiple well pumping tests that identified the aquifer to behave as a stratified aquifer. The conceptual model of the island is similar to that illustrated in Figure 6, with an upper unconfined aquifer, a deep semi-confined aquifer, and a low permeability layer separating the two aquifers. Such a model is of significance to Bribie Island. Burkett (1996) attained values for the hydraulic properties of transmissivity, horizontal hydraulic conductivity, vertical hydraulic conductivity, and specific yield for the upper unconfined aquifer. Following from the studies of Burkett (1996), numerical modelling of the cross-island water levels by Anderson et al. (2000) provided values of horizontal hydraulic conductivity for the deeper sediments and the low permeability unit of the stratified island aquifer. The analysis of Anderson et al. (2000) confirmed that the low permeability unit caused the elevation of the water table and that the layer provided some confinement of the deeper aquifer.

Additionally, aquifer heterogeneity can also impact on the groundwater chemistry of the island aquifer. Fresh groundwater typically flushes saline water from permeable zones more rapidly than from low permeable zones. For the case of Hatteras Island, differential flushing of saltwater water through the stratified permeable and relatively impermeable sediments has lead to more than one freshwater/saltwater water interface in the vertical section (Harris 1967). Therefore, the position of the interface is not governed by the DGH principle or by any of the modifications to this relationship that assume lithologic homogeneity.

Variable freshwater/saltwater water interface relationships have also been reported for other barrier islands where aquifer heterogeneity is prominent. The island aquifers of Grand Isle, Louisiana, USA, and Assateague Island, Maryland, Virginia, USA, are other examples where variations in hydraulic conductivity and permeability exist (Bolyard et al. 1979; Collins and Easley 1999).

2.4.6 Hydrochemistry

Results from geochemical studies of groundwater within barrier environments also indicate that aquifer heterogeneity not only affects the freshwater/saltwater water interface but can also affect major and minor ionic relationships (Laycock 1975; Reeve et al. 1985; Collins and Easley 1999; Suresh Babu et al. 2002). Evaporative processes typically result in an atmospheric supply of ions that reflect ionic ratios of local seawater. Since groundwater recharge in an island setting is dominated by rainfall, the resulting groundwater chemistry may also resemble local seawater ionic ratios. In addition, a low relief sand island such as Bribie Island is highly susceptible to salt spray and surface water chemistry (ionic ratios) may reflect seawater for this region (at least partially). Deviation of groundwater ionic ratios from the initial rainfall chemistry is largely the result of interaction between groundwater and the island sediment.

For a barrier island, the dominance of an almost entirely silicious dune complex may result in only minor dissolution of minerals due to the limited degree of weathering. Enrichment of silica in the groundwater body is typically the most common product of these weathering processes and serves as a useful indicator of flow path length

(Little and Roberts 1982). However, sodium, magnesium, calcium, chloride, bicarbonate and pH can also be used to discriminate between different water types that have been exposed to different aquifer materials. Where the aquifer includes organic rich indurated sand the water chemistry may show signs of ion exchange and the dissolution of minerals resulting in a groundwater of reduced pH and altered ionic ratios (Reeve et al. 1985).

As an example, recent hydrogeochemical analysis of groundwater samples from Valadares Island, Brazil, typically display a chemical signature of sodium, potassium, and chloride that indicate rainfall as the dominant recharge source (Suresh Babu 2002). However, the relative enrichment of sodium and the substantially lower amounts of magnesium and calcium were attributed to the high concentrations of organic carbon in the water table aquifer. Elevated concentrations of organic carbon within groundwater samples from numerous coastal barrier environments have often been associated with low permeability layers (Laycock 1975; Pye 1982; Reeve et al. 1985; Harbison 1998; Anderson et al. 2002). Indurated podsol layers are a common feature of many coastal areas around the world and particularly along the Australian eastern coastline. Where drainage is low, such as that on beach ridge plains, areas of humate deposition may cover wide areas (Pye 1982).

2.5 Nature of Indurated Sand

Humic substances are readily available in highly vegetated coastal areas. Soluble and colloidal humic substances form as a result of bacterial breakdown of organic matter and subsequent leaching of humus by rainwater (Pye 1982). The soluble and colloidal humic substances are rapidly eluviated from the vadose zone and deposited as cutans on quartz grains (Cox et al. 2002); the resulting layer of dark brown to black indurated sand is referred to locally as “coffee rock”. However, Pye (1982) suggests “humicrete” as a more suitably descriptive term for the largely humate- cemented sediments. Indurated sand has been classified as quartz sand grains cemented together by the infilling of pores by a variety of cements, predominately organic matter and clays (Farmer et al. 1983; Thompson et al. 1996; Cox et al. 2002).

Humate tends to remain soluble under alkaline conditions and to flocculate where pH is acidic (Pye 1982). Flocculation has been reported to occur at pH 4.5 and lower, although, Pye (1982) noted that flocculation of the Cape Flattery, north Queensland, humate only occurred at pH ≤ 2 and suggested that pH variation is unlikely to be the major control of humate precipitation. Additionally, since surface water and shallow groundwater of many coastal sand bodies often have an average pH > 2, it is also suggested that the prevailing acidic conditions are not the sole source of humate precipitation.

Therefore, the dominant mechanism for the deposition of humate material in barrier environments is likely to be mechanical. It is suggested that the repeated flushing of fresh humate into the sands and the subsequent drying during low rainfall seasons leads to thickening of cutans and infilling of void spaces (Pye 1982). In some cases the intergranular space of these sediments is completely filled by humate, dramatically reducing porosity and permeability (Thompson et al. 1996). This wetting and drying process is considered integral to the formation of the indurated layers and is considered to occur typically beneath drained beach ridges. For example, in areas that remain waterlogged such as the swale areas of barrier coasts, the absence of the drying phase may only result in very friable organic rich sands and not highly indurated sand layers.

The elevation of groundwater above indurated sand layers is a common occurrence due to reduced porosity of the sands. As a consequence streams and lakes associated with indurated sand layers are commonly formed at higher than normal elevations. An example of these perched lakes occur within the large quaternary sand masses of the southeast Queensland coastline, including Fraser Island, Moreton Island, North Stradbroke Island, and the Cooloola sand mass (Laycock 1975; Little and Roberts 1983; Reeve et al. 1985).

The Cooloola sandmass contains a prominent example of indurated sand development beneath the sand dunes. The Cooloola National Park and Forestry Reserve is approximately 100 km north of Bribie Island and consists of a massive episodic transgressive barrier complex. The sand dunes are dominantly quartz sands that reach elevations of 260 m above sea level. The sands are highly permeable and

the sandmass forms a large unconfined aquifer. Reeve et al. (1985) examined the chemical composition of waters from springs, creeks and lakes throughout the Cooloola area as part of a study of landscape dynamics in coastal sand dunes. Numerous lakes and streams occur at elevated levels above the regional water table and are considered to be perched above low permeability layers of indurated sand. These layers are associated with older dune systems (Reeve et al. 1985). The perched water is usually stained with organic matter (“black water”), where as the water emanating from the deep-seated main water table is colourless (“white water”). The organic rich perched water is also distinguished by lower concentrations of silica, and pH; additionally, higher concentrations of tritium indicate a shorter residence time than waters of the main storage system (Reeve et al. 1985).

Similarly, Laycock (1975) noted discernable differences between the water chemistry associated with indurated sand layers and water chemistry of the regional water table within North Stradbroke Island, southeast Queensland. Like the Cooloola sandmass, North Stradbroke Island is also classified as an episodic transgressive barrier. Geophysical investigations on North Stradbroke Island revealed a number of areas where indurated sand layers displayed a seismic velocity higher than the surrounding sandy units. This seismic reversal was thought to be due to the relatively impermeable nature of the indurated sand layer above which there was an observed saturated zone. This was considered to indicate an area of a perched water table (Laycock 1975). Surprisingly, the influence of indurated sand on the regional groundwater regime may in fact be quite localised for large systems such as North Stradbroke Island and the Cooloola sandmass. However, for smaller groundwater regimes, the influence of this type of aquifer heterogeneity may be a dominant feature of the island environment. The following study is focused on the influence of these heterogeneities on the groundwater regime of Bribie Island.

3.0 PHYSICAL SETTING OF BRIBIE ISLAND

3.1 Regional Setting

Bribie Island is located within northern Moreton Bay, southeast Queensland and is separated from the mainland coastline by the shallow tidal estuary of Pumicestone Passage (Figure 7). The island is situated approximately 65 km north of the capital city, Brisbane, has an approximate area of 144 km2, length of 30 km and an average width of 5 km.

Figure 7. Location of Bribie Island in Moreton Bay, Queensland, Australia. Outer islands which form Moreton Bay are also shown

Figure 8 illustrates that urban development is restricted to the southern one-third of Bribie Island, which is a popular retirement and tourist location with a rapidly growing permanent population. The current population is approximately 15 000 but

during summer holiday periods the population of the island can increase by up to three times (Harbison and Cox 1998). The island is additionally the location of a weather research station, an aquaculture research station, a water supply reserve, national park areas, and commercial pine plantations. Road systems in the northern two thirds of the island are unsealed forestry tracks only.

Figure 8. Geographical map of Bribie Island indicating drainage features, surface water bodies, residential areas, forestry tracks, and the adjacent mainland (GIS data sourced from NRM & E)

Bribie Island has a landscape more similar to the adjacent coastal lowlands than to the massive transgressive outer islands of Moreton and North Stradbroke (Coaldrake 1961). A significant proportion of the island is less than 5 m above sea level and the maximum elevation is 17 m above sea level. North-northwest trending dune ridges

(relict foredunes) occur as the dominant topographical features and form the highest point in the central-eastern section of the island. Figure 9 illustrates that two beach ridge systems are separated by a large swale (interconnected low-lying Melaleuca swamp system) extending through the long axis of the island. The central swale is a relict estuary and is the dominant drainage feature of the island. Surface water drainage across the island is not well developed due to rapid infiltration through transmissive surface sands and the low relief of the island. In the south of the island the natural drainage is via wetlands to Dux and Wright’s Creek, both of which are now modified. In the north the Central Swale discharges into Westaway Creek. A series of fresh and brackish lagoons fringe the east coast.

Figure 9. Bribie Island topographical map indicating drainage features, surface water bodies, and two dominant north-northwest trending dune ridge systems (GIS data sourced from NRM & E)

3.2 Geology

Bribie Island is composed of Pleistocene to Holocene sand to clayey-sand deposits overlying bedrock of Jurassic Landsborough Sandstone as illustrated in Figure 10. The Landsborough Sandstone is predominantly fine-grained quartzose sandstone. The sandstone contains shale beds, is underlain by a conglomerate base and is in excess of 100 m thick (Ishaq 1980). Sandstone does not crop out on Bribie Island. Depth to bedrock is confirmed by drilling.

Figure 10. Generalised geological map of Bribie Island indicating the predominance of Holocene to Pleistocene unconsolidated material overlying Jurassic Sandstone (GIS data sourced from NRM & E)

During long periods of lower sea level the surface of the sandstone bedrock was weathered and eroded before deposition of the Bribie Island sand sequences. The weathered profile of the sandstone bedrock on the mainland can vary in thickness from several metres to 20 m thick and exhibits laterite zonation (Oberhardt 2000; Ezzy et al. 2002). Previous studies on the adjacent mainland indicate the sandstone provides a limited resource of groundwater (Cox et al. 1996). Limited data exists relating to the weathered sandstone beneath Bribie Island. However, it is inferred that the weathered sandstone beneath the unconsolidated sediments of Bribie Island is of limited groundwater resources as per the mainland.

A palaeochannel within the sandstone bedrock extends from the mainland (Ezzy 2000; Oberhardt 2000) continuing northeast under Bribie Island as illustrated in Figure 11. This bedrock low is confirmed by drillhole data (Harbison 1998). The sediment profile is thickest in the vicinity of the palaeochannel with depths > 40 m.

Figure 11. Aquifer base contour map of Bribie Island from drillhole data (after Harbison 1998). Geographical features are also indicated

3.3 Geomorphology

The unconsolidated deposits result from sea level variations during the Pleistocene and Holocene (Coaldrake 1960; Lumsden 1964). The island has been formed by the deposition of sand supplied by the net northward movement of sands along the mainland coastline by the process of longshore drift (Isaacs and Walker 1983). The shallow sand profiles are typically comprised of well-sorted, reworked, fine to medium-grained sands (Harbison 1998), and are thinnest towards the north west of the island as illustrated in Figure 11.

The stratigraphic successions of Quaternary sand deposits of Bribie Island comprise four main units (Lumsden 1964; Hekel and Day 1976; Ishaq 1980; Harbison 1998): 1. Pleistocene beach ridge system 2. Holocene beach ridge system 3. active foredune system 4. estuarine tidal delta system

3.3.1 Pleistocene beach ridge system

The Pleistocene beach ridge sands constitute the most widespread unit within the island and consist of fine to medium quartz sand. Features such as the multiple beach ridges and parallel foredunes as illustrated in Figure 12 are related solely to progradation (Coaldrake 1960; Lumsden 1964; Pye and Bowman 1984). Prior to erosion, these ridges were “hinged” at a headland east of Caloundra Head and followed a gradual concave sweep to the south (Harbison 1998). The longitudinal axes of these ridges are aligned parallel with the prevailing southeast winds that can be readily seen in aerial photographs. The total thickness of the Pleistocene sediments varies from 5 to 25 m, and they dip gently to the south and east beneath the Holocene beach ridge sediments (Ishaq 1980).

Within the Pleistocene dune sands exists an extensive indurated sand layer at an approximate depth of 5-6 m with a maximum measured thickness of 9 m (Ishaq 1980). The indurated sand layer has good correlation between drill holes. Harbison (1998) graphically displayed the occurrence and thickness of the indurated sand layer

across the island (Figure 13), the indurated layer at its thickest is approximately 5-8 m thick, but over much of the island the thickness is 1-3 m.

Figure 12. Lithological map of Bribie Island indicating the four major types of geomorphology; Pleistocene beach ridges, Holocene beach ridges, active foredunes, and estuarine tidal delta deposits (GIS data sourced from NRM & E)

The greatest thickness of indurated sand is located centrally on the island beneath the main beach ridge system. Based on existing drill hole data the degree of induration decreases with depth to a zone of dark brown stained sands. Indurated sand is uncommon in the Holocene beach ridges south of the Woorim – Bongaree road and in the tidal delta areas (Harbison 1998). The top of indurated sand layer is generally 1-3 m above mean sea level.

Analysis of samples from Bribie Island using Scanning Electron Microscopy (SEM) has revealed the presence of cutans infilling the pores, suggesting that cementation is mainly by organic material (Harbison 1998). Results from Loss On Ignition (LOI) analysis of Bribie Island indurated sand samples indicate a range of organic carbon concentrations of 2.3 - 7.7 % (n=11) with an average of 4 % (Harbison 1998; Cox et al. 2002).

Figure 13. Thickness of indurated sand layer for Bribie Island based on drillhole data (after Harbison 1998)

3.3.2 Holocene beach ridge system

Holocene beach ridge sands occupy the southernmost part of Bribie Island. These sands consist of well-sorted quartz sand with shell rich fragments (Ishaq 1980). The beach ridges display varying alignments (Figure 11) that are most likely due to a change in recent marine current patterns within Moreton Bay (Armstrong 1990; Harbison 1998). These sediments display the ridge swale morphology similar to the older Pleistocene ridges. It is not possible to determine the boundary of younger and older sand deposits with any accuracy, because of the similarity in lithology and absence of a marker horizon (Ishaq 1980). Additionally, recent accretion of beach ridges in the south of the island is suggested to have occurred concurrently with erosion of the active foredune further to the north. Along the east coast of Bribie Island the ocean current trend is to the south, leading to the movement of eroded sediment in this direction. The southerly ocean current is in opposition to the northward longshore currents that dominate the rest of the regional coastline. The change in current direction is the result of refraction of northward moving longshore currents around the headland of Moreton Island (Jones 1992; Lester 2000).

3.3.3 Active foredune system

The active foredunes are typically between 5-10 m in height and occur as a narrow strip along the eastern coastline, as illustrated in Figure 9. Most of these dunes are stabilised by full vegetation. However, erosion is occurring along this section of the coastline creating erosion scarps (Jones 1992). Four large coastal lagoons are situated immediately behind the active foredunes. The active foredune system extends to the north and forms a narrow spit. The spit can experience severe erosion leading to a possible future breakthrough (Lester 2000).

3.3.4 Estuarine tidal delta system

Estuarine sediments predominately occur on the western part of Bribie Island (Figure 12) and are composed of sands and mud deposited in low energy bay and lagoonal environments (Hekel and Day 1976; Ishaq 1980). The estuarine deposits occur within the central swale between beach ridge deposits and in the tidal delta system (Harbison 1998). The central swale is suggested to have in-filled during the last 6000 years, initially from the south. Deltaic deposits are derived from local lithic

sources and marine sources; they consist of low-lying poorly sorted sediments and occur in the north and west of the island (Harbison 1998).

3.4 Drainage System

The drainage patterns of Bribie Island are ill-defined; however surface water exists in the form of highly ephemeral streams, marshy swales, and coastal lagoons. Most significant surface water flow occurs on the island notably after heavy rainfall periods. Additionally, significant flow of surface water occurs after heavy rainfall periods from the beach ridges towards the central swale and the coastal lagoons. Ponded water is often held in depressions where an organic silt seal often restricts the infiltration of surface water for days to weeks after a heavy rainfall event (Harbison 1998).

3.5 Climate

Bribie Island has a sub-tropical climate typical of coastal southeast Queensland with mean monthly maximum temperatures ranging from 20 oC to 29 oC. Currently there are no rainfall stations on Bribie Island registered with the Bureau of Meteorology. However, previous records from two abandoned registered stations in the south of the island give an annual rainfall amount of approximately 1350 mm (Isaacs and Walker 1983; Harbison 1998). Annual and monthly rainfall statistics are shown in Tables 3 and 4 respectively for the period of registered operation (Isaacs and Walker 1983).

Table 3. Annual rainfall from registered stations located on Bribie Island (after Werner 1998) 040697 040027 040685 040040 Station Number and 040284 Redcliffe Bribie Is. Bribie Is. Caloundra Location Beerburrum SES (Bongaree) (UQ) SS

Period 1981-1997 1931-1990 1978-1993 1898-2003 1899-1992

Average annual 1179 1358 1287 1444 1560 rainfall (mm/yr) Maximum annual 1530 (1983) 2471 (1974) 1639 (1988) 2802 (1974) 2560 (1974) rainfall (mm/yr) Minimum annual 721 (1993) 726 (1944) 940 (1979) 407 (1902) 726 (1902) rainfall (mm/yr)

Table 4. Mean monthly rainfall – Bongaree (after Isaacs and Walker 1983) Month J F M A M J J A S O N D Mean (mm) 173 190 178 108 105 84 70 49 46 102 103 132

In addition to rainfall stations, an isolated tipping-bucket rainfall gauge is situated on the central eastern coastline. The rainfall gauge is operated by the Queensland Department of Natural Resources, Mines and Energy and records values of rainfall that approximate 1400 mm per year (Harbison 1998). The wettest months are the summer period of December to March, and the winter is comparatively dry as illustrated in Figure 14. Summer cyclonic conditions are also occasional. There is an increase in annual rainfall in a northerly direction along the island of 20% as a result of rain shadow effects from the two large outer islands, Moreton Island and North Stradbroke Island (Harbison 1998).

Figure 14. Rainfall data for Bribie Island years 1993 to 2000. Data provided by the tipping bucket rainfall gauge operated by the Queensland Department of Natural Resources, Mines and Energy No. 540055

3.6 Evaporation

No evaporation data are published for Bribie Island. The nearest evaporation station is located at the Brisbane Airport approximately 60 km to the south. Results from a class A pan (Table 5) show the variation in evaporation during the year (Isaacs and

Walker 1983). These records indicate the mean annual evaporation at Brisbane is approximately 1570 mm.

Table 5. Mean monthly evaporation – Brisbane (after Isaacs and Walker 1983) Month J F M A M J J A S O N D Mean (mm) 180 142 142 117 83 66 72 100 131 157 176 202 Av. daily (mm/d) 5.8 5.1 4.6 3.9 2.7 2.2 2.3 3.2 4.4 5.1 5.9 6.5

Typical of coastal southeast Queensland, evaporation slightly exceeds mean annual rainfall. Additionally, Harbison (1998) indicates that potential evapotranspiration for Bribie Island for the period 1990-1995 has daily ranges between 17 mm and 1 mm per day, with an average day-to-day variation of 2 mm. The average annual potential evapotranspiration for the same period is 1770 mm/year (Harbison 1998); of note Bubb and Croton (2002) suggest that for the pine plantation evapotranspiration rates approximate 1100 mm/yr.

3.7 Groundwater Recharge

Harbison (1998) indicates that a comparison of rainfall amounts with monitoring well water levels indicates that four general situations occur, which have been quantified by correlation of hydrographs with mean cumulative rainfall. The four situations are summarised as follows: a) recharge is well-correlated with rainfall, which is typical of well-drained Holocene ridges (e.g. the area south of the Woorim-Bongaree Road); b) recharge is poorly-correlated with rainfall (i.e. the water table “under- responds’ to rainfall events). This situation is found in deeper boreholes in Pleistocene sand deposits overlain by indurated sand layers. c) recharge “over-responds” to rainfall. This is typical of swales where recharge has been laterally directed from topographically higher areas, either as surface runoff or as shallow seepage across indurated sand layers; and d) recharge and rainfall are poorly-correlated, but there are large hydrograph fluctuations. These fluctuations are common in areas under strong tidal influence.

Water levels in bores in the southern part of the island are also subject to anthropogenic influences, such as injection and extraction of water for irrigation and domestic uses. These factors can complicate natural discharge and tidal effects.

After rainfall, recharge to the regional water table generally occurs within 48 hours, which allows the response to be studied at spatially discrete points. Harbison (1998) estimated recharge (using the chloride accretion method) at 7% for the island as a whole and 18% for the southern part of the island respectively. Previous estimates of recharge to the southern part of the Bribie Island are 40-45% (Lumsden 1964) and 18% (Ishaq 1980). A previous estimate for the whole of island based on numerical modelling is 8% (DNR 1996).

3.8 Vegetation

Pine plantation has replaced large tracts of native vegetation across the central two thirds of the island. The pines are restricted predominantly to the two dune systems leaving native Melaleuca woodland to dominate the adjacent swales and coastal zones. Vegetation types in the less-disturbed areas on the island are related to soil water availability, soil nutrient status, salinity, waterlogging tolerance and landform age (Harbison and Cox 1998). As a result, zonation of vegetation communities and species can also serve as useful indicators of shallow groundwater occurrence (Harbison 1998).

3.9 Land use

The northern two thirds of Bribie Island is under the management of the Queensland Parks and Wildlife (QPW) organisation. However, the Queensland Department of Primary Industries – Forestry (DPI-Forestry), uses the majority of this area under special lease for the growth of pine plantations. Commercial pine plantations have been in service on Bribie Island since 1960 when Australian Paper Manufactures (APM) planted the first rotation. During the first rotation the pines suffered greatly from high stocking rates, minimal thinning, insect attack, drought and fire. Ownership of the plantation changed from APM to CSR Softwoods before DPI- Forestry took over the operation. Removal of the first rotation was finalised at the end of 2002 while planting of the second rotation occurred concurrently.

Remnant vegetation is mostly secured as National Park. The National Park area includes the entire northern spit, the active foredune of the east coast, the deltaic and tidal areas of the western coastline, and the area south of the pine plantation. Additionally, corridors through the plantation have been established to help minimise impact on fauna movement throughout the island. The remnant vegetation of the central swale is currently under the control of the Queensland Department of Natural Resources and Mines (NRM & E).

4.0 HYDROGEOLOGICAL STUDIES OF BRIBIE ISLAND

Since the opening of the Bribie Bridge in 1963, large urban expansion on the island has placed high demands on the potable water supply. Supply of potable water to the growing urban population on the island has been the priority of most groundwater investigations over the last four decades. The investigations have been almost entirely concentrated in the younger Holocene sands in the south of the island adjacent to the residential areas.

Groundwater management on the island was initiated in 1963. At the request of the Department of Local Government, the Geological Survey of Queensland (GSQ) carried out drilling of 31 wells at an average depth of 14 m (Lumsden 1964). An area of 2.6 km2 was proposed and set aside as a water reserve south of the cross- island road (Figure 15), this being considered the deepest part of the aquifer. Of the thirty-one wells, 3 were abandoned, 6 were established as extraction wells, 16 observation wells were placed along an east-west transect, and 6 observation wells were placed adjacent to the coastline. Further investigations in 1966-1967, included the drilling of an additional 21 extraction wells within the water reserve to supplement the existing system.

After continuing problems with the extraction wells due to iron fouling of the screens, groundwater extraction was converted in 1971 to a 3 km long and 5 m deep extraction trench located within the water reserve. John Wilson and Partners (1979) reviewed the performance of the water reserve, trench system, pumping plant, and the treatment processes. It was recommended that the water reserve be expanded to the west and north and the trench system be fully developed. The existing trench system was extended and a second trench north of the cross-island road was constructed. Both trenches were also subsequently deepened.

A hydrogeological reconnaissance of the southern part of the island was undertaken a second time by GSQ in 1980 (Ishaq 1980). The investigation considered the further expansion of the water reserves particularly south of the cross-island road (Figure 15). However, two other areas north of the cross-island road were also noted for

future consideration, the eastern coastal strip, and the area south of the pine plantation. Additional to field observation of water levels and water balance calculations, Ishaq (1980) analysed two pumping tests conducted by John Wilson and Partners in 1966. The pumping tests were designed to give estimates of aquifer parameters such as hydraulic conductivity and aquifer specific storage.

Groundwater modelling of the southern section of the island was initiated with a two- dimensional dynamic model (cross-sectional) to determine the response of the saline groundwater interface adjacent to the main water extraction trench (Isaacs 1983). To further develop the modelling process a finite difference numerical model (horizontal planar) of the same area was developed (Isaacs and Walker 1983). Both of these models worked from assumed hydraulic parameters and indicated that the groundwater heads should be raised between the extraction trench and the adjacent sea. The relocation of the effluent recharge beds to the southeast of the island was recommended to artificially increase the groundwater heads. The effects of effluent recharge, the fate of the recharged effluent, and the rate of change of water quality was investigated by Marsalek and Isaacs (1988).

The first whole-of-island hydrogeological investigation was initiated by the Water Resources Commission in 1992 and included the drilling of 23 observation wells along 7 cross-island transects from the north (adjacent to Westaway Creek) to the southern coastline as shown in Figure 15 (Department of Environment and Heritage 1993). Since 1992 regular monitoring of groundwater levels and chemistry from the extensive observation well network has been conducted and results have been stored within the NRM & E groundwater database. Additionally, two wells were fitted with continuous groundwater level logging devices and a rainfall gauge installed on the eastern coast beside one of the automated wells. To further the whole-of-island investigation, the Groundwater Assessment Group of NRM & E installed 6 additional observation wells across the island in 1995. From the observed groundwater levels a transient finite-difference numerical model was developed (Werner 1998). The model was designed to support management of the pine plantation clear-felling operation.

A similar process was also undertaken in 1998 where a transient finite-difference groundwater model was developed to investigate processes involved with the development of an extraction well field along the axis of the Pleistocene beach ridge in the north of the island (Werner 1998). The model incorporated varying recharge rates, hydraulic parameters and extraction rates. However, a limiting factor for the model was that the elevated water table was not included in the model nor was there consideration for low permeability areas. Hence the model found difficulty in achieving calibrated results.

Harbison (1998) also conducted an integrated study of the hydrogeology for the whole of Bribie Island with a goal of developing a conceptual groundwater model. Cross-sections across the existing DNRM & E transects A-G are included within the DNR (1996 unpublished) report. These transects were evaluated by Harbison (1998) to develop a conceptual model of Bribie Island. The groundwater regime of the island was defined in terms of geology, water level fluctuations, response to rainfall and geochemistry. Additionally, aquifer hydraulic properties were also attained through laboratory hydraulic testing. Harbison (1998) noted that the critical factors in the behaviour of the groundwater system are the elevation of the seawater boundary, the extent of low permeability layers and the degree of aquifer heterogeneity predominantly in the form of indurated sand layers.

The following study continues the investigation of the hydrogeological regime of Bribie Island. This study is focused on transect D-D’ across the middle of the island. This transect is referred to as the “reference transect” within the remainder of this study. In situ testing of the Bribie Island sand mass across the reference transect has been designed to quantify the hydraulic properties of the island aquifers. This data is required for further development of the conceptual groundwater model.

Figure 15. Previous monitoring well locations, transect lines, drainage features and surface water bodies

5.0 METHODS

A number of standard techniques for the assessment of physical and chemical properties of aquifer materials, water chemical character and determination of in situ permeability of the sand mass were applied. Prior to this testing a groundwater well drilling program was designed and implemented. The overall approach taken can be subdivided into three parts:

a) Drilling and hydraulic testing All existing data including monitoring wells locations and water level records were collated before hydraulic testing was performed. A comprehensive drilling program was undertaken to expand the monitoring well network and test the sand mass at different depths. The well network enabled time-series monitoring of groundwater levels and the performance of hydraulic testing.

b) Water and sediment sampling Each drill hole was progressively logged during drilling and samples were taken at intervals of interest for laboratory analysis. Selected sediment samples were also collected for age dating analysis. Groundwater samples were collected from the monitoring well network for testing of field physico-chemical properties and for total ion chemical analysis.

c) Data analysis Hydraulic test data were analysed by analytical methods to gain estimates of hydraulic conductivity and specific storage across the reference transect. Age dating of sediment samples by the optically stimulated luminescence (OSL) method was also performed to identify trends in island evolution and island stratigraphy. Both groundwater and surface water samples were analysed geochemically for chemical type and ionic ratios.

5.1 Drilling and Hydraulic Testing

It is possible to determine in situ hydraulic conductivity and specific storage values of a formation by means of tests carried out in monitoring wells. These tests typically involve the measurement of the water level around one or more monitoring wells during which the water level is raised or lowered. An array of monitoring wells were designed to monitor water levels from various levels within the formation.

5.1.1 Drilling program

Twenty-one groundwater monitoring wells were installed in March 2001 along two transects across the middle of Bribie Island. The new monitoring wells are sequentially numbered from 14100131 – 14100151 and their locations are illustrated in Figure 16. The numbering system compliments the existing Queensland Department of Natural Resources and Mines (NRM & E) groundwater monitoring well identification system. The prefix of 14100 will be omitted here for brevity.

The new drill holes were constructed using the rotary mud drilling method. 150 mm holes were drilled through the unconsolidated sand profile using a wash bore blade bit. The rotary mud drilling method is considered the most appropriate for unconsolidated material particularly for dune sand such as the Bribie Island aquifers (Land and Water Biodiversity Committee 2003). The rotary mud drilling method relies on the injection of drilling mud/water slurry to support the drill hole and to carry the cuttings to the surface. However, a consequence of injecting water into the drill hole is the contamination of the formation with drilling fluid. Well development necessitates the removal of the injected water before reliable groundwater levels and groundwater chemistry can be recorded. The removal of the drilling water is typically achieved by high volume pumping from the well. All drilling fluids were removed from each well before water levels and water chemistry monitoring.

Sediment samples from the drill holes were collected from 0.5 m intervals and at changes in lithology. Standard Penetration Tests (SPT) were also conducted to measure the resistance of various sediment units to penetration, particularly those units suspected of acting as semi-confining layers.

Figure 16. Location of groundwater monitoring wells (n=21) constructed during this program. Existing monitoring wells of NRM & E (n=16) and HLA (n=14) are also shown. All QUT and NRM & E monitoring well identifications are prefixed with 14100

SPT tests were conducted at sections of interest, particularly where indurated sand was encountered. A “splitspoon” sampler was attached to the bottom of a core barrel and lowered into position at the bottom of the drill hole. The sampler was driven into the formation by a drop hammer weighing 68 kg falling through a height of 0.76 m. The number of hammer blows required to drive the sampler three successive 150 mm increments (total of 450 mm) were recorded. The SPT N value, an indication of the formation stiffness, is the number of blows required to achieve penetration from 150-450 mm. For all holes that penetrated through the indurated sand layer, rotary drilling was continued to the weathered sandstone bedrock. At the bottom of the drill hole an SPT sample of weathered sandstone was collected to confirm the lithology change. Each drill hole was progressively logged as drilling continued; geological logs are presented in appendix D.

5.1.2 Well construction

Groundwater monitoring wells are typically of small diameter and are equipped for the purpose of taking groundwater samples and the monitoring of water levels. All newly constructed groundwater monitoring wells on Bribie Island were constructed to the requirements set by the Land and Water Biodiversity Committee (2003).

A detailed transect of the island is provided by NRM & E transect (D-D′) Figure 16. Sixteen of the new wells were established on the D-D' transect that is now comprised of twenty-three monitoring wells. The D-D′ transect is referred to as the “reference transect”. The reference transect is comprised of 8 nested monitoring well sites, and at these sites, multiple monitoring wells are slotted at different intervals. The types of wells along the transect and their positions within the profile of the island are summarised in Table 6.

Table 6. Well type and slotted casing lengths of monitoring wells across the reference transect Type of well Slot interval Number of wells Shallow - slotted above indurated sand 1 – 5 m 10 Intermediate - slotted within indurated sand 7 – 10 m 2 Deep - slotted beneath indurated sand 15 – 35 m 11

Five shallow monitoring wells (1-5 m depth) were also developed to the immediate south of the reference transect to further confirm aquifer character below the eastern dune system. The five shallow monitoring wells compliment the existing network of privately owned monitoring wells located to the west of the transect. The privately owned wells have been developed by the Pacific Harbour residential development and are situated within an area designated as a future golf course. The environmental consultancy group, HLA-Envirosciences Pty Limited, currently monitors the golf course monitoring wells. These wells will be referred to as HLA monitoring wells with the identification system of: 1s (monitoring well number one – shallow 1-5 m depth) to 8d (monitoring well number eight 8 – deep 20-30 m depth).

The monitoring wells were cased with 50 mm diameter class 12 PVC (Figure 17) and consist of 3 m lengths and joined by end threads. The machine slotted casing used for the monitoring wells consisted of the same material as the casing. The slotted casing also provides support for the formation material and retains openings into the sand formation. Filter packing around the slotted casing with 3 mm diameter quartz gravel provides additional support to the formation whilst increasing the effective diameter of the well. Efficiency and specific capacity of the well is increased as a result of the larger effective diameter of the well. Bentonite grouting with a thickness of at least 0.5 m above the slotted casing prevents lateral leakage.

The head works of the monitoring wells consists of standard NRM & E lockable galvanised steel protective collars. The bases of the collars were set in concrete and marker posts have also been used to increase visibility. Most monitoring wells have been located adjacent to forestry track intersections to also increase the visibility of the wells: and the likelihood the wells will not be destroyed by working forestry equipment. Monitoring well identification numbers have been listed on the PVC end cap. Following construction, each bore was surveyed to an accuracy of within ± 5 mm horizontally above Mean Sea Level.

Monitoring well survey heights were calibrated against the existing network of NRM & E monitoring wells. Monitoring well heights above sea level were measured using Leico automatic level survey equipment, and the wells located using Global Positioning system (GPS).

Figure 17. Typical construction method for monitoring wells installed during the 2001 drilling program

5.1.3 Water level monitoring

Monitoring of groundwater levels across Bribie Island has been conducted on a regular basis since the development of the NRM & E monitoring well network in 1992. Previous records are archived within the NRM & E groundwater database. Throughout this current study, monitoring of the expanded well network for groundwater levels occurred between August 2000 and June 2002 at the average interval of 1 month. The monitoring of approximately 50 wells included: 16 NRM & E wells, 14 HLA wells and 21 newly constructed wells. Groundwater levels were monitored both manually and by pressure transducers. Manual recordings were taken by a “dipper”, an electrical tape measure that emits an audible tone upon contact with water (Figure 18).

Figure 18. Manual electrified tape measure Figure 19. Automatic groundwater level for the monitoring of water levels within logging equipment installed at monitoring well observation wells 090 and tipping bucket rainfall gauge

Additional data were obtained from two NRM & E monitoring wells equipped with pressure transducers that are connected to continuous loggers (090 and 127). Monitoring well 127 is located within the centre of the island towards the northern end. Monitoring well 090 is located on the reference transect (NRM & E transect D- D′) and is situated on the east coast of the island. Figure 19 illustrates the automatic groundwater level logging equipment and the tipping bucket rainfall gauge located at NRM & E well 090. Additionally, pressure transducers were used to monitor groundwater levels during hydraulic testing.

However, monitoring well 090 is slotted in two different aquifers. It is possible that water levels in 090 are the result of two different water bodies, thus analysis of water level observations in this monitoring well is difficult.

The long-term hydrographs produced from the monitoring wells are used in the analysis of secular and seasonal fluctuations. Expected fluctuations in groundwater levels across the island will result from evapotranspiration, rainfall, barometric pressure, and pumping.

5.1.4 Bailer tests

Pumping tests are expensive to conduct, both in terms of the cost of installation of the pumping well and observation wells and also the time taken to perform the test (Fetter 1994). As an alternative to a pumping test, bailer tests are a cost effective estimate of the hydraulic properties of aquifers (Weight and Sonderegger 2000). Bailer tests can be performed relatively quickly, so that several point estimates can be collected.

A bailer test consists of measuring the recovery of head in a well after a near instantaneous change in the water level. The bailer test begins with the sudden removal of water via a bailer. Following the sudden change, the water level in the well returns to static conditions as water moves into the well from the surrounding aquifer. The rate at which the water level responds can be used to estimate the hydraulic conductivity of the formation. An important factor that must be taken into consideration during the analysis of bailer tests is the contribution of water from the gravel pack surrounding the slotted section of casing/screen.

Bailer tests are highly suited to the small diameter monitoring wells located throughout Bribie Island. The bailer consisted of a hollow cylinder of one litre volume, constructed from stainless steel, that has a bottom valve to allow water to enter but not exit during removal of the bailer from the well by the attached cable (Figure 20).

Figure 20. Schematic illustration of bailer hydraulic test

A total of thirty bailer tests were conducted on shallow wells slotted within the upper 10 m of the island sediment. One litre of water was instantaneously removed from the well resulting in a 0.5 m drawdown at time zero (t0). The rising head responses were monitored manually, and analysed for hydraulic conductivity using the methods of Hvorslev (1951) and Bouwer and Rice (1976).

5.1.5 Pumping tests

Although point estimates of aquifer properties can be obtained from bailer tests, the results obtained via pumping tests can be of far more use (Weight and Sonderegger 2000). Pumping tests are conducted to obtain estimates of the general properties of hydraulic conductivity and specific storage of an aquifer. Typically, a pumping test will sample a much larger section of the aquifer than any other testing method, therefore providing a more reliable estimate of the hydraulic properties of the aquifer.

Tests usually require a pumping well and at least one observation well. Ideally, two or more observation wells should be used to measure the effect of pumping at

different distances and at different heights within the aquifer. The water level in the pumping well is lowered when pumping extraction begins, and this drawdown creates a cone of depression around the pumping well. Observation wells within the radius of the cone of depression will also show a lowered water level as illustrated in Figure 21.

Figure 21. Schematic illustration of drawdown and cone of depression in a confined aquifer and the relationship between the water level in the pumping well and in the observation well

The cone of depression expands outwards until enough water is captured to meet the demands of the pumping rate (Weight and Sonderegger 2000). Additionally, the shape of the cone of depression also depends on the nature of the aquifer material. An aquifer of high hydraulic conductivity will produce a laterally extensive cone of depression with a low hydraulic gradient. On the other hand, an aquifer of low hydraulic conductivity will produce a cone of depression of steep hydraulic gradient but not laterally extensive as illustrated in Figure 22.

The inverse relationship between hydraulic conductivity and the shape of the cone of depression has a large impact on the design of a pumping test. Considering the aquifer hydraulic properties are often unknown prior to the test, the dimensions of the cone of depression are typically assumed via estimates. Thus, numerous observation wells are needed to adequately monitor the effects of pumping on the aquifer.

Figure 22. Schematic illustration of the differences in the shape of cones of depression in pumping wells based on aquifer hydraulic properties (after Weight and Sonderegger 2000). The term K = hydraulic conductivity

Additionally, the type of aquifer being tested also dictates the shape and size of the cone of depression. Typically, a confined aquifer has a storage coefficient range between 10-3 and 10-6, however, an unconfined aquifer has a specific yield range between 0.03 and 0.3 (Weight and Sonderegger 2000). The significance of the smaller storage value is that the cone of depression in a confined aquifer will extend faster and further away compared to an unconfined aquifer. Semi-confined aquifers are also common and have a large effect on the analysis of pumping tests. Layered sediments may induce delayed yield or other sources of recharge.

In a situation such as Bribie Island where there is the possibility of confinement from indurated sand layers, the pumping tests need to be designed accordingly. Particular care must be taken to place observation wells within the expected radius of the cone of depression and have numerous wells at various heights. These nested wells are needed to monitor movement of groundwater levels within different sections of the profile that may indicate confinement of the aquifer.

Four, 24 hour pumping tests were conducted in sets of partially penetrating nested- monitoring wells. Table 7 presents information regarding pumping well identification, duration of test, pumping rate and drawdown within the pumping well.

Table 7. Details of pumping tests Test Date Pumping well Pumping time Pumping rate Maximum drawdown (min) (L/s) (m) * 12/2/02 089 1380 0.30 0.607 1 20/3/02 101 1444 0.33 0.471 2 20/11/02 088 1443 0.33 4.316 3 5/8/03 089 1440 0.32 0.626 * = omitted from assessment due to unreliable test results

A Grundfos MP1 submersible groundwater-sampling pump with a discharge rate of 1.2 m3/hour was used for each test. Extracted water was discharged 300 m south (down gradient) of the reference transect. Manual dippers and pressure transducers monitored groundwater drawdown and recovery. During the pumping tests, observation wells located across the reference transect were monitored at distances up to 1.5 km away from the pumping well.

5.2 Hydraulic Tests Analysis

Data obtained from pumping tests and bailer tests includes water level drawdown and recovery rates for both test wells and observation wells. Analytical solutions of Theis, Theis Recovery, Cooper-Jacob and Stallman were used to estimate hydraulic conductivity (K) and specific storativity (Ss) from pumping test data.

Bailer test data was analysed by the Hvorslev (1951) method and the Bouwer and Rice (1976) method. The methods are quick to perform and are relatively simple in procedure. As for all single well tests, these methods account for estimates of hydraulic conductivity only - specific storage is not defined. Additionally, the estimates of hydraulic conductivity are restricted to a particularly small section of the aquifer immediately around the well slotted section/screen. The Hvorslev method can be applied to confined and unconfined aquifer conditions where the well is either fully or partially penetrating the entire thickness of the aquifer. When the bailer of water is removed from the well the maximum displacement value (h0) occurs instantly at time zero as illustrated in Figure 23. The water level within the well is measured (ht) at time intervals (t) as the water level returns to the original position. The ratio of ht/h0 is plotted on a graph verses time on semi-logarithmic paper. The ratio between ht/h0 is plotted on the y-axis on a log

scale, and time along the x-axis. There are no type curves to match the data. The time-recovery data should plot on a straight line. The graphical plot is required to identify the parameter of T0 (time taken for the water level to rise 37% of the initial maximum h0). The following formula applies: r 2 ln(L / R) K = (2) 2LT0 Where; K = Hydraulic conductivity (m/day) r = Radius of the well casing (m) R = Radius of well screen (m) L = Length of the well screen (m)

T0 = Time for water level to rise 37 percent of h0

Bailer test data was also analysed by the Bouwer and Rice method. The Bouwer and Rice method formula is as follows:

2 rc ln(Re / R)1  Ho  K = ln  (3) 2Le t  H t 

The Bouwer and Rice method uses slightly different notation compared to the Hvorslev method, but generally works on the same principle. The Bouwer and Rice method is specific to unconfined aquifer conditions and also accounts for the well geometry of partial penetration. Additionally, the Bouwer and Rice method accounts for a fall in water level within the screened portion of the well. An adjusting value needs to be calculated to account for the porosity of the packing material. This adjustment is not needed if the water level is always located within the well casing and does not fall below the top of the slotted section of casing. The Bouwer and Rice method is commonly used in conjunction with the Hvorslev method as a means of crosschecking values. In the following discussion of bailer test results the estimates of hydraulic conductivity are reported from both method types.

Figure 23. Schematic illustration of the mechanics of a bailer test

A pumping test is one of the most useful means of determining hydraulic properties of aquifers and confining layers (Kruseman and De Ridder 1979). Pumping tests result in reliable estimates of aquifer hydraulic properties typically over much larger areas than the point estimates of bailer tests. This is illustrated in Figure 23 & 24.

During each pumping test, water level time-drawdown data were plotted to identify if steady-state conditions had been reached. Steady-state conditions exist when the cone of depression ceases to expand and the water level within the pumping well and observation wells ceases to fall with continued pumping. Steady-state conditions are rarely achieved; however, it is necessary for the test to at least approach near steady- state conditions (Kruseman and De Ridder 1979; Fetter 1994; Weight and Sonderegger 2000). Additionally, if the aquifer is confined, the water must come from a reduction of storage within the aquifer; therefore the head will decline as long as the aquifer is effectively infinite (Kruseman and De Ridder 1979). Most

analytical solutions for pumping test analysis assume unsteady-state conditions; however, most solutions are more reliable when steady-state conditions are approached. Steady-state conditions are assumed when the rate of head decline is negligible. When steady state conditions are approached, the pump may be stopped and the second part of the pump test begins. The water level recovery within the pumped well and the observation wells is also very useful in the analysis of the hydraulic properties of the formation.

Figure 24. The mathematical region of flow for a pumping test, is a horizontal one-dimensional line through the aquifer, from r = 0 at the well to an infinite extremity

After each pumping test was completed the water level time-drawdown and time- recovery data was compiled from all observation wells and the pumped well. The data was initially processed via graphical analysis to identify drawdown within any observation wells. Observation wells that showed no sign of drawdown were omitted from further analysis.

Drawdown and recovery curves for the pumped well and the observation wells were also checked for signs of additional influence such as delayed yield and barometric influence. Barometric influence typically affects the water level within wells that are confined to semi-confined. Barometric efficiency is indicative of the degree of confinement; the more confined an aquifer the larger the barometric influence on the piezometric head. Pressure changes within the atmosphere cause the water level to fluctuate within well. For example, as atmospheric pressure increases, the water level within the well will fall slightly and vice versa. Therefore, atmospheric pressure must be monitored during the test. The influence of the barometric pressure must be removed from the water level time-drawdown data to find the correct levels during the pumping test. Well barometric efficiencies typically range from 20 to 70 % (Todd 1979). Barometric efficiency is calculated as follows: Water table fluctuation (cm) α = Pressure fluctuation (hPa) x conversion factor * (4)

* o Conversion factor = 0.9835 cm H2O / hPa @25 C

Semi-confined (leaky) aquifers are a common feature of many unconsolidated formations such as deltas, coastal plains, and lowland river valleys (Kruseman and De Ridder 1979). A delay in yield is often a result of semi-confined conditions where leakage from overlying or underlying confining layers contributes water to the tested aquifer. The rate of leakage is determined from the head difference between the aquifer and the confining layer and also the hydraulic conductivity of the confining layer. The hydraulic conductivity of the confining layer is typically several orders of magnitude lower than that of the aquifer (Weight and Sonderegger 2000). Time-drawdown graphical plots were analysed for evidence of delayed yield. Typically, the contribution of water to the aquifer from the confining layer results in a flattening of the time-drawdown curve. Evidence of delayed yield suggests that appropriate analytical solutions be used in the analysis of the pumping test data. If

delayed yield does not exist, the traditional analytical solutions for an unsteady-state confined aquifer can be used.

Both the Theis (1935) method and the Theis recovery method account for confined aquifers in unsteady-states. The following limiting conditions should be satisfied when using either of these analytical solutions (Kruseman and De Ridder 1979):

1. the aquifer has seemingly infinite areal extent 2. the aquifer is homogenous, isotropic and of uniform thickness 3. nearly horizontal piezometric surface prior to pumping 4. constant discharge rate 5. the well penetrates the entire thickness of the aquifer 6. the aquifer is confined 7. the flow to the well is unsteady-state 8. water removed from storage is discharged instantaneously with decline in head 9. the diameter of the pumped well is small (limited well storage)

The Theis method is a graphical means of solution based on type curves for the estimation of aquifer hydraulic conductivity (K) and storativity (S). The Theis equation is expressed (Driscoll 2003): Q s = 1 W (u) (5) 4π T W(u), the well function of u, is an abbreviation for the exponential integral:

∞ e− x u2 u3 u 4 dx = W (u) = −0.5772 − log u + u − + + + • • • ∫ e (6) u x 2 • 2! 3• 3! 4 • 4!

Where; Q = Pumping rate (L3/t) T = Transmissivity (L2/t) – hydraulic conductivity (K) x aquifer thickness (b) s = Drawdown (L)

W(u) = Well function of u (dimensionless)

The well function of u is expressed: r 2S u = (7) 4Tt Where; r = Radial distance to the pumping well (L) S = Storage coefficient (dimensionless) T = Transmissivity (L2/t) [hydraulic conductivity (K) x aquifer thickness (b)] t = Time (days)

In the equation, the infinite series in brackets is known as the well function (W(u)).

Reverse type curves are created by plotting values of the well function (W(u)) against

1/u on a logarithmic scale. Field data for drawdown (s = h0 – h) is then plotted against t/r2 on another sheet with the same logarithmic scale as the type curve. The curve of the plotted field data should be similar to the type curve as illustrated in Figure 25.

Figure 25. Analysis of data from pumping test with the Theis method (after Kruseman and De Ridder 1979)

The two curves are placed over each other and aligned so that the field data best matches a portion of the type curve. An arbitrary point is selected on the plots.

Typically the point selected has the coordinates of W(u) = 1, and 1/u = 10. From this

2 2 point the values for s and t/r are determined. The values of Q, W(u), 1/u, s, and t/r are then substituted into the rewritten equations of: Q Transmissivity T = W (8) 4πs (u) u4Tt Storativity S = (9) r 2 After the pumping test has ceased, the water level within the pumping well and observation wells begins to rise back to the original position. This portion of the test is referred to as the recovery of the well. The data obtained during the recovery period of the pumping test can only be used to calculate hydraulic conductivity. The results from recovery tests provide a check on the results of the pumping test data. The rise of the water in the well is termed the residual drawdown (s'). The residual drawdown is measured as the difference between the original water level prior to pumping and the actual water level measured at a certain moment (t') since pumping stopped. The residual drawdown is expressed by Theis (Kruseman and De Ridder 1979) as: Q  4Kbt 4Kbt' s'= ln − ln  (10) 4πKb  r2S r 2S'  Where; s' = Residual drawdown (L) R = Distance from pumped well to observation well (L) S' = Storage coefficient during recovery (dimensionless) S = Storage coefficient during pumping (dimensionless) t = Time since pumping started t' = Time since pumping stopped Q = Rate of discharge = rate of average recharge (L3/t)

For each observation well the residual drawdown is plotted on a semi-logarithmic scale against the ratio of t/t'. A straight line should be able to fit through most of the data, although early time data often does not fit well. The straight line through the plotted points has a residual drawdown difference per log cycle of t/t'. Therefore, when the S and S' are constant and u = r2S/4Kbt' is sufficiently small the equation can be rearranged to:

2.30Q Kb = (11) 4π∆s' Where; K = Hydraulic conductivity (L/t) b = Aquifer thickness (L) Q = Rate of discharge = rate of average recharge (L3/t) ∆s' = Residual drawdown difference per log cycle of t/t'

5.3 Water and Sediment Sampling

Samples of water and sediment are used extensively within this study to facilitate greater hydrogeological understanding; however the collection and storage of these samples require care.

Water sampling is best associated with the monitoring of trends in water properties over time. This time-series analysis often highlights important aspects of the groundwater regime. Sediment samples are typically taken during the drilling process. The collection and analysis of sediment samples enable the development of geological logs and detailed stratigraphic cross-sections through the profile of the formation.

5.3.1 Sediment samples

Sediment samples were collected at 0.5 m intervals during the drilling of each groundwater well. Formation samples were returned to the surface through the annulus around the drill rod and the drill hole in slurry of drilling fluid. The samples were directed into a settling tank from which the samples were collected. The samples were collected in marked bags and laid out in sequential order for detailed geological logging (Appendix D). Additionally, SPT samples were collected at intervals of interest, particularly through the indurated sand layers and at the lithology change of the sandstone bedrock. The geological logs were compiled to create a detailed geological cross-section through the profile of the island.

5.3.2 Age dating sampling

During the drilling of the monitoring well network, four samples were specially extracted for optically stimulated luminescence (OSL) age dating analysis. The four samples were removed from drill hole number 140 (Figure 16) at sections of the profile that showed clean marine derived quartz sands. The samples were extracted at depths of 1.5m, 4m, 10m, and 20m (Table 8). Samples were collected in the same manner as standard penetration tests (SPT) samples are obtained. Upon reaching the surface the SPT tube was slipped into an opaque sleeve to prevent sunlight entering the ends or the split of the sampling tube. Once the sampling tube was disconnected from the drill rod the tube was transferred into an opaque handling bag where the tube was opened and the contents transferred into air tight, opaque containers.

Table 8. Sediment sampled details for OSL analysis Sample Depth Sediment description No. (m) BI-1 1.5 – 1.9 Foredune and beach sands - med-fine grained sand BI-2 4 – 4.2 Indurated sand - dark brown/black, fine-med grained highly indurated sand BI-3 10 – 10.2 Weakly indurated sand - dark brown, med grained with some fine gravel BI-4 20 – 20.2 Brown sand - med-fine grained with some thin lenses of weakly indurated sand

5.3.3 Age dating analysis

This method of sediment dating makes use of the condition that daylight releases charge from light-sensitive electron traps in crystal lattice defects in minerals such as quartz and feldspar. This release of trapped charge by light resets the optically stimulated luminescence (OSL) signal; the process is commonly referred to as bleaching. When grains of quartz are buried and no longer exposed to light, they begin to accumulate a trapped-charge population due to the effects of ionising radiation, such as that arising from radionuclides naturally present in the deposit. This trapped-charge population increases with burial time in a measurable and predictable way. The OSL samples were sent to the CSIRO Land and Water laboratories in Canberra. The OSL method is detailed in appendix E.

5.3.4 Water Sampling

Water samples were collected across the central section of Bribie Island for both groundwater and surface water. The sampling period for both groundwater and surface water was conducted from September 2000 to July 2002; the interval between sample collections ranged between six months to one year. Groundwater and surface water samples were collected from all available wells and surface water bodies throughout the central section of Bribie Island as illustrated in Figure 16 and Figure 26.

AS/NZS 5667.11-1998 Water Quality - Sampling Part 11: Guidance on sampling of groundwaters, the 1992 ANZECC publication Australian Water Quality Guidelines for Fresh and Marine Waters and the MDBC Groundwater Working Group 1997, Murray-Darling Basin Groundwater Quality Sampling Guidelines, Technical Report No. 3, Murray Darling Basin Commission Groundwater Working Group, were used as the primary reference documents in the sampling/analysis of groundwater and interpretation of results.

Ninety-nine groundwater water samples were extracted. Typically, all monitoring wells were sampled three times during the sampling period. Groundwater samples were extracted from monitoring wells via small down-hole sampling pumps. Discharge was directed from the wellhead into the bottom of a small (10 L) container to minimise aeration of the sample. Purging of the monitoring well for at least three times the volume of the casing prior to collection of the sample ensured a representative sample from the formation. Collection and storage of a sample was within 500 mL polyethylene sample bottles. Sample bottles were prepared with a wash of 1:3 diluted HNO3 to avoid contamination, and separate bottles used to store samples for cation and anion analysis. Sample bottles for cation analysis were acidified with 1 mL HNO3 to slow chemical reactions and stable metals. Both cation and anion samples were cooled immediately and stored at 5 oC.

Surface water samples were collected with a similar technique for the collection of groundwater samples. Minimal aeration of water samples was best achieved by gentle insertion of the bottle beneath the water body surface. Forty-five surface

Figure 26. Locations of surface water sampling points. Samples were collected between September 2000 to July 2002 and in most cases represent wetlands

water samples were collected. Similar to groundwater samples, separate 500 mL sample bottles were used for cation and anion storage. Surface water samples were also stored in cool conditions.

Both groundwater and surface water samples were filtered at the School of Natural Resource Sciences (NRS) chemical laboratory. For most samples, the level of turbidity was not considered high enough to warrant field filtering of samples. Determination of alkalinity and elemental testing of cation and anion concentrations was also carried out within the laboratory. Groundwater and surface water samples were also analysed for non-volatile organic compounds. These natural non-volatile constituents include organic compounds such as fluvic, humic and tannin acids. Typically, samples with a pale yellow to brown appearance suggest a high concentration of organic compounds.

The physico-chemical parameters pH, electrical conductivity (EC), temperature (oC), redox potential (Eh), and dissolved oxygen (DO) were also determined in the field for both groundwater and surface water samples. These parameters were measured using a TPS 90 FL microprocessor multi-probe field analyser, and conducted at the time of sample collection.

The TPS 90 FL analyser was calibrated within the NRS laboratory prior to field use. EC measurements were calibrated against standards of comparable ionic strength. The pH probe was calibrated against buffered standards of pH 4 and pH 7. A standard Zobell solution was used for the calibration of the Eh probe. Field measurements of Eh were converted to standard hydrogen electrode units by adding +267 mV.

5.3.5 Elemental analysis

Elemental analysis of water samples was carried out in the NRS chemical laboratory. The cations Na, K, Ca, Mg, Fe, Al, Si, Mn, Zn were analysed via the Varian Liberty 200 Inductively Coupled Plasma – Optical Emission Spectrometer (ICP-OES), and calibrated against four synthetic cation standards. Anions Cl, HCO3, SO4, F, Br, N,

PO4 were analysed via the DX300 Dionex Ion Chromatograph. Alkalinity was determined by acid titration.

Organic carbon was analysed using the Shimadzu Total Organic Analyser (TOC- 5000A) in the School of Civil Engineering laboratory. The determination of total carbon and inorganic carbon was based on the combustion/non-dispersive infrared gas analysis method. When the total carbon and the inorganic component were determined, the organic carbon was calculated as “total carbon minus inorganic carbon”. In addition, the cation-anion balance was adjusted for the contribution of dissolved organic matter. From a measurement of the pH and TOC of a water sample, the mass action quotient of the fluvic and humic acids (organic anion A-) can be estimated using an empirical equation.

The sum of the positive and negative charges of all elements within the sample should approximate a balance. The accuracy of the analysis can therefore be checked by estimating the electro neutrality of the water sample expressed by:  cations + anions  Electro neutrality % =  ∑ ∑  ×100   (12)  ∑∑cations − anions  An error percentage of ± 10 % was considered tolerable.

6.0 RESULTS

This study of hydrogeology of the sand aquifers of Bribie Island integrates a number of separate aspects. Findings and results obtained during the course of this investigation from field, laboratory, and computer-based analysis can be summarised as follows:

a) Island stratigraphy Stratigraphic features of Bribie Island are identified using monitoring well log data. The well logs identify a stratigraphy of various units of unconsolidated and indurated layers throughout the island profile.

b) Island evolution and age Age dating analyses of sediment samples collected during the drilling program provide estimates of island evolution and age. The sediment age dates indicate stages of island formation relative to sea level fluctuation associated with major periods of glaciation throughout the Quaternary.

c) Island hydrology Data obtained from monitoring wells across an island transect illustrate a stratified aquifer system consisting of an elevated water table and basal groundwater. Groundwater flow directions are also analysed through contouring of groundwater heads across the island profile.

d) Water geochemistry Groundwater flow through Bribie Island is also expressed by groundwater and surface water geochemistry. Aquifer lithology can be distinguished via elemental chemistry that reflect different water bodies, plus mixing. Additionally, groundwater–surface water relationships can also be indicated.

e) Aquifer hydraulic tests Data obtained from hydraulic tests can confirm the heterogeneous structure of an aquifer system such as Bribie Island. Sections of the

island profile are assigned the hydraulic properties of hydraulic conductivity and specific storage. Confining layers are identified and their influence on the groundwater regime is assessed.

6.1 Island Stratigraphy

Typically, the exposed uppermost sediments often mask the subsurface geology of a barrier island. As a consequence, drill logs provide an understanding of the subsurface geology of these islands. The drill logs of Bribie Island identify a stratigraphy of various units of unconsolidated and indurated layers throughout the island profile. Figure 27 illustrates the depth of drilling of each drill hole across the reference transect (NRM & E D-D′) and also indicates where monitoring well slotted sections are located. Detailed geological logs are located within appendix D. The cross-section of Figure 27 also indicates topographical features.

6.1.1 Aquifer Description and Distribution

Palaeochannel Aquifer

At the bottom of the unconsolidated sediment profile (within the palaeochannel) is an 8-10 m thick unit consisting predominately of medium grained sand. The palaeochannel aquifer overlies the weathered sandstone bedrock and also includes some thin lenses of fine sand, coarse sand and a gravely base. This unit may represent tidal channel (inlet) or tidal-delta facies, however, both sequences are difficult to determine from geological logs due to the lack of observable bedding structures (e.g. Reinson 1984). Typically, both of these sequences are associated with barrier-inlet modes (stationary barriers) of barrier island formation (Figure 2).

Transgressive, regressive (progradational), and barrier inlet depositional conditions can occur in combination to produce mixed sequences which have affinities with more than one “end-member” mode of barrier island formation. Therefore, considering the formation and evolution of Bribie Island, it is suggested that a combination of modes may have existed. The existence of barrier inlet facies at depth is in contrast with the typical coarsening up profile associated with strandplain and progradational barrier island deposits (Figure 3). However, various episodes of

marine transgression and regression have the potential to truncate older sequences and add overlapping deposits (McCubbin 1984). The mode of deposition during these transgressions and regressions may vary and result in sequences of mixed modes. The deep tidal inlet unit at the base of the Bribie Island sand mass is considered to be remnant from an older truncated barrier island sequence, on which a progradational barrier island/strandplain sequence was deposited.

Typically, the vertical sequence model for progradational barrier deposits coarsens upward (Figure 28) from offshore deposits consisting of dominantly sandy silt with some thin beds of sand, to the lower shoreface where the sand fraction increases (Galloway and Hobday 1983). The lower shoreface coarsens upward into the upper shoreface where the fine to medium grained sand has been deposited in the sub-tidal region by wave surge and wave generated currents (McCubbin 1984). Foreshore and beach sequences of fine to medium grained sand are deposited by wave swash in the intertidal zone. The Bribie Island vertical sequence resembles this model.

Offshore Sandy Silt Aquifer

A sequence of offshore deposits consisting of sandy silts overly the palaeochannel aquifer. The sandy silts are light olive-grey in colour and contain thin lenses of fine sands and clay. The maximum thickness of this sequence is towards the centre of the island at 15-20 m. The top of the sequence of clayey sands is approximated by the depth of increased response in the gamma logs shown in Figure 27.

Shoreface Brown Sand Aquifer

Shoreface deposits of prograding sand dunes constitute the most widespread unit within the island and consist of fine-medium grained quartz sand. The colour of the sand is light brown. Across the reference transect, the brown sand aquifer is thickest towards the middle of the island at 12 m.

Figure 27. Geological cross-section of Bribie Island across the reference transect D-D′. Various identified sediment units are indicated by shading. Monitoring well casing and slotted sections are also indicated. Wells drilled by Queensland Department of Natural Resources and Mines: 088, 089, 090, 100, 101, 126 and 129; Wells drilled by Queensland University of Technology: 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150 and 151. Also shown are down hole gamma logs (NRM & E unpublished data) 67

Figure 28. Generalised vertical sequence of progradational barrier sequence from offshore to beach deposits (after McCubbin 1982)

Indurated Sand Layer

Contained within the shoreface sediments is a dark brown to black indurated sand layer at an approximate depth of 5-6 m. The layer has a maximum thickness of 9 m (Figure 27). The quartz sand grains have been cemented together by the infilling of pores by a variety of cements, predominately organic matter and clays (Farmer et al. 1983; Thompson et al. 1996; Cox et al. 2002). Shell and vegetative matter were not

detected in the indurated sand layer. Thin layers of coarse-grained indurated sand were often encountered.

Foreshore and Beach Sand Aquifer

Typically, the uppermost foreshore and beach medium-fine grained sand aquifer is white to grey in colour and has a thickness of approximately 5 m. The medium-fine grained sand often contains a limited amount of root and organic material to a depth of approximately 0.5 m. Shell material is considered by the Queensland Department of Primary Industries – Forestry to represent aboriginal midden heaps and are generally restricted to the surface and near surface sands (personal communication, Stan Ward, DPI-Forestry). The standing water table was typically intersected within a range from 0.5 m-1.5 m.

6.2 Island Evolution and Age

Age dating sediment samples were taken at various heights through the profile of the island during the drilling of monitoring well 140. The samples were from the following parts of the island sand profile; sample 1 from within the uppermost dune sands at a height of 1.5 m; sample 2 from within the indurated sand layer at a depth of 4 m; sample 3 from just beneath the indurated sand layer within weakly indurated sand at a depth of 10 m; and sample 4 from within the brown sand unit at a depth of 20 m. Table 9 lists the age determined for each sample.

Table 9. Calculated burial ages of sediment samples from Bribie Island drill hole (monitoring well 140) Sample Depth (m) Age (ky) BI-1 1.5 m 63.5 ± 8.5 BI-2 4 m 90 ± 18 BI-3 10 m 180 ± 40 BI-4 20 m 310 ± 70

The OSL derived ages from the sand samples of Bribie Island plot against a glacio- eustatic sea level curve for the last 340 000 years as illustrated in Figure 29. The curve can be used to give an indication of sea level cycles that may have affected Moreton Bay. The deposition of the sediment samples appears to have occurred

within three phases. Each sample was deposited during a period of regression associated with major glaciation events. The regression of mean ocean levels enabled the progradation of beach ridge systems and the formation of the Bribie Island strandplain/barrier island.

Due to the prograding nature of some barrier sand islands, the formation and evolution of the island can often be interpreted by the characteristic dune ridge structures. These dune ridge systems typically reflect the number of phases of development. The evolution of these dune systems is often illustrated with a series of time line approximations (Figure 3a).

The sediment age dates for Bribie Island suggest the island may have developed within three phases as illustrated in Figure 29. Older beach ridge series are situated landward (to the west of well 140) and are progressively less preserved and less defined westward. The western beach ridges are believed to have formed during separate pre-glacial progradations. Coastal dunes have formed along the fringe of the island as a result of a slight sea level fall within the last 6000 years (Jones 1992).

6.3 Island Hydrology

The groundwater resources across the reference transect can be divided into a shallow unconfined water table aquifer and basal semi-confined aquifers. These upper and lower aquifers are characterised by different hydrological processes, physico-chemical properties, and water chemistry.

6.3.1 Groundwater levels

Monitoring of groundwater levels throughout Bribie Island was undertaken to identify trends in groundwater recharge, migration and discharge. Typically, examination of shallow monitoring well hydrographs indicate a tendency for the water table to respond rapidly to rainfall events while the deeper wells beneath the indurated sand layer experience a slight delay in recharge; this trend was also reported by Harbison (1998). Detailed analysis and interpretation of groundwater levels across Bribie Island has identified that groundwater movement is partly controlled by the geological framework of the island. To better test this finding the reference transect was constructed with twenty-three monitoring wells such that shallow, intermediate and basal groundwater bodies are adequately monitored.

Long-term hydrographs of nests of monitoring wells across the reference transect are illustrated in Figure 30. Appendix F contains groundwater level data. Each hydrograph illustrates a nest of wells from the eastern beach ridge (A) to the western beach ridge (H) for the period of April 2001 and June 2002.

Unconfined conditions prevail in the upper dune sands. The hydrographs indicate monitoring wells slotted within the upper dune sands above the indurated sand layer have consistently elevated water level trends (Figure 30). The water table contour generally follows local topography forming distinct mounds beneath the two beach ridge systems. The water table is often proximal to the surface and has an approximate maximum elevation towards the centre of the island at 7 m above mean sea level (Figure 30).

Groundwater levels illustrated on Figure 30 (Appendix F) show significant decline in water levels in wells located near the central swale (i.e. wells 129, 144, 146 &147) during the period of measurement. This decline in head near the central swale may be the result of reduced groundwater flow from the more elevated dune systems. The reduced groundwater flow may result in a decline in the hydraulic head within the dune system during drought conditions

Monitoring wells slotted beneath the indurated sand layer show lower water level trends than the elevated water table (Figure 30). Due to the confining nature of the indurated layer the basal groundwater occurs under semi-artesian conditions and has a piezometric surface that is relatively flat across the island. The piezometric surface typically ranges between 2-3 m above mean sea level with a slight mound beneath the eastern beach ridge.

The continuous groundwater level monitoring of two NRM & E wells (127 and 090) by automated data loggers also show the hydraulic gradient of the contrasting heights between the water table and the piezometric surface as illustrated in Figure 31. Monitoring wells 127 and 090 both display significant response to rainfall events (Figure 31), however, the response is greater for the shallow monitoring well 127. Both wells also show significant correlation with rainfall events. Delayed recharge is negligible within the deeper monitoring well 090, however, it is possible that well construction may impact on these results.

The construction of well 090 includes two slotted sections both of which are located beneath the indurated sand layer (Figure 27). Additionally, the annulus between the drill hole and the well casing has not been installed with seals between the two slotted sections nor is there a seal within the indurated sand layer. These seals would prevent drainage from other sections of the aquifer and from above the indurated sand layer. The connectivity between aquifers may result in anomalous results that suggest a negligible delayed yield and an exaggerated response to rainfall for the deeper well.

Figure 30. Hydrographs of water levels from nested monitoring wells across the reference transect (Figure 27) plotted against rainfall for the period April 2001 to May 2002: A (eastern beach ridge) to H (western beach ridge). Monitoring wells slotted within the upper dune sands above the indurated sand layer consistently show elevated water level trends. Appendix F contains groundwater level data

Figure 31. Hydrographs from automatic loggers on monitoring wells 127 and 090 illustrate a rapid response to rainfall

The stratification of head gradients across the reference transect contrasts with the “classical” domed water table conceptual model expected of a barrier island. The hydraulic gradient that exists between the water table and the piezometric surface is illustrated in Figure 32. The vertical head gradient is steepest through the centre of the island where topography is also greatest. Equipotential lines and flow direction identify the shallow hydraulic gradient within the central swale.

In three dimensions, the discharge from the foreshore and beach sand unit is likely to be southwards towards Wright’s Creek. The low vertical gradient in the upper shoreface deposits rather implies lower vertical flow within the central swale.

Contouring head values across the reference transect enables an appreciation of aquifer heterogeneity. The flow net illustrated in Figure 33 accounts for the different hydraulic properties across Bribie Island as determined from the geological and

hydraulic analysis. The flow net shows high hydraulic gradients through the low permeability units, and low hydraulic gradients within high permeability units.

Figure 32. Water level contours across the reference transect for 10 April, 2001 which clearly demonstrate the elevated water table and the piezometric surface of the basal aquifers

Groundwater flow within the upper dunes has a distinct lateral flow as well as vertical flow. Seepage of shallow groundwater has been observed as “return flow” across the top of indurated sand exposures along the coastline. Groundwater migrates downward through the indurated sand layer to the basal water body where groundwater flow is directed towards both coastlines (Figure 33). The equipotential lines illustrated in Figure 33 are shown as sub-horizontal within the upper shoreface deposits indicating the predominant direction of groundwater flow is likely to be vertical in the low permeability unit (indurated sand). Measured heads from wells

142 and 143 indicate a large vertical hydraulic gradient at the top of the upper shoreface deposits, suggesting that the indurated sand zone might be least permeable at the upper surface of the unit.

6.4 Barometric Efficiencies

Water levels observed in wells are commonly affected by barometric pressure (Davis and Rasmussen 1993). The rate of the change in the water level in a well to the change in atmospheric pressure that produces it is known as the barometric efficiency (Clark 1967). An inverse relationship exists where an increase in barometric pressure produces an apparent decline in water within the well. These water level fluctuations often create difficulties during the analysis of regional water levels and pumping test data. Water level fluctuations must therefore be eliminated to highlight the true trend of the water level over time. Obtaining an estimate of barometric efficiency from a record of water levels and barometric pressures is not straight forward when there are large variations in water level due to causes other than changes in barometric pressure, such as temporal variations in regional recharge and discharge rates and earth tides (Davis and Rasmussen 1993).

A method developed by Clark (1967) involves determining the incremental changes in the water level, ∆W, and in the barometric pressure, ∆B. Clark’s method assumes that the barometric efficiency is a constant and that rapid equilibration occurs between a change in barometric pressure and water level response in wells (Davis and Rasmussen 1993). The Clark method eliminates incremental changes in the water level that are not attributed to barometric influence by the use of the following four rules:

Figure 33. Flow net across the reference transect using averaged groundwater levels. The steep hydraulic gradient through the indurated sand layer (illustrated by th 78 equipotential lines) indicates the layer may have a reduced hydraulic conductivity. Based on water levels data recorded on 10 April 2001

1. when ∆B is zero, neglect the corresponding value of ∆W in obtaining Σ∆W, 2. when ∆W and ∆B have like signs, add ∆W in obtaining Σ∆W, 3. when ∆W and ∆B have unlike signs, subtract ∆W in obtaining Σ∆W, and 4. the value of ∆W is given a positive sign when the water level is rising, and ∆B is given a positive signs when the atmospheric pressure is decreasing.

The barometric efficiency of the well is then estimated by: α = Σ∆W / Σ∆B (13) Where; α = Barometric efficiency (%) ∆W = Change in water level elevation (L) ∆B = Change in barometric pressure head (L) The Clark method was used on water level records from monitoring wells 088, 089, 100 and 101. Water level and barometric records were taken over a one-month period at time intervals of 0.5 hr (wells 088 and 101) and 2 hr (wells 089 and 100). Cumulative absolute changes in water level (Σ∆W) were plotted against corresponding values of Σ∆B (Figure 34). The slope of a linear trend through the data was taken to equal barometric efficiency. Barometric efficiencies for each well are presented in Table 10; also included are the standard error for each regression slope. Percentage error for each barometric efficiency approximates 0.1 %.

Table 10. Barometric efficiencies (expected value ± one standard error) Harbison Clark’s method Well Stratigraphic Unit (1998) % S.E. % % 088 Offshore deposits - sandy silts aquifer 7 ± 0.72 12 089 Channel deposits – palaeochannel aquifer 3 ± 0.14 11 100 11 ± 0.15 40 Upper/lower shoreface deposits - brown sand aquifer 101 58 ± 0.09 88 Standard error reported as percentage of estimate

Also included within Table 10 are results presented by Harbison (1998). The curve matching approach used by Harbison (1998) adjusts water levels to a constant atmospheric pressure using assumed values for barometric efficiency. The curve matching method requires the use of personal judgement and hence, barometric efficiency may be overestimated. For this reason it is suggested that the values of barometric efficiency for wells 088, 089, 100 and 101 derived by the Clark method are a more robust estimate.

Following the method of Rasmussen and Crawford (1997), step response functions for wells (088, 089, 100 and 101) were generated by ordinary least squares (OLS) analysis of barometric pressure and water levels. Standard error terms were calculated from sum of square errors. Data was initially de-trended by subtraction of 26-hour running means. Residual water levels in two wells (100 and 101) demonstrated step responses typical of aquifer confinement (Figure 35). For borehole 100, a slight delay in response indicates a "skin effect" in the response function. For two deeper wells (088 and 089), the barometric efficiency is considerably less, and the component of water levels affected by barometric pressure are difficult to de-trend. As a result, standard errors for these wells are greater than the step response values. Nevertheless, slow rising step response indicates that a skin effect is possible for wells 088 and 089 (Figure. 35).

81 Figure 34. Computation of barometric efficiency for monitoring wells A) 088 = 7 %, B) 089 = 3 %, C) 100 = 11 % and D) 101 = 58 %

Figure. 35 Barometric response functions for wells 088, 089, 100 and 101

6.5 Water Geochemistry

Groundwater flow through Bribie Island is also reflected through groundwater and surface water chemistry. Aquifer lithology can be distinguished via elemental chemistry and physico-chemical characteristics; in addition, groundwater-surface water relationships are also evident.

6.5.1 Physico-chemical properties

Field measurements of dissolved oxygen (DO), electrical conductivity (EC), redox potential (Eh), pH and temperature were determined for 45 surface water samples and 99 groundwater samples (Appendix G). Physico-chemical averages of groundwater and surface water samples collected through the sampling period of September 2000 to July 2002 further characterise the different water bodies on Bribie Island as illustrated in Table 11.

Table 11. Average physico-chemical parameters for groundwater and surface water of Bribie Island Sample DO (ppm) EC (µS/cm) Eh (mV) pH Temp. (oC) 0.7 355 216 6.2 22 Semi-confined groundwater (0.1-1.0) (50-1100) (137-333) (4.4-7.1) (18-24) 2.8 279 279 3.9 20 Unconfined groundwater (05-6.0) (56-568) (185-387) (3.0-4.7) (17-24) 4.8 220 413 3.5 23 Wetlands and Excavations (1.9-7.2) (87-516) (249-576) (2.2-4.4) (17-29) 7.8 44 750 389 7.5 28 Coastal lagoons (7.3-8.7) (44 400-45 100) (383-395) (7.0-8.1) (25-30) September 9th 2000 to July 30th 2002 Range of values shown in brackets

Electrical Conductivity

The majority of groundwater and surface waters on Bribie Island are fresh, with the exception of coastal lagoons, tidal creeks, and saline influenced groundwater. Groundwater within the unconfined dune sands typically has low EC values with a range of 56-568 µS/cm, with an average of 279 µS/cm (Table 11). Typically, the values for EC from wetlands and surface excavations range from 87-516 µS/cm, similar to the values for the shallow unconfined groundwater. Surface water contained within coastal lagoons has EC values up to 45 100 µS/cm indicating seawater as a large constituent of lagoon volume. Groundwater within the sediments beneath the indurated sand layer has a range of EC values from 50-1100 µS/cm, with an average of 335 µS/cm.

Groundwater influenced by differing processes may be distinguished by differences in pH trends (Driscoll 2003). The pH of groundwater contained within sediments beneath the indurated sand layer is approximately two units more alkaline than either unconfined groundwater or surface water as illustrated in Table 11. The basal groundwater has the highest pH values of groundwater within the island ranging from 4.4-7.1, with an average of 6.2. Groundwater contained within the unconfined foredune and beach sands has pH values ranging from 3-4.7, with an average of 3.9. Values of pH from wetlands and surface excavations range from 2.2-4.4, with an average of 3.5. The acidic pH values of the unconfined groundwater and surface

water result from the decomposition of organic matter originally derived from vegetation. Fallen leaf litter decomposes to produce organic acids and dissolved organic carbon.

Colour

Rainfall events flush organic acids and dissolved organic carbon into the island wetlands, where they percolate down to the unconfined water table (Harbison 1998). A dark colouring of the unconfined groundwater and surface water is attributed to high concentrations of dissolved organic carbon. The dark brown to black colouring of this low pH water is often referred to as “black water”, and is common of many low-lying poorly drained coastal settings (Laycock 1975; Revee et al. 1985; Pye 1982). The unconfined dark coloured groundwater has a range of colour of 441- 2080 Hazen units; surface waters are typically very dark coloured and have a range of 910-6560 Hazen units. The deeper semi-confined groundwater in comparison is clear to colourless water with a range of 11-467 Hazen units.

Redox potential and dissolved oxygen

All groundwater and surface water samples from throughout Bribie Island indicate oxidising conditions. Unconfined groundwater typically has a range of Eh values of +185 to +387 mV, with an average of +279 mV (Table 11). Typically, the values of Eh from wetlands and surface excavations range from +249 to +576 mV. Groundwater sourced from beneath the indurated sand layer has a range of Eh values from +137 to +333 mV, with an average of +216 mV. Dissolved oxygen concentration is greatest within the coastal lagoons with an average of 7.8 mg/L, while other surface waters such as wetlands and excavations have average DO values of 3.2 and 7.2 mg/L, respectively.

6.5.2 Major ion chemistry

Major and minor ion concentrations have been determined for 99 groundwater and 45 surface water samples sourced from throughout the extensive monitoring well network of Bribie Island. These samples were collected during the sampling period of September 2000 to July 2002. This hydrochemical data has been incorporated with existing data collected by NRM&E and is presented in Appendix H. Harbison

(1998) conducted an extensive interpretation of the hydrochemistry of groundwater and surface water on Bribie Island. However, due to previously limited data available for the upper unconfined aquifer, new analysis is included here to enable further characterisation of groundwater and surface water. Average major ion concentrations of groundwater and surface water are illustrated in Table 12.

Table 12. Average major ion concentrations for groundwater and surface water samples of Bribie Island Major cations Major anions + + 2+ 2+ - - 2- Sample Na K Mg Ca Cl HCO3 SO4 Water type mg/L mg/L mg/L mg/L mg/L mg/L mg/L

Na-Cl,HCO3 Semi-confined 47 3 6 5 73 44 7 Na,Ca- groundwater Cl,HCO3 Unconfined Na-Cl 25 1 5 2 46 0.5 4 groundwater Na,Mg-Cl Na-Cl Surface water 30 1 5 3 48 0.07 6 Na,Mg-Cl September 9th 2000 to July 30th 2002

6.5.3 Water types

The classification of water types based on the system of Davies and DeWiest (1966) identifies hydrochemical groupings of water samples from throughout Bribie Island. These groupings can be related to the source of the sample and aquifer lithology.

The major ions of Na, Mg, Ca, Cl, HCO3 and SO4 are included in the classification of water types. The tri-linear Piper diagram of Figure 36 illustrates the relative concentrations of these major ions in % meq/L.

The similarities in ionic chemistry of both unconfined groundwater and surface water suggest that groundwater-surface water interactions exist. Both surface water and unconfined groundwater are typically Na-Cl or Na,Mg-Cl water types (Table 12), and have chemical ratios similar to local rainfall confirming precipitation as the primary source of recharge. The enrichment of Ca is attributed to carbonate lenses (remnant shell material) scattered throughout the beach ridge sediments (Figure 36). Due to the short residence time and low pH of both surface water and unconfined

groundwater, bicarbonate (HCO3) concentrations are negligible within these water bodies.

Relatively limited ion-exchange and weathering processes are evident throughout all water types on Bribie Island. However, semi-confined groundwater beneath the indurated sand layer shows signs of enrichment of HCO3. Bicarbonate enrichment may result from an increased residence time and a possible contribution of continental water from the weathered sandstone bedrock. Calcium enrichment is also evident within deeper groundwater and may be a result of similar processes.

Water types for the semi-confined groundwater are typically Na-Cl,HCO3 or Na,Ca-

Cl,HCO3.

Figure 36. Tri-linear diagram of major ion chemistry for groundwater and surface water. Water types and aquifer lithology relationships are represented by colour coded points. Arrows indicate principle directions of hydrochemical evolution

6.5.4 Organic Carbon Content

Dark coloured surface waters and unconfined groundwater are also distinguished from deeper semi-confined groundwater by total organic carbon concentrations (TOC). Total organic carbon of surface waters typically range in concentration from 65-142 mg/L, with an average of 103 mg/L as detailed in Table 13. The unconfined dark coloured groundwater has TOC concentrations ranging from 55-219 mg/L, with an average of 108 mg/L. Deeper semi-confined groundwater has TOC concentrations of 18-83 mg/L, with an average of 35 mg/L.

The acidity contribution of humic substances is equivalent to the A-, carboxylate anion. Concentration of the organic anion can be estimated for water samples and good ionic balances (± 6 %) are possible for coloured waters when A- is included as illustrated in Table 13. Calculation of the organic anion from dissolved organic matter is tabulated in Appendix I.

Table 13. Average total dissolved organic carbon concentrations and charge balances of water bodies and the influence of organic acid (A-) concentration Semi-confined Unconfined Surface water Element groundwater groundwater (meq/L) (meq/L) (meq/L) Na 2 1.1 1.5 Mg2+ 0.5 0.4 0.5 Ca2+ 0.2 0.07 0.2 K+ 0.08 0.03 0.04 Σ cations 2.78 1.6 2.24 Cl- 2 1.2 1.7

HCO3 0.7 0.01 0 2- SO4 0.1 0.05 0.15 A- 0.1 0.4 0.4 Σ anions 2.9 1.66 2.25 Σ cations/ 0.96 0.96 0.99 Σ anions TOC (mg/L) 35 108 103

6.6 Aquifer Hydraulic Testing

A range of hydraulic testing methods from single bailer tests to a more complex assessment of pumping test data is used to confirm the hydraulic properties of the Bribie Island aquifers. The various tests carried out were conducted on the multiple depth wells established on the reference transect.

6.6.1 Bailer tests

Most of the thirty bailer tests conducted throughout Bribie Island occurred across the reference transect as illustrated in Figure 37. Additional wells adjacent to the transect were tested; however only two wells (114 and 115) could be reliably tested. Due to the use of manually recording the rising head, some of the tested wells recovered faster than reliable readings could be taken (eg. 101 and 100). Additionally, deeper wells such as 089 and 088 were difficult to reliably test due to their lower initial heads. Typically, within these deeper wells the rising head was near completely recovered before the manual recorder (“dipper”) reached the water surface. Of the thirty wells tested only thirteen wells produced reliable results, which are illustrated in Figures 38, 39, and 40. Wells considered unsuitable for bailer tests were investigated for their suitability to pumping tests.

Figure 37. Summarised profile across the reference transect D-D' showing wells that were tested by the use of bailer tests. Two wells (114 and 115) not included on this transect are located to the south (refer to Figure 16)

89 Figure 38. Rising head plots derived from bailer tests of wells slotted within the upper foredune and beach sand aquifer. Plots A-I indicate damped conditions

From the reliably recorded bailer tests, three distinct groups of well settings can be identified based on the time taken for recovery; a) the foreshore and beach sand aquifer (unconfined), b) the swale deposits and c) the upper shoreface deposits (indurated sand layer). The rising head plots of Figure 38 illustrate wells slotted within the upper foredune and beach sands. These wells are slotted within clean medium grained sand and feature fast recovery rates. The rising head curves follow consistent trends with most recovery occurring within 10-20 seconds from t0. The organic rich sands of the central swale deposits (wells 129 and 146) typically show slower recovery rates as indicated in Figure 39. Significant recovery occurred within

20-40 seconds from t0. The highly indurated sand of the upper shoreface deposits (wells 143 and 150) have the slowest recovery rates from all tested wells (Figure 40). Significant recovery greater than 100 seconds was measured in both wells. Results from all tested wells indicate damped conditions.

Figure 39. Rising-head plots derived from bailer tests of wells slotted within the swale deposits (organic rich). Both plots A and B indicate damped conditions

Figure 40. Rising-head plots derived from bailer tests of wells slotted within the upper shoreface deposits (highly indurated sand). Both plots A and B indicate damped conditions

6.6.2 Pumping test 1

Pumping test 1 was conducted for 24 hours at a constant pumping rate of 1.2 m3/hour. The purpose of the test was to hydraulically test the semi-confined

shoreface brown sand aquifer below the indurated sand layer. Groundwater was extracted from well 101, while observation wells 139, 140, 141, 142, 143, 088, 144 and 145 were monitored as illustrated in Figure 41. The pumping well slotted section is located directly below the indurated sands (Figure 27 and 41). Partial penetration is limited as the slotted section approximately penetrates the entire sediment thickness between the indurated layer and the sandy silts below.

Figure 41. Vertical cross-section of transect D-D′ showing drawdown results from pumping test 1. Pumping and observation wells are included. Also indicated are schematic representations of induced flow from the pumping wells

Figure 42 shows time-drawdown plots of wells 142, 143 and 101. As illustrated in Figure 41, these nested wells are slotted within differing sedimentary units. Stratification of the water levels throughout the aquifer is particularly obvious in pumping test results (Figure 42) as was also shown in the flow net (Figure 33). The unconfined water table observed within well 142 is located at a height of

approximately 7.4 m above MSL and shows no signs of pumping influence. Observation well 143 is slotted within highly indurated sands and indicates a hydraulic head at approximately 2.9 m above MSL. Pumping influences are noticed within the time-drawdown plot for observation well 143. Observation well 143 is the only well during the pumping test to respond to pumping influence. A drawdown of approximately 0.05 m was recorded and indicates that some hydraulic connectivity may exist between the highly indurated sands (aquitard) and the weakly indurated sands immediately below. The pumped well (101) drawdown was approximately 0.47 m. Conditions of steady state flow were approached.

Figure 42. Response of pumping well (101) and observation wells (142 and 143) to pumping test 1. Heights of wells above bottom of aquitard are indicated by z

6.6.3 Pumping test 2

A second pumping test was conducted for a period of 24 hours at a constant pumping rate of 1.2 m3/hour. The second test extracted water from the offshore sandy silt

aquifer (well 088) beneath the shoreface brown sand aquifer. Observation wells 139, 140, 141, 142, 143, 101, 144 and 145 were monitored as illustrated in Figure 43. No observation wells responded during the test. Drawdown in the pumping well exceeded 4 m. Partial penetration of the sandy silt aquifer by the pumping well slotted section may have resulted in non-radial and non-horizontal flow paths. Placement of the slotted section at the bottom of the aquifer against the weathered sandstone bedrock may have reduced some of the effects of partial penetration.

Figure 43. Vertical cross-section of transect D-D′ showing drawdown results from pumping test 2. Pumping and observation wells are included. Also indicated are schematic representations of induced flow from the pumping wells

Time-drawdown plots of wells 142, 143, 101 and 088 are shown in Figure 44, and illustrate that pumping influence was not evident within any of the nested observation wells. Pumping influence was also not observed within wells 140 and 145. These wells are slotted within the same unit as the pumping well 088 (sandy silts with lenses of clay and fine sand). The inactivity within the wells 140 and 145

may have resulted from the effects of partial penetration; however it is more likely that these observation wells were located outside the cone of depression surrounding the pumping well. The size and shape of the drawdown curve for pumping well 088 indicates that the surrounding aquifer material has a relatively lower hydraulic conductivity compared to the material tested in pumping test 1. In addition, the cone of depression also reached near steady state conditions relatively quickly (<400 min). A contributing recharge source is unlikely responsible for the steady state conditions as drawdown was not observed within any of the observation wells located within or above the tested aquifer.

Figure 44. Response of pumping well (088) and observation wells (142, 143, and 101) to pumping test 2

Additionally, the effects of barometric pressure had to be included within the analysis of observation well data for the second pumping test. Observation well 101 recorded anomalous readings during the period of pumping as illustrated in Figure 45. The influence of barometric pressure on the water level within well 101 caused head values to rise and fall during the test. Where the influence of barometric pressure has been removed, the corrected head values indicate well 101 has not responded to pumping influences. Barometric efficiency of well 101 approximates 58 % suggesting highly semi-confined conditions for the slotted portion of aquifer (Table 10). Other nested wells (142 and 143) did not necessitate the removal of barometric pressure effects, as no effects were evident within their readings.

Figure 45. Influence of barometric pressure is evident in the uncorrected raw water level data for observation well 101 during pumping test 2. The corrected head shows that well 101 has not been affected by pumping and the natural drainage rates are low. Barometric efficiency of well 101 approximates 58%

6.6.4 Pumping test 3

The third pumping test was also conducted for a period of 24 hours at a constant pumping rate of 1.2 m3/hour. The third test extracted water from the deepest section of the reference transect within the palaeochannel aquifer (well 089). In addition, observation wells 090, 137, 138, 089, 100, 139, 140 and 141 were also monitored as illustrated in Figure 46. The third pumping test was a re-run of an earlier abandoned test where discharge of water proximal to the pumping well resulted in localised recharge to adjacent unconfined wells. As a consequence, data from the abandoned test are omitted from the results.

Figure 46. Vertical cross-section of transect D-D′ showing drawdown results from pumping tests 3. Pumping and observation wells are included. Also indicated are schematic representations of induced flow from the pumping wells.

The time-drawdown plot of the pumping well (089) and observation well (136) is shown in Figure 47. Well 136 is located approximately 440 m east of the pumping well and also slotted within the channel deposits (Figure 46). No other observation wells responded during the test. Drawdown within well 089 was 0.63 m, while drawdown within observation well 136 was 0.15 m. Partial penetration of the pumping well is limited as illustrated in Figure 46. However, despite the possibility of partial penetration of the pumping well, horizontal flow conditions can be assumed at the observation well as the radial distance to the observation well (r) is greater than two times the aquifer thickness (b): r > 2b (Kruseman and De Ridder 1979). Additionally, use of small diameter wells should result in negligible well storage effects.

Neither the pumping well nor the observation well attained steady state conditions. However, the period of pumping was adequate for steady state conditions to at least be approached therefore validating the use of analytical solutions such as the Theis drawdown, and Theis recovery methods. It is also noticed within Figure 47 that observation well 136 does not approach steady state conditions in the same manner as the pumping well. It is apparent that the rate of drawdown within the observation well may not decline as expected during the test. Barrier boundary conditions are often associated with increased drawdown within observation wells during pumping testes. Barrier conditions may be present within the palaeochannel sediments due to the bounding effects of the weathered bedrock. The influence of barrier boundaries must therefore be taken into account when analysing for aquifer hydraulic properties.

Figure 47. Graph of drawdown verses time for both the pumping well 089 and observation well 136

7.0 HYDRAULIC TEST ANALYSIS AND INTERPRETATION

7.1 Bailer Tests

Bailer tests of the foreshore and beach sand unconfined aquifer provide a range of horizontal hydraulic conductivity (Kh) estimates of 11-4.4 m/day with an average Kh estimate of 6 m/day (Table 14). Additionally, an estimate of specific yield of 0.25- 0.30 for the medium-fine grained sand aquifer can be adapted from the literature (Fetter 1994; Laycock 1975; Aschenbrenner 1996). Also notable are the hydraulic conductivity estimates for the shallow organic rich sands that occur within the central swale. The Kh estimates for the swale deposits range between 1-3 m/day (Table 14).

Table 14. Hydraulic conductivity values determined from bailer tests Elevation a Length of Well (m.a.s.l) Depth a (m) slots (m) K b (m/day) K c (m/day) Foreshore and beach sand aquifer (unconfined) 114 1.2 4.5 1 11 9 115 1.8 4.0 1 5.6 4.4 126 2.9 3.5 1 7.9 5.2 137 2.5 1.7 3 5.8 4.3 138 2.5 3.3 3 7.7 9 139 2.4 4.2 3 5.7 4.3 142 5.0 3.2 3 6.0 6.2 145 2.3 1.7 3 6.8 6.7 149 2.8 2 3 4.4 4.3 Organic rich sand (swale deposit) 129 -0.2 3.6 1.5 2.9 1.6 146 1.2 2.5 3 1.8 1.2 Indurated sand Layer (aquitard) 143 -0.5 8.5 3 0.09 0.12 150 -0.7 5.5 3 0.25 0.20 a midpoint of slots c Mean values from Hvorslev (1951) analysis b mean values from Bouwer and Rice (1979) analysis

Based on bailer testing, the highly indurated sand profile has an estimated Kh with an order of magnitude less (0.09 m/day and 0.25 m/day) than the overlying dune sands. Plots of recovery data versus time illustrate two examples from each lithological grouping (Figure 48).

Figure 48. Examples of bailer test results from the lithological groupings; A) foredune and beach sand aquifer, B) organic rich sand of the swale deposits, and C) the indurated sand layer

An average Kh of 0.17 m/day for the indurated sand layer is not insignificant. If this figure of Kh translates to vertical hydraulic conductivity (Kv), significant vertical leakage may occur despite the reduced porosity and permeability of the indurated sand layer. Therefore, the elevated groundwater heads observed across Bribie Island may be a result of significantly reduced Kv within the indurated sand layer.

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Inspections of drill core samples indicate induration is highly variable over short vertical distances. Bailer testing within the indurated sands may neglect the influence of these layers, particularly where they are thin and interposed with layers of moderate Kh.

Head gradients are significantly increased within, and above, the indurated sand layer

(Figure 33). Vertical head gradients can be used to gain estimates of Kv based on the Darcian flow equation: Q = −KAi refer to (1) The equation can be rewritten when annual recharge (W) is in one dimension: W = Ki (14) Where; W = Recharge (L) K = Hydraulic conductivity (L/t) i = Hydraulic gradient (dimensionless) Vertical head gradients are taken from the nested observation wells 142, 143, 101 and 088 (Figure 33). The hydraulic head gradients are illustrated in Table 15.

Table 15. Analysis of vertical head gradients of nested wells 142-088 via Darcy’s law. Vertical hydraulic conductivity (K m/day) is estimated for each section of aquifer separated by the nested wells. Estimated K values are generally much lower than provided by bailer tests and pumping tests 142-143 143-101 101- 142- units 088 088 When recharge (W) 5.6-4 5.6-4 5.6-4 5.6-4 m/day = Let gradient = 4 1 0.02 5 m head difference between slots 5.3 7.5 21 33.8 m vertical distance between slots Hydraulic gradient 7.5-1 1.3-1 9.5-4 1.5-1 dimensionless (i) Estimated K 7.3-4 4.1-3 5.7-1 3.7-3 m/day (m/day) Rainfall (R) = 1300 mm/year Evapotranspiration (ET) = 1100 mm/year Refer to section 3.6 (Bubb and Croton 2002) Recharge (W = R - ET) = 200 mm/year = 0.00056 m/day

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Substitution of the hydraulic head gradients and a value for recharge into the Darcy flow equation results in estimates of vertical hydraulic conductivity as illustrated in

Table 15. Estimated Kv of the highly indurated sand is approximately between

0.0007 m/day and 0.004 m/day. These estimated values of Kv are on average two to three orders of magnitude less the Kh estimates for the same unit determined via bailer test methods. In addition, the estimates displayed in Table 15 also illustrate that the upper portion of the highly indurated sands has the lowest Kv estimate. Physical observation of well logs confirms the section between observation wells 142 and 143 is the most highly indurated. The Kv of the highly indurated sands is also two to three order of magnitude less than the sand silt material between observation wells 101 and 088, confirming the indurated sands as a leaky aquitard.

7.2 Pumping Tests

Recovery analysis of pumping well data and drawdown analysis of observation well data produce the hydraulic conductivity estimates listed in Table 16.

Table 16. Hydraulic conductivity (K) and specific storage (Ss) values determined from pumping tests

Test Well Stratigraphic Unit Kh Ss (m/day) (Dimensionless) 1 101a Upper/lower shoreface deposits - weakly indurated 25† - brown sands 2 088a Offshore deposits - sandy silts with lenses of clay and 1† - fine sand 3 089a Channel deposits - medium sand (lenses of fine and 7† - coarse sand) 3 136b 6* 4.5 x 10-6 3 136b Channel deposits - medium sand (lenses of fine and 7‡ 3.5 x 10-6 coarse sand) 3 136b 5• 9.7 x 10-6 a Pumping well b Observation well † Theis recovery method * Theis drawdown method ‡ Cooper-Jacob straight line method • Stallman method

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7.2.1 Pumping test 1

Theis Recovery analysis of pumping well 101 slotted within the shoreface brown sand aquifer (Figure 49) estimates horizontal hydraulic conductivity as 25 m/day (Table 16). An estimate of storativity cannot be calculated due to the absence of drawdown in observation wells located within the same unit.

Maximum drawdown within the pumped aquifer was approximately 0.5 m, while maximum drawdown within the overlying highly indurated sand profile (well 143) was approximately 0.05 m as illustrated Figure 42. Observation well 143 is located at a radial distance of 3 m and vertical distance of 1.5 m from the pumping well 101. Assuming the indurated sand layer provides a degree of confinement to the pumped aquifer, flow to the pumping well is assumed to be horizontal within the aquifer and vertical within the overlying indurated sand aquitard (Kruseman and De Ridder 1979).

Figure 49. Analysis of recovery data from pumping test 1, well 101, with the Theis recovery method

Pumping tests with observation wells in the aquitard have often been used to obtain reliable estimates of vertical hydraulic conductivity within an aquitard (Neuman and Witherspoon 1972; Rodrigues 1983; Keller et al. 1986; Neuman and Gardner 1989). The tests rely on measurement of head changes within the aquitard induced by changes of head in an underlying or overlying aquifer (van der Kamp 2001). The method developed by Neuman and Witherspoon (1972) applies the ratio between drawdown within the aquitard against drawdown within the aquifer to a set of type

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curves. The theoretical analysis is based upon one-dimensional diffusion of pressure transients into a uniform homogeneous aquitard (van der Kamp 2001).

The Neuman and Witherspoon (1972) ratio method yields values of hydraulic diffusivity (Kv/Ss), hence to obtain a value for Kv for the indurated sand aquitard, an independent estimate of Ss is required. Laboratory values of Ss are generally used in such situations. However, values obtained via laboratory analysis often do not approximate in situ conditions (van der Kamp 2001). An estimate of Ss for the indurated sand layer is not available. However, Ss may be considered very low due to the predominately sandy matrix of the indurated layer.

Additionally, the careful set-up of the pumping test is also necessary to provide reliable values. It is recommended that observation wells in the aquitard be placed at a radius of several aquifer thicknesses away from the pumping well (Neuman and Witherspoon 1972). At this distance the effects on drawdown due to strain and deformation within the aquitard are greatly reduced. This effect is termed the “Noordbergum effect” and can induce anomalous changes in head near the well at the beginning and end of pumping (Rodrigues 1983; Hsieh 1996; Burbey 1999; van der Kamp 2001). Unfortunately, as noted above, the placement of the aquitard observation well 143 is less than the required distance from the pumping well.

Observation wells placed in the aquitard close to the pumping well may also be susceptible to leakage through the annulus around the casing of the pumping well. Therefore, the annulus around the casing should be properly sealed to prevent leakage. The pumping well 101 has no such seal suggesting that leakage is highly likely. The resulting drawdown within the observation well located in the overlying aquitard may be very misleading and should therefore be considered with caution.

Despite the limiting factors noted above, the hydraulic character of the highly indurated sand layer (aquitard) can be determined. The recovery of heads in the brown sand aquifer and the indurated layer display no comparable time lag. Therefore, a negligible storage term exists for both units. This is not surprising as both units have a dominantly sand composition, thus reducing the likelihood of matrix compressibility.

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Water level drawdown for observation well 143 (s′) and pumping well 101 (s) were measured from the hydrograph illustrated in Figure 41. A drawdown ratio (s′/s) of 0.076 was determined at time 58 min. Values to determine hydraulic diffusivity

(Kv/Ss), were derived from ratio-method type curves provided by Neuman and Witherspoon (1972). The storativity of the aquifer was assumed to be low at 1x10-5, however the influence of aquifer storativity on overall results is negligible.

Hydraulic diffusivity (Kv/Ss) of the highly indurated sand aquitard is estimated at 2 2 2.7x10 m /day, which is more than 6 orders of magnitude less than Kv/Ss for the pumped shoreface brown sand aquifer at 2.5x108 m2/day. Due to the uncertainty of - Ss of the indurated sand aquitard, a range of specific storage is proposed from 1.0x10 4 to1.0x10-6. Therefore, based on the Neuman and Witherspoon (1972) ratio method -1 an estimate of Kv for the indurated sand aquitard may range between 2.7x10 m/day and 2.7x10-3 m/day.

7.2.2 Pumping test 2

Due to the silty composition of the offshore deposits, these deposits have a lower hydraulic conductivity (Kh) compared to the shoreface sand aquifer located above. Figure 50 illustrates a Theis Recovery plot generated from residual drawdown data collected during the second test. Theis recovery analysis of pumping well 088 estimates hydraulic conductivity as 1 m/day (Table 16). An estimate of storativity cannot be calculated due to the absence of drawdown in observation wells located within the same unit.

Figure 50. Analysis of recovery data from pumping test 2, well 088, with the Theis recovery method

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7.2.3 Pumping test 3

Drawdown data from observation well 136 for the period between 120 min and 460 min match the Theis type curve (Figure 51). Typically, initial results are often not closely represented by the Theis theoretical drawdown curve equation and so less weight should be placed upon these readings (Kruseman and De Ridder 1979). Therefore, late time data is typically used as a more reliable indication of aquifer conditions.

For the period between 120 min and 460 min the match between measurements and the Theis type curve indicate values of: Hydraulic conductivity (K) = 6.06 m/day Aquifer thickness (b) = 9 m Transmissivity (T) = 54.4 m2/day Storativity (S) = 0.000041

Deviation of late time data from the Theis type curve suggests an increase in drawdown during the latter stages of the test. Changes in the shape of time- drawdown curves after initial fitment to the Theis type curve are often associated with barrier boundary conditions.

Figure 51. Matching of data from pumping test 3 of observation well 136 to the Theis type curve. Early time data after 120 min fit the Theis type curve; however deviation from the curve during late time data may suggest barrier boundary conditions

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The assumption that aquifers are of infinite areal extent is typically used solely for mathematical convenience. However, aquifers are always bounded by geological features such as faults, bedrock contacts, facies changes and also recharge areas such as streams and lakes. As a result it is typical for some boundary effects to impact on well hydrographs. When the cone of depression reaches an impermeable boundary, the drawdown within the area of influence has to increase to produce the same amount of discharge because of no inflow from the boundary.

The influence of barrier boundary conditions can also be illustrated when drawdown data are analysed by the Cooper-Jacob straight line method. The well function (W(u)) of the Theis equation can be modified to a logarithmic term when u is < 0.01 (Weight and Sonderegger 2001). Values of u greater than 0.01 can create errors. The Theis equation can be rewritten:

2.3Q  2.25Tt  s = log  (15) 4πT  r 2S  Where; s = Drawdown (L) S = Storage (dimensionless) T = Transmissivity (m2/day) t = Time (t) Q = Pumping rate (L3/t)

When drawdown data from an observation well are plotted versus time the results fall along a straight line (under confined conditions). If barrier conditions are present and have influenced the drawdown data, the slope of the line will double as a result from the increased drawdown as illustrated in Figure 52. The initial slope of the early time data can be used to calculate aquifer properties before barrier boundary conditions prevail.

Using the Cooper-Jacob method the data for the period between 120 min and 460 min indicate values of:

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Hydraulic conductivity (K) = 7.57 m/day Aquifer thickness (b) = 9 m Transmissivity (T) = 68 m2/day Storativity (S) = 0.000031

Additionally, as time approaches the “inflection point” the data indicates apparent leakage (Figure 52). This leakage may be attributed to a differential drainage process. The channel deposits include lenses of fine sand, coarse sand and gravel, all of which may drain at comparably different rates resulting in some limited recharge to the drawdown data.

Typically, the effects of more than one barrier boundary are observed at later time periods. Figure 52 illustrates the development of a possible third slope prior to the end of the pumping period. With continued pumping this data may have been evaluated with more certainty.

Figure 52. Cooper-Jacob plot from pumping test 3 of observation well 136. Straight line behaviour in drawdown versus time exists until t = 460 min. Increased drawdown results from barrier boundary effects

The effects of barrier boundaries can be simulated by the addition of image wells in conjunction with the principle of superposition. The introduction of image wells

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transforms the system to one that can be analysed by use of pre-established flow analyses. For each barrier that is encountered during the pumping period an image well must be included (Kruseman and De Ridder 1979). When one barrier is uncounted, only one image well need be included within the analysis as illustrated in Figure 53. The position of the image well reflects the position of the real pumping well. However, the image well is located on the other side of the barrier and at right angles to it (Fetter 1994). For barrier boundaries, the image well discharges at the same rate as the real pumping well. The combined drawdown of the two wells approximates the effect of the barrier boundary. The actual drawdown is the sum of the drawdown from the real well and the drawdown from the image well (Figure 53).

Figure 53. Schematic cross-section and plan of an aquifer with a straight barrier boundary, A) natural conditions, B) equivalent system with an image well, C) plan (after Kruseman and De Ridder 1979)

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Well functions of both the real well and the image well are expressed: r 2 S r 2 S u = , u = i (16) 4Tt i 4Tt Therefore, the flow equation for a system that includes barrier effects can be expressed as: Q Q = W (u) + W (u ) (17) 4πT 4πT i Q = [W (u) +W (u )] (18) 4πT i Where; u = Well function of real well (dimensionless)

ui = Well function of image well (dimensionless) r = distance between the observation well and the real pumped well (L)

ri = distance between the observation well and the image well (L) T = Transmissivity (m2/day) t = Time (t) S = Storage (dimensionless) Q = Pumping rate (L3/t)

In addition, the use of a drawdown versus time graph such as the Cooper-Jacob plot, the distance, ri, between the observation well and the image well can be calculated.

As illustrated in Figure 54, a drawdown value (s1) is selected from the period where the boundary effect is not evident. The time of this value is recorded as t1. On the second segment of the time-drawdown data where the boundary effect prevails, the time (t2) is recorded where the drawdown (s2) is equal to the initial drawdown value

(s1). These values are then substituted into the flow equation as illustrated below.

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Figure 54. Cooper-Jacob plot of drawdown versus time. The distance of ri can be calculated when the values of s1 at t1 and si at t2 are calculated and substituted into the flow equation

Since s1 at t1 equals s2 at t2:

2 2 Q  r S  Q  ri S  W   = W   (19) 4πT  4Tt1  4πT  4Tt2  r 2S r 2S = i (20) 4Tt1 4Tt2 r 2S r 2S = i (21) 4Tt1 4Tt2 r 2 r 2 = i (22) t1 t2 Therefore, when: 4402 r 2 = i (23) 100 830 4402 12682 = (24) 100 830

ri = 1268 m distance from observation well to image pumping well

However, to find the exact location of the image well at the radius of ri, at least three observation wells are required. The position of the boundary can then be calculated.

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In the case of Bribie Island the established depth to bedrock contours give an approximate position of the barrier boundary. This approximate location of the barrier boundary has been included within the schematic illustration of Figure 55.

Since analytical solutions have been developed for the drawdown distribution in a confined aquifer with infinite lateral extent, these solutions can also be adapted to include bounded aquifers. Stallman’s method, as described by Kruseman and De Ridder (1979), enables the evaluation of aquifer properties from the portion of data that has resulted from the increased drawdown associated with a barrier boundary. The type curve method relies upon the matching of data points obtained during the pumping test to a series of type curves. This method can be applied if the following limiting conditions are satisfied (Kruseman and De Ridder 1979):

1. all limiting conditions that apply to the Theis method, and 2. within the zone influenced by the pumping test, the aquifer is crossed by one or more straight fully-penetrating recharge or discharge boundary.

The ratio of ri/rr = β, is used to identify the appropriate type curve for best fit of the data. The numerical values of the well function of the Stallman type curve

W(u,β1→n) are typically given within published references such as Kruseman and De Ridder (1979). In cases where one boundary exists there are only two terms: the term (Q/4πKb) W(u) describing the influence of the real pumping well and the term (Q/4πKb) W(β2u) describing the influence of the image well. r 2S r 2S β 2r 2S u = r , u = i = r = β 2u (25) 4Kbt i 4Tt 4πKb One straight barrier, as illustrated in Figure 55: Q s = {W (u) +W (β 2u)} (26) 4πKb Q s = W (u, β ) (27) 4πKb B

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Figure 55. Schematic cross-section of transect H-H' indicating location of pumping well 089 and observation well 136. Both wells are located within the deepest part of the palaeochannel. The weathered sandstone bedrock results in barrier boundary conditions during pumping of adjacent wells

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Using the Stallman method (Figure 56) data for the period after 460 min indicate values of: Hydraulic conductivity (K) = 5.2 m/day Aquifer thickness (b) = 9 m Transmissivity (T) = 47.5 m2/day Storativity (S) = 0.000061

Figure 56. Curve fit of late time data (>494 min) from observation well 136 to the Stallman type curve (β = 3)

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8.0 DISCUSSION

8.1 Comparison of Hydraulic Conductivities

Previous investigations of the hydraulic properties of the Bribie Island aquifers have focused on the southern section of the island in relation to water supply management options (Lumsden 1964; Ishaq 1980; Isaacs and Walker 1983). Morphology of the Holocene dune system in the south of the island differs from the northern Pleistocene dune system. Both sandy silt sediments and indurated sand development are not as extensive in the younger sediments. Therefore, aquifer heterogeneity has not been considered a key component in previous hydrogeological investigations.

Laboratory testing of sediments by Harbison (1998) provide estimates of hydraulic conductivity for sediments taken mostly from the southern section of the island. Table 17 has been adapted from Harbison (1998) and illustrates the large range of K values that have been estimated for Bribie Island.

Table 17. Summary of previous estimates of hydraulic conductivity for Bribie Island and North Stradbroke Island using grain size analysis, pumping tests, tidal damping, falling head tests and water balance analysis (after Harbison 1998) Hydraulic Conductivity, K (m/day) Author Grain size Pumping test/ Laboratory hydraulic test/ analysis Tidal damping † Water balance analysis ∗ Lumsden (1964) 13 - 4 Laycock (1975) 15 6 0.09–155 John Wilson and Partners (1979) - 15–75 13-30 ∗ Ishaq (1980) 17 - - Harbison (1998) 25 a 1-8† 9 a, 0.4–0.8 b a foreshore and beach sand aquifer (unconfined aquifer) b indurated sand layer (aquitard)

Grain size analysis and laboratory hydraulic tests are likely to produce erroneous results for effective porosity and hydraulic conductivity due to the disturbance of samples during removal and relocation (Todd 1959; Fetter 1994). However, laboratory estimates are a useful means to provide a check on results obtained via other methods. It was noted by Harbison (1998) that falling head tests were conducted at a much higher hydraulic gradient compared to field conditions. Elution

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of fines from the sample during the falling head tests may be attributed to the high hydraulic gradient during the tests. It is therefore suggested that the K estimates of Harbison (1998) may be over-estimated.

In addition, laboratory testing limits the spatial integration of K to a very small scale (Millham and Howes 1995). Therefore, in situ hydraulic testing such as tidal response, bailer tests and pumping tests should be considered more reliable methods for the estimation of aquifer properties.

Obtaining satisfactory results from pumping tests on sand islands is complicated by the required long pumping times and the disposal of extracted water. In 1979 John Wilson and Partners (unpublished data) conducted two pumping tests in the southern section of Bribie Island and the estimates of hydraulic conductivity varied between 15 m/day to 75 m/day (Table 17). These high K estimates may be due to errors attributed to the short duration of pumping (8 hours). Also, the results may reflect the differences in sedimentary material between the south and the north of the island.

In addition, Laycock (1975) conducted six pumping tests on the neighbouring megadune sand island, North Stradbroke Island (NSI). The results of these pumping tests indicate an estimate of hydraulic conductivity of 6 m/day (Table 17), reflecting the results of the unconfined aquifer of Bribie Island. Indurated sand development and preservation within the massive dune sands of NSI is less extensive than for Bribie Island. As a result, only localised perching of groundwater exists on NSI. Laycock (1975) noted that the form of the log-log drawdown curve typically fit well for the unconfined conditions. The delay in yield to the water table was considerable; the return of the drawdown log-log curve to the Theis equilibrium curve did not occur during even the longest test of 12 days. The specific yield determined using Boulton curves approaches the value of 0.2.

Laboratory hydraulic tests of sediment similar to Bribie Island have also been analysed by Acworth and Dasey (2003). Laboratory tests of the coastal barrier sediments, from the coastline of New South Wales, Australia, indicate a significant difference between the fine sand aquifer and a poorly cemented indurated sand layer. From grain size analysis the hydraulic conductivity of the fine sand aquifer was

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estimated at 20 m/day. Additionally, minimally disturbed core samples of the poorly cemented indurated sand gave estimates of 2 m/day (Acworth and Dasey 2003). As with Harbison (1998), the estimates of Acworth and Dasey (2003) may also be overestimated due to errors resulting from the method of testing.

Examples of pumping tests within similar physical settings to Bribie Island are available in the literature (i.e. Harris 1967; Burkett 1996; Suresh Babu et al. 2002), and are summarized in Table 18. The estimates of hydraulic conductivity obtained from these pumping tests agree well with the values determined for the aquifers of Bribie Island. Of particular note are the estimates of Anderson et al. (2000) for Hatteras Island, North Carolina. Extending from the results of the pumping tests by Burkett (1996), numerical solutions were developed to simulate observed elevated water table levels across the sand island. In order to achieve a satisfactory simulation, the numerical model focused on the hydrogeologic framework of the sand island and incorporated regional heterogeneities. What was termed a “buried wetland” produced significant influence on the surrounding water table observations. Similar to Bribie Island, the relatively high permeability of the North Hatteras Island aquifers may also exacerbate the significance of the heterogeneities. Numerical solutions estimated a hydraulic conductivity of 0.05 m/day for the low permeability material. Anderson et al. (2000) concluded that this heterogeneity was responsible for the elevation of the water table, however, did not indicate whether this material could also act as a confining layer.

Table 18. Comparative estimates of hydraulic conductivity (K) for characteristically similar sand masses/islands Hydraulic cond., Author Sediment type K (m/day) Harris (1967) 5 Fine-medium sand, moderately-well sorted Burkett (1996) 21 Medium-coarse sand, lenses of shells Anderson et al. (2000) 25 a, 12.5 b, 0.05 c a Medium-coarse sand, b Fine sand-silt, c buried Suresh Babu et al. (2002) 11 Very fine-fine sands Acworth and Dasey (2003) 20 a, 2 b a Fine sand well sorted, b poorly indurated sand

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8.2 Conceptual Hydrogeological Framework

This study of Bribie Island demonstrates how detailed measurement of stratigraphy, groundwater levels, rainfall, barometric pressure and hydraulic testing can be used in conjunction to identify and assess aquifer heterogeneity within a sand island environment.

The stratification of water levels across the reference transect and the relatively flat piezometric surface are in contrast with the classical “domed” water table aquifer expected of a barrier island (Harris 1967; Vacher 1988; Collins and Easley 1999). Stratified head gradients through the Bribie Island aquifers suggest groundwater migration to depth is impeded by the indurated sand layer. An elevated shallow water table results from the mounding of water above the indurated sand layer. The indurated sand layer is extensive across the reference transect.

Seepage of fresh unconfined shallow groundwater over indurated sand layers onto beach faces has been observed in numerous locations on the island. Additionally, lateral drainage also occurs beneath the indurated layer. The basal groundwater discharge is generally sufficient to restrict saltwater encroachment and a measurable freshwater-saltwater interface exists off the coastline around the perimeter of the island (Harbison 1998).

The shallow unconfined water table aquifer responds rapidly to rainfall events, while aquifers located beneath the indurated sand layer show a delay in recharge of up to 48 hours (Harbison 1998). Vertical leakage through the indurated sand layer recharges basal aquifers.

Wells slotted immediately beneath the indurated sand layer indicate high barometric efficiencies (up to 58 %). Confined aquifers typically measure barometric efficiencies of 40-70% (e.g. Clark 1967; Davis and Rasmussen 1993; Rasmussen and Crawford 1997). The “skin effect” shown by well 100 is attributed to a greater proportion of finer grained sediment within the brown sand aquifer matrix. Wells slotted within the sandy silt (088) and palaeochannel aquifers (089) have reduced responses to barometric pressure. Despite low barometric efficiencies, the deep

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wells do not show rainfall responses typical of the unconfined aquifer. Therefore it is suggested that the barometric efficiency of these wells is masked by a large skin effect; rather than connected to the shallow unconfined aquifer system.

It is important to acknowledge the limitations of the pumping tests. Inability to hydraulically stress the system sufficiently to induce drawdown in nearby observation wells creates difficulties in assessing hydraulic properties. However, pumping tests were able to confirm general hydrogeological concepts in regard to aquifer heterogeneity across the reference transect. The indurated sand layer is not impermeable. However, the porosity and permeability of the indurated sand layer is reduced compared to the surrounding aquifers.

Estimates of vertical hydraulic conductivity of the indurated sand layer have been calculated via hydraulic testing and vertical head gradients. The differing methods produce estimates of Kv that fall within a broad range. Despite the range of estimates it is noted that Kv is typically two to three orders of magnitude less than the values derived for Kh.

The groundwater resource of Bribie Island is of commercial and environmental importance. Extensive pine plantations tap the shallow unconfined groundwater table while discharge of groundwater supports extensive estuarine and wetland habitats. Potable water, principally for domestic use, is currently extracted from the sand aquifer in the populated south of the island via a trench system, and a well field is under consideration for the central section of the island.

The quality of the extracted groundwater on Bribie Island has occasionally been reduced due to elevated iron, manganese, organic content, nutrient discharge and salinity (Harbison 1998). Fresh groundwater typically flushes saline water from permeable zones more rapidly than from low permeable zones. It is therefore possible that within some areas, excessive groundwater extraction may lead to more than one freshwater/saltwater water interface in the vertical section as illustrated in Figure 57. Variable freshwater/saltwater water interface relationships have been reported for other barrier islands where aquifer heterogeneity is prominent. The island aquifers of Grand Isle,

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Louisiana, USA, and Assateague Island, Maryland, Virginia, USA, are examples where variations in hydraulic conductivity and permeability exist (Bolyard et al. 1979; Collins and Easley 1999).

There are no legislated restrictions for extraction of groundwater on Bribie Island, which allows uncontrolled use of groundwater and a lack of coordination between a range of users and interest groups. There is a need for effective management practices to assure continued availability of good quality groundwater on the island.

Figure 57. Conceptual hydrogeology of Bribie Island including aquifer heterogeneity and the main types of use

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9.0 CONCLUSION

A summary of the main findings from this study is as follows:

• The stratigraphy of Bribie Island consists of sediment profiles with distinctive hydraulic characteristics. Hydraulic tests performed across a central reference transect confirm aquifer heterogeneity and quantify aquifer parameters such as hydraulic conductivity and specific storage. The heterogeneities within the stratified aquifer conceptual model have profound effects on groundwater occurrence and flow within the island.

• Aquifer heterogeneity resulting from the stratification of island sediments can produce a complex hydrological system as identified within Bribie Island. Such variations in hydraulic conductivity are very important in controlling groundwater levels, groundwater migration and groundwater chemistry through a sand island environment.

• Consistent differences in ionic chemistry exist between “black” and “white” waters. The wetlands and shallow groundwater are typically “black water” with low pH values and high organic anion concentrations. The basal aquifers contain “white water” with near neutral pH and low organic anion concentrations.

• A laterally extensive indurated sand layer at shallow depth is observed in drill hole correlations and hydraulic test data. Hydraulic tests confirm that the indurated sand layer has a significantly reduced permeability that restricts the downward migration of shallow groundwater; resulting in elevated water tables and shallow lateral drainage.

• The groundwater beneath the indurated sand layer occurs under semi-artesian conditions resulting in a shallow hydraulic gradient across the island.

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Hydraulic conductivity within the basal aquifer beneath the indurated sand layer is considered moderate.

• Connectivity between the overlying indurated sand layer and the basal aquifers suggests the indurated sand layer acts as an aquitard reducing the rate of recharge to the basal aquifer. The basal aquifers exist in a semi-confined state.

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Appendices

Section A: Associated publications

Appendix A

Chemical character of surface waters on Bribie Island: a preliminary assessment. (extended abstract)

Presented: PASSCON 2000, Pumicestone Passage and Deception Bay Catchment Conference, QUT, November 2000

Chemical Character of Surface Waters on Bribie Island: A Preliminary Assessment

TIMOTHY ARMSTRONG

School of Natural Resource Sciences, Queensland University of Technology, Brisbane, QLD

INTRODUCTION

Bribie Island is a large barrier sand island in northern Moreton Bay approximately 65 km north of Brisbane. Bribie Island is the eastern boundary of the Pumicestone Passage catchment and is separated from the mainland by the shallow estuarine wetlands of the passage. Over the past few decades the entire catchment, including Bribie Island, has experienced very rapid growth in terms of urbanisation and agricultural development. While urban development is restricted to the southern extent of the island, pine plantations and National Park occupy the northern two thirds of the island.

The assessment of surface waters on Bribie Island is of particular importance due to the size of the catchment area, the activity on the island and most importantly runoff into the passage. Bribie Island has four major surface water outlets that drain into Pumicestone Passage. Most of the water from these creeks originates from areas that drain pine plantations and National Parks.

This paper provides a brief overview and evaluates the present conditions related to natural surface water chemistry, distribution and interactions it has with other processes on the Island. This description of surface waters is part of a larger study investigating the shallow hydrogeology of the forested areas, and does not consider the populated southern quarter of the island.

Appendix A – Passcon Conference extended abstract

PHYSICAL SETTING

Bribie island has very low relief with a mean elevation of 5 m and a maximum elevation of 17 m above sea level. The island consists predominantly of two successive beach ridge systems separated by a major swale (interconnected low- lying melaleuca swamps) extending through the long axis of the island. The central swale is the dominant drainage feature on the island. Pine plantations are generally restricted to the two major beach ridge systems.

The sediments of Bribie Island consist of Quaternary aeolian sand deposits. The two major beach ridge systems are aligned to the current coastline and represent sedimentation during Pleistocene interglacial periods (Harbison, 1998). Sediments are composed of fine to medium grained sands deposited by prevailing south-east winds.

Contained within the beach ridge sediments is a layer of indurated sands at an approximate depth of 5-6 m and has a maximum thickness of 9 m. While the indurated sand (coffee rock) has a reduced permeability that affects water movement, it comprises a significant volume of the aquifer (Harbison & Cox, 1998).

Due to the reduced permeability of the coffee rock, it acts as a partial confining layer for the groundwater beneath it. A perched water table results as recharge (rainfall) is unable to percolate easily through the coffee rock layer. This shallow water table is directly related to the surface waters.

Methods

Surface water monitoring of 19 sites has consisted of monthly infield testing of physico-chemical parameters over the past three months. During one round, water samples were collected for laboratory analysis of major cations and anions, metals (Fe, Al, and Mn), and nutrients (NO3, PO4).

Appendix A – Passcon Conference extended abstract

The present sampling program has also been aided by the compilation of data from outside sources such as HLA Envirosciences Pty Ltd. and Department of Natural Resources.

Transects across the island have been established that tie in with the existing bore network. Early in 2001 an extensive shallow bore network will be developed along these transects.

RESULTS

Surface water distribution and drainage:

Most surface waters on Bribie Island occur naturally in low-lying depressions ranging in size from meters to tens of meters in area. These local low points occur as minor swales forming between minor ridges that are contained within the larger ridge system. In several coastal locations there are small lakes, which sometimes are breached during storms. The other major form of surface water on the island is man-made fire fighting dams. Due to their depth, some dams act as windows into the shallow groundwater. These windows contribute greatly to the permanent surface water supply

Organic silts and clays are transported into these depressions where upon settling can create a type of seal that reduces the infiltration of the surface water (Harbison, 1998). For this reason surface water can remain in lows for a period of several weeks after significant rainfall.

The drainage patterns on Bribie Island are ill defined. The most significant flows are from the two major beach ridge systems into the central swale. In general the central swale has a northerly flow discharging into Pumicestone Passage via Westerways Creek in the north of the island. The southern portion of the central swale flows to the south and discharges into the passage via Wright’s Creek.

Appendix A – Passcon Conference extended abstract

Physico-chemical Parameters:

The pH of surface waters on Bribie Island is generally low. The pH range for most surface waters is between 2.9-4.5 (average pH ≈ 3.6), hence the majority of surface waters on Bribie Island can be classified as acidic waters. The few exceptions are saline waters of the coastal lagoons and tidal creeks that have a typical pH > 6.

The cause of these acidic surface waters on Bribie Island can solely be attributed to organic acids. Rainfall events flush organics and humic substances into surface water depressions, where over time organic matter will percolate down to the shallow water table. Decomposition of the organic matter eventually produces the organic acids found in these waters, such as fluvic acid (Drever, 1997). However, the exact chemical type of acid has not yet been determined. In some sites contribution to low pH may also be related to carbonic acids.

The obvious colour of surface waters can also be attributed to humic substances, and these waters are often referred to as “black water”. The colour of these Bribie Island waters is therefore due to the colour of the acid-soluble organics and particulates in the water and not a staining due to oxidation of metals such as iron.

Most of the surface waters on Bribie Island are exceptionally fresh. The conductivity ranges from 20-500 µS/cm, while rainfall in this area is typically 20- 40 µS/cm. There seems to be no apparent trend to conductivity distribution, except for surface water contained in coastal lagoons.

The coastal lagoons along the east coast of the island have conductivities as high as 44000 µS/cm (similar to the conductivity for sea water). In this study only two sites with saline waters were analysed, Mermaid Lake and Wright’s Creek. As these saline samples are not entirely representative of the area, these records are not included in most averages.

Appendix A – Passcon Conference extended abstract

Ionic Chemistry:

The surface waters on Bribie Island typically have a Na,Mg-Cl water type (Group 1, Figure 1). Similarly, shallow groundwaters have a dominant water type of Na,Mg-Cl. The more saline waters and some surface waters however, have a water type closer to Na-Cl, reflecting chemical ratios similar to local rainfall and seawater.

Most surface waters and shallow groundwaters generally show Ca enrichment with one particular sample showing significant increases in Ca (Figure 1). Enrichment of Ca may be attributed to carbonate fragments (remnant shell material) scattered throughout some of the sediments. The enriched samples have a water type of Na,Ca-Cl. There also appears to be two distinct groups of surface waters characterised by their Ca concentrations (≈ 1-2 mg/L and ≈ 4-6 mg/L).

Origin of Sample Deep groundwater Shallow groundwater Group 2 Bribie Island rain Na,Mg-Cl 80 80 Surface water Na-Cl Average seawater

Deeper groundwaters 60 60 & some surface water Group 1 40 40 Group 3 Na,Mg-Cl Na-Cl-HCO3 Na-Cl 20 20 Na,Ca-Cl-HCO3 Surface water & Deep Groundwaters Shallow groundwater Mg SO4

80 80

60 60

S 40 40 o 4 e n r ic 20 20 h m HCO3 enrichment e n Ca enrichment t 80 60 40 20 20 40 60 80 Ca Na HCO3 Cl

Figure 1. Trilinear diagram of major ion chemistry for surface waters and groundwaters.

Due to the low pH of the surface waters on Bribie Island and the character of local rainfall HCO3 concentrations have been drastically reduced, with most surface waters containing nil HCO3 (Group 1, Figure 1). HCO3 enrichment is therefore restricted to mostly deeper waters that lie underneath the coffee rock layer where there is a corresponding higher pH level (Groups 2 & 3, Figure 1).

Appendix A – Passcon Conference extended abstract

Sulfate concentrations are generally low for surface waters (average. ≈ 5.5 mg/L) (Figure 1) and are a reflection of the low concentrations in local rainfall. Also, the island’s sediments have provided little additional input.

The dominant metals in the surface waters are Fe and Al although both of these metals have low concentrations, ranging from 0.19-2.85 mg/L (average. ≈ 1 mg/L) for Al and 0.05-2.39 mg/L (average. ≈ 1 mg/L) for Fe.

SURFACE AND SHALLOW GROUNDWATERS

As previously suggested, the shallow groundwaters and surface waters of Bribie Island are related physically and chemically due to infiltration and seepage. Both are similar water types (Na,Mg-Cl) and both have similar concentrations of major ions. Physico-chemical parameters such as pH, conductivity, and colour are also very similar naturally.

Physical changes to the shallow groundwater regime, such as clearing of the pines, will also affect surface waters. Clearing of the pine plantation since 1996 has resulted in a considerable rise in the perched shallow groundwater level. Hydrographs of water levels indicate a rise of up to one meter in some areas since clearing began. The increased water levels have a direct impact on surface water distribution and permanency of wetlands. With the increased water levels more low-lying ares have become waterlogged. In addition to this is the marked seasonal distribution of surface water related to rainfall.

CONCLUSION

Surface waters on Bribie Island are of significance to the natural ecosystems on the island itself and Pumicestone Passage due to their outflow into the passage. Additionally, surface water on Bribie Island is of importance due to its relationship with the perched shallow groundwater regime on the island. It is therefore vital to understand the interaction between surface and groundwater on this island.

Appendix A – Passcon Conference extended abstract

ACKNOWLEGEMENTS

This project has been funded by the Natural Heritage Trust, DPI-Forestry, and Caboolture Shire Council, while special thanks is given to DNR, National Parks, HLA Envirosciences Pty. Ltd., and Pacific Harbour.

REFERENCES

Harbison, J. E. 1998. The Occurrence and Chemistry of Groundwater on Bribie Island, A large Barrier Island in Moreton Bay, Southeast Queensland. Masters Thesis, QUT, Brisbane, QLD. Harbison, J.E. and Cox, M.E. 1998. General features of the Occurrence of Groundwater on Bribie Island, Moreton Bay. In: Tibbetts, I.R., Hall, N.J. and Dennison , W.C.eds. Moreton Bay and Catchment. pp.11-24 School of Marine Science, UQ, Brisbane. Drever, J. I. 1997.The geochemistry of natural waters: Surface and Groundwater Environments. 3rd. Prentice Hall, New Jersey.

Appendix A – Passcon Conference extended abstract

Appendix B

The relationship between groundwater and surface water character and wetland habitats, Bribie Island, Queensland (conference paper)

Presented: International Association of Hydrogeologists, Balancing the Groundwater Budget Conference, Darwin 2002

THE RELATIONSHIP BETWEEN GROUNDWATER AND SURFACE WATER CHARACTER AND WETLAND HABITATS, BRIBIE ISLAND, QUEENSLAND.

ARMSTRONG, T.J. AND COX, M.E.

Abstract

Bribie Island is a large barrier island in northern Moreton Bay, southeast Queensland. The island is experiencing rapid urban and forestry development, while use of the groundwater resource is unrestricted and unregulated. Here we consider the hydrogeological regime of Bribie Island, and establish the relationship groundwater has on surface water character and occurrence. Establishing relationships between surface water and groundwater is essential when considering land use impacts and changes as well as the island’s wetland habitats. Examples of likely changes to the hydrological regimes on the island are the current harvesting and re-planting of a commercial pine plantation which will result in increased transpiration, the development of an abstraction bore field that has the potential to affect water supply to the pine forest plus the potential to encourage seawater encroachment, and the construction of a residential golf course which may increase nutrient loads and affect environmental flow.

Preliminary results of groundwater elevations indicate that the surficial sands of Bribie Island host an extensive perched water table commonly at a depth of 1 metre below the ground surface. Additionally, the water table indicates a rapid response to rainfall as a result of highly permeable beach ridge sands. Consequently, surface water runoff is limited. Most surface water expressions, therefore, result from the shallow groundwater table intersecting the surface in zones of low relief, particularly those of the Melaleuca dominated swales between the sand ridges. Support for the close relationship between surface water and shallow groundwater are their similarities in chemistry. For example, physico- chemical parameters such as pH, Eh, and EC are all closely related. Additionally,

Appendix B – IAH conference paper

both waters have similar major dissolved ion concentrations and a high concentration of dissolved organic material giving both surface water and shallow groundwater a distinctive black colour, “black water”.

Key Words groundwater/surface water interactions, coastal aquifers, recharge, unconsolidated sediments, island hydrogeology, Queensland, Australia.

INTRODUCTION

The coastal environment of southeast Queensland, and particularly the area of Moreton Bay, hosts a diverse range of environmental settings such as marine, estuarine, freshwater, streams/rivers, and islands. Moreton Island and North Stradbroke Island form the outer barrier for Moreton Bay and are composed of megadune systems with profiles extending 200 meters above sea level. Bribie Island lies in northern Moreton Bay approximately 65 km north of Brisbane. Bribie is a large low-lying barrier sand island separated from the mainland by the shallow estuarine wetlands of Pumicestone Passage (Fig 1). Unlike the massive sand masses of the two outer islands, Bribie Island is significantly smaller in terms of size and water resources.

Figure 1. Moreton Bay showing the main sand islands and the location of the study

Appendix B – IAH conference paper

Over the past few decades the entire Pumicestone Passage catchment, including Bribie Island, has experienced rapid growth in terms of urbanisation and agriculture. Urban development is restricted to the southern extent of Bribie Island, while pine plantations and National Park occupy the northern two-thirds of the island. Development such as forestry plantations and residential estates has been in question due to the recent degradation of water quality of some parts of Pumicestone Passage and surrounding area. As development continues to occur on Bribie Island, the finite water resources of the island and wetland habitats, largely fed by groundwater could be degraded. It is, therefore, necessary to understand the hydrological regimes of the island for effective land and water management.

In an environment such as Bribie Island, quite complex relationships exist between groundwater and surface water. As with many sand islands, an unconfined shallow groundwater table exists over an extensive area of the island. The shallow groundwater table is in direct contact with surface water and the interaction between the two is considered important in terms of both physical processes and chemical properties. This study aims to identify the main hydrogeological controls and processes that effect groundwater on Bribie Island, and summarise how these factors affect surface water character and related habitats.

PHYSICAL SETTING

Bribie Island experiences a sub-tropical climate with mean daily temperatures between 15 - 29 oC in summer, and 9-20 oC in winter. The island receives rainfall throughout the year, however there is a distinctly wetter period through the summer months (December - March), including the occurrence of infrequent cyclones. Pan evaporation at Brisbane Airport is approximately 1570 mm per year. The island has very low relief with a mean elevation of 5 m and a maximum elevation of 17 m above sea level. As a consequence of the low relief of the island combined with the high permeability of the sand formation, surface drainage is poor resulting in large swampy areas that are inundated during the wetter months.

Appendix B – IAH conference paper

The surface topography of the island is dominated by two large accretionary beach ridge systems that are aligned to the present shoreline and extend through the long axis of the island. A major swale (interconnected low-lying Melaleuca swamps) separate the two beach ridge systems and is the dominant drainage feature of the island (Fig 2). In the far north, Bribie Island tapers towards the northern entrance of Pumicestone Passage as a narrow sand spit. The western side of the island is dominated by low-lying marine clayey sands that have been incised by Pumicestone Passage. Southern Bribie Island consists of younger

Figure 2. Bribie Island locality map showing piezometer network, and transect A-A’ for figure 3. Appendix B – IAH conference paper

accretionary beach ridges. The eastern foredunes occur as a narrow strip along the eastern coast. These dunes are approximately 10 m high and protect coastal lagoons situated immediately behind them.

There are four coastal lagoons along the eastern shoreline and three tidal creeks on the western shoreline. Furthermore, two large tidal canal networks have been excavated along the south-western shore to drain the extensive urban development in the area. In the north of the island is a single creek system, Westaways Creek that drains the central swale (Fig. 2).

The exotic slash pine (Pinus Elliottii) has replaced large tracts of native vegetation in the northern two-thirds of the island but is generally restricted to the two major beach ridge systems. The water logged low-lying interdune depressions are dominated by native remnant Melaleuca. The pine plantation has experienced considerable difficulties during its first rotation such as fire, water logging and insect attack. The plantation has undergone harvesting since 1996 and will cease at the end of 2001. Queensland Parks and Wildlife (QPW) has recently acquired the northern two-thirds of Bribie Island including the pine plantation from private ownership. QPW has subsequently granted special lease to the Queensland Department of Primary Industries - Forestry, to continue reduced forestry operations and commence with planting the second rotation of trees.

The areas not used as pine plantations still exist in their natural state and are preserved as National Parks. The major areas are along the coastal strip. The vegetation types of Bribie Island reflect local sediment type and soil water/shallow groundwater occurrence. The beach ridges are dominated by Banksia robur, while Melaleuca, as previously stated, dominates the interdune depressions. Red Gum (Eucalyptus tereticornis) and Swamp box (Lophostemon suaveolens) dominate the western section of the island and parts of the central swale. Acacia, Callitris, and Eucalyptus dominate the southern younger beach ridge sediments. Small patches of sedgeland also exist and are dominated by Gahnia seiberana, Lepironia articulata and Restio pallens (Coaldrake, 1961).

Appendix B – IAH conference paper

METHODS

The hydrology of Bribie Island is currently being investigated by ongoing monitoring of a comprehensive groundwater bore network and a selection of surface water sites throughout the island. The groundwater monitoring program is

Figure 3. East-west transect of Bribie Island, A-A’. The unconfined water table is shown as in blue. The potentiometric water level is shown in red. focused on a west – east transect of bores central to the island initially established by the Queensland Department of Natural Resources and Mines (DNMR). An additional drilling program in March 2001 by Queensland University of Technology (QUT) added sixteen new piezometers to the transect. This reference transect is now comprised of twenty-three piezometers and has provided a highly detailed cross-section through the wide section of the island enabling stratigraphic correlations to be better defined and hydraulic gradients measured (Fig. 3). The main objectives of the drilling were to: 1) better define the shallow perched water table gradients across the island, 2) enable water samples to be collected from various stratigraphic heights throughout the profile of the island, 3) allow better definition of the coffee rock layer, and 4) constrain the character of the underlying sandstone bedrock. Analysis of drilling returns from this program and evaluation

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of previous drilling programs confirms that the stratigraphy of the island results in distinct heterogeneity of aquifer material.

Monitoring of all piezometers for water levels has occurred on a monthly basis since August 2000. This monitoring program has been designed to record seasonal changes in hydraulic gradients across the island and provide hydrological evidence to confirm a two layered aquifer conceptual model of shallow unconfined groundwater body perched above partially confined groundwater.

The piezometers have also made possible the monitoring of groundwater for the physico-chemical parameters pH, Eh, electrical conductivity (EC), temperature and dissolved oxygen (DO). Field measurements of the parameters have been monitored at an interval of every two to three months. Thirty-one surface water expressions across the island have also been seasonally monitored for physico- chemical parameters. Water samples have been collected from both groundwater and surface waters at three to four month intervals. These samples have been analytically analysed for major and minor ions as well as dissolved organic carbon.

GEOLOGICAL FRAMEWORK

The combination of previous drilling programs and the more recent Queensland University of Technology (QUT) drilling program has enabled a detailed investigation of the geologic framework of the island. The complex form of the island is a result of sea level variations during the Late Pleistocene and Holocene. The island is composed of Quaternary sand deposits, overlying bedrock of Lower Jurassic sandstone (Fig 3).

This arkosic sandstone is light grey in colour, medium to coarse grained, with some shale bands and thin conglomerate lenses (Ishaq, 1980). There are no outcrops of sandstone on Bribie Island. The weathered profile of the sandstone can vary in thickness from several meters to 20 m thick on the adjacent mainland (Ezzy et al., 2000). The weathered profile exhibits laterite zonation. At the base of the weathered profile exists saprolite which then grades upward into a more

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extensively weathered mottled silty clay. Capping the weathered profile is the most extensively weathered and leached unit represented by a ferricrete crust.

Overlying the weathered sandstone is a sequence of clayey sands that have been deposited in low energy bay and lagoonal environments (Hekel and Day, 1976; Ishaq, 1980). The kaolinite rich clays are generally grey to white to green in colour and contain thin lenses of fine gravel and fine sands (Harbison and Cox, 1998).

The surficial sediments of Bribie Island consist of Holocene to Pleistocene beach sands. The Pleistocene accretion ridges and swales formed from deposition of beach sands by eustatic oscillations (Lumsden, 1964; Coaldrake, 1960) during periods of beach ridge propagation. The Pleistocene sands constitute the most widespread unit within the island and consist of fine to medium quartz sand. The ridges longitudinal axis are aligned parallel with the prevailing southeast winds (Harbison and Cox, 1998). The total thickness of the Pleistocene sediments vary from 5 to 25 m, and dip gently to the south and east beneath the Holocene beach ridge sediments (Ishaq, 1980).

Contained within the Pleistocene sediments is an extensive podsol horizon at an approximate depth of 5-6 m with a maximum measured thickness of 9 m. This layer of dark coloured indurated sand is referred to locally as “coffee rock”. It has been described as quartz sand grains cemented by the in-filling of pores by a variety of cements, predominately organic matter and clays (Farmer et al., 1983 and Thompson et al., 1996). Considerable amounts of Fe and Al are also associated with coffee rock formation (Farmer, 1983). Due to the reduced porosity and permeability of the sand profile, coffee rock plays an important role in hydrological processes across Bribie Island; of note is the perching of shallow unconfined groundwater.

Appendix B – IAH conference paper

HYDROGEOLOGY

Groundwater occurrence

The heterogeneous material forming the sand mass of the island produces distinct water bodies that have differing characters and are controlled by a variety of

Figure 4. Water levels of the east west transect on 10 April, 2001. processes. The groundwater resource can be divided into two water bodies, shallow perched unconfined groundwater and deep (basal) partially confined groundwater. These bodies have differing hydrological processes, physico- chemical properties and water composition. The deep partially confined groundwater occurs underneath the leaky confining coffee rock horizon contained within the Pleistocene beach ridge sands. Monitoring of the extensive network of piezometers on the island has indicated that the potentiometric surface of the partially confined basal aquifer has an approximate maximum height of 3 m above

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the Australian Height Datum (AHD). The potentiometric surface mound is therefore very slight and typically occurs toward the centre of the island.

Across the island the unconfined water table contour generally follows local topography forming two distinct groundwater mounds within the two main beach ridge systems. The water table is commonly at 1 m depth while it has an approximate maximum elevation of 6 m AHD. Contouring of both the unconfined water table and the potentiometric surface results in a clearly defined view of the two systems (Fig. 4).

Groundwater – surface water interaction

With the unconfined water table being in such close proximity to the ground surface, interdune depressions, drains and fire-fighting trenches are often discharge points for environmental flow from the beach ridge systems. Widespread areas of the island are covered by naturally low-lying depressions ranging in size from metres to tens of metres in diameter. These local low points occur as minor swales forming between minor ridges that are contained within the larger beach ridge system. The other major source of surface water on the island is contained within fire-fighting trenches. These excavations result in some sites to be permanently connected and acting as a window to the shallow unconfined water table. Most of these excavations have been strategically placed to drain particular areas and hence, some drainage patterns of the area have been altered. Additionally, there are a series of large coastal lagoons that occur along the eastern coast behind the beach foredunes. These form from the mixing of fresh groundwater discharge and over dune wash from large tides and storm surges.

Another occurrence of surface water on the island results from organic silts and clays being transported into the low-lying areas where, upon settling, create a type of seal that reduces the infiltration rate of the surface water after rainfall (Harbison and Cox, 1998). For this reason surface water can remain in these lows for extended periods after a significant rainfall event before the water either evaporates or infiltrates.

Appendix B – IAH conference paper

The drainage system on Bribie Island is not well developed. The most significant surface water flow is from the two major beach ridge systems into the major central swale. In general, the central swale has a slow northerly flow discharging into Pumicestone Passage via Westerways Creek in the north of the island. The southern section of the central swale flows south and discharges into the passage via Wright’s Creek. This southerly flow is attributed to topographic changes, however, the southern causeway across the central swale may have caused a reduction of flow to the north. Evapotranspiration on Bribie Island is another substantial loss of unconfined groundwater. Field observations and hydrographs indicate that pine plantation growth and harvest have a substantial effect on unconfined groundwater levels across the island, influencing discharge volume to wetland areas.

HYDROCHEMISTY

Ionic chemistry

The similarities in ionic chemistry of both unconfined groundwater and surface water suggest that groundwater-surface water interactions exist. Both surface

Figure 5. Piper diagram of major ion chemistry for surface water and groundwater. Arrow

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water and unconfined groundwater typically are Na-Cl or Na, Mg-Cl water types (Fig. 5); they have chemical ratios similar to local rainfall indicating this as the primary recharge source. The enrichment of Ca is attributed to carbonate lenses (remnant shell material) scattered throughout the beach ridge sediments. Due to the low pH of both surface water and unconfined groundwater, HCO3 concentrations have been drastically reduced. Bicarbonate enrichment increases with depth and is restricted to the partially confined groundwater underlying the coffee rock horizon (Armstrong, 2000).

The partially confined groundwater is depleted in sulfate as a result of sulfur reduction and loss of H2S. The reducing environments of the unconfined aquifer and wetland areas promote the enrichment of sulfate.

The dominant minor elements in unconfined groundwater and surface water are Fe and Al, both of which have low concentrations. This may be attributed to the complexing of Fe and Al by organic acidic solutes, which results in leaching them from the upper horizons and depositing them in deeper layers. This process is documented in the formation of coffee rock (Thompson et al., 1996) and indicates a poorly buffered unsaturated zone.

Physico-Chemical Properties

Physico-chemical averages of groundwater and surface water samples collected through the sampling period of August 2000 – October 2001 further characterise the different water bodies on Bribie Island (Table. 1). The majority of groundwater and surface water on Bribie Island is fresh, with the exceptions of coastal lagoons, tidal creeks, and tidally influenced groundwater. A notable difference between the water bodies is the value of pH. The pH of partially confined groundwater is approximately three units more alkaline than either unconfined groundwater or surface water. The acidic pH values of the unconfined groundwater and surface water result from the decomposition of organic matter. Fallen leaf litter decomposes to produce organic acids and dissolved organic carbon.

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Table 1. Average physico-chemical parameters for groundwater and surface water of Bribie Island for August 2000 – October 2001. Sample DO EC Eh pH T ppm µS/cm mV oC Partially confined 0.7 335 216 6.2 22.2 groundwater Unconfined groundwater 2.8 203 279 3.9 20 Wetlands 4.8 220 413 3.5 23 Excavations 3.2 270 364 3.5 23 Coastal lagoons 7.8 44 000 383 7.0 25.3

Rainfall events flush the organic acids and dissolved organic carbon into the islands wetlands, where the substances percolate down to the unconfined water table. A dark colouring to the unconfined groundwater and surface water is attributed to the high concentrations of dissolved organic carbon. The dark brown to black colouring of this low pH water is often referred to as “black water”, and is common to many low-lying poorly drained coastal settings.

FUTURE DEVELOPMENT IMPLICATIONS

The interrelationships between the physical settings and the hydrological processes of Bribie Island are of great significance in the management of the island habitats. Harvesting of the first rotation of pines will be complete in 2002. A significant reduction in the evapotranspiration rate has occurred since the removal of the pines. Hydrographs indicate a considerable rise in the unconfined water table has resulted from this reduction in evapotranspiration. The increased height of the unconfined water table has directly impacted on surface water distribution by creating new and extending the existing water logged areas. The permanency of these wetland areas has also increased as a consequence of the greater volume of groundwater discharge into these areas.

Initial re-planting of the plantation started in 2001. Regrowth of the pines should reverse some of the harvesting affects on the hydrological regime of the island. Once the new plantation is established evapotranspiration rates should return to pre-harvest levels. The increased rate of evapotranspiration may lead to a decline in the water table level, which should decrease the amount of groundwater

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discharge to the low-lying areas. Some wetlands will completely dry out while others will only reduce in size. However, these relationships still need to be quantified.

Previous groundwater modelling of the island has overlooked aquifer heterogeneities such as the coffee rock horizon. Coffee rock has a reduced porosity and permeability that affects groundwater storage and movement (Fig. 3). Harbison and Cox (1998) estimated the volume of coffee rock to be 7.8 x 108 m3 or approximately 37 % of the aquifer volume. Therefore, disregarding such a significant component of the hydrological regime results in an over estimate of the water resource. Recent modelling indicates that for a 10 ML/day extraction rate, water levels surrounding the bore field may fall to under 1 m AHD. As suggested by Ishaq (1980) withdrawal of water from the bore field is likely to lower the water table beneath part of the pine plantation, which could affect the growth of pine trees. Additionally, if over pumping occurs and hydraulic gradients are reversed groundwater discharge to wetland habitats and surface water runoff may be greatly reduced while seawater intrusion may also occur.

The construction of a new residential golf course in the southwest corner of the existing pine plantation adjoining the Pacific Harbour canal residential estate will commence in the first half of 2002. Fertilizers and pesticides applied to a golf - + course need to be considered. The potential for nitrate (NO3 ), ammonium (NH4 ), 3- and phosphate (PO4 ) to enter the unconfined groundwater and surface water must be defined.

CONCLUSION

This study illustrates the close relationship between the perched unconfined groundwater and much of the wetland areas of Bribie Island. These relationships exist both physically and chemically. A detailed transect shows that the topography across the island effects the hydraulic gradients of the unconfined water table which directs environmental flow into low-lying areas. Groundwater discharge into these low-lying areas results in water logged conditions for many parts of the island. These water logged areas are an important environmental

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setting as they support wetland habitats. The wetlands and shallow groundwater are typically dark brown – black coloured with low pH values and water types of Na-Cl and Na, Mg-Cl. Hydrochemistry through the profile of the island displays different groundwater composition with depth. Water composition highlights the relationship between surface water, the unconfined groundwater and the evolution of these waters into the basal partially confined aquifer. Aquifer heterogeneities such as the leaky confining unit (the coffee rock horizon) dominate the hydrological processes of the island and should be considered when assessing the environmental setting and the water resources of Bribie Island.

ACKNOWLEDGEMENTS

The authors are grateful for funding support by the Natural Heritage Trust program, Caboolture Shire Council, and Queensland Department of Primary Industries – Forestry. Assistance by staff of the Department of Natural Resources and Mines (Peter Cochrane and Robert Ellis), Department of Primary Industries – Forestry (Stan Ward and Dr. Ken Bubb), Queensland Parks and Wildlife, Pacific Harbour (Greg Smith and Warren Russell), and HLA Envirosciences Pty. Ltd. (Peter Scott) in providing data, expertise, and field equipment is greatly appreciated. Thanks are extended to Dr. Micaela Preda of the Queensland University of Technology for helpful reviews and discussion.

REFERENCES

Armstrong T (2000) Chemical character of surface waters on Bribie Island: a preliminary assessment. In: Cox ME (ed) proc PASSCON 2000, Pumicestone Passage & Deception Bay Catchment Conference, 22-23 November, pp 77-79 Coaldrake JE (1960) Quaternary history of the coastal lowlands of southern Queensland. Journal of the Geological Society of Australia 7:403-408 Coaldrake JE (1961) The ecosystem of the coastal lowlands (“wallum”) of southern Queensland. CSIRO Bulletin No. 283, Melbourne Ezzy T, Cox ME, Brooke B (2000) The geological setting and its control over groundwater within the Meldale coastal plain. In: Cox ME (ed) proc PASSCON 2000, Pumicestone Passage & Deception Bay Catchment Conference, 22-23 November, pp 23-25 Farmer VC, Skjemstad JO, Thompson CH (1983) Genesis of humus B horizons in hydromorphic humus podzols. Nature 304/5924: 342-344.

Appendix B – IAH conference paper

Harbison JE, Cox ME (1998) General features of the occurrence of groundwater on Bribie Island, Moreton Bay. In: Tibbitts IR, Hall NJ, Dennison WC (ed) Moreton Bay and Catchment. School of Marine Science, The University of Queensland, Brisbane 11-24 Hekel H, Day RW (1976) Quaternary geology of the Sunshine Coast, southeast Queensland. Geological Survey of Queensland Record 1979/16, Brisbane Ishaq S (1980) Bribie Island water supply – hydrogeological reconnaissance of the southern part of Bribie Island. Geological Survey of Queensland Record 1980/44, Brisbane Lumsden AC (1964) Bribie Island water supply. Geological Survey of Queensland Record, 1964/8, Brisbane Thompson CH, Bridges EM, Jenkins DA (1996) Pans of humic podzols (Humods and Aquods) in coastal southern Queensland. Australian Journal of Soil Research 34:161-182

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Appendix C

Controls over aquifer heterogeneity within a large sand island and analysis by hydraulic testing, Bribie Island, Queensland, Australia (accepted manuscript - Hydrogeology Journal)

Appendices

Section B: Data

Appendix D Stratigraphic Logs

Appendix D – Stratigraphic logs

Appendix E

Sediment Age Dating

Appendix F

Groundwater Level Data

Appendix F groundwater– level data Well No. Ground Groundwater Level (m) level (m) 13/12/00 15/2/01 1/5/01 22/5/01 4/7/01 1/8/01 19/9/01 12/10/01 19/10/01 13/11/01 TOC -2.02 -1.40 -1.34 -1.88 -1.90 -2.10 -2.16 -2.17 MW1 AHD 7.80 5.777 6.397 6.457 5.917 5.897 5.697 5.637 5.627 TOC -2.03 -1.17 -1.24 -1.59 -1.58 -2.11 -2.27 -2.28 -2.13 MW2 AHD 7.36 5.328 6.188 6.118 5.768 5.778 5.248 5.088 5.078 5.228 MW3 TOC -1.88 -0.81 -1.00 -1.10 -1.39 -1.36 -1.78 -1.88 -1.79 -1.59 (S) AHD 6.93 5.054 6.124 5.934 5.834 5.544 5.574 5.154 5.054 5.144 5.344 MW3 TOC -5.34 -5.19 -5.28 -5.39 (D) AHD 7.05 1.71 1.86 1.77 1.66 MW4 TOC -4.31 -2.86 -2.36 -2.51 -2.46 -2.63 -2.67 -2.66 -2.51 (S) AHD 5.50 1.19 2.64 3.14 2.99 3.04 2.87 2.83 2.84 2.99 MW4 TOC -5.15 -4.67 -4.84 -4.96 -4.92 -5.24 -5.25 -5.18 -5.17 (D) AHD 5.81 0.65 1.14 0.97 0.85 0.89 0.57 0.56 0.63 0.64 MW5 TOC -2.17 -1.57 -1.85 -2.02 -1.95 -2.19 -2.26 -2.24 -1.97 (S) AHD 5.54 3.37 3.97 3.69 3.52 3.59 3.35 3.28 3.30 3.57 MW5 TOC -4.69 -4.18 -4.33 -4.46 -4.44 -4.81 -4.86 -4.82 -4.82 (D) AHD 5.62 0.93 1.44 1.29 1.16 1.18 0.81 0.76 0.80 0.80 MW6 TOC -1.04 -0.61 -0.68 -0.85 -0.77 -1.06 -1.08 -0.96 -0.71 (S) AHD 7.07 6.03 6.46 6.39 6.22 6.30 6.01 5.99 6.11 6.36 MW6 TOC -5.60 -5.36 -5.47 -5.60 -5.65 -5.86 -5.86 -5.83 -5.93 (D) AHD 6.91 1.31 1.55 1.44 1.31 1.26 1.05 1.05 1.08 0.98 MW7 TOC -1.22 -0.48 (S) AHD 7.31 6.09 6.83 MW7 TOC -5.73 -5.50 -5.78 -5.79 -5.91 -5.89 -5.83 -5.90 (D) AHD 7.15 1.42 1.65 1.37 1.36 1.24 1.26 1.32 1.25 MW8 TOC -2.02 -1.48 -1.62 -1.66 -1.85 -1.77 -2.08 -2.12 -2.09 -1.84 (S) AHD 8.09 6.07 6.61 6.47 6.43 6.24 6.32 6.01 5.97 6.00 6.25 MW8 TOC -6.13 -5.99 -6.06 -6.30 -6.36 -6.45 -6.39 -6.36 -6.46 (D) AHD 8.31 2.18 2.32 2.25 2.01 1.95 1.86 1.92 1.95 1.85

Appendix F – groundwaterAppendix level data Well No. Ground Groundwater Level (m) level (m) 21/12/01 10/1/02 15/2/02 22/3/02 18/4/02 25/7/02 TOC -2.10 -1.77 -1.66 MW1 AHD 7.80 5.697 6.025 6.137 TOC -2.28 MW2 AHD 7.36 5.078 MW3 TOC -1.80 -1.99 -1.60 -1.23 (S) AHD 6.93 5.134 4.944 5.331 5.704 MW3 TOC (D) AHD 7.05 MW4 TOC -2.56 -2.50 -2.65 -2.64 -2.47 -2.32 (S) AHD 5.50 2.94 3.00 2.85 2.86 3.03 3.18 MW4 TOC -5.19 -5.15 -5.36 -5.46 -5.23 -5.10 (D) AHD 5.81 0.61 0.65 0.45 0.35 0.58 0.71 MW5 TOC -2.03 -2.00 -2.12 -2.01 -1.82 -1.79 (S) AHD 5.54 3.51 3.54 3.42 3.53 3.72 3.75 MW5 TOC -4.76 -4.77 -5.07 -5.19 -4.93 -4.72 (D) AHD 5.62 0.86 0.85 0.55 0.43 0.69 0.90 MW6 TOC -0.91 -0.87 -1.05 -1.06 -0.83 -0.89 (S) AHD 7.07 6.16 6.20 6.02 6.01 6.24 6.18 MW6 TOC -5.75 -5.80 -6.02 -6.14 -5.98 -5.78 (D) AHD 6.91 1.16 1.11 0.89 0.77 0.94 1.13 MW7 TOC (S) AHD 7.31 MW7 TOC -5.91 -5.90 -6.01 -6.05 -5.91 (D) AHD 7.15 1.24 1.25 1.14 1.10 1.24 MW8 TOC -1.92 -1.87 -2.13 -2.19 -1.94 -1.76 (S) AHD 8.09 6.17 6.22 5.97 5.91 6.15 6.33 MW8 TOC -6.33 -6.39 -6.54 -6.64 -6.49 -6.30 (D) AHD 8.31 1.98 1.92 1.77 1.68 1.82 2.01

Appendix F groundwater– level data Well No. Ground level Groundwater Level (m) (m) 22/8/00 4/9/00 10/10/00 7/11/00 13/12/00 15/2/01 6/3/01 10/4/01 1/5/01 22/5/01 6/6/01 TOC -1.90 -1.77 -1.90 0084 3.37 AHD 1.47 1.60 1.47 TOC -0.69 -0.62 -0.68 -0.68 0085 2.77 AHD 2.08 2.15 2.09 2.09 TOC 0086 3.94 AHD TOC -6.37 -6.40 -6.53 -6.46 -6.56 -6.51 -6.54 -6.42 -6.44 -6.48 -6.51 0088 8.86 AHD 2.49 2.46 2.34 2.40 2.30 2.35 2.32 2.44 2.42 2.38 2.35 TOC -3.71 -3.77 -3.90 -3.85 -4.06 -3.65 -3.67 -3.82 -3.91 -3.98 -4.03 0089 6.02 AHD 2.31 2.25 2.12 2.17 1.96 2.37 2.35 2.20 2.11 2.04 1.99 TOC -3.26 -3.29 -3.33 -3.31 -3.56 -3.25 -3.27 -3.39 -3.44 -3.57 -3.65 0100 6.06 AHD 2.80 2.77 2.73 2.75 2.50 2.81 2.79 2.67 2.62 2.49 2.41 TOC -6.33 -6.40 -6.49 -6.41 -6.52 -6.40 -6.43 -6.31 -6.33 -6.44 -6.51 0101 8.83 AHD 2.50 2.43 2.34 2.42 2.31 2.43 2.40 2.52 2.50 2.39 2.32 TOC -1.48 -1.19 -1.59 -1.02 -1.06 -1.03 -1.13 -1.10 -1.17 0114 5.67 AHD 4.20 4.48 4.08 4.65 4.61 4.64 4.54 4.57 4.50 TOC -1.10 -1.20 -1.44 -1.21 -1.48 -0.84 -0.86 -0.92 -1.07 -1.06 -1.17 0115 6.96 AHD 5.86 5.76 5.52 5.75 5.48 6.12 6.10 6.04 5.89 5.90 5.79 TOC -8.89 -8.96 -9.15 -9.12 -9.11 -9.10 0120 10.87 AHD 1.98 1.91 1.72 1.75 1.76 1.77 TOC -3.99 -3.79 -3.68 0123 6.84 AHD 2.85 3.05 3.16 TOC -3.13 -3.19 -3.37 -3.18 -3.33 -2.80 -2.83 -2.93 -3.04 -3.13 -3.21 0126 6.81 AHD 3.68 3.62 3.44 3.63 3.48 4.01 3.98 3.88 3.77 3.68 3.60 TOC -1.10 -1.38 -1.52 0129 3.49 AHD 2.39 2.11 1.97 TOC 0121 9.89 AHD

Appendix F – groundwaterAppendix level data Well No. Ground level Groundwater Level (m) (m) 15/6/01 5/7/01 1/8/01 19/9/01 12/10/01 19/10/01 13/11/01 21/12/01 10/1/02 15/2/02 22/3/02 TOC -2.06 -2.06 -2.42 -2.48 -2.48 -2.37 -2.80 0084 3.37 AHD 1.31 1.31 0.95 0.89 0.89 1.00 0.57 TOC -0.73 -1.08 -1.12 -1.04 -0.65 -1.64 0085 2.77 AHD 2.04 1.69 1.65 1.73 2.12 1.13 TOC -3.04 -3.33 0086 3.94 AHD 0.90 0.61 TOC -6.53 -6.60 -6.64 -6.79 -6.83 -6.82 -6.81 -6.78 -6.78 -6.92 -7.01 0088 8.86 AHD 2.33 2.26 2.22 2.07 2.03 2.04 2.05 2.08 2.08 1.95 1.85 TOC -4.07 -4.14 -4.15 -4.27 -4.29 -4.27 -4.21 -4.10 -4.09 -4.28 -4.30 0089 6.02 AHD 1.95 1.88 1.87 1.75 1.73 1.75 1.81 1.92 1.93 1.74 1.72 TOC -3.66 -3.74 -3.74 -3.84 -3.82 -3.76 -3.74 -3.60 -3.63 -3.84 -3.92 0100 6.06 AHD 2.40 2.32 2.32 2.22 2.24 2.30 2.32 2.46 2.43 2.22 2.14 TOC -6.49 -6.59 -6.62 -6.81 -6.82 -6.73 -6.84 -6.64 -6.70 -6.94 -7.10 0101 8.83 AHD 2.34 2.24 2.21 2.02 2.01 2.10 1.99 2.19 2.13 1.90 1.73 TOC -1.27 -1.25 -1.47 -1.44 -1.32 -1.18 -1.42 -1.77 0114 5.67 AHD 4.40 4.42 4.20 4.23 4.35 4.49 4.25 3.90 TOC -1.30 -1.27 -1.50 -1.54 -1.42 -1.21 -1.35 -1.34 -1.62 -1.74 0115 6.96 AHD 5.66 5.69 5.46 5.42 5.54 5.75 5.61 5.62 5.34 5.22 TOC -9.13 -9.16 -9.26 -9.28 -9.26 -9.33 -9.69 0120 10.87 AHD 1.74 1.71 1.61 1.59 1.61 1.54 1.18 TOC -3.77 -3.75 -4.09 -4.10 -4.09 -3.95 -4.36 0123 6.84 AHD 3.07 3.09 2.75 2.74 2.75 2.89 2.48 TOC -3.25 -3.34 -3.32 -3.53 -3.60 -3.61 -3.46 -3.50 -3.36 -3.63 -3.69 0126 6.81 AHD 3.56 3.47 3.49 3.28 3.21 3.20 3.35 3.31 3.45 3.18 3.12 TOC -1.53 -1.58 -1.53 -1.83 -1.93 -1.91 -1.79 -1.95 -1.89 -2.20 -2.39 0129 3.49 AHD 1.96 1.91 1.96 1.66 1.56 1.58 1.70 1.54 1.60 1.29 1.10 TOC -8.16 -8.43 -8.40 -8.39 -8.30 -8.82 0121 9.89 AHD 1.73 1.46 1.49 1.50 1.59 1.07

Appendix F groundwater– level data Well No. Ground Groundwater Level (m) level (m) 18/4/02 25/7/02 TOC -2.79 -2.68 0084 3.37 AHD 0.58 0.69 TOC -0.93 -1.21 0085 2.77 AHD 1.85 1.56 TOC -3.23 -3.15 0086 3.94 AHD 0.71 0.79 TOC -6.96 -6.78 0088 8.86 AHD 1.90 2.08 TOC -4.43 -3.89 0089 6.02 AHD 1.59 2.13 TOC -3.70 -3.53 0100 6.06 AHD 2.36 2.53 TOC -6.93 -6.77 0101 8.83 AHD 1.90 2.06 TOC -1.47 -1.32 0114 5.67 AHD 4.20 4.35 TOC -1.47 -1.31 0115 6.96 AHD 5.49 5.65 TOC -9.53 -9.46 0120 10.87 AHD 1.35 1.41 TOC -4.12 0123 6.84 AHD 2.72 TOC -3.48 -3.53 0126 6.81 AHD 3.33 3.28 TOC -2.25 -2.29 0129 3.49 AHD 1.24 1.20 TOC -8.56 -8.58 0121 9.89 AHD 1.33 1.31

Appendix F – groundwaterAppendix level data Well No. Ground Groundwater Level (m) level (m) 10/4/01 1/5/01 22/5/01 5/6/01 15/6/01 3/7/01 1/8/01 19/9/01 12/10/01 19/10/01 13/11/01 TOC -1.13 -1.26 -1.32 -1.39 -1.52 -1.47 -1.73 -1.79 -1.75 -1.53 0131 6.73 AHD 5.60 5.47 5.41 5.34 5.21 5.26 5.00 4.94 4.98 5.20 TOC -0.91 -1.05 -1.03 -1.10 -1.20 -1.15 -1.48 -1.54 -1.41 -1.19 0132 6.18 AHD 5.27 5.13 5.15 5.08 4.98 5.03 4.70 4.64 4.77 4.99 TOC -2.21 -2.47 -2.45 -2.95 -3.03 -2.96 -3.08 -3.17 -3.09 -3.07 0133 5.71 AHD 3.50 3.24 3.26 2.76 2.68 2.75 2.63 2.54 2.62 2.64 TOC -1.08 -1.25 -1.23 -1.32 -1.45 -1.35 -1.62 -1.68 -1.56 -1.35 0134 4.73 AHD 3.65 3.48 3.50 3.41 3.28 3.38 3.11 3.05 3.17 3.38 TOC -1.76 -2.01 -2.23 -2.34 -2.51 -2.57 -2.75 -2.79 -2.81 -2.75 0135 3.82 AHD 2.06 1.81 1.59 1.48 1.31 1.25 1.07 1.03 1.01 1.07 TOC -2.64 -2.74 -2.80 -2.86 -2.90 -2.96 -2.97 -3.10 -3.11 -3.09 -3.03 0136 4.49 AHD 1.85 1.75 1.69 1.63 1.59 1.53 1.52 1.39 1.38 1.40 1.46 TOC -0.94 -1.20 -1.30 -1.41 -1.53 -1.58 -1.52 -1.87 -1.91 -1.81 -1.56 0137 4.67 AHD 3.73 3.47 3.37 3.26 3.14 3.09 3.15 2.80 2.76 2.86 3.11 TOC -1.39 -1.44 -1.43 -1.51 -1.58 -1.60 -1.49 -1.78 -1.77 -1.67 -1.39 0138 6.40 AHD 5.01 4.96 4.97 4.89 4.82 4.80 4.91 4.62 4.63 4.73 5.01 TOC -1.13 -1.28 -1.29 -1.41 -1.46 -1.49 -1.36 -1.64 -1.57 -1.42 -1.13 0139 7.14 AHD 6.01 5.86 5.85 5.73 5.68 5.65 5.78 5.50 5.57 5.72 6.01 TOC -5.41 -5.41 -5.58 -5.57 -5.56 -5.73 -5.77 -5.89 -5.91 -5.89 -5.88 0140 8.07 AHD 2.66 2.66 2.49 2.50 2.51 2.34 2.30 2.18 2.16 2.18 2.19 TOC -0.96 -0.99 -0.99 -1.06 -1.19 -1.18 -1.08 -1.36 -1.30 -1.19 -1.01 0141 8.00 AHD 7.04 7.01 7.01 6.94 6.81 6.82 6.92 6.64 6.70 6.81 6.99 TOC -1.15 -1.25 -1.28 -1.34 -1.41 -1.39 -1.27 -1.58 -1.48 -1.36 -1.15 0142 8.69 AHD 7.54 7.44 7.41 7.35 7.28 7.30 7.42 7.11 7.21 7.33 7.54 TOC -3.87 -4.57 -5.24 -5.19 -5.02 -5.02 -4.83 -4.82 -4.98 -5.19 -5.14 0143 8.45 AHD 4.58 3.88 3.21 3.26 3.43 3.43 3.62 3.63 3.47 3.26 3.31

Appendix F groundwater– level data Well No. Ground Groundwater Level (m) level (m) 21/12/01 10/1/02 15/2/02 22/3/02 18/4/02 25/7/02 TOC -1.62 -1.59 -1.84 -1.91 -1.70 -1.53 0131 6.73 AHD 5.11 5.14 4.89 4.82 5.03 5.20 TOC -1.34 -1.32 -1.57 -1.63 -1.26 -1.19 0132 6.18 AHD 4.84 4.86 4.61 4.55 4.92 4.99 TOC -3.11 -3.04 -3.12 -3.15 -3.07 -2.83 0133 5.71 AHD 2.60 2.67 2.59 2.56 2.63 2.88 TOC -1.50 -1.47 -1.72 -1.75 -1.42 -1.45 0134 4.73 AHD 3.23 3.26 3.01 2.98 3.31 3.28 TOC -2.75 -2.74 -2.90 -2.97 -2.81 -2.31 0135 3.82 AHD 1.07 1.08 0.92 0.85 1.01 1.51 TOC -2.92 -2.90 -3.13 -3.16 -2.96 -2.70 0136 4.49 AHD 1.57 1.59 1.36 1.33 1.53 1.79 TOC -0.94 -0.92 -1.29 -1.06 -0.77 -0.85 0137 4.67 AHD 3.73 3.75 3.38 3.61 3.90 3.82 TOC -1.39 -1.34 -1.44 -1.36 -1.15 -1.30 0138 6.40 AHD 5.01 5.06 4.96 5.04 5.25 5.10 TOC -1.15 -1.13 -1.36 -1.28 -1.18 -1.10 0139 7.14 AHD 5.99 6.01 5.78 5.87 5.97 6.04 TOC -5.84 -5.84 -5.94 -5.99 -5.99 -5.81 0140 8.07 AHD 2.23 2.23 2.13 2.08 2.08 2.26 TOC -1.12 -1.09 -1.30 -1.24 -1.00 -1.16 0141 8.00 AHD 6.88 6.91 6.70 6.76 7.00 6.84 TOC -1.31 -1.27 -1.54 -1.51 -1.43 -1.47 0142 8.69 AHD 7.38 7.42 7.15 7.18 7.26 7.22 TOC -4.70 -4.62 -4.70 -4.77 -4.67 -4.77 0143 8.45 AHD 3.75 3.83 3.75 3.68 3.78 3.68

Appendix F – groundwaterAppendix level data Well No. Ground Groundwater Level (m) level (m) 10/4/01 1/5/01 22/5/01 5/6/01 15/6/01 3/7/01 1/8/01 19/9/01 12/10/01 19/10/01 13/11/01 TOC -2.10 -2.15 -2.21 -2.28 -2.32 -2.38 -2.36 -2.83 -2.96 -2.87 -2.69 0144 4.25 AHD 2.15 2.10 2.04 1.97 1.93 1.87 1.89 1.42 1.29 1.38 1.56 TOC -1.34 -1.34 -1.29 -1.36 -1.40 -1.40 -1.34 -1.53 -1.49 -1.37 -1.28 0145 4.41 AHD 3.07 3.07 3.12 3.05 3.01 3.01 3.07 2.88 2.92 3.04 3.13 TOC -1.45 -1.52 -1.54 -1.63 -1.71 -1.75 -1.76 -2.15 -2.26 -2.25 -2.09 0146 4.08 AHD 2.63 2.56 2.54 2.45 2.37 2.33 2.32 1.93 1.82 1.83 1.99 0147 TOC -2.10 -2.07 -2.11 -2.17 -2.23 -2.27 -2.25 -2.70 -2.79 -2.71 -2.63 4.13 AHD 2.03 2.06 2.02 1.96 1.90 1.86 1.88 1.43 1.34 1.42 1.50 TOC -4.16 -4.30 -4.39 -4.44 -4.50 -4.56 -4.60 -4.96 -5.02 -4.98 -4.91 0148 6.83 AHD 2.67 2.53 2.44 2.39 2.33 2.27 2.23 1.87 1.81 1.85 1.92 TOC -0.94 -1.05 -0.93 -1.16 -1.24 -1.20 -1.12 -1.47 -1.56 -1.48 -1.29 0149 5.18 AHD 4.24 4.13 4.25 4.02 3.94 3.98 4.06 3.71 3.62 3.70 3.89 TOC -2.01 -2.58 -2.79 -2.15 -2.10 -2.26 -2.40 -2.86 -3.11 -2.98 -2.88 0150 5.24 AHD 3.23 2.66 2.45 3.09 3.14 2.98 2.84 2.38 2.13 2.26 2.36 TOC -3.24 -3.36 -3.41 -3.48 -3.52 -3.56 -3.56 -3.95 -4.03 -3.98 -3.92 0151 5.19 AHD 1.95 1.83 1.78 1.71 1.67 1.63 1.63 1.24 1.16 1.21 1.27

Appendix F groundwater– level data Well No. Ground Groundwater Level (m) level (m) 21/12/01 10/1/02 15/2/02 22/3/02 18/4/02 25/7/02 TOC -2.80 -2.80 -3.39 -3.53 -3.12 -2.96 0144 4.25 AHD 1.45 1.45 0.87 0.72 1.14 1.29 TOC -1.42 -1.39 -1.56 -1.56 -1.48 -1.50 0145 4.41 AHD 2.99 3.02 2.85 2.85 2.93 2.91 TOC -2.35 -2.30 -2.58 -2.56 -2.45 -2.39 0146 4.08 AHD 1.73 1.78 1.50 1.52 1.63 1.69 TOC -2.85 -2.83 -3.27 -3.38 -3.11 -3.00 0147 4.13 AHD 1.28 1.30 0.86 0.75 1.02 1.13 TOC -5.03 -4.99 -5.36 -5.44 -5.20 -5.18 0148 6.83 AHD 1.80 1.84 1.48 1.39 1.63 1.65 TOC -1.41 -1.35 -1.62 -1.59 -1.44 -1.40 0149 5.18 AHD 3.77 3.83 3.56 3.59 3.74 3.78 TOC -3.07 -3.02 -3.32 -3.29 -3.05 -2.28 0150 5.24 AHD 2.17 2.22 1.92 1.95 2.19 2.96 TOC -4.06 -4.03 -4.39 -4.49 -4.35 -4.17 0151 5.19 AHD 1.13 1.16 0.80 0.70 0.85 1.02

Appendix G

Physico-chemical Data

Well Water Water Date D.O. Cond. pH Eh Temp Colour No. level level (m bgl) (m AHD) (ppm) (uS/cm) (mV) (oC) Wells screened within palaeochannel aquifer 089 22/08/00 -3.32 2.31 0.0 395 5.9 134 23 Nil 089 4/09/00 -3.38 2.25 4.5 390 5.7 247 23 Nil 089 10/10/00 -3.51 2.12 0.0 386 5.5 256 23 Nil 089 7/11/00 -3.46 2.17 1.1 387 5.9 285 23 Slight 089 1/05/01 -3.52 2.11 0.7 371 5.8 165 23 Nil 089 19/09/01 -3.88 1.75 0.8 364 5.9 186 21 Nil 089 12/10/01 -3.90 1.73 0.6 364 5.7 226 21 Nil 089 25/07/02 -3.50 2.13 2.0 408 5.0 142 23 Nil 136 1/05/01 -2.34 1.75 0.1 268 4.5 278 23 Slight 136 5/06/01 -2.46 1.63 1.0 291 4.5 253 23 Slight 136 19/09/01 -2.70 1.39 0.6 270 4.7 187 21 Slight 136 12/10/01 -2.71 1.38 0.6 285 4.9 233 22 Slight 136 25/07/02 -2.30 1.79 1.4 306 5.0 223 23 Slight Wells screened within sandy silt aquifer 088 22/08/00 -6.07 2.49 0.2 354 5.7 195 22 Nil 088 4/09/00 -6.10 2.46 0.8 374 6.6 192 23 Nil 088 10/10/00 -6.23 2.34 0.7 349 5.9 190 24 Nil 088 7/11/00 -6.16 2.40 0.8 348 5.9 230 23 Nil 088 1/05/01 -6.14 2.42 0.8 336 6.0 155 23 Nil 088 19/09/01 -6.49 2.07 0.8 326 5.6 214 22 Nil 088 12/10/01 -6.53 2.03 0.8 311 5.8 198 21 Nil 088 25/07/02 -6.48 2.08 0.6 309 6.0 137 23 Nil 140 1/05/01 -4.96 2.66 0.6 3 4.9 279 23 Dark 140 19/09/01 -5.44 2.18 0.7 289 5.0 225 21 Medium 140 12/10/01 -5.46 2.16 0.7 278 5.2 285 22 Slight 140 25/07/02 -5.36 2.26 0.4 328 5.3 217 23 Slight 144 5/06/01 -1.87 1.97 0.6 1119 5.7 198 21 Slight 144 19/09/01 -2.42 1.42 0.7 1109 5.5 177 21 Medium 144 12/10/01 -2.55 1.29 0.6 1106 5.6 183 20 Slight 144 25/07/02 -2.55 1.29 0.6 1359 5.4 213 22 Medium 147 22/05/01 -1.72 2.02 5.1 81 5.9 280 23 Medium 147 5/06/01 -1.78 1.96 1.0 109 5.1 256 22 Medium 147 19/09/01 -2.31 1.43 0.4 49 4.8 218 21 Medium 147 12/10/01 -2.40 1.34 0.7 58 5.0 271 22 Slight 147 25/07/02 -2.61 1.13 0.9 91 4.8 240 19 Slight 148 19/09/01 -4.61 1.87 0.6 65 4.5 333 22 Nil 148 25/07/02 -4.83 1.65 0.9 83 4.6 282 23 Slight 151 22/05/01 -2.94 1.78 0.1 225 4.1 304 23 Medium 151 19/09/01 -3.48 1.24 0.4 262 4.3 277 21 Medium 151 25/07/02 -3.70 1.02 1.0 251 4.4 262 22 Medium Wells screened within shoreface brown sand aquifer 100 22/08/00 -2.88 2.8 2.5 400 4.7 90 23 Slight 100 4/09/00 -2.91 2.77 0.3 389 4.5 230 23 Slight 100 10/10/00 -2.95 2.73 0.0 373 4.9 271 23 Medium 100 7/11/00 -2.93 2.75 3.6 375 4.9 273 23 Medium 100 1/05/01 -3.06 2.62 0.5 333 4.5 243 23 Medium 100 19/09/01 -3.46 2.22 0.5 351 4.9 203 21 Medium 100 12/10/01 -3.44 2.24 0.6 342 4.6 234 21 Medium

Appendix G – physico-chemical data

Well Water Water Date D.O. Cond. pH Eh Temp Colour No. level level (m bgl) (m AHD) (ppm) (uS/cm) (mV) (oC) 100 25/07/02 -3.15 2.53 1.2 354 5.0 22 22 Medium 101 22/08/00 -5.99 2.5 0.1 177 3.5 368 23 Strong 101 4/09/00 -6.06 2.43 0.7 148 4.7 226 23 Medium 101 10/10/00 -6.15 2.34 0.7 123 4.9 266 23 Medium 101 7/11/00 -6.07 2.42 0.0 149 4.8 165 23 Medium 101 1/05/01 -5.99 2.5 0.8 60 4.5 286 23 Slight 101 19/09/01 -6.47 2.02 0.5 118 4.5 236 22 Medium 101 12/10/01 -6.48 2.01 0.4 111 4.7 265 21 Slight 101 25/07/02 -6.43 2.06 0.9 192 4.7 225 23 Slight MW4D 19/09/01 -4.64 0.57 0.5 341 5.3 272 21 Slight MW5D 19/09/01 -4.21 0.81 1.6 251 5.1 302 21 Nil MW6D 19/09/01 -5.26 1.05 0.5 316 5.5 238 21 Medium MW7D 19/09/01 -5.46 1.24 0.6 287 5.3 241 21 Medium MW8D 19/09/01 -5.90 1.86 0.5 338 5.0 271 21 Medium Wells screened within indurated sand 143 1/05/01 -4.20 3.88 0.1 56 4.0 326 24 V.dark 143 19/09/01 -4.45 3.63 0.5 72 3.8 288 21 V.dark 143 12/10/01 -4.61 3.47 0.6 84 3.9 329 21 V.dark 143 25/07/02 -4.40 3.68 3.0 108 3.9 302 23 V.dark 150 22/05/01 -2.34 2.45 0.5 335 3.1 314 23 V.dark 150 19/09/01 -2.41 2.38 1.2 262 3.5 300 18 V.dark 150 12/10/01 -2.66 2.13 1.0 247 3.6 312 19 V.dark 150 25/07/02 -1.83 2.96 4.0 267 3.5 314 19 V.dark Wells screened within foreshore and beach sand aquifer 114 10/10/00 -0.90 4.20 3.6 193 3.8 339 22 Dark 114 7/11/00 -0.61 4.48 3.7 230 4.0 339 23 Dark 114 19/09/01 -0.89 4.20 0.9 245 3.7 206 20 V.dark 115 21/08/00 -0.45 5.86 3.6 354 3.4 120 21 Dark 115 4/09/00 -0.55 5.76 0.4 372 3.1 300 21 Dark 115 9/10/00 -0.79 5.52 3.4 371 3.6 356 22 Dark 115 7/11/00 -0.56 5.75 3.4 356 3.8 350 22 Dark 115 19/09/01 -0.85 5.46 0.9 336 3.6 248 20 V.dark 115 25/07/02 -0.66 5.65 4.0 338 3.4 281 21 V.dark 126 22/08/00 -2.79 3.68 4.3 85 4.9 231 21 V.dark 126 4/09/00 -2.85 3.62 4.4 81 4.5 387 22 V.dark 126 10/10/00 -3.03 3.44 3.7 77 4.5 410 23 V.dark 126 7/11/00 -2.84 3.63 3.7 73 4.7 354 23 V. dark 126 19/09/01 -3.19 3.28 0.4 75 4.3 350 21 V. dark 126 25/07/02 -3.19 3.28 3.2 78 4.4 342 25 V.dark 129 19/09/01 -1.66 1.66 0.4 87 4.1 375 19 Dark 129 12/10/01 -1.56 1.56 0.6 100 4.2 521 20 Dark 129 25/07/02 -1.20 1.20 3.6 85 4.4 374 19 V.dark 131 5/06/01 -0.99 5.34 3.0 90 4.1 302 24 V.dark 131 19/09/01 -1.33 5.00 0.9 53 4.2 295 20 V.dark 131 25/07/02 -1.13 5.20 3.2 67 4.2 306 21 Dark 132 5/06/01 -0.62 5.08 2.6 280 3.9 223 23 V.dark 132 19/09/01 -1.00 4.70 0.7 252 3.8 202 19 V.dark 132 25/07/02 -0.71 4.99 3.3 314 3.8 264 20 V.dark 133 19/09/01 -2.69 2.63 2.1 292 3.5 204 17 V.dark

Appendix G – physico-chemical data

Well Water Water Date D.O. Cond. pH Eh Temp Colour No. level level (m bgl) (m AHD) (ppm) (uS/cm) (mV) (oC) 133 25/07/02 -2.44 2.88 6.6 417 3.4 307 18 V.dark 134 5/06/01 -0.89 3.41 3.1 250 4.5 265 23 V.dark 134 19/09/01 -1.19 3.11 0.7 232 3.8 259 18 V.dark 134 25/07/02 -1.02 3.28 3.5 314 3.7 274 18 V.dark 135 5/06/01 -1.69 1.48 3.4 577 3.4 294 22 Medium 135 19/09/01 -2.10 1.07 0.7 295 3.8 240 19 Medium 135 25/07/02 -1.66 1.51 3.6 568 3.6 288 19 Medium 137 1/05/01 -0.69 3.47 0.4 235 3.8 318 24 Medium 137 5/06/01 -0.90 3.26 4.4 265 4.0 292 21 Medium 137 19/09/01 -1.36 2.80 3.4 230 4.0 271 18 V.dark 137 12/10/01 -1.40 2.76 4.4 231 4.4 277 20 Medium 137 25/07/02 -0.34 3.82 4.6 381 3.9 319 17 V.dark 138 1/05/01 -0.83 4.96 0.8 196 3.8 293 25 V. dark 138 5/06/01 -0.90 4.89 4.7 254 3.1 278 22 V.dark 138 19/09/01 -1.17 4.62 0.6 245 3.7 207 19 V.dark 138 12/10/01 -1.16 4.63 0.6 235 3.8 238 20 V.dark 138 25/07/02 -0.69 5.10 5.0 295 3.8 300 20 V.dark 139 1/05/01 -0.80 5.86 0.8 344 4.3 255 25 V.dark 139 5/06/01 -0.93 5.73 3.4 334 4.4 243 23 V.dark 139 19/09/01 -1.16 5.50 0.5 291 4.3 185 20 V.dark 139 25/07/02 -0.62 6.04 3.7 332 4.5 264 20 V.dark 141 1/05/01 -0.52 7.01 4.5 82 4.0 313 24 V.dark 141 5/06/01 -0.59 6.94 4.5 97 4.4 273 19 V.dark 141 19/09/01 -0.89 6.64 1.3 99 4.2 267 19 Dark 141 12/10/01 -0.83 6.70 0.7 103 4.4 300 20 V.dark 141 25/07/02 -0.69 6.84 4.4 163 4.6 267 19 V.dark 142 1/05/01 -0.75 7.44 0.8 53 3.8 322 25 V.dark 142 5/06/01 -0.84 7.35 3.1 80 4.1 313 22 V.dark 142 19/09/01 -1.08 7.11 0.5 71 3.9 281 19 V.dark 142 12/10/01 -0.98 7.21 0.7 71 4.0 323 20 V.dark 142 25/07/02 -0.97 7.22 3.1 102 3.9 298 20 V.dark 145 5/06/01 -0.91 3.05 3.9 185 3.5 357 23 V.dark 145 19/09/01 -1.08 2.88 0.8 162 3.6 317 19 V.dark 145 12/10/01 -1.04 2.92 1.4 138 3.7 336 19 V.dark 145 25/07/02 -1.05 2.91 4.8 198 3.5 345 18 V.dark 146 22/05/01 -1.13 2.54 2.9 46 5.6 276 26 V.dark 146 5/06/01 -1.22 2.45 3.8 69 4.4 276 24 V.dark 146 19/09/01 -1.74 1.93 3.6 57 4.3 255 23 V.dark 146 12/10/01 -1.85 1.82 3.1 57 4.6 293 23 V.dark 146 25/07/02 -1.98 1.69 4.7 74 4.4 274 23 V.dark 149 22/05/01 -0.55 4.25 3.6 195 3.4 370 24 V.dark 149 5/06/01 -0.78 4.02 2.9 275 3.4 362 22 V.dark 149 19/09/01 -1.09 3.71 1.1 201 3.5 327 18 V.dark 149 25/07/02 -1.02 3.78 2.6 249 3.2 346 18 V.dark MW2S 19/09/01 -1.51 5.25 3.4 248 4.2 304 19 V.dark MW3S 19/09/01 -1.18 5.15 0.5 174 4.8 247 19 Dark MW4S 19/09/01 -2.03 2.87 4.6 265 3.6 410 22 V.dark MW5S 19/09/01 -1.59 3.35 2.8 387 3.9 338 21 V.dark MW6S 19/09/01 -0.46 6.01 0.5 180 4.1 293 19 V.dark

Appendix G – physico-chemical data

Well Water Water Date D.O. Cond. pH Eh Temp Colour No. level level (m bgl) (m AHD) (ppm) (uS/cm) (mV) (oC) MW8S 19/09/01 -1.58 6.01 0.6 102 3.9 339 21 Dark Surface water S1 21/08/00 2.3 292 3.2 290 17 Strong S1 7/11/00 5.1 386 3.5 556 26 Dark S5 28/08/00 5.4 209 3.4 293 15 Dark S5 5/09/00 6.5 213 3.1 468 24 V.dark S5 10/10/00 6.2 209 3.6 434 27 V.dark S5 7/11/00 4.3 168 3.9 432 25 V.dark S5 5/07/01 5.1 280 3.6 417 22 V.dark S6 5/09/00 5.9 176 3.1 502 28 V.dark S6 10/10/00 4.4 238 3.5 465 27 V.dark S6 7/11/00 5.1 162 3.6 451 30 v.dark S9 4/09/00 7.3 44400 7.0 383 25 Slight S10 5/09/00 4.0 87 3.6 473 24 V.dark S10 10/10/00 3.9 97 3.8 409 28 V.dark S10 7/11/00 5.3 124 3.7 408 24 V.dark S10 5/07/01 5.1 177 3.5 417 19 V.dark S11 5/09/00 4.7 198 3.3 536 22 V.dark S11 10/10/00 5.6 283 3.4 497 31 V.dark S11 7/11/00 3.2 184 3.6 458 24 V.dark S11 5/07/01 4.8 239 3.4 430 18 V.dark S12 5/09/00 8.4 194 4.3 453 23 Slight S12 7/11/00 7.2 88 4.9 440 28 V.slight S13 5/09/00 4.3 162 3.7 543 23 V.dark S13 10/10/00 4.8 159 3.6 526 28 V.dark S13 7/11/00 4.0 151 3.6 522 22 v.dark S14 5/09/00 3.4 291 2.9 576 25 V.dark S14 7/11/00 2.6 314 3.4 556 25 V.dark S15 5/09/00 5.4 254 3.3 556 23 V.dark S15 10/10/00 1.5 234 3.8 428 26 V.dark S15 7/11/00 2.0 271 3.8 416 25 V.dark S15 5/07/01 4.3 320 3.5 4.54 15 V.dark S16 5/09/00 6.0 302 3.3 532 19 V.dark S16 10/10/00 6.2 352 3.6 460 33 V.dark S16 7/11/00 4.0 349 3.6 473 28 V.dark S16 5/07/01 4.4 428 3.7 361 17 V.dark S17 6/09/00 4.4 516 3.5 562 20 V.slight slight- S17 10/10/00 1.7 514 3.8 521 24 med S17 7/11/00 3.0 517 3.7 530 22 Med S18 6/09/00 3.7 101 3.5 565 23 Dark S18 10/10/00 4.3 101 3.8 506 30 V.dark S18 7/11/00 6.1 137 3.8 512 27 V.dark S19 6/09/00 2.1 159 3.4 563 25 V.dark S19 10/10/00 5.1 131 3.7 492 28 V.dark S19 7/11/00 3.4 131 3.8 474 25 V.dark S19 5/07/01 3.6 150 3.7 438 19 V.dark S20 6/09/00 6.8 98 3.4 562 24 V.dark S20 10/10/00 4.7 103 3.8 470 29 V.dark

Appendix G – physico-chemical data

Well Water Water Date D.O. Cond. pH Eh Temp Colour No. level level (m bgl) (m AHD) (ppm) (uS/cm) (mV) (oC) S20 7/11/00 6.7 111 3.7 536 25 V.dark S20 5/07/01 5.4 100 3.7 400 23 V.dark S21 10/10/00 5.2 741 3.9 470 33 Dark S22 10/10/00 3.1 57 4.3 465 27 Dark S22 7/11/00 1.4 79 4.2 382 23 Dark S23 5/07/01 4.0 215 3.4 419 19 V.dark S24 5/07/01 5.4 363 3.3 397 21 V.dark S25 5/07/01 5.8 377 3.7 368 21 V.dark S26 5/07/01 6.2 585 3.7 378 20 V.dark S27 5/07/01 10.7 378 3.7 366 22 V.dark S28 5/07/01 8.2 573 3.4 376 22 V.dark S29 5/07/01 4.9 396 3.3 4.11 23 V.dark S30 5/07/01 1.6 191 3.5 400 21 Medium S31 5/07/01 5.8 354 3.2 421 20 V.dark S32 5/07/01 5.0 257 3.7 350 18 V.dark S33 5/07/01 3.3 248 3.8 362 20 V.dark

Appendix G – physico-chemical data

Appendix H

Major and Minor Ion Chemistry

Appendix G – major and minorAppendix G – ion chemistry

Well No. Date pH Cond. Na Mg Ca K Cl HCO3 SO4 DOC SiO2 Mn Fe Zn Cu Br Al uS/cm mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L Wells screened within palaeochannel aquifer 089 01-Feb-92 5.1 410 53 9.0 12.0 5.9 80 105 0.0 14 0.2 6.9 089 01-Mar-92 6.2 830 81 33.0 51.0 4.3 72 450 0.0 24 8.6 13.0 089 09-Sep-95 7.6 454 52 14.0 20.0 3.7 69 160 0.0 21 3.0 0.2 0.00 0.06 0.00 089 08-Aug-96 6.1 565 46 8.7 16.0 4.1 66 110 0.0 19 1.8 0.0 0.01 0.00 0.00 089 14-Sep-00 5.7 390 44 6.6 11.1 4.7 63 88.3 0.1 0.9 15.9 0.02 0.00 0.15 0.00 089 19-Sep-01 5.9 364 44 6.8 11.2 5.1 61 110 0.6 28 0.8 16.4 0.03 0.01 0.18 0.14 089 30-Jul-02 5.0 408 44 6.8 9.8 4.4 61 60 0.6 22 27 0.5 13.5 0.02 0.01 0.18 0.05 136 05-Jun-01 4.5 291 45 4.7 4.0 4.9 74 2.9 4.2 5 0.1 6.8 0.04 4.86 0.13 0.20 136 19-Sep-01 4.7 270 62 5.1 1.6 2.9 84 20 2.4 51 17 0.0 2.0 0.04 0.01 0.24 0.41 136 30-Jul-02 5.0 306 43 4.3 2.5 3.4 78 10.5 0.0 26 18 0.0 3.0 0.06 0.01 0.12 0.26 Wells screened within sandy silt aquifer 088 01-Feb-92 6.6 385 57 6.0 7.7 4.3 68 98 2.2 17 0.1 5.0 088 01-Mar-92 6.4 420 64 8.2 14.0 5.3 82 125 4.5 20 0.3 9.0 088 09-Sep-95 7.1 320 49 7.1 8.7 4.6 50 105 0.0 16 0.0 0.3 0.03 0.08 0.00 088 08-Aug-96 6.0 332 51 6.9 6.4 4.9 46 110 0.0 16 0.0 0.1 0.03 0.00 0.00 088 14-Sep-00 6.6 374 49 6.8 6.2 5.3 46 99.8 0.2 0.0 12.2 0.04 0.00 0.11 0.02 088 19-Sep-01 5.6 326 49 7.0 6.6 5.4 52 120 1.4 24 0.0 12.4 0.03 0.01 0.12 0.00 088 30-Jul-02 6.0 309 49 6.2 6.1 4.3 43 80 0.7 42 26 0.0 10.8 0.01 0.01 0.12 0.02 140 19-Sep-01 5.0 289 45 5.1 2.8 3.2 77 27 2.2 22 20 0.0 5.8 0.03 0.00 0.15 0.35 140 30-Jul-02 5.3 328 44 4.0 2.8 3.7 73 23 2.2 20 0.0 4.9 0.02 0.01 0.20 0.16 144 05-Jun-01 5.7 1119 166 20.4 12.4 10.1 257 2.43 79.8 20 0.1 7.8 0.02 0.00 0.67 0.15 144 19-Sep-01 5.5 1109 93 13.3 7.9 9.7 54 180 17.6 20 0.1 5.4 0.00 0.00 0.14 0.20 144 30-Jul-02 5.4 1359 177 24.4 14.4 9.8 455 40 194.7 38 21 0.1 8.5 0.03 0.01 1.81 0.19 147 05-Jun-01 5.1 81 16 2.0 1.7 1.7 24 2.23 1.4 9 0.0 1.2 0.05 0.00 0.10 0.66 147 19-Sep-01 4.8 50 5 0.9 0.5 1.6 11 4.1 0.7 30 9 0.0 0.4 0.02 0.01 0.06 1.33 Appendix G–major andminor ion chemistry Appendix

Well No. Date pH Cond. Na Mg Ca K Cl HCO3 SO4 DOC SiO2 Mn Fe Zn Cu Br Al uS/cm mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L 147 30-Jul-02 4.8 91 11 2.0 1.4 1.2 24 0 3.1 33 9 0.0 0.9 0.04 0.01 0.12 0.86 148 19-Sep-01 4.5 65 14 1.5 0.3 0.2 22 5.3 0.8 13 0.0 0.3 0.00 0.01 0.09 0.38 148 30-Jul-02 4.6 83 11 1.4 0.5 1.3 21 0 14.8 29 14 0.0 0.3 0.02 0.01 0.09 0.52 151 19-Sep-01 4.3 262 55 3.6 1.9 3.0 64 0 0.4 14 0.1 2.4 0.09 0.01 0.20 0.76 151 30-Jul-02 4.4 251 36 2.8 1.8 1.3 59 0 6.5 84 15 0.0 1.6 0.03 0.01 0.18 0.58 Wells screened within shoreface brown sand aquifer 100 01-Feb-92 4.7 400 57 9.0 6.4 2.5 105 30 2.0 12 0.1 0.2 100 01-Mar-92 4.8 345 53 6.9 2.9 1.2 89 22 0.0 12 0.1 2.7 100 09-Sep-95 5.2 328 52 5.8 2.3 1.6 90 15 2.9 12 0.0 0.3 0.12 0.04 1.06 100 08-Aug-96 4.9 349 53 7.0 2.9 1.3 92 15 0.0 12 0.0 0.5 0.10 0.00 1.62 100 14-Sep-00 4.5 389 55 8.0 1.0 1.4 99 18 0.7 0.0 0.7 0.00 0.00 0.31 1.92 100 19-Sep-01 4.9 351 55 4.3 0.8 2.3 102 10 0.6 15 0.0 0.4 0.04 0.00 0.25 1.49 100 30-Jul-02 5.0 354 50 6.4 1.2 1.5 87 7.5 37.0 1 17 0.0 0.4 0.03 0.01 0.23 1.78 101 01-Feb-92 4.4 330 41 8.2 10.0 2.4 77 26 2.0 6 0.1 0.7 101 01-Mar-92 4.6 170 24 5.3 5.0 1.3 30 26 0.0 7 0.1 3.5 101 09-Sep-95 4.6 108 11 3.2 0.9 0.6 22 9.2 1.5 4 0.0 0.6 0.20 0.06 1.08 101 08-Aug-96 4.7 112 14 2.5 1.9 0.5 28 5.2 3.0 6 0.0 0.5 0.04 0.01 1.54 101 14-Sep-00 4.7 148 23 2.7 0.8 1.2 37 9 0.7 0.0 1.7 0.01 0.00 0.11 1.55 101 19-Sep-01 4.5 118 16 2.9 0.6 0.2 31 10 0.3 11 0.0 3.4 0.04 0.02 0.10 1.73 101 30-Jul-02 4.7 192 28 3.1 1.1 1.5 44 0.5 0.6 41 13 0.0 1.5 0.05 0.01 0.13 1.14 MW3D 26-Apr-00 5.4 344 50 4.00 2.00 2.00 85 20.00 0.50 0.1 5.9 5.10 MW3D 17-Jul-00 48 4.00 3.00 3.00 83 10.00 1.00 0.0 9.8 1.00 MW4D 26-Apr-00 5.4 351 52 4.00 3.00 3.00 88 20.00 0.50 0.0 9.3 0.70 MW4D 17-Jul-00 49 5.00 5.00 4.00 88 9.00 7.00 0.0 2.2 0.13 MW4D 19-Sep-01 5.3 341 50 4.34 3.60 4.33 92 19.00 0.36 18 0.0 10.0 0.03 0.01 0.22 0.10 Appendix G – major and minorAppendix G – ion chemistry

Well No. Date pH Cond. Na Mg Ca K Cl HCO3 SO4 DOC SiO2 Mn Fe Zn Cu Br Al uS/cm mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L MW5D 19-Sep-01 5.1 251 41 3.18 1.82 3.57 67 18.00 0.63 18 0.0 3.5 0.02 0.00 0.15 0.20 MW6D 19-Sep-01 5.5 316 45 5.38 5.41 5.20 76 27.00 0.22 22 0.1 7.3 0.03 0.00 0.16 0.06 MW7D 19-Sep-01 5.3 287 51 4.44 3.26 0.02 78 32.00 0.44 18 0.0 10.1 0.03 0.02 0.17 0.14 MW8D 19-Sep-01 5.0 338 53 5.12 1.71 3.23 96 20.00 2.23 4 0.0 6.1 0.02 0.00 0.24 0.29 Wells screened within indurated sand 143 05-Jun-01 4.0 56 7 1.2 0.8 0.3 9 0 0.6 12 0.0 0.3 0.05 0.00 0.06 0.23 143 19-Sep-01 3.8 72 7 1.5 0.5 0.4 11 0 1.3 137 9 0.0 1.5 0.01 0.02 0.06 1.26 143 30-Jul-02 3.9 108 8 4.1 1.9 2.0 12 0 2.9 91 13 0.0 0.6 0.29 0.01 0.12 1.91 150 19-Sep-01 3.5 262 30 4.5 1.9 0.7 45 2 1.1 6 0.0 1.0 0.03 0.01 0.14 1.80 150 30-Jul-02 3.5 267 25 5.4 3.1 0.8 43 0 3.2 171 7 0.0 1.0 0.16 0.01 0.16 2.37 Wells screened within foreshore and beach sand aquifer 114 09-Sep-95 4.5 140 18 2.8 4.1 1.1 29 3.6 1.2 5 0.0 0.3 0.13 0.08 0.36 114 08-Jul-96 4.0 145 18 3.1 1.9 0.5 30 6.7 0.4 5 0.0 0.3 0.03 0.01 0.35 114 19-Sep-01 3.7 245 30 6.3 0.6 1.3 51 4.6 4.4 5 0.0 0.4 0.01 0.01 0.16 0.51 115 09-Sep-95 4.0 145 20 1.5 1.4 0.7 27 0 0.6 0.0 0.2 0.14 0.06 0.45 115 07-Aug-96 3.6 217 20 1.8 0.3 0.5 27 0 0.0 6 0.0 0.2 0.06 0.01 0.68 115 14-Sep-00 3.1 372 40 7.0 0.8 2.6 76 0 2.1 8 0.0 0.5 0.10 0.00 0.24 0.93 115 15-Nov-00 3.3 40 6.4 0.7 0.8 78 0 1.2 7 0.0 0.7 0.01 0.00 0.25 0.76 115 19-Sep-01 3.6 336 36 5.9 0.4 1.7 70 0 1.4 113 7 0.0 0.3 0.05 0.01 0.21 0.66 115 30-Jul-02 3.4 338 34 5.3 0.6 0.8 65 0 2.1 84 9 0.0 0.4 0.03 0.01 0.26 0.73 126 14-Sep-00 4.5 81 11 1.7 5.0 0.7 12 0 3.6 0.1 4.4 0.14 0.00 0.04 0.92 126 15-Nov-00 4.8 10 1.9 5.4 1.0 12 0 3.0 3 0.0 3.4 0.01 0.00 0.04 0.52 126 19-Sep-01 4.3 75 10 1.9 3.4 0.8 12 0 2.7 81 4 0.0 3.3 0.04 0.03 0.07 0.68 126 30-Jul-02 4.4 78 8 2.7 4.6 0.0 11 0 3.2 104 7 0.0 4.3 0.08 0.01 2.03 129 19-Sep-01 4.1 87 10 2.3 6.0 0.6 20 0.8 4.9 4 0.0 0.2 0.02 0.01 0.05 0.45 129 30-Jul-02 4.4 85 8 3.1 9.4 0.9 11 0 3.8 55 8 0.0 0.9 0.06 0.01 0.92 Appendix G–major andminor ion chemistry Appendix

Well No. Date pH Cond. Na Mg Ca K Cl HCO3 SO4 DOC SiO2 Mn Fe Zn Cu Br Al uS/cm mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L 131 05-Jun-01 4.1 90 11 1.3 0.9 0.0 13 0 0.8 4 0.0 0.7 0.05 0.00 0.05 0.51 131 19-Sep-01 4.2 53 9 1.2 1.0 0.0 20 0 1.6 89 5 0.0 0.8 0.02 0.00 0.08 0.68 131 30-Jul-02 4.2 67 8 2.6 2.2 1.0 10 0 1.7 59 7 0.0 1.2 0.09 0.02 0.57 132 05-Jun-01 3.9 280 38 7.9 0.7 0.1 254 0 78.9 135 9 0.0 1.1 0.14 0.00 0.65 2.18 132 19-Sep-01 3.8 252 19 4.9 0.3 0.4 52 0 1.1 211 9 0.0 0.4 0.03 0.01 0.31 1.75 132 30-Jul-02 3.7 314 34 9.8 0.7 0.0 61 0 1.3 9 0.0 0.6 0.07 0.01 0.41 2.45 133 19-Sep-01 3.5 292 36 5.1 1.2 1.3 50 1.3 0.3 3 0.1 1.5 0.04 0.01 0.06 1.04 133 30-Jul-02 3.4 417 44 8.7 1.9 0.7 82 0 6.9 138 4 0.0 1.9 0.21 0.01 0.26 2.69 134 05-Jun-01 4.5 250 32 4.9 1.2 2.9 46 0 0.5 0 0.0 0.6 0.09 0.00 0.15 1.63 134 19-Sep-01 3.8 232 31 5.2 0.9 1.6 47 0 1.1 2 0.0 0.5 0.04 0.02 0.13 1.32 134 30-Jul-02 3.7 314 37 8.3 2.3 1.6 59 0 8.3 119 3 0.0 1.1 0.06 0.01 0.11 2.66 135 05-Jun-01 3.4 577 66 9.9 0.6 0.6 124 0 19.8 2 0.0 1.1 0.03 0.00 0.28 3.21 135 19-Sep-01 3.8 295 34 4.5 0.6 0.4 63 0.9 5.6 53 7 0.0 1.4 0.02 0.00 0.24 2.66 135 30-Jul-02 3.6 568 72 7.4 0.6 1.6 135 0 24.3 34 8 0.0 0.8 0.03 0.02 0.33 5.95 137 06-May-01 4.0 292 37 7.1 1.2 0.3 59 0 2.0 0 0.0 0.6 0.04 0.00 0.26 2.22 137 19-Sep-01 4.0 230 34 7.3 1.2 1.0 53 0 0.8 138 3 0.0 0.7 0.03 0.02 0.23 3.02 137 30-Jul-02 3.9 381 47 16.6 3.3 2.1 89 0 1.2 157 5 0.0 2.7 0.08 0.01 0.35 3.93 138 05-Jun-01 3.1 254 30 5.4 1.3 0.9 51 0 1.0 125 1 0.0 1.3 0.03 0.00 0.21 2.71 138 30-Jul-02 3.8 295 34 5.8 1.6 0.4 60 0 0.0 154 7 0.0 1.6 0.07 0.01 0.39 4.16 139 05-Jun-01 4.4 334 52 10.6 0.9 0.5 80 0 2.2 6 0.0 1.4 0.09 0.00 0.36 2.21 139 19-Sep-01 4.3 291 36 6.0 0.4 0.6 69 0.4 0.8 177 9 0.0 0.6 0.03 0.01 0.32 1.89 139 30-Jul-02 4.5 332 46 11.2 0.8 0.4 72 0 1.7 133 10 0.0 0.7 0.09 0.01 0.46 3.36 141 05-Jun-01 4.4 97 14 3.6 0.8 0.5 18 1.19 0.7 10 0.0 0.6 0.03 0.00 0.12 3.37 141 19-Sep-01 4.2 99 11 1.9 0.4 2.9 20 0.8 0.4 77 12 0.0 0.4 0.02 0.00 0.09 2.19 141 30-Jul-02 4.6 163 20 9.2 2.9 4.4 29 0 2.0 102 16 0.0 5.5 0.20 0.01 0.17 2.79 142 19-Sep-01 3.9 71 7 1.5 0.8 2.6 10 0.5 2.8 16 0.0 0.4 0.02 0.02 0.07 0.24 Appendix G – major and minorAppendix G – ion chemistry

Well No. Date pH Cond. Na Mg Ca K Cl HCO3 SO4 DOC SiO2 Mn Fe Zn Cu Br Al uS/cm mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L 142 30-Jul-02 3.9 102 7 3.5 3.8 2.8 10 0 1.0 100 30 0.0 0.9 0.07 0.01 0.12 0.54 145 05-Jun-01 3.5 185 15 2.2 0.4 0.6 18 0 0.5 3 0.0 0.3 0.10 0.00 0.07 1.57 145 19-Sep-01 3.6 162 15 2.6 0.1 1.2 21 0.9 3.9 166 4 0.0 0.5 0.03 0.02 0.09 1.23 145 30-Jul-02 3.5 198 13 4.5 0.2 2.0 24 0 3.9 5 0.0 0.7 0.12 0.00 0.10 2.18 146 05-Jun-01 4.4 69 11 1.6 1.6 1.0 10 1.71 0.8 5 0.0 0.6 0.04 0.00 0.05 1.44 146 19-Sep-01 4.3 57 31 2.6 1.4 0.4 56 0.6 1.8 81 7 0.0 3.2 0.03 0.01 0.19 2.60 146 30-Jul-02 4.4 74 10 1.9 2.0 1.3 12 0 1.4 67 8 0.0 0.3 0.05 0.02 0.11 4.13 149 05-Jun-01 3.4 275 29 3.0 1.2 1.8 36 1.24 0.7 4 0.0 0.9 0.23 0.01 0.18 0.93 149 19-Sep-01 3.5 201 18 1.5 0.6 1.3 26 0 0.7 219 4 0.0 0.5 0.03 0.02 0.10 0.78 149 30-Jul-02 3.2 249 20 2.6 1.1 0.2 28 0 4.9 228 4 0.0 1.2 0.41 0.00 0.09 1.15 MW2S 19-Sep-01 4.2 248 53 9.4 4.8 0.3 106 0 11.2 7 0.1 9.5 0.02 0.01 0.47 2.54 MW3S 26-Apr-00 4.7 239 23 6.0 2.0 0.5 52 0.5 0.5 0.0 2.7 8.35 MW3S 17-Jul-00 21 4.0 1.0 0.3 40 0.2 4.0 0.0 0.8 1.44 MW3S 19-Sep-01 4.8 174 15 3.6 1.4 1.2 44 0.4 0.7 6 0.0 1.1 0.09 0.02 0.17 1.13 MW4S 26-Apr-00 3.7 264 21 4.0 0.5 0.5 43 0.5 3.0 0.0 2.4 8.55 MW4S 17-Jul-00 21 4.0 1.0 0.7 34 0.6 11.0 0.0 0.9 0.99 MW4S 19-Sep-01 3.6 265 31 5.1 1.0 1.5 49 0 5.4 5 0.1 4.0 0.28 0.19 0.17 1.40 MW5S 19-Sep-01 3.9 387 47 11.0 6.8 0.8 90 0.9 8.1 16 0.5 15.3 0.05 0.01 0.24 5.36 MW6S 19-Sep-01 4.1 100 35 6.1 2.6 0.4 63 0.6 3.9 10 0.0 3.9 0.02 0.01 0.22 2.75 MW8S 19-Sep-01 3.9 102 9 1.1 0.6 1.2 13 0.8 3.6 19 0.0 0.6 0.02 0.00 0.04 0.47 Surface water S1 26-Apr-00 3.7 194 17 3.0 0.5 0.5 36 0 0.5 0.0 1.0 0.03 0.00 0.41 1.70 S1 17-Jul-00 30 4.0 1.0 0.5 58 0.5 3.0 0.0 0.6 0.03 0.00 0.25 1.18 S1 15-Nov-00 3.4 53 9.5 3.0 0.7 79 0 18.0 1 0.1 1.2 0.02 0.00 0.14 0.76 S2 17-Jul-00 3.4 47 7.0 0.9 0.7 91 0.5 10.0 0.0 1.3 0.04 0.00 0.61 2.59 S3 26-Apr-00 6.2 2079 374 32.0 9.0 15.0 661 16 57.0 0.0 0.6 0.01 0.00 0.17 0.73 Appendix G–major andminor ion chemistry Appendix

Well No. Date pH Cond. Na Mg Ca K Cl HCO3 SO4 DOC SiO2 Mn Fe Zn Cu Br Al uS/cm mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L S3 22-May-00 6.5 463 48.0 16.0 19.0 814 29 92.0 0.0 0.7 0.02 0.05 0.26 1.19 S3 20-Jun-00 5.6 136 15.0 5.0 5.0 239 3 29.0 0.0 0.3 0.01 0.00 0.10 0.66 S3 17-Jul-00 6.3 3730 418.0 140.0 153.0 6680 24 937.0 0.0 0.7 0.01 0.00 0.10 0.87 S4 26-Apr-00 4.0 230 20 4.0 4.0 0.5 46 0 3.0 0.0 0.6 0.04 0.00 0.12 1.02 S4 22-May-00 4.5 23 5.0 5.0 0.5 50 0 9.0 0.0 0.7 0.35 S4 20-Jun-00 4.2 24 5.0 4.0 0.5 54 0 7.0 0.0 0.8 0.67 S4 17-Jul-00 4.0 40 6.0 4.0 1.0 76 0.5 11.0 0.0 0.4 0.01 0.00 0.07 0.63 S5 13-Sep-00 3.1 213 19 3.0 0.6 0.5 34 0 1.5 1 0.0 0.8 0.65 0.01 0.06 0.46 S5 15-Nov-00 3.4 21 2.8 0.8 1.3 30 0 3.6 1 0.0 0.4 0.03 0.00 0.06 0.24 S5 12-Jul-01 32 5.4 1.4 3.6 52 0 0.4 6 0.0 0.4 0.04 0.00 0.06 0.27 S6 13-Sep-00 3.1 176 16 2.7 0.5 0.8 21 0 2.2 2 0.1 0.5 0.19 0.00 0.06 0.70 S6 15-Nov-00 3.2 17 2.6 0.9 0.8 26 0 4.5 1 0.0 0.4 0.02 0.00 0.08 0.42 S9 14-Sep-00 7 44400 4390 529 163 159 16806 70 2274.0 91 0.0 0.3 0.04 0.00 0.11 0.80 S10 13-Sep-00 3.6 87 11 2.2 1.4 1.3 11 0 1.7 16 0.0 0.3 0.02 0.00 0.20 0.24 S10 15-Nov-00 3.5 11 2.8 1.9 1.2 15 0 1.5 0 0.0 0.3 0.01 0.00 0.08 0.22 S10 12-Jul-01 12 3.4 2.0 1.2 30 0 0.4 0 0.0 0.5 0.08 0.00 0.08 0.78 S11 13-Sep-00 3.3 198 21 2.2 0.8 1.0 24 0 1.7 2 0.0 0.3 0.01 0.00 0.06 0.61 S11 15-Nov-00 3.4 21 2.3 0.9 1.1 27 0 3.9 2 0.0 0.5 0.03 0.00 0.16 0.93 S11 12-Jul-01 21 2.0 0.8 0.5 31 0 1.9 3 0.0 0.2 0.06 0.00 0.14 0.56 S12 14-Sep-00 4.3 194 31 3.3 0.8 0.9 54 0 3.2 4 0.0 0.4 0.13 0.00 0.11 0.63 S12 15-Nov-00 5.5 17 1.9 1.1 1.8 22 2.32 7.0 2 0.0 0.5 0.00 0.00 0.09 0.29 S13 14-Sep-00 3.7 162 12 2.2 0.6 0.8 21 0 1.8 2 0.1 0.6 0.15 0.01 0.13 1.49 S13 15-Nov-00 3.5 15 2.5 0.5 0.5 26 0 2.4 1 0.0 1.5 0.01 0.00 0.17 1.42 S14 14-Sep-00 2.9 291 51 7.5 3.9 1.6 44 0 0.7 0 0.0 0.4 0.01 0.00 0.20 1.61 S14 15-Nov-00 3.2 32 5.4 1.6 46 0 18.0 1 0.6 0.6 0.13 0.01 0.14 1.25 S15 14-Sep-00 3.3 254 31 6.2 4.8 1.1 45 0 3.2 2 0.0 0.8 0.03 0.00 0.18 1.25 Appendix G – major and minorAppendix G – ion chemistry

Well No. Date pH Cond. Na Mg Ca K Cl HCO3 SO4 DOC SiO2 Mn Fe Zn Cu Br Al uS/cm mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L S15 15-Nov-00 3.5 34 6.9 1.5 0.8 52 0 8.8 3 0.0 0.7 0.05 0.00 0.24 1.55 S15 12-Jul-01 35 6.5 1.2 0.3 59 0 5.6 0 0.0 1.4 0.02 0.00 0.30 0.77 S16 14-Sep-00 2.3 302 35 7.8 68.0 1.1 61 0 6.3 1 0.0 4.5 0.01 0.01 0.30 0.98 S16 15-Nov-00 3.4 45 6.5 2.0 1.1 66 0 8.7 1 0.0 0.3 0.01 0.00 0.06 0.46 S16 12-Jul-01 57 8.0 1.9 4.2 79 0 10.4 1 0.0 0.5 0.00 0.00 0.07 0.24 S17 14-Sep-00 3.5 516 60 13.2 5.5 1.4 116 0 44.3 11 0.0 0.4 0.01 0.00 0.08 0.55 S17 15-Nov-00 3.5 61 11.8 5.1 1.2 117 0 45.5 9 0.0 0.2 0.09 0.00 0.09 0.81 S18 14-Sep-00 3.5 101 12 2.1 2.0 0.9 17 0 1.1 6 0.0 0.6 1.06 S18 15-Nov-00 3.8 18 2.0 1.6 1.2 21 0 4.5 2 0.0 0.5 0.03 0.00 0.09 0.58 S19 15-Nov-00 3.7 17 3.0 2.5 1.1 24 0 4.0 1 0.0 0.4 0.10 0.00 0.06 0.59 S19 12-Jul-01 15 2.6 2.2 0.0 25 0 5.6 1 0.0 0.2 0.02 0.00 0.03 0.54 S20 15-Nov-00 3.3 11 2.1 1.0 1.3 15 0 3.4 4 0.0 2.2 0.35 S20 12-Jul-01 10 2.3 1.1 1.8 20 0 3.6 5 0.0 2.2 0.58 S22 15-Nov-00 4.0 10 2.3 3.8 1.4 10 0 7.0 5 0.0 0.7 0.19 S23 12-Jul-01 20 2.7 0.4 2.7 28 0 1.1 4 0.1 0.2 0.29 S24 12-Jul-01 42 6.3 1.5 1.2 66 0 1.8 0 0.1 2.2 1.15 S25 12-Jul-01 45 8.1 3.2 2.3 81 0 1.3 2 0.1 2.9 1.36 S26 12-Jul-01 85 14.6 2.7 5.7 113 0 6.3 17 0.1 1.7 1.20 S27 12-Jul-01 52 8.3 2.5 3.0 79 0 0.4 1 0.1 2.4 2.85 S28 12-Jul-01 78 11.1 2.5 2.9 113 0 5.1 1 0.0 0.7 0.07 0.00 0.06 0.83 S29 12-Jul-01 42 5.8 1.6 4.0 67 0 2.8 5 0.0 0.5 0.01 0.00 0.07 0.50 S30 12-Jul-01 16 3.0 0.3 1.1 30 0 2.7 3 0.0 1.1 0.02 0.00 0.20 1.17 S31 12-Jul-01 29 2.9 1.1 0.1 46 0 3.8 0 0.0 0.5 1.69 0.00 0.08 0.53 S32 12-Jul-01 34 5.3 1.1 3.8 53 0 3.0 1 0.0 0.7 0.03 0.00 0.09 0.36 S33 12-Jul-01 1 3.9 1.1 3.4 51 0 6.0 1 0.0 0.1 0.09 0.23 56.00 3.98 Appendix G–major andminor ion chemistry Appendix

Well No. Date pH Cond. Na Mg Ca K Cl HCO3 SO4 DOC SiO2 Mn Fe Zn Cu Br Al uS/cm mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L seawater 10500 1350.0 400.0 380.0 19000 142 2700.0 6 0.0 65.00 seawater 8.2 10060 1300.0 445.0 395.0 2100 150 2180.0 5 local rain 18-Feb-97 5.7 22 2 0.4 0.9 0.1 3 > .1 > .1 1 local rain 18-Feb-97 5.6 7 0 0.1 0.2 0.0 1 > .1 > .1 > 1 local rain 18-Feb-97 7.4 20 0 0.1 0.1 0.0 2 > .1 > .1 > 1 local rain 18-Feb-97 6.3 55 3 0.5 7.0 0.2 4 2.7 > .1 7 local rain 18-Feb-97 5.9 35 3 0.7 2.8 0.6 5 0.6 > .1 1 local rain 14-Oct-00 4.3 3 0.4 0.5 0.1 3 0 1.3 0.0 0.0 0.11 0.01 0.31

Appendix I

Calculation of Organic Anion Concentration

Calculation of Anion Contribution from Dissolved organic matter:

concentration of Anions contributed by dissolved organic matter. [A-] = In eq/l ie. Ionised carboxyl groups - [A ] = K [CT] K + [H+]

Where [CT] = organic (fluvic + humic acid concentrations in eq/L ie. Total carboxyl groups K = mass action quotient

Calculation of K pK = 0.96 + 0.90pH - 0.09(pH)2

Where pK = negative log of K (-logK) ... K = 10-(0.96 + 0.90pH - 0.09(pH)2 eq/L

Calculation of [CT] A carboxyl content of 10 eq/mg organic carbon is assumed (Oliver et al, 1983)

[CT] = [Dissolved mg/L organic carbon] x 10 µeq/mg = ….µeq/L

eg. Sample: S18 [H+] = 1.622 [H+] = - pH: 3.79 x 10-4 logpH [CT] = 9.9945 TOC: 99.45 mg/L x 10-4

Calc of K pK = 0.96 + 0.90 x 3.79 - 0.039 (3.79) 4.371 - 0.5602 pK = 3.81 K = 1.549 x 10-4

Calc of [A-] - [A ] = k [CT] K + [H+] = (1.549 x 10-4) x 9.945 x 10-4 1.549 x 10-4 + 1.622 x 10-4 = 1.540 x 10-7 3.171 x 10-4 = 4.86 x 10-4 eq/L = 0.486 meq/L

Cation = 1.0995 Anion = 0.7203 + 0.486 = 1.206 Balance = -4.60%

Appendix I – calculation of organic anion concentration

Sample 140 141 132 146 133 88

pH 5.3 4.6 3.7 4.4 3.4 6 TOC mg/L 22.31 102.3 134.7 67.25 138.1 41.93 Cation total meq/L 2.85 2.11 2.36 0.76 2.8 3.46 Anion total meq/L 2.65 0.92 1.72 0.39 2.5 2.54

[H+] mg/L 5E-06 2.5E-05 0.0002 4E-05 0.0004 1E-06 Ct eq/L 0.00022 0.00102 0.00135 0.00067 0.00138 0.00042

pK 4.63 4.27 3.76 4.16 3.57 4.96 K eq/L 2.3E-05 5.3E-05 0.00018 6.8E-05 0.00027 1.1E-05

[A-] eq/L 0.00018 0.00069 0.00063 0.00043 0.00056 0.00038 =K[Ct]/(K+[H+])

[A-] meq/L 0.1835 0.6946 0.6301 0.4251 0.5577 0.3846

Old Ion balance % -3.5 39.3 14.9 31.9 5.7 15.3 New Ion Balance % 0.3 13.3 0.2 -3.5 -4.4 8.4

Sample 139 145 136 101 149 100

pH 4.5 3.5 5 4.7 3.2 5 TOC mg/L 132.9 2.473 26.47 40.47 227.8 0.8411 Cation total meq/L 3.01 1.04 2.54 1.62 1.19 2.82 Anion total meq/L 2.09 0.88 2.37 1.3 0.91 3.35

[H+] mg/L 3.2E-05 0.00032 0.00001 2E-05 0.00063 0.00001 Ct eq/L 0.00133 2.5E-05 0.00026 0.0004 0.00228 8.4E-06

pK 4.22 3.63 4.49 4.33 3.44 4.49 K eq/L 6E-05 0.00023 3.3E-05 4.7E-05 0.00036 3.3E-05

[A-] eq/L 0.00087 1E-05 0.0002 0.00028 0.00083 6.4E-06 =K[Ct]/(K+[H+])

[A-] meq/L 0.8714 0.0105 0.2028 0.2840 0.8313 0.0064

Old Ion balance % 18.0 8.5 3.4 11.0 12.9 -8.5 New Ion Balance % 0.8 7.7 -0.6 1.1 -18.8 -8.7

Appendix I – calculation of organic anion concentration

Sample 144 89 150 142 151 143

pH 5.4 5 3.5 3.9 4.4 3.9 TOC mg/L 37.65 22.26 171.2 99.99 83.94 90.72 Cation total meq/L 11 3.6 1.74 0.87 1.93 0.87 Anion total meq/L 17.59 2.74 1.34 0.36 1.84 0.58

[H+] mg/L 4E-06 0.00001 0.00032 0.00013 4E-05 0.00013 Ct eq/L 0.00038 0.00022 0.00171 0.001 0.00084 0.00091

pK 4.68 4.49 3.63 3.88 4.16 3.88 K eq/L 2.1E-05 3.3E-05 0.00023 0.00013 6.8E-05 0.00013

[A-] eq/L 0.00032 0.00017 0.00073 0.00051 0.00053 0.00047 =K[Ct]/(K+[H+])

[A-] meq/L 0.3159 0.1705 0.7267 0.5133 0.5306 0.4657

Old Ion balance % -23.0 13.5 13.1 41.4 3.7 20.3 New Ion Balance % -23.9 10.6 -8.6 -0.2 -10.2 -9.2

Sample 134 131 148 147 138 126

pH 3.7 4.2 4.6 4.8 3.8 4.4 TOC mg/L 118.9 58.67 29.01 33.02 153.8 103.9 Cation total meq/L 2.47 0.74 0.65 0.79 2.12 0.97 Anion total meq/L 1.84 0.35 0.91 0.76 1.7 0.4

[H+] mg/L 0.0002 6.3E-05 2.5E-05 1.6E-05 0.00016 4E-05 Ct eq/L 0.00119 0.00059 0.00029 0.00033 0.00154 0.00104

pK 3.76 4.05 4.27 4.38 3.82 4.16 K eq/L 0.00018 8.9E-05 5.3E-05 4.2E-05 0.00015 6.8E-05

[A-] eq/L 0.00056 0.00034 0.0002 0.00024 0.00075 0.00066 =K[Ct]/(K+[H+])

[A-] meq/L 0.5562 0.3428 0.1970 0.2390 0.7541 0.6567

Old Ion balance % 14.7 35.8 -17.0 1.6 10.9 41.6 New Ion Balance % 1.5 3.3 -26.0 -11.7 -7.3 -4.3

Appendix I – calculation of organic anion concentration

Sample 115 129 137 115 121 123

pH 3.4 4.4 3.9 3.34 5.01 3.9 TOC mg/L 83.92 55.22 157.1 113.1 18.23 100.9 Cation total meq/L 1.98 1.13 3.74 2.3712 2.2995 1.1235 Anion total meq/L 1.88 0.57 2.54 2.2833 1.9075 0.9314

[H+] mg/L 0.0004 4E-05 0.00013 0.00046 9.8E-06 0.00013 Ct eq/L 0.00084 0.00055 0.00157 0.00113 0.00018 0.00101

pK 3.57 4.16 3.88 3.53 4.49 3.88 K eq/L 0.00027 6.8E-05 0.00013 0.00029 3.2E-05 0.00013

[A-] eq/L 0.00034 0.00035 0.00081 0.00044 0.00014 0.00052 =K[Ct]/(K+[H+])

[A-] meq/L 0.3389 0.3490 0.8065 0.4432 0.1400 0.5180

Old Ion balance % 2.5 33.1 19.2 1.89 9.32 21.14 New Ion Balance % -5.7 10.3 5.6 -6.969 5.797 -12.665

Sample 126 S5 S6 S11 S12 S13

pH 4.75 3.4 3.2 3.36 5.49 3.46 TOC mg/L 80.97 80.03 127.2 144 20.05 105.6 Cation total meq/L 1.0981 1.2404 1.0815 1.2112 1.0259 0.9436 Anion total meq/L 0.468 0.9731 0.8886 0.8587 0.8127 0.8224

[H+] mg/L 1.8E-05 0.0004 0.00063 0.00044 3.2E-06 0.00035 Ct eq/L 0.00081 0.0008 0.00127 0.00144 0.0002 0.00106

pK 4.36 3.57 3.44 3.54 4.73 3.61 K eq/L 4.4E-05 0.00027 0.00036 0.00029 1.9E-05 0.00025

[A-] eq/L 0.00058 0.00032 0.00046 0.00057 0.00017 0.00044 =K[Ct]/(K+[H+])

[A-] meq/L 0.5772 0.3232 0.4642 0.5700 0.1711 0.4394

Old Ion balance % 40.23 12.08 9.79 17.03 11.6 6.86 New Ion Balance % 2.468 -2.203 -11.144 -8.237 2.096 -14.429

Appendix I – calculation of organic anion concentration

Sample S15 S16 S17 S18 S20 S22

pH 3.5 3.41 3.52 3.79 3.34 4.03 TOC mg/L 133 142.1 20.02 114.1 92.38 65.3 Cation total meq/L 2.2763 2.7161 4.2104 1.0995 0.783 0.9017 Anion total meq/L 1.6695 2.063 4.2537 0.7203 0.5783 0.4484

[H+] mg/L 0.00032 0.00039 0.0003 0.00016 0.00046 9.3E-05 Ct eq/L 0.00133 0.00142 0.0002 0.00114 0.00092 0.00065

pK 3.63 3.58 3.64 3.81 3.53 3.95 K eq/L 0.00023 0.00027 0.00023 0.00015 0.00029 0.00011

[A-] eq/L 0.00056 0.00058 8.6E-05 0.00056 0.00036 0.00036 =K[Ct]/(K+[H+])

[A-] meq/L 0.5645 0.5767 0.0858 0.5568 0.3620 0.3551

Old Ion balance % 15.38 13.67 -0.51 20.84 15.04 33.57 New Ion Balance % 0.937 1.426 -1.510 -7.474 -9.126 5.756

Appendix I – calculation of organic anion concentration