Manly Lagoon Dredging Project - Manly Council - NSW Government

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Manly Lagoon Dredging Project – Review of Environmental FactorsPrepared for Manly and Warringah CouncilsExecutive SummaryThis Review of Environmental Factors (REF) has been prepared to assess the impacts ofdredging the section of Manly Lagoon between the footbridge at Nolan Reserve and the endof Riverview Parade, and dewatering the dredge sediments using equipment sited at NolanReserve.The dredging methodology proposed uses an innovative dewatering technique, which isperceived to offer a number of environmental and operational advantages when compared toother options considered. In particular, the method, which involves treatment with a polymerand dewatering using geotextile bags, offers the following benefits:A reduction in the volume of material which requires movement away from theLagoon;Potentially allowing the dredge spoil to be beneficially reused at other locations(subject to physical and chemical material testing), rather than being sent to landfill;Avoidance of, or reduction in landfill charges, which would otherwise be significantand reduce the viability of the project from an economic perspective.In consultation with Manly Council, the Land and Property Management Authority and theDepartment of Environment, Climate Change and Water, a dredging trial has beenundertaken (Appendix C) which successfully demonstrated the capability of the technologyto effectively dewater sediment from the lagoon. During the trial, water and sedimentsamples were collected and analysed to inform both the process design and this REF.In developing the REF, a wide range of potential impacts of the project have beenconsidered. These include impacts on:Topography, Geology and soils (including acid sulfate soils);Climate and Air Quality;Water Quality and Hydrology;Biodiversity (Flora and Fauna);Heritage (Aboriginal and Non-Aboriginal);Noise and Vibration;Traffic and Access;Utilities and Services;Visual Amenity and Aesthetics;Hazards and Waste;Socio-Economic Factors;Cumulative Environmental Impacts.Of these, the greatest direct risk is to water quality, with associated direct and indirect risksto biodiversity in the lagoon. In recognition of this, a number of specialist studies have beenundertaken with the objectives of quantifying current conditions in the lagoon, evaluating themagnitude of expected impact, and identifying mitigation measures which should beemployed to minimise or mitigate the level of expected impact. These studies are included2 July 2010 Cardno (NSW/ACT) Pty Ltd iiiH:\Doc\2010\Reports.2010\Rep2580v4.doc
Manly Lagoon Dredging Project – Review of Environmental FactorsPrepared for Manly and Warringah Councilsas appendices to this REF, and include a water quality study, benthic fauna survey, andseagrass survey.Based upon the findings of the specialist reports, it can be concluded that provided themitigation measures contained in this REF are followed, the proposed dredging anddewatering activities are not expected to have any significant negative impact on waterquality, flora or fauna within the lagoon. Similarly, discussion within this REF shows thatprovided mitigation measures are implemented as described, no significant negativeenvironmental impact is expected to occur.Extensive consultation has been carried out with relevant agency stakeholders during thepreparation of this REF which was preceded by community consultation in the originalformulation of the project. All key stakeholder concerns have been considered in themitigation measures contained within this REF. No issues were raised during theconsultation that were incompatible with the project.Manly and Warringah Councils will develop a Community Consultation Plan as a means toinform the community of the project and provide ongoing information to the public for theduration of the project.This REF has been produced in accordance with the requirements of sections 5A and 111 ofthe EP&A Act, and concludes that there are no significant environmental impacts, nor anysignificant effects on any threatened species, populations or ecological communities, andthat as such, a Species Impact Statement (SIS) and / or an Environmental Impact Statement(EIS) will not be required for the project.It is considered that the processes and mitigation measures described in this reportrepresent an appropriate scope of works to dredge the subject section of the lagoon whilstminimising the risk to the environment. It is therefore recommended that dredging proceedsin accordance with the mitigation measures described in this REF.2 July 2010 Cardno (NSW/ACT) Pty Ltd ivH:\Doc\2010\Reports.2010\Rep2580v4.doc
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Manly Lagoon Dredging Project - Manly Council - NSW Government

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