Knowledge report Temperate Highland Peat Swamps on Sandstone: evaluation of mitigation and remediation techniques This report was commissioned by the Department of the Environment on the advice of the Interim Independent Expert Scientific Committee on Coal Seam Gas and Coal Mining and prepared by Water Research Laboratory, School of Civil and Environmental Engineering, University of New South Wales. August 2014 Temperate Highland Peat Swamps on Sandstone: evaluation of mitigation and remediation techniques Copyright © Copyright Commonwealth of Australia, 2014. Temperate Highland Peat Swamps on Sandstone: evaluation of mitigation and remediation techniques, Knowledge report is licensed by the Commonwealth of Australia for use under a Creative Commons By Attribution 3.0 Australia licence with the exception of the Coat of Arms of the Commonwealth of Australia, the logo of the agency responsible for publishing the report, content supplied by third parties, and any images depicting people. For licence conditions see: http://creativecommons.org/licenses/by/3.0/au/ This report should be attributed as ‘Commonwealth of Australia 2014, Temperate Highland Peat Swamps on Sandstone: evaluation of mitigation and remediation techniques, Knowledge report, prepared by the Water Research Laboratory, University of New South Wales, for the Department of the Environment, Commonwealth of Australia’. The Commonwealth of Australia has made all reasonable efforts to identify content supplied by third parties using the following format ‘© Copyright, [name of third party]’. Enquiries concerning reproduction and rights should be addressed to: Department of the Environment, Public Affairs GPO Box 787 Canberra ACT 2601 Or by email to: [email protected] This publication can be accessed at: www.iesc.environment.gov.au Acknowledgements This report was commissioned by the Department of the Environment on the advice of the Interim Independent Expert Scientific Committee on Coal Seam Gas and Coal Mining. It was prepared by Erica Davey (Project Engineer), Dr William Glamore (Principal Engineer) and Grantley Smith (Manager and Principal Engineer) at the Water Research Laboratory (University of New South Wales) and peer reviewed by Mr Roger Good (Good Environmental Systems). Following discussions with the report author, the peer reviewers’ comments have been incorporated into the report, appearing as either changes to the text, footnotes, end of chapter notes or appendices. Additional references have been provided by the reviewers. New South Wales Government agencies were provided the draft report for comment, through the National Partnership Agreement Reference Group, established between the Commonwealth and signatory state governments under the National Partnership Agreement on Coal Seam Gas and Large Coal Mining Development. Disclaimer The views and opinions expressed in this publication are those of the authors and do not necessarily reflect those of the Australian Government or the Minister for the Environment or the Interim Independent Expert Scientific Committee on Coal Seam Gas and Coal Mining or the statutory Independent Expert Scientific Committee on Coal Seam Gas and Large Coal Mining Development (IESC). While reasonable efforts have been made to ensure that the contents of this publication are factually correct, the Commonwealth and IESC do not accept responsibility for the accuracy or completeness of the contents and shall not be liable for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the contents of this publication. page 2 of 106 Temperate Highland Peat Swamps on Sandstone: evaluation of mitigation and remediation techniques Contents Summary ................................................................................................................................................. 7 Abbreviations ........................................................................................................................................... 9 Glossary................................................................................................................................................. 10 1 Introduction ...................................................................................................................................... 14 2 Upland peat swamps ....................................................................................................................... 16 2.1 Importance of the THPSS community .................................................................................... 16 2.2 Other upland peat swamp communities ................................................................................. 18 2.3 Formation and characteristics of upland peat swamps .......................................................... 20 2.4 Representative swamp conceptual models ........................................................................... 22 2.4.1 Headwater swamps ........................................................................................................... 22 2.4.2 Valley infill swamps ............................................................................................................ 22 2.4.3 Hanging swamps ............................................................................................................... 23 2.5 Chapter synthesis and knowledge gaps ................................................................................ 23 Note on EPBC listing ............................................................................................................................. 24 3 Impacts of longwall mining and subsidence .................................................................................... 25 3.1 Underground coalmining techniques ..................................................................................... 25 3.2 Longwall mining in the Sydney region ................................................................................... 27 3.2.1 Southern Coalfield ............................................................................................................. 28 3.2.2 Western Coalfield .............................................................................................................. 29 3.3 Historical context .................................................................................................................... 30 3.4 Impact mechanisms ............................................................................................................... 32 3.5 Impacts of mining on upland peat swamps and water bodies in the Sydney Basin .............. 41 3.5.1 Observed longwall mining impacts on upland peat swamps ............................................. 42 3.5.2 Observed longwall mining impacts on water bodies ......................................................... 55 3.6 Internationally reported impacts ............................................................................................. 61 3.7 Chapter synthesis and knowledge gaps ................................................................................ 63 4 Prediction, mitigation, management and monitoring of impacts ..................................................... 64 4.1 Prediction of mining impacts on upland peat swamps ........................................................... 64 4.2 Mitigation of longwall mining impacts ..................................................................................... 66 4.3 Time lag between mining and observation of impacts ........................................................... 66 4.4 Trigger action response plans ................................................................................................ 67 4.5 Monitoring .............................................................................................................................. 68 4.5.1 Surface subsidence ........................................................................................................... 69 4.5.2 Groundwater monitoring .................................................................................................... 69 4.5.3 Subsurface monitoring ....................................................................................................... 70 4.5.4 Ecological monitoring ......................................................................................................... 71 4.6 Chapter synthesis and knowledge gaps ................................................................................ 71 page 3 of 106 Temperate Highland Peat Swamps on Sandstone: evaluation of mitigation and remediation techniques Peer review comments on Chapter 4 .................................................................................................... 72 5 Remediation techniques .................................................................................................................. 73 5.1 Remediation of fracture networks and vertical seepage ........................................................ 75 5.1.1 Surface sealing techniques ................................................................................................ 76 5.1.2 Injection grouting ............................................................................................................... 77 5.1.3 Permeation grouting .......................................................................................................... 80 5.1.4 Cross-bore injection of gels