Investigation Into Acid Sulfate Soil Discharge in the Mooball Creek

Acid Sulfate Soils in the Mooball Creek Estuary

Investigation into Acid Sulfate Soil Discharge in the

Mooball Creek Catchment Scale, Severity, Identification of Landscape Processes and a Prioritised

Remediation Plan

FINAL REPORT

Adele Jones Richard Collins

May 2015

Acid Sulfate Soils in the Mooball Creek Estuary

DOCUMENT STATUS RECORD

Project Title: INVESTIGATION INTO ACID SULFATE SOIL DISCHARGE IN THE MOOBALL CREEK CATCHENT: Scale, Severity, Identification of Landscape Processes and a Prioritised Remediation Plan Client: Tom Alletson Waterways Program Leader Tweed Shire Council Document Title: INVESTIGATION INTO ACID SULFATE SOIL DISCHARGE IN THE MOOBALL CREEK CATCHENT: Scale, Severity, Identification of Landscape Processes and a Prioritised Remediation Plan (Final Report) Document Number: 2015/1 File Name: Final_Report_Mooball_May2015

Signatures Issue No. Date of Issue Description Authors Checked Approved 1 05/05/2015 Draft for Council review AJ/RC RC RC 2 10/06/2015 Final version AJ/RC RC RC

Disclaimer: 1. The Water Research Centre has taken all reasonable steps to ensure that the information contained within this report is accurate at the time of production. In some cases, we have relied upon the information supplied by the client. 2. This report has been prepared in accordance with good professional practice. No other warranty expressed or implied is made as to the professional advice given in this report. 3. The Water Research Centre maintains no responsibility for the misrepresentation of results due to incorrect usage of the information contained within this report. 4. This report should remain together and be read as a whole. 5. This report has been prepared solely for the benefit of the client listed above. No liability is accepted by the Water Research Centre with respect to the use of this report by third parties without prior written approval.

Contact Details: Water Research Centre Name: Adele Jones School of Civil and Environmental Engineering Email: [email protected] University of New South Wales Physical: Name: Richard Collins Building H22, Vallentine Annexe Email: [email protected] Botany Street Gate 11 Kensington. Postal: UNSW, Sydney, 2052 Telephone: (02) 9385 5017 Fax: (02) 9313 8624

Acid Sulfate Soils in the Mooball Creek Estuary

Table of Contents

Executive Summary ...... 4 1. Introduction ...... 6 1.1 Background to the Study Site ...... 6 1.2 An Introduction to Acid Sulfate Soils ...... 8 2. Methodology ...... 9 2.1 Soil Survey, Sampling and Analyses ...... 9 2.2 Long-term Drainwater Monitoring ...... 11 2.3 Long-term Groundwater Monitoring ...... 11 2.4 Rainfall Event Monitoring ...... 12 3. Results ...... 13 3.1 Catchment ASS Assessment – Scale & Severity ...... 13 3.2 ASS Discharge – Rainfall Event Monitoring ...... 16 3.3 Landscape Processes – Long-term Monitoring ...... 21 3.4 Preliminary Prioritised Remediation Plan ...... 24 3.4.1. Burringbar Creek ...... 24 3.4.2. XY Drain & Crabbes Creek ...... 24 3.5 Further Investigative Works ...... 25 4. Conclusions ...... 27 5. Acknowledgements ...... 28 6. References ...... 29 Appendix A ...... 30 Appendix B ...... 31 Appendix C ...... 32 Appendix D ...... 35 Appendix E ...... 37 Appendix F ...... 39 Appendix G ...... 40

Acid Sulfate Soils in the Mooball Creek Estuary

Executive Summary

This report details the results of field investigations and water quality monitoring studies which aimed to determine the scale and relative severity of ASS discharge in the Mooball Creek Catchment, culminating in a preliminary remediation plan. The study was undertaken in-line with the final scoping report “Draft Scope for ASS Investigations: Mooball Catchment”, prepared in February 2014. Works undertaken during this study include field investigations in March, May and November 2014 and two rainfall event monitoring campaigns which were carried out in September 2014 and late December 2014/early January 2015.

The key findings of this study are summarized in point form below:

• Sulfidic clay sub-soils lie adjacent to the upper to mid-lower reaches of Burringbar Creek (Main Drain), Crabbes Creek (OP Drain), XY Drain and Sheens Creek. These potential acid sulfate soils (PASS) are mostly used for cattle grazing (i.e. pasture). In contrast, actual acid sulfate soils (AASS) dominate soils used for sugarcane cultivation with most having a sand texture.

• The upper reaches of Crabbes Creek and the unnamed drain lying near Kellehers Rd (directly west of southern Pottsville) lie adjacent to non-sulfidic soils, and therefore these soils will not contribute to ASS discharge.

• During this study ASS discharge from Burringbar Creek contributed the greatest quantities of aluminium (Al), relative to Crabbes Creek and the XY Drain. For example, 5- fold greater quantities (on average) of Al were released from Burringbar Creek during the 2 rainfall events monitored.

• Unrestricted tidal flushing in the entire catchment has a positive effect on pH and ASS contaminant concentrations in drainage waters.

• Field drains around the intersection of Hull Rd and Willis Way were identified to be contributing to ASS discharge into Burringbar Creek and appear to be the area of greatest concern in this catchment. As such, modifications to these drains would be considered a preliminary priority remediation measure to undertake.

• The upper reaches of the XY drain, between Pottsville Rd and Willis Way, were also observed as being the major source of ASS discharge into this drainage system. Limited drainage around this area indicates that the XY drain itself and adjacent soils are most

Acid Sulfate Soils in the Mooball Creek Estuary

likely responsible for this observation. As such, shallowing of the XY drain in this area could be considered as a secondary priority remediation measure, if further studies establish that field drains are not the primary source of ASS discharge.

• Limited access to sites adjacent to Crabbes and Sheens Creeks has precluded a thorough preliminary investigation of the landscape processes and areas responsible for the discharge of ASS contaminants in the respective catchments. However, the limited data obtained suggest that ASS contaminants are being discharged into these creeks from areas south/east (downstream) of Crabbes Creek upstream crossing with Wooyung Road and Sheens Creek. Further investigative work is required in these areas to develop prioritised (and suitable) remediation plans.

Acid Sulfate Soils in the Mooball Creek Estuary

1. Introduction

1.1 Background to the Study Site The key area of investigation in this report is the Mooball Creek Catchment (Figure 1), located mainly south, south-east of Pottsville on the coast of the Pacific Ocean. Acid flows from acid sulfate soil (ASS) disturbance, and a decline in the general health of the Mooball Creek, have been identified as issues of concern in the Mooball Creek Estuary (Tweed Shire Council, 2013). Indeed, based on ground surface elevation, areas within the catchment have been designated as a ‘high probability of occurrence of ASS’ on the New South Wales Natural Resource Atlas (Appendix A).

Figure 1. Map of the Mooball Creek Catchment indicating the location of Sheens Creek, Burringbar Creek (Main Drain), Crabbes Creek (OP Drain) and the XY Drain. These are the 4 major waterways which drain into the Mooball Creek Estuary. The red circles indicate the location of water quality monitoring loggers installed by Tweed Shire Council in July/August 2014.

Within the catchment a number of constructed drainage channels enter the Mooball Creek estuary from the west. These drainage channels connect Mooball Creek Estuary to three of the

Acid Sulfate Soils in the Mooball Creek Estuary major waterways in the catchment – Sheens Creek, Burringbar Creek and Crabbes Creek. There are at least six other minor (modified) creeks which discharge into the estuary. While Crabbes and Burringbar Creeks exist in a modified natural form in the upper catchment, within the floodplain the creeks have been heavily modified for the purposes of drainage.

There is currently a lack of information regarding the extent and severity of ASS discharge into the Mooball creek estuary, despite extensive work on ASS identification and remediation for more than 20 years in the Tweed River, Clothiers/Reserve and Cudgera/Christies Creek catchments. Based on ASS mapping, and an assessment of landscape, drainage works and aerial photography, an ASS problem in the Mooball Creek Catchment is presumed to exist. Observations of the channels draining into the estuary also display large amounts of orange staining (Figure 2) indicative of high concentrations of iron (Fe) being discharged into the estuary, however, the acidity and concentrations of aluminum (Al) and Fe being discharged, and the location of ASS discharge hotspots (if they exist), have not been determined. As such, one of the major goals of this study was to establish the scale and relative severity of ASS discharge into the Mooball Creek estuary.

Figure 2. Iron staining of drain sediments in the XY Drain (09/03/2014) near the water quality monitoring logger.

Acid Sulfate Soils in the Mooball Creek Estuary

1.2 An Introduction to Acid Sulfate Soils Recognisant of the various backgrounds of stakeholders having vested interests in the Mooball catchment and estuary we believe that a brief chemical introduction to ASS is warranted. Acid sulfate soils refers to soils which contain, or previously contained, elevated concentrations of metal sulfides, principally pyrite (FeS2) and/or mackinawite (FeS). The latter is often referred to as monosulfidic black ooze (MBO). Sulfides are reduced inorganic species which readily undergo oxidation when exposed to oxygen, resulting in the generation of acidity (i.e. H+) according to equation 1 (in the case of pyrite).

FeS + O + H O Fe + 2SO + 2H (1) 7 2+ 2− + 2 2 2 2 → 4 The resultant acidity is able to dissolve naturally occurring minerals containing Al and Fe in the soil, resulting in the release and discharge of toxic concentrations of these metals into neighbouring waterways. The release of Al and Fe can trigger large-scale fish kills and the deoxygenation of waterways; affect the hatching, survival and growth rates of a wide range of aquatic species; reduce fish migration; and alter water plant communities as a result of weed invasion by acid-tolerant species (Tulua, 2007).

Much of the toxic effects associated with Fe and Al are due to chemical transformations which occur following the release of dissolved forms of these metals from the soil. For example, the 2+ oxidation and precipitation of ferrous iron (Fe ) consumes large amounts of oxygen (O2) and produces acidity (H+) according to equation 2.

Fe ( ) + O + H O Fe(OH) ( ) + 2H (2) 2+ 1 5 + aq 2 2 2 2 3 s → 3+ Similarly, the precipitation of dissolved aluminium (Al (aq)) results in the production of acidity (H+), as demonstrated in equation 3.

Al ( ) + 3H O Al(OH) ( ) + 3H (3) 3+ + aq 2 → 3 s In addition to the toxic effect of the acidity produced, Al toxicity also results from the

precipitation and deposition of Al colloids (i.e. Al(OH)3(s)) onto the gills of fish, and the formation of certain Al species which disturb ion regulation and respiration, ultimately starving fish of oxygen (Gensemer and Playle, 1999). The precipitation of solid iron oxides (or Fe(OH)3 (s)) can also affect fish respiration, and also presents aesthetic issues, as this results in unsightly red/orange “stains” in the estuary.

Acid Sulfate Soils in the Mooball Creek Estuary

Soils, such as ASS, which contain metal sulfides are termed “sulfidic” soils. Upon oxidation, the 2- + soils become “sulfuric” due to the production of sulfuric acid (SO4 and H ), as indicated in equation 1. Acid sulfate soils which are not oxidised (i.e. sulfidic) are often termed potential acid sulfate soils, represented by the acronym PASS. Conversely, if a particular ASS soil has undergone oxidation of (part of) its sulfidic horizon, the soil horizon is known as an actual acid sulfate soil (AASS). Figure 3 demonstrates a typical acid sulfate soil and its various soil horizons.

Figure 3. Typical acid sulfate soil profile displaying soil horizons which are likely to be present.

The oxidation of metal sulfides in these soils can occur due to natural weathering processes, such as seasonal climatic changes, but is also accelerated by their exposure to air, as occurs when these soils are excavated or when rates of drainage or evapotranspiration are increased.

2. Methodology

2.1 Soil Survey, Sampling and Analyses To obtain a basic determination of the spatial extent of ASSs within the Mooball Creek catchment, 21 soil samples were collected in March and May 2014. Soil profiles were excavated with a 10 cm-diameter hand auger to depths up to 2 m below the ground surface. 9

Acid Sulfate Soils in the Mooball Creek Estuary

The soil sampling locations are shown in Figure 4 and the associated GPS coordinates are provided in Appendix B. The depth of any ASS fronts were determined as required, and the soils inspected for the presence of iron oxides (i.e. orange or red rust-like stains), providing an indicator of ASS oxidation. Field notes, made during sampling, are recorded in Appendix C.

Figure 4. Map of the Mooball Creek Catchment indicating the location of soil sampling sites. GPS coordinates are provided in Appendix B.

Soil samples from AASS and PASS horizons (where present/could be obtained) were preserved in air-tight bags and transported to UNSW in coolers for further analysis. Samples which possessed an obvious sulfidic layer (as indicated by the presence of a deep blue/grey soil layer) were analysed for chromium (Cr) reducible sulfur (S), and other related parameters, at the Environmental Analysis Laboratory, Southern Cross University. Samples which displayed visible ASS oxidation (i.e. the presence of red/orange mottles) were also analysed for pH as well as porewater and exchangeable Al concentrations. Porewater and exchangeable Al were determined on 1:5 weight/weight soil:solution extracts using field moist soils (adjusted to oven- dry soil weight). Porewater Al was obtained after equilibration with high purity water (> 18.2 MΩ/cm) for 24 hr. Similarly, exchangeable Al was also determined from suspensions

Acid Sulfate Soils in the Mooball Creek Estuary equilibrated for 24 hr with 1 M potassium chloride (KCl). Following equilibration, porewater pH was measured and samples from both extractions were then filtered through 0.22 µm filters for analysis of Al via inductively coupled plasma-optical emission spectroscopy (i.e. ICP-OES). All samples were measured in duplicate.

2.2 Long-term Drainwater Monitoring Based on the results of the soil survey completed in May 2014, three water quality monitoring (WQM) loggers, that continuously measure pH, redox potential, conductivity, temperature and dissolved oxygen concentrations every hour, were stationed along the XY Drain, Burringbar Creek (Main Drain) and Crabbes Creek (OP Draink) at positions indicated by the red circles in Figure 1. These were installed by Tweed Shire Council in July/August 2014. A WQM logger was not placed in Sheens Creek as agreement with the landholder could not be reached.

2.3 Long-term Groundwater Monitoring In order to observe how groundwater levels in fields adjacent to the drains fluctuated in response to changing drainwater levels, Odyssey capacitance probes were installed at 3 sites adjacent to Burringbar Creek and the XY Drain, located near soil sampling sites 3, 6 and 13 (Figure 4). These sites were selected as they represent three of the major ASS types/land use combinations in the catchment i.e. heavy clay/pasture (site 3), heavy clay/cane (site 13) and sandy soil/cane (site 6). Holes for the capacitance probes were hand-augered to approximately 1.5 to 2 m deep along a transect perpendicular to the drain, and at 3 increasing distances from the drain edge (Appendix D). Brief details including the location of each site and the distance of the holes from the drain edge are provided in Table 1 below. All capacitance probes within a transect were surveyed to a capacitance probe installed in the drain. Therefore, water height measurements within a transect are relative, but internally consistent.

Table 1. Location of sites where capacitance probes were installed for groundwater monitoring, and the distance of each capacitance probe to the drain edge (see Appendix D). Distance of holes to drain edge Site Hole 1 Hole 2 Hole 3 Cane field adjacent to Main Drain ~50 m 5.6 m* 15.3 m 33.5 m upstream from WQM Cane field adjacent to XY Drain ~25 m 1.1 m 6.2 m 19.5 m upstream from WQM Pasture adjacent to XY Drain near Hull’s Rd 1.8 m 7.5 m 25.3 m *Note: There is a road between the cane field and the drain and, therefore, we were unable to place the first capacitance probe any closer to the drain.

Acid Sulfate Soils in the Mooball Creek Estuary

2.4 Rainfall Event Monitoring Following rainfall events in late August and late December 2014 (Figure 5), drainwater samples were collected at the same locations as the WQM loggers. In most cases, auto-samplers were used to collect 500 mL drainwater samples every 1 to 2 hr over a 3 (September) or 6 day period (December/January). During the second rainfall event, grab samples were also taken throughout the catchment to further identify sources of ASS contaminants being discharged into the drains.

80 70 (a) 60 50 40 30

Rainfall (mm) Rainfall 20 10 0 15-Aug 16-Aug 17-Aug 18-Aug 19-Aug 20-Aug 21-Aug 22-Aug 23-Aug 24-Aug 25-Aug 26-Aug 27-Aug 28-Aug 29-Aug 30-Aug 31-Aug 1-Sep 2-Sep 3-Sep 4-Sep 5-Sep 6-Sep 7-Sep 8-Sep 9-Sep 10-Sep 11-Sep 12-Sep 13-Sep 14-Sep 15-Sep 16-Sep 17-Sep 18-Sep 19-Sep 20-Sep 21-Sep 22-Sep 23-Sep 24-Sep 25-Sep 26-Sep 27-Sep 28-Sep 29-Sep 30-Sep

Day/month 100 (b) 80

Rainfall (mm) Rainfall 20

0 15-Dec 16-Dec 17-Dec 18-Dec 19-Dec 20-Dec 21-Dec 22-Dec 23-Dec 24-Dec 25-Dec 26-Dec 27-Dec 28-Dec 29-Dec 30-Dec 31-Dec 1-Jan 2-Jan 3-Jan 4-Jan 5-Jan 6-Jan 7-Jan 8-Jan 9-Jan 10-Jan 11-Jan 12-Jan 13-Jan 14-Jan 15-Jan 16-Jan 17-Jan 18-Jan 19-Jan 20-Jan 21-Jan 22-Jan 23-Jan 24-Jan 25-Jan 26-Jan 27-Jan 28-Jan 29-Jan

Day/month Figure 5. (a) Rainfall in the Mooball Catchment area from the 1st of August until 30 September 2014, with the event monitoring dates circled in red. (b) Rainfall in the Mooball Catchment area from the 1st of December 2014 until 30 January 2015. Event monitoring dates are circled in red. Rainfall data was sourced from the Bureau of Meteorology (BOM), from the closest available record (Fairview Farm, Mullumbimby, 16.7 km from the catchment).

All water samples were filtered (0.22µm) and acidified (1: 1000 vol/vol using 70% HNO3) in the field and stored in the dark until they could be refrigerated, and then transported to UNSW for analysis. The pH of the samples was determined from the associated WQM data. Elemental analyses for Al and Fe were performed by ICP-OES. Appropriate quality controls were performed including the analysis of blanks, frequent recalibration and the recovery of spiked blanks, to ensure meaningful data was obtained.

Drainwater level heights (hdrainwater, t) were automatically recorded at 15 minute intervals with

Odyssey capacitance probes and corresponding water velocity measurements (νdrainwater, t) were

Acid Sulfate Soils in the Mooball Creek Estuary manually recorded for each drainwater sample collected using a SonTek Acoustic Doppler Velocimeter. Note that the velocity measurements were only measured when the drains were discharging to the Mooball estuary, and not when tidal water was moving upstream, to ensure that measures of discharge, only, were acquired.

The capacitance probes were surveyed to the drain transects and the cross-sectional area of the drainwater section at a specific time interval (Adrainwater, t) was determined. These data were

used to calculate the drainwater discharge (volume) at a specific time interval (Qdrainwater, t), according to equation 4. Using the contaminant concentrations determined on drainwater

samples collected with the auto-samplers (Ccontaminants, t) at the corresponding time interval, an

elemental discharge or flux (Fcontaminants, t) for that time point was determined according to equation 5.

Qdrainwater, t = νdrainwater, t + Adrainwater, t (4)

Fcontaminants, t = Qdrainwater, t + Ccontaminants, t (5)

3. Results

3.1 Catchment ASS Assessment – Scale & Severity Of the 21 soil sampling sites, 13 had an identifiable PASS soil horizon (Appendix C). Samples from 12 of these sites were sent to Environmental Analysis Laboratory (Southern Cross University) for measurements of reduced inorganic sulfur (RIS) and other related parameters (Appendix E). Reduced inorganic sulfur is a measure of the concentration of iron sulfides in the soils. At 4 sites, augering had to be abandoned at various depths as groundwater was encountered which made further removal of soils from the hole impractical (Appendix C). It is, therefore, unknown if these sites also had PASS at depth. The PASS soil materials generally had either a fine clay or coarse sand texture (Appendix E). Accordingly, the fine clay PASS materials generally had much higher RIS concentrations than their coarse sand counterparts (Table 2 and Appendix E). The exception to this observation was the PASS collected at site 16 in the upper reaches of Crabbes Creek which returned a % RIS value of 0.071 - indicating that this sample was, in fact, not a PASS. Otherwise according to their texture, all samples that were tested can be considered as PASS (Appendix E).

In order to better visualise these results in context to the location of the sampling sites, Figure 6 segregates the sites according to the % RIS measured in the PASS. While the cutoff of 0.5% RIS is arbitrary, it is clear from Figure 6 that those sites having the highest % RIS occur in the upper reaches of Sheens Creek and XY Drain and in the middle reaches of Burringbar and Crabbes

Acid Sulfate Soils in the Mooball Creek Estuary

Table 2. Percentage of reducible inorganic sulfur (% RIS) in PASS and average porewater pH and porewater/extractable Al concentrations in AASS at each sampling site. Grey shading highlights those soils which did not possess a visible AASS horizon. Values in bold red indicate a high ASS risk and those in bold orange indicate a moderate ASS risk.

Soil Site # % Al Al AASS Sample pH porewater*** extractable Soil Type Soil Texture (nearby) RIS (mg Al/kg soil) (mg Al/kg soil) Depth (cm) 1 (Kellehers Rd) - * -** -** -** - Non-ASS Sand 2 (Kellehers Rd) - - - - - Non-ASS Sand 3 (XY drain) 2.29 - - - - AAS (PASS at 0.85m +) Clay 4 (XY drain) 0.51 3.23 24.6±9.8 155±28 60 ASS (PASS at 0.9m +) Sand 5 (XY drain) 0.14 4.45 1.2±0.01 632±40 40 ASS (PASS at 1.3m +) Sand 6 (XY drain) 0.27 4.96 0.6±0.1 61.4±0.1 80 ASS (PASS at 1.2m +) Sand 7 (XY drain) 0.37 5.23 1.6±0.4 27.6±0.2 60 ASS (PASS at 1.2m +) Sand 8 (XY drain) - 5.48 1.4±0.3 15.7±0.1 40 Non-ASS Sand 9 (Main drain) - 4.72 1.9±0.7 694±16 100 ASS (no PASS <2m) Clay 10 (Main drain) - 4.47 1.2±0.01 934±32 40 ASS (no PASS <2m) Clay 11 (Main drain) 0.78 4.55 2.0±0.1 934±70 80 AAS (PASS at 1.1m +) Clay 12 (Main drain) 4.43 3.84 18.4±3.3 1210±26 95 AAS (PASS at 1.5m +) Clay 13 (Main drain) - 3.87 10.1±0.9 1200±89 150 ASS (PASS at 1.9m +) Clay/sand 14 (Main drain) - 5.18 1.5±0.2 24.8±0.05 60 Non-ASS Sand 15 (Main drain) - 4.32 1.1±0.03 38.9±1.1 70 Non-ASS Sand 16 (OP drain) 0.07 - - - - Non-ASS Clay 17 (OP drain) 2.79 - - - - ASS (PASS at 1.1m +) Clay 18 (OP drain) 3.08 - - - - ASS (PASS at 0.75m +) Clay 19 (OP drain) - - - - - Non-ASS Sand 20 (Sheens Ck) 2.46 5.26 0.8±0.02 17.0±0.01 70 ASS (PASS at 1.0m +) Clay 21 (Sheens Ck) 0.30 5.05 1.2±0.01 755±1 30 ASS (PASS at 1.4m +) Sand * Dash(-) indicates % RIS not determined due to a lack of a visible (blue) sulfidic reduced PASS horizon or PASS sample could not be obtained. ** Dash(-) indicates pH or extractable Al not determined due to a lack of a visible oxidised soil horizon.

Acid Sulfate Soils in the Mooball Creek Estuary

Creeks. Disturbance of PASS in these areas will, therefore, generate the most deleterious environmental impacts.

Figure 6. Map of the Mooball Creek Catchment showing colour-coded soil sampling sites based on the %RIS measured in the PASS soil horizons.

At sites where soils displayed an oxidised AASS horizon, porewater pH and concentrations of porewater Al and extractable Al were measured. For those ASS which did not display any oxidation, the amount of Al able to be extracted from these soils will be small and the pH will not be highly acidic as it is the oxidation of iron and sulfur within these soils which results in the formation of acidity, and the subsequent mobilization of Al. As such, measurements on these soils were not undertaken.

Figure 7 indicates that soils with the highest concentrations of extractable Al are generally concentrated along Burringbar Creek (Main Drain) and around the mid to upper reaches of the XY Drain and also along Sheens Creek. While limited sampling along Sheens Ck prevents any estimates of the scale of ASS risk in this area, the results shown in Figure 7 suggest that the

Acid Sulfate Soils in the Mooball Creek Estuary current greatest ASS risks are located around the mid-section of Burringbar Creek. This represents an area of approximately 4 km2 in total and broadly corresponds to soils with a clay- like texture, high % RIS in the PASS horizons (when present) and which are used for sugarcane cultivation.

Figure 7. Map of the Mooball Creek Catchment showing colour-coded soil sampling sites based on the concentration of extractable Al in the AASS soil horizons.

3.2 ASS Discharge – Rainfall Event Monitoring Acid sulfate soil discharge is of greatest concern after heavy rainfall events that saturate the soil profile, which then facilitates acidic groundwater flow towards the drains. Although a first ‘flush’ of ASS contaminants is often observed during these events, the highest concentrations of Fe and Al are generally released later in the hydrograph, i.e. 1 to 2 days after the rainfall has ceased. However, acidic conditions can persist for weeks depending on the drainage conditions of the catchment. Acid sulfate soil discharge (principally Al) was investigated following periods of intense rainfall in August 2014 and again in late December 2014/early January 2015.

Acid Sulfate Soils in the Mooball Creek Estuary

Figure 8 details the amounts of Al (in kg) which discharged through Burringbar Creek, Crabbes Creek and the XY Drain every hour during outgoing tidal movements in early September 2014, and over late December/early January 2015, as a result of heavy rainfall prior to these periods (Figure 5). The results have been normalised to the volume of water discharged and represent the amount of Al exported over a 1 m length. It is evident from Figure 8 that the quantities of Al which discharged through Burringbar Creek were often considerably larger than those at Crabbes Creek and the XY Drain.

Figure 8. Measurements of the quantity of Al (in kg) discharged through Burringbar Creek (Main), Crabbes Creek (OP) and the XY drain (at the WQM loggers) over the rainfall event monitoring periods in (a) early September, 2014 and (b) late December 2014/early January 2015. Note that measurements were only made when the creeks/drain were discharging into the Mooball estuary, and not when tidal flow was creating a negative discharge.

Indeed, the amount of Al which discharged through Burringbar Creek was up to 5-fold greater following rainfall in late December 2014 (Figure 8). The concentrations of Al measured in

Acid Sulfate Soils in the Mooball Creek Estuary

Burringbar and Crabbes Creeks following this rainfall event, however, were quite similar (Figure 9). As Burringbar Creek is much deeper and wider than Crabbes Creek and the XY Drain it is therefore able to discharge larger volumes of water, and also tends to discharge water at a faster rate. This explains the much higher quantities of Al being discharged via Burringbar Creek. Iron discharge demonstrated similar trends to Al, albeit at slightly lower concentrations (data not shown).

Figure 9. Concentrations of Al measured at the WQM loggers in Burringbar Creek (Main), Crabbes Creek (OP) and the XY Drain over the rainfall event monitoring period in late December 2014/early January 2015.

The significant decrease in Al concentrations in Burringbar Creek (and Crabbes Creek) around the 1st of January (Figure 9) coincided with heavy rainfall in the Burringbar Hills during the night of the 31st December. As a result this water, bright orange in colour (Appendix F), diluted any ASS discharge from adjacent soils in Burringbar Creek for approximately 24 hr. The freshwater ‘pulse’ through Crabbes Creek was less rapid but also maintained low Al concentrations for about 12 hr. During the December rainfall event monitoring, aluminium concentrations measured at the WQM logger in the XY Drain were generally much lower than at the other two sites. Conductivity readings (data not shown) were also much higher in this drain indicating that pH was being buffered from saline tidal water. These results indicate that insufficient rainfall had fed into the XY Drain to flush the system and induce ASS discharge. Given these types of differences in hydrological dynamics, it is difficult to directly compare results between the creeks and drains for each event. However, for the two events monitored, Burringbar Creek consistently discharged the highest quantities of Al (Figure 8).

In order to gain a broader perspective of the scale of ASS in this area, and to further determine major sources of ASS discharge, grab samples from side drains and upstream from the WQMs over the period 30th December 2014 to 3rd January, 2015 were also collected. An example of

Acid Sulfate Soils in the Mooball Creek Estuary the results obtained along Burringbar Creek is shown in Figure 10 where it can be noted that four side drains, near the intersection of Hulls Rd and Willis Way, are ASS “hotspots” possessing very high concentrations of aluminium and acidity (Table 3). Samples collected upstream from these drains indicated good water quality, further implicating these four drains as the major contributors to ASS discharge into Burringbar Creek. Nevertheless, water samples were not collected from drains along the southern side of Burringbar Creek (between Hulls Rd and the WQM, Figure 10). It is, therefore unclear if these drains were also contributing to ASS discharge.

Figure 10. Map indicating side drains and upstream sites along Burringbar Creek where grab samples were taken on the 30th December 2014. Sites marked red = extreme and orange = high contributor to ASS discharge in terms of the measured Al concentrations and acidity in these samples (refer to Table 3 for specific results). White dots indicate sites where Al concentrations and acidity were low and therefore do not present an ASS discharge problem. Samples were not taken from the drain indicated in blue (unknown) and all other drains on the southern side of Burringbar Creek.

Based on the results shown in Table 3, it would also appear that ASS hotspots occur around the ‘Upstream’ sampling site of the XY Drain (Appendix G) and at some point downstream from the ‘Upstream 2’ sampling site in Crabbes Creek (Appendix G). Both of these areas are currently under pasture and used for cattle grazing, although drainage patterns indicate that at least some of the land was used for sugarcane production at some stage in the past. Due to either inaccessibility and/or time constraints, further grab samples around these areas were not obtained. However, it was noted that many field drains around the ‘Upstream’ site of the XY Drain did not appear to connect directly into the drain.

Acid Sulfate Soils in the Mooball Creek Estuary

Table 3. Aluminium concentrations (mg/L) and pH values of grab samples taken from various sites around the Mooball catchment from 30th December 2014 to 3rd January 2015. Sites for Burringbar Creek are noted in Figure 10, while the sites for the XY Drain and Crabbes Creek are shown in Appendix G. Note: red = extreme, orange= high and yellow = moderate contributor to ASS discharge. Burringbar Ck Upstream 1 Upstream 2 Drain 1 Drain 2 Drain 3 Drain 4 WQM Date

30/12/14 pH 6.43(11.00am) 5.11(11.05am) 4.29(10.55am) 3.84(10.40am) 3.16(10.45am) 3.04(11.55am) 4.56(11.00am) Al 0.02 0.12 3.48 11.3 16.7 34.1 5.16

31/12/14 pH 5.99(11.10am) 5.24(11.15am) 4.21(11.00am) Al 0.02 0.08 8.26

2/1/15 pH 6.14(12.05pm) 5.42(12.00pm) 4.01(1.00pm) 3.74(1.03pm) 3.36(1.05pm) 3.23(1.05pm) 4.67(1.00pm) Al 0.04 0.05 3.55 8.96 14.1 42.8 0.42

3/1/15 pH 6.56(4.05pm) 5.35(4.00pm) 4.52(4.00pm) Al 0.02 0.07 5.37

XY Drain Upstream WQM

31/12/14 pH 3.74(11.35am) 5.23(12.00pm) Al 2.36 0.13

1/1/15 pH 3.58(3.15pm) 4.73(3.00pm) Al 3.44 0.96

2/1/15 pH 3.49(10.15am) 5.51(10.00am) Al 3.08 0.26

3/1/15 pH 3.43(4.12pm) 4.67(4.00pm) Al 2.74 1.36

Crabbes Ck Upstream 1 Upstream 2 WQM

30/12/14 pH 5.73(12.25pm) 4.77(12.20pm) -* Al 0.09 0.46 7.59(12.12pm)

31/12/14 pH 5.48(12.15pm) 4.89(12.20pm) 3.74(12.10pm) Al 0.06 0.33 10.2

1/1/15 pH 6.24(2.50pm) 6.22(2.45pm) - Al 0.04 0.08 6.60(2.30pm)

2/1/15 pH 6.22(11.50am) 5.79(11.45am) - Al 0.04 0.08 0.11(11.30am)

3/1/15 pH 6.03(3.52pm) 5.76(3.50pm) - Al 0.14 0.01 3.45(3.30pm) * Dash(-) indicates pH not determined due to WQM logger failure.

Acid Sulfate Soils in the Mooball Creek Estuary

3.3 Landscape Processes – Long-term Monitoring Following both rainfall events the pH in Burringbar Creek and the XY Drain decreased by approximately 2 to 3 pH units (Figure 11). Given the log scale of pH, this represents a 100- to 1000-fold increase in acidity concentrations. Although WQM logger failure prevented the capture of pH data for Crabbes Creek (OP Drain) during both rainfall events monitored, over the long-term it can be seen that large fluctuations in pH also occur in this creek. The data shown in Figure 11 also indicate that ASS discharge (measured as acidity in this case) is primarily associated with rainfall events > 75 mm/day (based on rainfall data from Fairview Farm) over the period of time monitored. At other times the drain/creek water pH rebounds towards neutral pH values due to tidal flushing. These observations indicate that the unrestricted tidal flushing practiced in the catchment effectively increases pH during dry spells and, consequently, assists with mitigating the severity of ASS discharge into the Mooball Creek Estuary.

During approximately the first 1½ months of groundwater monitoring at the cane field sites located adjacent to Burringbar Creek and the XY Drain, groundwater levels remained below the maximum depth of the capacitance probes (Figure 12). Due to logger failure, drain water levels at the XY Drain pasture site were only recorded until the 3rd January 2015. However, it can be seen that tidal fluctuations were only recorded at this site at very high tides. These tidal movements are also reflected in groundwater levels measured at 1.8 and 7.5 m from the drain at these times indicating sub-surface hydraulic connectivity. However, similar groundwater fluctuations were not recorded at the hole 25.3 m from the drain suggesting that connectivity between the drain and groundwaters is at least limited to around < 10 m. Two other important features that can be ascertained from the data for this site is that groundwater fluctuations are much less pronounced (< 1 m) compared to the cane sites (> 2 m) and that groundwater levels consistently remained higher than the PASS soil horizon (Figure 11). The former observation is linked to the low evapotranspiration rates of pastures, compared to sugar cane, while the latter would explain why no AASS horizon was observed at this site. Taken together, any ASS discharge from this site would likely arise from the drain itself or limited areas (< 10 m) adjacent to the drain.

In contrast, groundwater levels measured in all the holes at the other two sites (when above the maximum depth of the capacitance probes) showed hydraulic connectivity to the creek/drain (Figure 12). At Burringbar Creek, tidal fluctuations can be observed 33.5 m from the drain edge at depths of ~1.75 m below the ground surface indicating that mole drains, if present, are not assisting with this connectivity. Similar conclusions can be made for the cane site on the XY Drain. Therefore, ASS discharge (from areas like these in the catchment) into the creeks or drains are likely to occur through field drains (Figure 10 and Table 3) as well as directly through sub-surface flow.

Acid Sulfate Soils in the Mooball Creek Estuary

Figure 11. Long-term WQM drain/creek water pH values and rainfall during the study period. Cyclical peaks in pH indicate the intrusion of higher pH estuarine water due to tidal influx. Main (Burringbar Creek), OP (Crabbes Creek). Missing data are a result of WQM logger failure. Rainfall data are from Fairview Farm, Mullumbimby (16.7 km from Pottsville).

Acid Sulfate Soils in the Mooball Creek Estuary

Figure 12. Groundwater levels relative to creek/drain water levels over the study period at sites located along Burringbar Creek and the XY Drain (shown in Appendix D). Data marked with a distance represents a groundwater measuring point at that distance from the drain edge. XY Drain (Pasture) is located upstream from XY Drain (Cane) near soil sampling site 3.

Acid Sulfate Soils in the Mooball Creek Estuary

3.4 Preliminary Prioritised Remediation Plan

3.4.1. Burringbar Creek While acknowledging the preliminary nature of this study, the obtained results indicate that the highest loads of Al and acidity are discharged through Burringbar Creek, relative to Crabbes Creek and the XY drain (Figure 8), with the source of these ASS contaminants corresponding to adjacent AASS containing high concentrations of exchangeable Al (Figure 7). Rainfall event monitoring suggests that the most problematic areas lie east and south of Hulls Rd to the bridge used for WQM on Burringbar Creek (Figure 10). In this area, ASS contaminants and acidity enter Burringbar Creek through at least four field drains (Figure 10) and possibly via sub-surface flow, though the latter was not directly quantified in this study. The four field drains are connected to drains north of Hulls Rd and, therefore, ASS contaminants and acidity could also be derived from these further afield cane fields. Further studies would be required to confirm this supposition.

In terms of severity, the peak maximum quantity of Al exported through Burringbar Creek during the December 2014/January 2015 rainfall event was comparable to an event measured at Black’s Drain in August 2007 (~130 kg/hr) (Collins et al. 2009) which was a known ASS ‘hotspot’ at the time. As such, preliminary remediation efforts would be best focused at reducing ASS contaminant and acidity discharge from the area discussed above adjacent to Burringbar Creek.

The four drains around the intersection of Willis Way and Hulls Rd are relatively deep on the southern side of Hulls Rd (Figure 13), presumably to allow for drainage from the cane fields north of Hulls Rd. Based on the two closest soil survey results (sites 11 and 12), the depth to AASS horizons around this area are also relatively deep at ~ 80-90 cm below the ground surface (Table 3). Therefore, further investigations would be required to identify the primary source of ASS contaminants and acidity in these drains. Nevertheless, it is clear that (parts of) this drainage system require(s) some modifications (i.e. shallowing) to help ‘retain’ the acidity and ASS contaminants in the soils and is, therefore, the most obvious remediation priority.

3.4.2. XY Drain & Crabbes Creek In this study, ASS ‘hotspots’ have also been delineated in areas upstream around the XY Drain and at Crabbes Creek downstream from the highest point the creek crosses Wooyung Rd. These areas are entirely used as pastures for cattle grazing with much less intensive drainage than that used for sugar cane cultivation. Based on the long-term groundwater monitoring at the upstream site of the XY Drain, hydraulic connectivity between ground- and drain-waters is restricted to soils around < 10 m from the drain. The soil survey result from site 18 adjacent to 24

Acid Sulfate Soils in the Mooball Creek Estuary

Crabbes Creek, being similar to the soils upstream along the XY Drain, suggests that this would likely be the case in this area as well. The limited hydraulic connectivity between ground- and drain-waters in these soil types/land uses has been a common observation in previous studies carried out around Christies Creek (Kinsela et al. 2009) and Black’s Drain (Collins et al. 2009).

Although less severe ASS contaminant discharge was measured at Crabbes Creek and the XY Drain, the groundwater monitoring results suggest that the ASS sources lie within the Drain/Creek itself and limited areas adjacent to them. As a secondary priority, shallowing of these drains in these areas to above the PASS horizon would be the most effective means to mitigate ASS discharge. However, further studies may be necessary to quantify ASS discharge from field drains that may still be directly connected to Crabbes Creek and the XY Drain.

Figure 13. Three of the four drains around the intersection of Willis Way and Hulls Rd.

3.5 Further Investigative Works The Mooball Estuary Catchment is large comprising a number of significant drains and creeks that are hydrologically dynamic and diverse. Major investigative activities of this study were limited to three major drainage systems - Crabbes Creek, Burringbar Creek and the XY Drain. Quantification of ASS discharge through Sheen’s Creek and the north arm of the XY Drain was not undertaken. Therefore, the unknown state of these two drainage lines need to be taken into consideration when assessing the remedial priorities provided in this report. Based on limited soil sampling (Table 2) and evidence of iron staining in creek sediments (Figure 14), it can be presumed that ASS discharge is occurring through Sheen’s Creek. Further studies are required to assess the relative severity of ASS discharge through this creek compared to that quantified in this report.

Acid Sulfate Soils in the Mooball Creek Estuary

Figure 14. Sheen’s Creek, looking east at the intersection of the Dunloe Sands bridge. Iron (red) staining is evident along the creek banks.

While preliminary ASS hotspots, and the landscape processes leading to ASS discharge, have been identified along Crabbes Creek, Burringbar Creek and the XY Drain, further studies that could improve remediation outcomes include:

Burringbar Creek 1) Quantifying the relative importance of ASS discharge from the southern drains leading into Burringbar Creek adjacent to the 4 drains identified in this study. - Are they as important a contributor to ASS discharge as the 4 northern drains? 2) A more intensive soil sampling program to determine depths to AASS horizons in the fields adjacent to the drains (both north and south of Hulls Rd), depths of field and mole drains (if present) and identifying the connectivity of the drainage systems.

Acid Sulfate Soils in the Mooball Creek Estuary

- This would aid in further delineating ASS hotspots and landscape processes resulting in ASS discharge and so lead to a better choice of drain/land management/remediation options. 3) Quantification of sub-surface ASS discharge into Burringbar Creek through the creek banks. - While any modifications to Burringbar Creek are unlikely to be feasible and/or practicable, the quantity of ASS discharge through groundwater flow was not measured in this study. The relative importance of drainwater to groundwater ASS discharge is, therefore, unknown.

Crabbes Creek 1) Soil sampling and general observations around the ASS hotspot identified were limited in scope and landscape processes leading to ASS discharge have been inferred from the results obtained at the XY Drain - where similar soils exist and land management is identical. While this is not an unreasonable supposition based on previous studies (Kinsela et al. 2009; Collins et al. 2009), ground truthing this section of Crabbes Creek would eventually be required to confirm these conclusions before any remedial works were to be undertaken.

XY Drain 1) Quantifying the relative importance/occurrence of ASS discharge from field drains around the upstream section of the XY Drain. - Are they an important contributor to ASS discharge? 2) Long-term groundwater/drainwater height measurements that cover a significant dry spell to determine if groundwater (and drainwater) levels decrease sufficiently to stimulate PASS oxidation in the drain and adjacent soils or if unrestricted tidal movement maintains sufficient drainwater levels to prevent oxidation occurring. This type of study would also be beneficial at Crabbes Creek.

4. Conclusions This is the first study of its kind to attempt to establish the scale, relative severity and landscape processes leading to ASS discharge into the Mooball Creek Estuary. Acid sulfate soils are widespread in the catchment draining into the estuary and most parent soils either consist of clay- or sand-textured PASS. The clay PASS contain significantly higher quantities of RIS and, if disturbed, will lead to a greater discharge of ASS contaminants and acidity when drainage allows. This preliminary study has shown that disturbed/oxidised ASS containing the highest concentrations of exchangeable Al occur adjacent to Burringbar Creek, which itself contributed

Acid Sulfate Soils in the Mooball Creek Estuary the greatest quantities of Al and acidity to the Mooball creek estuary, relative to Crabbes Creek and the XY Drain during two rainfall events that were monitored. Acid sulfate soil discharge into the Mooball Creek Estuary from Sheen’s Creek and the north-arm of the XY Drain was not quantified. As such, their contribution to ASS discharge into the estuary, relative to Burringbar Creek, Crabbes Creek and the XY Drain remains unknown. Further studies are suggested, particularly in Sheen’s Creek, to obtain a full quantitative picture of ASS discharge into the Mooball Creek Estuary.

Unrestricted tidal flushing in Burringbar Creek, Crabbes Creek and the XY Drain has a positive effect on pH and ASS contaminant concentrations in drainage waters, particularly during dry spells, and should be maintained across the catchment.

Field drains around the intersection of Hulls Rd and Willis Way were identified to be directly contributing to ASS discharge into Burringbar Creek and this area appears to be a priority for mitigating problems associated with ASS in this catchment. Further studies should be undertaken around this area to better delineate AASS horizons, drain connectivity, drain depth, and the presence of mole drains before any drain modifications be undertaken. A study exploring the quantity of ASS contaminants discharge from drains south of Burringbar Creek, adjacent to these areas, is also suggested to quantify their relative importance to the budget of ASS contaminants discharged.

Acid sulfate soil discharge from Crabbes Creek and the XY Drain was measured as being of secondary importance to Burringbar Creek. In the case of the XY Drain, an area between Pottsville Rd and Willis Way was observed as being the major source of ASS discharge into this drainage system. Long-term groundwater monitoring indicated that the XY drain itself and adjacent soils are most likely responsible for this observation. As such, if this is confirmed from future studies that establish that local field drains are not the primary source of ASS discharge in this area, shallowing of the XY drain could be considered as a secondary priority remediation measure. Based on (1) similarities between soils and land use/management and (2) previous studies undertaken in the Tweed Shire, it has been hypothesized that similar conditions to those observed upstream in the XY Drain occur along Crabbes Creek downstream (south/east) from Wooyung Rd, similar remedial works would, therefore, also be envisioned for this area.

5. Acknowledgements The authors wish to thank Peter Willis and Trevor, Colin and Gordon Forster for discussions about the history of their properties as well as permission to collect soil and water samples and install field equipment. Tweed Shire Council is also acknowledged for facilitating this study and providing the long-term WQM data. 28

Acid Sulfate Soils in the Mooball Creek Estuary

6. References Collins R, Jones A, Melville MD and Waite TD (2009) Suggested remedial works for the Black’s Drain catchment of the Tweed River floodplain. Findings from the ARC Linkage Project LP0455697 (2005 to 2008). Report 2009/24, Centre for Water and Waste Technology, The University of New South Wales, Sydney, NSW 2052, Australia. p. 16. Gensemer RW and Playle RC (1999) The bioavailability and toxicity of aluminium in aquatic environments. Critical Reviews in Environmental Science and Technology 29, 315-450. Kinsela A, Waite TD and Collins R (2009) Stream and groundwater quality relating to acid sulfate soil discharge: Christies Creek, north east NSW. Final Report. Report 2009/23, Centre for Water and Waste Technology, The University of New South Wales, Sydney, NSW 2052, Australia. p. 29. Tweed Shire Council (2013) Coastal zone management plan for the Tweed Coast Estuaries. Prepared on behalf of Tweed Shire Council by Hydrosphere Consulting Pty Ltd. pp. 161. Tulua MJ (2007) Acid sulfate soils remediation guidelines for coastal floodplains in New South Wales. NSW Department of Environment and Climate Change. pp. 136.

Acid Sulfate Soils in the Mooball Creek Estuary

Appendix A Screen shot of the New South Wales Natural Resource Atlas focusing on the Mooball Creek catchment. Areas shaded in red indicate locations where there is a ‘high probability’ of ASS occurrence, whereas brown indicates a ‘low probability’ of ASS occurrence. (http://www.nratlas.nsw.gov.au/)

Acid Sulfate Soils in the Mooball Creek Estuary

Appendix B GPS Coordinates of soil sampling sites.

1. 28°24’18.69” S, 153°32’41.00” E 2. 28°24’22.85” S, 153°32’50.36” E 3. 28°25’58.79” S, 153°32’03.19” E 4. 28°26’04.79” S, 153°32’11.01” E 5. 28°26’19.75” S, 153°32’30.78” E 6. 28°26’11.32” S, 153°32’41.09” E 7. 28°26’11.59” S, 153°32’52.96” E 8. 28°26’18.72” S, 153°33’11.08” E 9. 28°26’32.71” S, 153°31’10.27” E 10. 28°26’45.89” S, 153°30’53.01” E 11. 28°26’39.42” S, 153°31’28.35” E 12. 28°26’39.66” S, 153°32’02.37” E 13. 28°26’47.15” S, 153°32’29.04” E 14. 28°26’43.41” S, 153°32’43.74” E 15. 28°26’42.56” S, 153°32’58.27” E 16. 28°27’20.92” S, 153°31’00.69” E 17. 28°27’15.93” S, 153°31’44.29” E 18. 28°27’21.29” S, 153°32’17.53” E 19. 28°27’41.41” S, 153°32’24.19” E 20. 28°25’01.80” S, 153°32’03.57” E 21. 28°25’21.01” S, 153°32’43.73” E

Acid Sulfate Soils in the Mooball Creek Estuary

Appendix C Soil horizon descriptions.

Depth (cm) Observations

Site 1 Land use: Pasture 0-90 sand, no sign of ASS oxidation products

Site 2 Land use: Pasture 0-90 sand, no sign of ASS oxidation products

Site 3 Land use: Pasture 0-68 peat 68-85 fibrous organic matter intermixed with PASS 85-180 gelatinous, blue PASS

Site 4 Land use: Cane 0-50 Organic horizon (not peaty) 50-60 thin layer of actual acid sulfate soil (clay like) 60-65 transition zone, brown, oxidized 65-90 brown sand (oxidised?) 90-120 blue sand

Site 5 Land use: Cane 0-20 Organic horizon (not peaty) 20-30 Brown sand 30-38 dark clay with evidence of ASS oxidation 38-43 sand, oxidation zone 43-56 clay, gelatinous, evidence of oxidation 56-131 yellow sand (oxidized?), pH 4.5 131-160 blue sand

Site 6 Land use: Cane 0-49 Organic horizon (not peaty) 49-80 yellow sand, oxidized? 80-121 orange oxidised sand, pH 4.7 121-150 blue sand

Site 7 Land use: Cane 0-19 organic horizon (not peaty) 19-55 white beach sand 55-110 brown oxidised sand

Acid Sulfate Soils in the Mooball Creek Estuary

110-120 brown sand 120-150 blue sand

Site 8 Land use: Abandoned orchard 0-50 beach sand 50-66 AASS?, then abandoned as sand too wet

Site 9 Land use: Cane 0-87 loamy clay, dark brown topsoil 87-200 AASS??/Transition zone/ Very heavy, sticky, hard clay

Site 10 Land use: Cane 0-30 dark brown topsoil 30-75 AASS 75-100 Heavy dark brown transition zone? 100-165 very bright orange, very heavy, dry clay

Site 11 Land use: Cane 0-80 dark brown top soil 80-190 transition zone?? 190- PASS (at least to 200cm)

Site 12 Land use: Cane 0-65 top soil 65-95 AASS, very dark and little evidence of oxidation 95-150 AASS 150-190 PASS, starting to get more sandy with depth

Site 13 Land use: Cane 0-150 dark brown top soil 150-170 transition zone 170-190 sand layer (with traces of oxidation products) 190- blue clay/sand mixed layer

Site 14 Land use: Cane 0-95 dark brown top soil 95-170 white sand 170 abandoned as sand too wet

Site 15 Land use: Pasture 0-30 top soil 30-65 brown/white sand 65-90 AASS? Traces of oxidation products

Acid Sulfate Soils in the Mooball Creek Estuary

90-160 white sand 160 abandoned as sand too wet

Site 16 Land use: Cane 0-90 top soil, but more clay-like consistency 100-140 very fibrous, almost peat like layer in clay 140-155 PASS??

Site 17 Land use: Cane 0-60 very dark top soil 60-110 very fibrous, almost peat like layer in clay 110-170 clay PASS

Site 18 Land use: Pasture 0-75 organic peaty top soil 75-200 clay PASS

Site 19 Land use: Pasture 0-30 top soil 30-100 white sand 100 abandoned as sand too wet

Site 20 Land use: Pasture 0-70 organic rich, black top soil 70-100 brown clay, still organic rich 100-200 blue PASS

Site 21 Land use: Pasture 0-30 topsoil 30-55 brown sand 55-100 sand with oxidation products 100-135 white sand 135-180 blue sand

Acid Sulfate Soils in the Mooball Creek Estuary

Appendix D Transect of capacitance probes at the XY Drain located near the WQM logger. Distances are not to scale.

Transect of capacitance probes at the XY Drain (upstream, near soil sampling site 3). Distances are not to scale.

Acid Sulfate Soils in the Mooball Creek Estuary

Transect of capacitance probes at Burringbar Creek located near the WQM logger. Distances are not to scale.

Acid Sulfate Soils in the Mooball Creek Estuary

Appendix E Results of acid sulfate soil analyses performed by Environmental Analysis Laboratory, Southern Cross University.

Acid Sulfate Soils in the Mooball Creek Estuary

Appendix F Burringbar Creek facing west at the site of the WQM logger 1st January 2015, 11:57am.

Burringbar Creek facing east at the site of the WQM logger 1st January 2015, 11:57am.

Acid Sulfate Soils in the Mooball Creek Estuary

Appendix G Grab sample sites along the XY Drain.

Grab sample sites along Crabbes Creek.