Manly Lagoon Dredging Project - Manly Council - NSW Government
Manly Lagoon Dredging Project - Manly Council - NSW Government Manly Lagoon Dredging Project - Manly Council - NSW Government
Manly Lagoon Dredging Project – Review of Environmental FactorsPrepared for Manly and Warringah CouncilsFollowing completion of the works all areas which have been disturbed by the works,including Nolan Reserve and the lagoon banks, should be restored via revegetation withspecies native to the area as soon as practicable. Nolan Reserve and all access routesthrough the Reserve will need to be restored to their original condition and this will involvethe contractor undertaking a dilapidation survey prior to the commencement of works. It isnoted that the use of a cutter suction dredge which conveys material to shore via a floatingpipe is expected to inherently reduce the impact on vegetation by minimising therequirement for shore based mobile machinery.The contractor will not be permitted to stockpile or store equipment or material not requiredfor immediate use outside of the compound area to minimise the visual impacts of the works.Geobags used during dewatering should be a dark or neutral colour to minimise theirvisibility.Complete site fencing around the works area (in accordance with the Technical Specificationin Appendix K) must also be established and is an important mitigation measure that willprovide a visual barrier between the works area and the surrounding public areas for theduration of the works.2 July 2010 Cardno (NSW/ACT) Pty Ltd 110H:\Doc\2010\Reports.2010\Rep2580v4.doc
Manly Lagoon Dredging Project – Review of Environmental FactorsPrepared for Manly and Warringah Councils5.10 Hazards and WasteExisting EnvironmentHazardsManly Lagoon conveys both day to day and flood flows from its catchment to the ocean.There is the potential, although considered unlikely, that a major storm event will result in theflooding of Manly Lagoon and surrounding areas during the proposed works. The Lagooncatchment extends north-west and west, with key tributaries being Brookvale Creek, ManlyCreek and Burnt Bridge Creek. The main portion of Manly Lagoon has only limited hydrauliccapacity and relatively regular flood events, such as a 5 year ARI flood event, can exceedthe banks of the Lagoon and inundate areas surrounding the Lagoon (MHL, 1992).The former landfill site located at T.S. Condamine, which has a current EPA notice as aremediation site (Appendix D), is known to contain contaminants such as cadmium, copper,lead, zinc and asbestos. Sediments in the lagoon have been shown to have a high acidsulfate soil potential.According to the Bushfire Prone Land Maps contained in the Manly and Warringah LEPs,Manly Lagoon and the surrounding areas are not classified as bushfire prone land. Due tothe grassed and vegetated nature of the majority of the Lagoon foreshore, although bushfirewill be unlikely during the proposed works, the potential for fire still needs to be considered.WasteIn the current proposal it is expected that there will be no substantial amounts of wastegenerated as a result of the activities, as it is anticipated that all treated dredge spoil will besuitable for beneficial reuse. However, if the chemical and physical composition is such thatthe dredge spoil is not deemed suitable for reuse, then the material will need to be disposedof safely to an appropriate landfill site.Large items removed from the lagoon prior to dredging (such as shopping trolleys) and thegeobag fabric will require recycling or disposal. Also there is the chance that unplannedwaste could be generated (i.e. unexpected materials found on the bed of the lagoon).Packaging for the polymer additive and lime will be recycled where possible, or disposed ofappropriately.Impact AssessmentHazardsThere are several potential hazards associated with the proposed works including:Flooding of Manly Lagoon and the surrounding low-lying lagoon banks could causesediment and erosion control measures such as the silt curtains to fail, as well asinundate or mobilise plant and equipment located in Nolan Reserve;Encountering and exposing contaminated sediments, particularly in the vicinity of theT.S. Condamine site, during dredging operations;2 July 2010 Cardno (NSW/ACT) Pty Ltd 111H:\Doc\2010\Reports.2010\Rep2580v4.doc
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<strong>Manly</strong> <strong>Lagoon</strong> <strong>Dredging</strong> <strong>Project</strong> – Review of Environmental FactorsPrepared for <strong>Manly</strong> and Warringah <strong>Council</strong>sFollowing completion of the works all areas which have been disturbed by the works,including Nolan Reserve and the lagoon banks, should be restored via revegetation withspecies native to the area as soon as practicable. Nolan Reserve and all access routesthrough the Reserve will need to be restored to their original condition and this will involvethe contractor undertaking a dilapidation survey prior to the commencement of works. It isnoted that the use of a cutter suction dredge which conveys material to shore via a floatingpipe is expected to inherently reduce the impact on vegetation by minimising therequirement for shore based mobile machinery.The contractor will not be permitted to stockpile or store equipment or material not requiredfor immediate use outside of the compound area to minimise the visual impacts of the works.Geobags used during dewatering should be a dark or neutral colour to minimise theirvisibility.Complete site fencing around the works area (in accordance with the Technical Specificationin Appendix K) must also be established and is an important mitigation measure that willprovide a visual barrier between the works area and the surrounding public areas for theduration of the works.2 July 2010 Cardno (<strong>NSW</strong>/ACT) Pty Ltd 110H:\Doc\2010\Reports.2010\Rep2580v4.doc
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