Exploiting Natural Processes to Effectively Remediate ... Cudgen Lake (Clothiers & Reserve Cks) is the coastal catchment immediately south of the Tweed River which has been the subject

Exploiting Natural Processes to Effectively Remediate Acidified Coastal Environments

ARC Linkage Project LP110100480

Annual Progress Report for 2011

Richard Collins, Yliane Yvanes-Giuliani and Jackie Stroud

April 2012

DOCUMENT STATUS RECORD

Project Title: Exploiting Natural Processes to Effectively Remediate Acidified Coastal Environments

Client: Tweed Shire Council, Sebastien Garcia-Cuenca Andrew Tickle and Robert Quirk, NSW Cane Growers Association Rick Beattie, NSW Sugar Milling Co-operative

Document Title: Exploiting Natural Processes to Effectively Remediate Acidified Coastal Environments. ARC Linkage Project LP110100480. Annual Progress Report for 2011

Document Number: 2012/1 File Name: LP110100480 APR for 2011

Issue No.

Date of Issue Description Signatures Authors Checked Approved

1 2nd April 2012 Annual Progress Report

RC RC RC

Notes

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(s) 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: UNSW Water Research Centre School of Civil and Environmental Engineering University of New South Wales Physical: Building H22, Vallentine Annexe Botany Street Gate 11 Kensington. Postal: UNSW, Sydney, 2052 Telephone: (02) 9385 5017 Fax: (02) 9313 8624

Name: Richard Collins Email: [email protected]

© Water Research Centre

Commercial-in-confidence 3

TableofContents

EXECUTIVE SUMMARY .......................................................................................................................................... 4

INTRODUCTION ........................................................................................................................................................ 5

BACKGROUND ............................................................................................................................................................ 5

UNSW PROJECT PERSONNEL ..................................................................................................................................... 7

PROJECT METHODS ................................................................................................................................................ 7

RESULTS ...................................................................................................................................................................... 8

BLACKS DRAIN ........................................................................................................................................................... 8

CHRISTIES CK ........................................................................................................................................................... 13

ALUMINIUM SOLUBILITY IN ASS USED FOR SUGAR CANE CULTIVATION ................................................................... 15

CONCLUSIONS ......................................................................................................................................................... 16

ACKNOWLEDGEMENTS ....................................................................................................................................... 17

REFERENCES ........................................................................................................................................................... 17

Commercial-in-confidence 4

ExecutiveSummary

This report details the annual progress of the Australian Research Council (ARC) Linkage project

LP110100480 ‘Exploiting Natural Processes to Effectively Remediate Acidified Coastal Environments’

which commenced in 2011 with industry partners the Tweed Shire Council, NSW Cane Growers

Association and NSW Sugar Milling Co‐operative. The main aims of the project are to undertake:

1) Research which identifies acid sulfate soil (ASS) hotspots within 3 catchments in the Tweed Shire

and then the most suitable remediation strategies to reduce ASS discharge on a catchment scale;

2) On‐ground remedial works identified in (1) above; and

3) Field measurements to determine the efficacy of the remedial works in reducing the discharge of

problematic contaminants (particularly iron and aluminium) from the 3 catchments.

The major field research undertakings in 2011 focused on two catchments, namely Blacks Drain and

Christies Ck. In the former catchment, research was aimed at determining how effective remedial works

conducted in 2009 have been in reducing the discharge of iron and aluminium from the upper catchment

area. In the latter catchment, previous research was utilised with limited further sampling to identify

problematic ASS areas and potential techniques to improve water quality from this catchment. Some of

the key findings are summarised in point form below:

Examination of comparable (i.e. wet season) individual rainfall events prior to and after the

remediation was carried out at Blacks Drain in 2009 indicates that the discharge of iron from this

catchment has decreased by approximately 20‐fold. Data interpretation is continuing to identify the

processes responsible for such a dramatic response to remediation;

Based on a number of previous field studies, a hydraulically isolated sugar cane block in the

downstream portion of Christies Ck was selected as an area of priority for remediation. Remedial

works proposed for this area included a) optimisation of the drain pumping regime discharging into

Christies Ck, and b) drain shallowing of the 2 major drains at least to the invert of the field drains.

Actual remedial works undertaken in August/September 2011 included limited drain shallowing in

one of the major drains, improvements to the drain batters and a liming trial at 1 and 2

tonne(s)/acre (to increase soil pH). Wet weather has so far precluded field measurements, post‐

remediation, at this site.

Laboratory studies on ASS, all of which are used for sugar cane cultivation, taken from the

catchments of Blacks Drain, McLeods Ck and Christies Ck have shown that aluminium solubility

actually increases above pH 5 in ASS that contain high % concentrations of organic carbon (i.e. the

organic soil surface horizon). Based on these results, it is recommended that current best

management practices used in the NSW Sugar Industry for ASS in regards to optimal pH be re‐

evaluated when considering environmental impact.

This project was awarded funding for a three year period and similar annual progress reports will be

issued soon after the conclusion of 2012 and 2013.

Commercial‐in‐confidence 5

Introduction

Background

In November 2010 it was announced by the Australian Research Council (ARC) that the Linkage project

LP110100480 ‘Exploiting Natural Processes to Effectively Remediate Acidified Coastal Environments’ was

awarded funding for 3 years for collaborative research between the University of New South Wales

(UNSW), the Tweed Shire Council, NSW Cane Growers Association and NSW Sugar Milling Co‐operative.

The project commenced in January 2011 and the first meeting between stakeholders was held on 28th

January 2011 in the Buchannan Room at the Council Depot. The results outlined in this report were

presented to all stakeholders on the 27th March 2012 at the first annual meeting of the project which

was also held at the Council Depot.

For reference, the main aims of this ARC Linkage project are reiterated below:

1) Undertake research which identifies acid sulfate soil (ASS) hotspots within 3 catchments in the

Tweed Shire and then the most suitable remediation strategies to reduce ASS discharge on a

catchment scale;

2) Conduct on‐ground remedial works identified in (1) above; and

3) Obtain field measurements to determine the efficacy of the remedial works in reducing the

discharge of problematic contaminants (particularly iron and aluminium) from the 3 catchments.

The 3 catchments in the Tweed Shire identified as acid sulfate ‘hotspots’ to be investigated were in

various stages of remediation prior to the commencement of this project (Figure 1).

Blacks Drain, a highly‐modified tributary of the Tweed River, was remediated in 2009/2010 as an

outcome of the research findings from a previous ARC Linkage project LP0455697 (Collins et al. 2009).

Major remediation work was conducted by the Tweed Shire Council in collaboration with landholders Jim

and Les Dickinson within the pasture section (Figure 1) of the catchment (drain infilling, drain widening

and shallowing, drain bank revegetation, acid scald capping and liming, stock exclusion, and the

construction of packed‐bed limestone channels) whilst only minor adjustments to the downstream

sugarcane section were made on the Stainlay’s property (drain bank revegetation). We have significant

pre‐remediation data on this catchment from research activities conducted in LP0455697.

Christies Creek is a coastal catchment dominated by sugar cane cultivation and pasture in the upper

catchment and native forest and residential areas in the lower catchment. Over the last 3 years this

catchment has come to the attention of the Tweed Shire Council owing to the occurrence of fish kills,

heavy iron flocs and, more recently, arsenic concentrations exceeding ANZECC (2000) water quality

guidelines (Kinsela et al. 2009a). The source of the arsenic and indeed other contaminants identified in

the catchment (iron and aluminium) is the underlying ASS. No remediation work at Christies Ck had been

carried out prior to 2011, although a limited‐scale monitoring program was established in this catchment

in 2009/2010 with the collaboration of landholders Ross Hardy, Ray Dooley, Craig King and Mr and Mrs

Colin Love.


Figure 1: Aerial view of the three catchments in northern NSW to be investigated in this project.

Previous remedial work undertaken in Blacks Drain and Clothiers Ck/Reserve Ck are detailed. Catchment

boundaries are denoted by the dot‐dash lines.

Cudgen Lake (Clothiers & Reserve Cks) is the coastal catchment immediately south of the Tweed River

which has been the subject of previous research and remediation studies (e.g. LP0219475 & NSW

Environmental Trust ASS Hot Spot Remediation Program 2000‐2004). Cudgen Lake has been subjected

to poor water quality over many years, due to the construction of an adjacent golf course and residential

development that was abandoned before its completion. This resulted in major fish kills in 1991 and

1998, and an overall degradation of aquatic life. Research from LP0219475 has shown that the problem

is mainly due to rain‐induced discharges from oxidising ASS in the catchment (Macdonald et al. 2004).

The Hot Spot Remediation Program resulted in approximately 6 km of drains being filled (Figure 1) and

almost 11,000 m2 of severely degraded ‘acid scald’ being remediated. Despite these measures, large fish

kills continue to occur within Cudgen Lake and adjoining waterways (Perkins 2010).

The ultimate objective of this project is to sustainably engineer problematic agricultural acid sulfate soils

on the east coast of Australia into areas that are both environmentally benign and economically

profitable.

1 0 km

R ‐‐ Residential F ‐‐ Forest

Pacific Ocean

P

P F

F

R

R

R

C ‐‐ Cane P ‐‐ Pasture

C

C

P

Christies Creek Catchment

1 0 km

Clothiers & Reserve Creek Floodplain

Clothiers Ck

Modified or in‐filled drain

Cudgen Lake

Reserve Ck

P

P P

P

Main drain shallowed & widened

Drains in‐filled

Downstream export to Tweed River

10

km

0.50

km

Tweed River

Blacks Drain Catchment

P P

P

C

C


UNSWProjectPersonnel

During 2011, Miss Yliane Yvanes‐Giuliani (March) and Dr Jackie Stroud (August) were recruited to the

project to undertake, respectively, PhD studies and post‐doctoral research in the research areas specified

in the Introduction. Both positions are fully‐funded by the project.

Dr Jackie Stroud has a PhD in soil science from Lancaster University, UK and was working at Rothamsted

Research prior to commencing working on the project in August 2011. She has a strong research

background in trace element mobility and bioavailability in soils.

Miss Yliane Yvanes‐Giuliani obtained her Honours degree in environmental science from the University of

Plymouth, UK and started her PhD at UNSW in March 2011. She is undertaking her PhD studies into

aluminium geochemistry in ASS as a co‐tutelle program between UNSW and the University Aix‐

Marseilles, France. She also obtained an Australian Nuclear Science and Engineering top‐up scholarship

in July 2011 which will facilitate her use of certain scientific instruments at the Australian Nuclear Science

and Technology Organisation (ANSTO).

Dr Richard Collins was responsible for the day‐to‐day management of the previous ARC Linkage project

(LP0455697) with the Tweed Shire Council and NSW Cane Growers Association and has developed a

strong rapport with both Council staff and local landholders. He leads this research project and

contributes to both laboratory and field research activities of Jackie and Yliane. His role (at 0.2 Full Time

Equivalent) in the project is not remunerated from project funding.

ProjectMethods

During 2011, continuous water quality monitoring (i.e. pH, redox, dissolved oxygen, conductivity and

water temperature) was undertaken in all 3 catchments. As significant metal contaminant discharge

from ASS catchments has been linked to rainfall events, automatic water samplers were also deployed

along Blacks Drain in October and November after two rainfall events that exceeded >100 mm/day.

These auto‐samplers collected water samples at approximately 3 hr intervals for periods up to 6 days

after rainfall with pH and redox measurements being conducted in the field. All water samples were

filtered (0.22 µm) and subsequently acidified (70% HNO3) in the field. They were stored in the dark until

they could be refrigerated and then transported to UNSW for analysis. Elemental analyses were

performed by Inductively Coupled Plasma (Optical Emission Spectrometry or Mass Spectrometry) at

UNSW. Appropriate quality controls included analysis of blanks, frequent recalibration and the recovery

of spiked blanks, ensuring meaningful data were extracted.

Samples from the auto‐samplers were complemented by water velocity measurements made during

water sample collection / deployment. The measurements of water velocity (Vt) were made using a

Pygmy Ott meter, which when combined with drain dimensions (At) can be used to calculate drain

discharge (Qt), viz. Equation 1. Furthermore, when the contaminant concentration (Ct) is known, an

elemental export (or flux, Ft) can be extrapolated from the data according to Equation 2.

Qt = Vt × At [1]

Ft = Qt × Ct [2]


In addition, transects across Blacks Drain were established that facilitated continuous measurements of

groundwater and drainwater levels (Odyssey capacitance probes) and spot sampling of groundwater

samples for elemental analyses. These data are still being compiled and interpreted and are not

reported here.

A campaign was also undertaken in April to collect soil samples from the three catchments. As access to

Clothiers and Reserve Ck was restricted at this time, samples from McLeods Ck were obtained in lieu.

These samples were used to examine the geochemistry of aluminium in ASS.

Results

BlacksDrain

Research undertaken at Blacks Drain in the ARC Linkage project LP0455697 (2005‐2008) indicated that

the upper catchment area, i.e. beyond the area used for sugar cane cultivation, contributed the most to

contaminant discharge (Collins et al. 2009a). This was evidenced by continuous acidic pH readings of

drainwater at the upper catchment site indicated in Figure 2 and also comparable or larger quantities of

iron (Fe) exported from this site, than that from other downstream sites, during a wet season rainfall

event monitored in January 2008 (Figure 3). This rainfall event is designated a ‘wet‐season’ event as we

have noted that Fe is typically of higher concentrations in drainage waters during the summer/autumn

wet season whereas aluminium (Al) is the major acid‐generating contaminant of concern during

winter/spring dry season rainfall events (Collins et al. 2009a).

Continuous drainwater monitoring after remediation has indicated an improvement in water quality at

the site designated ‘upper catchment’ in Figure 2 in that pH was consistently higher during 2010 than

when compared to 2007 (Figure 4). Due to a number of technical and maintenance issues with the water

quality measurement stations, only limited data was collected in 2011. However, the results are largely

in line with that obtained in 2010 (data not shown). If the average pH values are compared between the

two years a value of pH 4.8 is obtained in 2010, which is significantly higher than the pH 3.7 obtained

during 2007.

In 2011 drainwater and groundwater samples were also collected during two rainfall events so as to

compare the quantity of iron and aluminium discharged from the upper catchment area before and after

remediation. The results between 2008 and 2011 are compared in Figure 5. It is immediately obvious

from Figure 5 that there is a dramatic decrease in the quantity of iron being exported from the pasture

site during the rainfall event measured in November 2011 (aluminium concentrations in the drainwaters

were negligible during both rainfall events). To be able to compare these values on a somewhat

normalised basis, the total quantity of iron exported during the two events was calculated based on the

total volume of water exported during the measurement frame (i.e. 9 days in 2008 and 6 days in 2011).

These calculations indicated that prior to remediation 55 tonnes of iron were exported per gigalitre from

this area whereas it was only 2.5 tonnes of iron per gigalitre during the 2011 event. Despite some of the

uncertainties inherent in these types of calculations, such a difference would suggest that the remedial

work carried out in late 2009 has made a dramatic improvement to the quality of water draining from

the site in Blacks Drain.


Figure 2: (Upper) Aerial photograph of the Black’s Drain catchment (catchment boundary shown in red).

Sites on Black’s Drain where the continuous water quality monitoring stations were located in 2007 have

been circled and are colour designated as such in the graph (Lower) which represents hourly pH (and

daily rainfall) measurements during 2007. The black lines on the aerial photograph represent the major

drainage lines of the catchment.

TVW

Upper Catchment

Weather Station

Airport

TVW

Upper Catchment

Weather Station

Airport


Figure 3: (Upper) Aerial photograph of the Black’s Drain catchment (catchment boundary shown in red).

Sites on Black’s Drain where drainwater samples were collected every 3 hours over a 9 day period in

January 2008 (after a rainfall event) have been circled and are colour designated as such in the graph

(Lower) which represents the quantity of iron (Fe) exported on an hourly basis.

Further rainfall

Pasture


Figure 4: Comparison of drainwater pH, with associated daily rainfall, at the upper catchment site in

Blacks Drain designated in Figure 2. The data shown for 2007 is the same as that shown in Figure 2.


Figure 5: Comparison of the quantity of (dissolved) iron exported from Blacks Drain, after a rainfall event,

at the drainwater pasture site indicated in Figure 3 in 2008 (9 days of measurements) and 2011 (6 days of

measurements). Note the dramatic decrease in the load of Fe exported (kg/hr) during 2011.


ChristiesCk

Based on a number of studies undertaken within the Christies Ck catchment (e.g. Kinsela et al. 2009b), it

was identified that a hydrologically isolated cane farm (noted as site 6 in Figure 6) was a major

contributor of Al to the lower reaches of Christies Creek (Table 1), with internal drainage networks

(Figure 7) and pumping regimes identified as being below best‐management‐practices.

Figure 6: Location of Christies Creek major drainage lines and the subcatchments (designated as sites on

the Figure) monitored for the export of iron and aluminium (Kinsela and Collins, 2011).

Table 1: Export of aluminium from Christies Creek across a 6‐month sampling period (Kinsela et al. 2009b). The cane farm is site 6 and the Christies Ck data is a site just upstream from site 6.

Scenario Analyte Representation within 6‐month study (days)1

Outflow volume (L) in

study2

Analyte concentration

(mg/L)

6‐monthly export total

(kg)

Christies Creek Baseline Flow

Al 147 7.62 × 109 0.05 381

Christies Creek Rain Event Flow

Al 34 1.44 × 1010 0.2 2 880

Cane farm Baseline Flow

Al 147 1.32 × 108 3 395

Cane farm Rain Event Flow

Al 34 2.64 × 108 15 3960

CC South.

Site 6.

Site 3.Site 2.

Site 1.

Reserve Ck.

Site 4.

Site 5.


Figure 7: Photos of one of the major drains within site 6 (Kinsela and Collins, 2011).

During an on‐site meeting in August 2011 with Sebastian Garcia‐Cuenca, Richard Collins, Ross Hardy and

Robert Quirk, it was agreed that the following suitable remediation work at Site 6 would be undertaken

(refer to Figure 8):

‐ Cap and lime (2 tonnes/acre) the western headland of the north‐south drain to reduce sub‐

surface drainage from the cane block into the drain;

‐ Drain shallowing of the major east‐west and north‐south running drains with additional liming at

5 tonnes/acre, and;

‐ Trail the of liming cane blocks and field drains at 1 or 2 tonnes/acre.

These on‐ground works either comply with the NSW Sugar Industry’s best management practices or

were suggested in Kinsela and Collins (2011). Shallowing of the major east‐west and north‐south drains

should reduce the cyclical oxidation and acidification of exposed sulfidic sediments within the drains and,

as such, the generation of aluminium. These changes should, therefore, result in the decreased discharge

of aluminium to downstream environments, whilst not causing water‐logging to the sugarcane crop. It is

suggested that the western most point of the east‐west drain should be shallowed to the invert of the

field drains with a fall of approximately 0.5 m to the junction with the north‐south drain. It is, therefore,

expected that the depth of the north‐south drain will not greatly exceed the maximum depth of the east‐

west drain. Recognising that this drainage system may still allow groundwater transport to the major

drains (i.e. via field drains), the liming of cane blocks was trialled so that sub‐surface pH be raised to at

least pH 4.

In September/October 2011 the majority of these works were carried out, however, it should be noted

that drain shallowing of the major east‐west and north‐south running drains was restricted to only a


portion of the western end of the major east‐west drain. It is recommended that the full‐suite of

remedial works be undertaken to completion at the site.

Soil sampling and monitoring of the site since the works have been undertaken has so far been limited

due to wet weather. As such, these studies will continue into 2012.

Figure 8: Locations of agreed on‐ground works and liming rates at site 6 (as at 5th August 2011).

AluminiumsolubilityinASSusedforsugarcanecultivation

In previous studies we have observed, surprisingly, that soluble Al concentrations in organic surface soil

horizons from acid sulfate soils in the Tweed Shire used for sugar cane cultivation increase above pH 5

(Collins et al. 2009b). This result is surprising because it would normally be expected that soluble Al

concentrations decrease due to the metal’s propensity to precipitate with increasing pH values.

However, analyses of a large range of organic surface soils collected in 2011 across the Tweed Shire have

confirmed these previous results (Figure 9).

While we are still investigating the nature of this phenomenon, we currently hypothesise that natural

organic matter becomes more soluble as pH increases and that this soluble organic matter can form

soluble complexes with Al – hence increasing soluble Al concentrations. Nevertheless, it is clear from

Blocks & field drains limed at 1t/ acre Blocks & field drains limed at 2t/ acre E/ W drain shallowed and limed at 5t/ acre N/ S drain shallowed and limed at 5t/acre


these results that increasing the pH (e.g. via liming) of these acid sulfate soils above pH 5.5 will actually

lead to an increase in the discharge of Al from these sites. In light of these findings, it is suggested that

current best management practices in regards to both optimum soil pH and discharge waters (for

environmental benefits) be revisited in the near future.

Figure 9: Soluble aluminium concentrations in soils collected from around the Tweed Shire that are used

for sugar cane cultivation. Concentrations were determined on 1:5 soil:solution extractions in Millipore

(ultra‐pure) water and have been normalised in the graph to a soil:solution ratio of 1:1

Conclusions

Whilst still in the early stages of the project, significant progress has been made towards the project’s

objectives and a number of promising findings have been obtained in regards to the efficacy of the

remediation work carried out at Blacks Drain in 2009. More specifically, the data obtained in 2011 has

shown that the discharge of iron from Blacks Drain has decreased by approximately 20‐fold during

comparable rainfall events. Data interpretation is continuing to identify the processes responsible for

such a dramatic response to remediation.

Remedial work has been undertaken at a site within the Christies Ck catchment with a view to

minimising aluminium discharge in drainwaters. Wet weather has so far precluded field measurements,

post‐remediation, at this site to assess any changes induced by the on‐ground works. These studies are

continuing in 2012.


Laboratory studies on organic soil surface horizons taken from three catchments in the Tweed Shire

have shown that in these types of soils aluminium solubility actually increases above pH 5.5. While we

have initially speculated that this results from the formation of soluble aluminium‐natural organic

matter complexes, these results nonetheless indicate that the optimal soil pH to minimise aluminium

discharge is pH 4.5 – 5. As such, current best management practices in regards to the pH of acid sulfate

soils and discharge waters requires further consideration when assessing environmental impact.

Acknowledgements

The assistance of Sebastien Garcia‐Cuenca (Tweed Shire Council) and the landowners who have also

assisted in the work detailed in this report and who have also allowed us to conduct environmental

monitoring on their properties is gratefully acknowledged. This includes special thanks to Jim and Les

Dickinson, Nicola Stainlay, Robert Quirk, Ross Hardy, Harry Boyd and Ian and Rhonda Taggett.

References

ANZECC (2000). Australian and New Zealand guidelines for fresh and marine water quality. Volume 2:

Aquatic Ecosystems. Australian and New Zealand Environment and Conservation Council,

Agriculture and Resource Management Council of Australia and New Zealand, Canberra, Australia.

Collins R, A Jones, MD Melville and TD Waite (2009a). 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 2008/17, version 1, Centre for Water and Waste Technology, The University of

New South Wales, Sydney, NSW 2052, Australia. p. 16.

Collins RN, D Fink, C Mifsud, TE Payne and TD Waite (2009b) The use of 26Al Accelerator Mass

Spectrometry to investigate aluminium chemistry in coastal lowland acid sulfate soils. Proceedings

of 16th AINSE Conference on Nuclear and Complementary Techniques of Analysis, Lucas Heights,

Australia, November 2009. http://www.ainse.edu.au/__data/assets/pdf_file/0004/48685/NCTA‐

15_Collins‐revised1.pdf.

Kinsela A and R Collins (2011). Suggested remedial works for Christies Creek to reduce the discharge of

aluminium and iron from acid sulfate soils. Final Report, version 2. UNSW Water Research Centre

publication 2011/10, The University of New South Wales, Sydney, NSW 2052, Australia. p.25

Kinsela A, R Collins and TD Waite (2009a). Sources, concentrations and bioavailability of arsenic in

sediments: Christies Creek, north east NSW. UNSW Water Research Centre publication 2009/15,

The University of New South Wales, Sydney, NSW 2052, Australia. p.27.

Kinsela A, Waite D, Collins R (2009b). Stream and groundwater quality relating to acid sulfate soils

discharge: Christies Creek, north east NSW. Final Report. UNSW Water Research Centre

publication 2009/23, The University of New South Wales, Sydney, NSW 2052, Australia. p.31.

Macdonald BCT, J Smith, AF Keene, M Tunks, A Kinsela and I White (2004). Impacts of runoff from

sulfuric soils on sediment chemistry in an estuarine lake. Science of the Total Environment

329:115‐130.

Perkins J (2010). Fish kill occurs in Cudgen Creek. Tweed Daily News (12th April 2010).

Documents

Exploiting Natural Processes to Effectively Remediate ... Cudgen Lake (Clothiers & Reserve Cks) is the coastal catchment immediately south of the Tweed River which has been the subject