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 1 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 © Water Research Centre 2 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 3 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 4 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. 5 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