Fremantle Port Inner Harbour and Channel ... - Fremantle Ports

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Bathymetric surveys of the Gage Roads Offshore Disposal Area showed that sedimentredistribution (depostion or erosion) has potentially occurred subsequent to the IHD Project;however, quantitative analysis to determine whether this is actual sediment redistribution orwithin the bounds of survey accuracy could not be undertaken due to the limited spatialextent of bathymetric survey.This medium-term study has been designed to be completed in three phases. In summary,this report shows the methods and results from the Phase I survey and describes the'baseline' for comparison with subsequent surveys. The Phase II survey will be conducted inNovember-December of 2012 to assess seagrass recovery and potentially controllingsediment parameters within and surrounding the Offshore Disposal Area. A Phase III surveymay also be conducted in November-December 2013, subject to the outcomes of the Phase IIsurvey.viOceanica: Fremantle Ports: FP – Gage Roads Offshore Disposal Area Seagrass Recovery Project, Phase I – Initial Survey
1. Introduction1.1 BackgroundThe Gage Roads Offshore Disposal Area is located approximately 6 km from the entrance ofFremantle Harbour in Western Australia (Figure 1.1). The Offshore Disposal Area was utilisedduring 2010 to dispose of approximately 1.5 million m 3 of dredge material associated withthe Inner Harbour and Channel Deepening (IHD) Project. The site had not previously beenused as a disposal site, but it is used as an anchoring ground for commercial vessels awaitingcargo at the Fremantle Port facilities; and therefore has a history of seabed disturbance fromanchors.Prior to the IHD Project, it was estimated that approximately 15.4 ha of seagrass habitat waspresent within the Offshore Disposal Area (Figure 1.2) (Oceanica 2010a). Immediatelysurrounding the disposal area, it was estimated that a further 7.9 ha of seagrass habitat waspresent within a predicted zone of potential loss, plus 48.7 ha within a predicted zone ofpotential effect (from sediment deposition and light deprivation associated with the offshoredisposal plume from the IHD Project) (Oceanica 2010a).To facilitate an estimate of seagrass loss within the Gage Roads region post-completion of theIHD Project, a benthic habitat map was compiled. However, the actual loss within theOffshore Disposal Area or adjacent area to the south-west could not be confirmed (due to thepresence of an apparent algal bloom preventing visual penetration to the benthicenvironment and consequent inability to map habitats) (Oceanica 2010a).Seagrass habitat survey within and surrounding the Offshore Disposal Area subsequent to theIHD Project is being undertaken to facilitate seagrass impact assessment particularly toinform future disposal campaigns and complete a benthic habitat map for reference.Fremantle Ports seeks to investigate the rate and controlling mechanisms of recovery of theseagrass Posidonia angustifolia (Cambridge and Kuo) at the Offshore Disposal Area andsurrounding areas following disturbance (i.e. from burial, smothering and light deprivation).This study will aid Fremantle Ports' development of a long-term dredge material disposal planthrough a greater understanding of impacts upon seagrass after disposal of materials andthrough an updated benthic habitat map for the Gage Roads area.1.2 Scope of this documentThis document describes the initial (Phase I) survey of seagrass health, coverage andcoincident sediment physicochemical data, comprising a 'baseline' for a medium term (up to3 years) investigation into seagrass recovery within and around the Gage Roads OffshoreDisposal Area. This document collates relevant historical data and outlines methods used forthe Phase I survey, also intended for subsequent surveys, to ensure consistent standardoperating procedures in the assessment of seagrass recovery.Oceanica: Fremantle Ports: FP – Gage Roads Offshore Disposal Area Seagrass Recovery Project, Phase I – Initial Survey 1
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Fremantle Port Inner Harbour and Ch
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Client: Fremantle PortsDocument his
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ContentsExecutive Summary .........
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Executive SummaryProject StatusFrem
Page 11 and 12: 1. Introduction1.1 Background and p
Page 13 and 14: Figure 1.1Dredge areas, reclaimed a
Page 15 and 16: Table 2.2 Audit tableAuditCode801:M
Page 17 and 18: AuditCodeSubject Action How Evidenc
Page 19 and 20: 3. Annual Survey Footprint of Offsh
Page 21 and 22: Figure 3.2 Differences in bathymetr
Page 23: A one in five year storm event (as
Page 26 and 27: 5. SummaryThere were zero non-compl
Page 29: 6. ReferencesDEC (2009) Guidelines
Page 33 and 34: STATUS OF THIS DOCUMENTThis documen
Page 35 and 36: Report shall be 15 months from the
Page 37 and 38: 6-3 If the Water Quality Monitoring
Page 39: Table 2: Summary of key proposal ch
Page 47: Fremantle Ports1 Cliff StreetFREMAN
Page 51: Fremantle Ports - Gage RoadsOffshor
Page 55: Client: Fremantle PortsRevisions hi
Page 58 and 59: Figure 1.1Figure 1.2Figure 1.3Figur
Page 61: Executive SummaryOceanica Consultin
Page 65 and 66: Figure 1.2Gage Roads habitat map in
Page 67 and 68: Figure 1.3Bathymetry for Gage Roads
Page 69 and 70: Figure 1.4 Benthic habitat within G
Page 71 and 72: 2. Methods2.1 Benthic habitat surve
Page 73 and 74: 2.2 Seagrass recovery2.2.1 Permanen
Page 75 and 76: Table 2.1Seagrass sites, zone desig
Page 77 and 78: Table 2.3Limits of Reporting (LOR)
Page 79 and 80: Sediment nutrients and metalsNutrie
Page 81 and 82: 3. Results3.1 Benthic habitat mapA
Page 83 and 84: Figure 3.2 Benthic habitat post dis
Page 85 and 86: 3.2 Seagrass recovery3.2.1 Seagrass
Page 87 and 88: Table 3.4PERMANOVA table of results
Page 89 and 90: Table 3.7Data ranges and detection
Page 91 and 92: The bathymetry data for December 20
Page 93 and 94: Bathymetry data from December 2011
Page 95 and 96: 4. DiscussionWithin the Offshore Di
Page 97 and 98: 6. AcknowledgementsThis report was
Page 99: Appendix AGeo Oceans Report
Page 102 and 103: Benthic Habitat AssessmentTowed Vid
Page 104 and 105: 1. IntroductionGeo Oceans was commi
Page 106 and 107: Table 2 Tide predictions for the Po
Page 108 and 109: Figure 1 Substrate and biota habita
Page 110 and 111: Figure 2 Depth data collected durin
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Appendix 1: Video analysis biologic
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Appendix BGeoImage Report
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Table of ContentsIntroduction......
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Figure 1: Study site overview for s
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Project 1Project 1 aimed to generat
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Figure 2: Tier 1 classification res
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Limitations and assumptionsA number
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Appendix CSeagrass Monitoring Site
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Appendix ESeagrass Shoot Count Data
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Appendix GSediment Field Log
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Appendix INutrient and Metals Data
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MarineandFreshwaterResearchLaborato
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