Cairns Harbour Dredging LTDSDMP 2005-2010
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CAIRNS HARBOUR DREDGING LONG TERM DREDGE SPOIL DISPOSAL MANAGEMENT PLAN Prepared For: CAIRNS PORT AUTHORITY Prepared By: ENVIRONMENT NORTH in association with HYDROBIOLOGY & NIWA AUSTRALIA Environment North Job No 379 P.O. Box 616N © 2 March 2005 NORTH CAIRNS Q 4870 Telephone: (07) 4031 6619 Facsimile: (07) 4051 5386 Email: [email protected] Cairns Port Authority Long Term Dredge Spoil Disposal Management Plan ENVIRONMENT NORTH DOCUMENT CONTROL CERTIFICATE PROJECT AND CLIENT DETAILS Project name: Cairns Harbour Dredging Job Number : 379 Title: Long Term Dredge Spoil Disposal Management Plan Client: Cairns Port Authority Contact: Kim Kelleher Description of report: This report provides information required in support of a sea dumping permit under the Impact of Proposals (Sea Dumping) Act 1981 and the Great Barrier Reef Marine Park Act 1975. It includes: • a history and background to dredging and disposal of dredged material at the Port of Cairns, • a consideration of options for dredge spoil disposal, • a description of current and future dredging needs (including an identification of the long term dredging needs for the term of the permit (5 years) and methods to be used for dredging and off-shore disposal), • a description of the marine environment of Trinity Bay and Trinity Inlet, • a detailed summary of previous environmental monitoring of dredging and sea disposal (including a description of the properties of the dredge spoil and the condition of the Spoil Ground), • an examination of the potential impacts of dredging and sea disposal and of the opportunities for minimising dredging (reduce quantity) and for mitigating contamination (increase quality), and • a proposed monitoring program. PREPARATION AND DISTRIBUTION DETAILS Version Purpose Prepared by Checked by Date 1a-1g Internal draft David Rivett et al. Various to 10 May 2004 (see Table 1.2) 2 Client Review David Rivett Tas Graham 17 May 2004 3 Issue (CPA Final Review) David Rivett Tas Graham 11 August 2004 4 Issue David Rivett - 5 November 2004 5 Revised after GBRMPA review David Rivett Ross Smith 2 March 2005 and 2nd TACC meeting Jamie Corfield © Environment North P.O. Box 616N NORTH CAIRNS Q 4870 Telephone: (07) 4031 6619 Facsimile: (07) 4051 5386 This document is and shall remain the property of Environment North. It may only be used for the purposes for which it was commissioned and in accordance with the terms of engagement. Form ENDQ/01 (D) 30 March 1998 Cairns Port Authority Long Term Dredge Spoil Disposal Management Plan CONTENTS 1. INTRODUCTION 1 1.1 OUTLINE OF PROJECT AND ITS AIMS AND OBJECTIVES 1 1.2 TERMS OF REFERENCE 1 1.3 APPROVALS REQUIRED 2 1.4 NATIONAL OCEAN DISPOSAL GUIDELINES FOR DREDGED MATERIAL 2 1.5 STUDY TEAM 3 1.6 CONSULTATION SUMMARY 4 1.6.1 INTRODUCTION 4 1.6.2 TECHNICAL ADVISORY AND CONSULTATIVE COMMITTEE 4 1.6.3 ROLE OF TACC IN DEVELOPING THE LTDSDMP 5 2. BACKGROUND TO DREDGING AND DISPOSAL 7 2.1 INTRODUCTION 7 2.2 PREVIOUS STUDIES 7 2.3 HISTORY AND DEVELOPMENT OF THE PORT OF CAIRNS 8 2.3.1 EARLY YEARS 8 2.3.2 CURRENT SITUATION 9 2.4 ANALYSIS OF DREDGING AND DUMPING ISSUES 12 2.4.1 INTRODUCTION 12 2.4.2 SEDIMENT SOURCES, TRANSPORT PATHS AND SINKS 12 2.4.3 DREDGING AND DUMPING ISSUES 13 2.5 DETAILS OF CURRENT AND PREVIOUS PERMITS 13 2.6 CURRENT SPOIL GROUND 14 2.6.1 LOCATION 14 2.6.2 SEDIMENT ACCUMULATION RATE 14 2.6.3 CAPACITY FOR LIFE OF 5-YEAR PERMIT 14 3. DREDGE SPOIL DISPOSAL OPTIONS 17 3.1 INTRODUCTION 17 3.2 PHASE 1 STUDY (1990) 17 3.2.1 OVERVIEW 17 3.2.2 SPOIL DISPOSAL OPTIONS 17 3.2.3 FINDINGS 19 3.3 PHASE 2 STUDY (1992) 21 3.3.1 OVERVIEW 21 3.3.2 SPOIL DISPOSAL OPTIONS 22 3.3.3 CONCLUSIONS 24 3.4 POST-1992 DECISIONS 24 3.4.1 DUMPING 24 3.4.2 STATE AND REGIONAL COASTAL MANAGEMENT PLANS 25 3.4.3 CONSTRAINTS TO TERRESTRIAL DISPOSAL 26 3.5 CONCLUSIONS 27 Project Report – Version 5 (i) Environment North in association with Hydrobiology and NIWA Australia Cairns Port Authority Long Term Dredge Spoil Disposal Management Plan 4. CURRENT AND FUTURE DREDGING NEEDS 29 4.1 INTRODUCTION 29 4.2 SUMMARY OF RECENT DREDGING (SINCE 1973) 29 4.3 AVERAGE DISPOSAL QUANTITIES 30 4.3.1 ASSESSING LONG TERM AVERAGES 30 4.3.2 ESTIMATED LONG TERM AVERAGE 31 4.4 ESTIMATED LONG TERM DREDGING NEEDS 32 4.5 CURRENT AND FUTURE DREDGING METHODS 32 4.5.1 INTRODUCTION 32 4.5.2 THE BRISBANE DREDGE 32 4.5.3 THE WILLUNGA DREDGE 33 4.6 ASSESSMENT OF FUTURE CAPITAL DREDGING NEEDS 33 5. THE MARINE ENVIRONMENT OF TRINITY BAY AND TRINITY INLET 35 5.1 INTRODUCTION 35 5.2 PHYSICAL ENVIRONMENT OF TRINITY BAY AND INLET 35 5.2.1 INTRODUCTION 35 5.2.2 GEOMORPHOLOGICAL HISTORY OF TRINITY BAY AND INLET 35 5.2.3 REGIONAL ASPECTS OF SEDIMENT TRANSPORT IN TRINITY BAY 37 5.2.4 WATER QUALITY OF TRINITY BAY AND INLET 40 5.2.5 SEDIMENTOLOGY OF TRINITY BAY AND INLET 42 5.2.6 SPOIL GROUND 45 5.3 ECOLOGICAL ENVIRONMENT OF TRINITY BAY AND TRINITY INLET 47 5.3.1 INTRODUCTION 47 5.3.2 MANGROVE FORESTS 47 5.3.3 SEAGRASS BEDS 48 5.3.4 TIDAL MUDFLATS AND SANDFLATS 49 5.3.5 CLAYPANS AND SALTMARSHES 49 5.3.6 OPEN WATERS 49 5.3.7 ECOLOGICAL ENVIRONMENT IN THE VICINITY OF THE SPOIL GROUND 50 5.4 CULTURAL VALUES 52 5.4.1 INTRODUCTION 52 5.4.2 LOCATIONS OF VALUE 52 5.4.3 GENERAL SITES OF VALUE 53 5.4.4 MARINE SITES 54 6. SUMMARY OF PREVIOUS ENVIRONMENTAL MONITORING OF DREDGING AND SEA DISPOSAL 55 6.1 INTRODUCTION 55 6.2 SEDIMENT QUALITY 56 6.2.1 INTRODUCTION 56 6.2.2 SOURCES OF CONTAMINANTS IN SEDIMENTS 56 6.2.3 SEDIMENT QUALITY CONDITIONS AND MONITORING REQUIREMENTS IN CPA’S PREVIOUS SEA DUMPING PERMIT 57 6.2.4 CPA SAMPLING AND ANALYSIS PLANS 58 6.2.5 GHD (2000) SEDIMENT QUALITY REVIEW FOR HMAS CAIRNS 60 6.3 WATER QUALITY 61 6.3.1 OVERVIEW OF PREVIOUS WATER QUALITY MONITORING STUDIES 61 6.3.2 TURBIDITY 62 6.3.3 TRACE METALS AND HYDROCARBONS 62 6.3.4 NUTRIENTS, IN-SITU MEASUREMENTS AND COLIFORMS 63 6.3.5 TBT 63 6.3.6 ASSESSMENT OF LEVEL OF CONCERN FOR CONTAMINANTS 64 Project Report – Version 5 (ii) Environment North in association with Hydrobiology and NIWA Australia Cairns Port Authority Long Term Dredge Spoil Disposal Management Plan 6.4 BENTHOS 67 6.4.1 DREDGING SITES AND INFLUENCED AREAS 67 6.4.2 SPOIL GROUND 68 6.5 MARINE PESTS 69 7. POTENTIAL IMPACTS OF DREDGING AND SEA DISPOSAL, RISK EVALUATION AND TESTABLE IMPACT HYPOTHESES 75 7.1 INTRODUCTION 75 7.2 SCHEDULE OF QUANTITIES FOR FIVE YEAR PERMIT 75 7.3 OPPORTUNITIES FOR DREDGE MATERIAL REDUCTION AND MITIGATION OF CONTAMINANT SOURCES 75 7.3.1 INTRODUCTION 75 7.3.2 DREDGE MATERIAL QUANTITY REDUCTION INITIATIVES 76 7.3.3 SEDIMENT QUALITY IMPROVEMENT INITIATIVES 77 7.4 POTENTIAL IMPACTS, MECHANISMS OF IMPACTS AND RISK EVALUATION 78 7.4.1 INTRODUCTION 78 7.4.2 SHORT-TERM IMPACTS 79 7.4.3 LONG-TERM IMPACTS 83 7.5 RISK EVALUATION 90 7.6 DEFINITION OF TESTABLE IMPACT HYPOTHESES 102 7.6.1 INTRODUCTION 102 7.6.2 IMPACT HYPOTHESES – IMPACTS ON WATER QUALITY 102 7.6.3 IMPACT HYPOTHESES – IMPACT ON BENTHOS 103 7.6.4 IMPACT HYPOTHESES – IMPACT ON MARINE FAUNA (OTHER THAN BENTHOS) 104 7.6.5 IMPACT HYPOTHESES – IMPACT ON THE NATURE OF SEDIMENT 105 7.6.6 IMPACT HYPOTHESES – IMPACT ARISING FROM ACCUMULATION OF CONTAMINANTS 105 7.6.7 IMPACT HYPOTHESES – IMPACT ON TURBIDITY LEVELS FROM SEDIMENT RESUSPENSION 105 7.6.8 IMPACT HYPOTHESES – RECOVERY BETWEEN DUMPING EPISODES 106 7.6.9 IMPACT HYPOTHESES – MARINE PEST INFESTATION 106 7.6.10 IMPACT HYPOTHESES – IMPACT ON HABITAT FOR IMPORTANT FAUNA 107 7.6.11 IMPACT HYPOTHESES – IMPACT ON INDIGENOUS CULTURAL VALUES 108 8. PROPOSED MANAGEMENT AND MONITORING OF DREDGING AND SEA DISPOSAL 109 8.1 INTRODUCTION 109 8.2 LONG TERM ARRANGEMENTS 109 8.2.1 REGULATORY ARRANGEMENTS 109 8.2.2 LONG TERM ROLE OF TACC 109 8.3 PROPOSED ENVIRONMENTAL MANAGEMENT ACTIONS 110 8.3.1 INTRODUCTION 110 8.3.2 DREDGING EMPS 110 8.3.3 QUALITY IMPROVEMENT 111 8.3.4 QUANTITY REDUCTION 111 8.4 PROPOSED ENVIRONMENTAL MONITORING PROGRAM 112 8.4.1 INTRODUCTION 112 8.4.2 ONGOING SAP ASSESSMENTS OF DREDGE MATERIAL SUITABILITY FOR SEA DISPOSAL 112 8.4.3 MONITORING TO BETTER UNDERSTAND THE SOURCES, FATE AND BIOLOGICAL IMPACT OF TBT IN TRINITY INLET 114 8.4.4 MONITORING FOR SHORT-TERM IMPACTS 114 8.4.5 MONITORING FOR LONG-TERM IMPACTS 115 8.4.6 INITIAL RECOMMENDATIONS FOR MONITORING 119 8.4.7 MONITORING OF UNSCHEDULED EMERGENCY DREDGING 129 8.4.8 STUDY DESIGN CONSIDERATIONS FOR BENTHIC MONITORING 129 8.5 COMMUNITY AND AGENCY RELATIONS STRATEGY 130 8.6 CORPORATE MANAGEMENT PROGRAM 131 Project Report – Version 5 (iii) Environment North in association with Hydrobiology and NIWA Australia Cairns Port Authority Long Term Dredge Spoil Disposal Management Plan 9. SUMMARY 133 10. REFERENCES 135 FIGURES Figure 3.1 Phase One Study Area............................................................................................... 18 Figure 3.2 Sites Investigated in Second Stage Screening ........................................................... 21 Figure 5.1 Changes in Cairns Shoreline and Harbour.................................................................. 36 Figure 5.2 Section through Cairns City showing Sand Ridges and Mud Flats.............................