Manly Lagoon Dredging Project - Manly Council - NSW Government

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Manly Lagoon Dredging Project – Review of Environmental FactorsPrepared for Manly and Warringah CouncilsWasteEncountering and exposing acid sulfate soils during dredging operations;Bushfire occurring at the proposed site during operations;The movement of heavy vehicles and equipment, particularly around local streetsduring the sediment relocation operations, which will pose a potential hazard toconstruction workers, motorists, cyclists and pedestrians both on and off site; and Accidental spills on site of fuel, lime and/or polymer ULTIMER 7757.In the current proposal there will ultimately be minimal waste generated as a result of theactivities, as all dredge spoil will be dewatered to reduce the volume and wherever possibletreated dredge spoil will be beneficially reused, reducing the volume of material sent tolandfill. It should be noted that due to the nature of the material (potentially containing acidsulfate soils and other waste) and the method with which it will be processed (via dosing anddewatering), the material cannot be classified as VENM, as defined by the PoEO Act. Thiswill affect where the material can be reused, however, this beneficial reuse is not assessedin this REF. If the dredge spoil is determined to be unsuitable for reuse, then upto 6,400m 3of treated dredge spoil will require disposal of to an appropriate landfill site.Wherever possible, water extracted from the lagoon along with the sediment will ultimatelybe returned to the lagoon. If water quality does not allow this, offsite disposal of runoff waterfrom the dewatering process will be required.During the proposed works the following additional waste streams will be generated:The single use geotextile bags (geobags) used during the sediment dewateringprocess will need to be recycled or disposed of to landfill;Gross pollutants, shopping trolleys, etc extracted from the Lagoon sediments will bedisposed of to landfill; andIf contaminated sediments are encountered during the works this waste would alsoneed to be treated and disposed of appropriately to landfill.Mitigation MeasuresHazardsA Hazards Management Plan will be required prior to commencement of the proposedworks, and the Plan must be followed by all contractors. The following measures should beincluded to reduce the risk of hazards during the operations:Weather reports should be monitored daily to receive Severe Weather Warnings andSevere Thunderstorm Warnings from the Bureau of Meteorology issued for thegeneral catchment area to identify the potential for flash flood conditions;During periods of heavy rainfall dredging works should cease to avoid sedimentationissues downstream due to increased flows;If unanticipated contamination is encountered during the proposed works, worksshould cease. DECCW (EPA) would need to be contacted and the material wouldneed to be classified via chemical assessment according to DECC’s WasteClassification Guidelines (2009d) as discussed in Section 5.1. Once the waste2 July 2010 Cardno (NSW/ACT) Pty Ltd 112H:\Doc\2010\Reports.2010\Rep2580v4.doc
Manly Lagoon Dredging Project – Review of Environmental FactorsPrepared for Manly and Warringah Councilsmaterial is classified, appropriate management options need to be considered, asrequired under the PoEO Act and the associated regulations;All site workers should be made aware of hazards before they enter the site;The proposed works area and contractor’s compound will both be fenced off fromgeneral public access (in accordance with the Technical Specification in AppendixK);Adequate signage for motorists, cyclists and pedestrians should be erected aroundthe site to warn them of the works; andContinuing pedestrian access to the lagoon banks should be safely facilitated aroundthe works area.The Hazards Management Plan must also describe the clean up method to be employed inthe event of an accidental spill. The method for cleaning up accidental spills of ULTIMER7757 must be in accordance with Section 6 (Accidental Release Measures) of the ProductSafety Data Sheet (PSDS) in Appendix I. The polymer will not be stored on site or used insuch a way that would allow the concentration to reach a level which is toxic to fish orinvertebrates, as indicated in Section 12 of the PSDS (Appendix I).Due to the high potential for encountering acid sulfate soils within Manly Lagoon an ASSMPhas been developed (Appendix E), in accordance with the Acid Sulfate Soils Manual(ASSMAC, 1998). The Plan identifies the need for measures to ensure neutralisation of thedredge spoil prior to reuse or disposal, as discussed in Section 5.1. This will be achieved bydosing the dredge spoil with lime. This ASSMP must be followed by the selected contractorand the contractor must ensure their dredging methodology is compatible with and complieswith the standards set out in the ASSMP (Appendix E).An Incident Management Plan should also be prepared for the works and should define anddetail all stop work triggers as identified in this REF. Council’s site superintendent will havethe authority to stop or suspend works at any time, and this decision may be taken inresponse to a pre-determined stop work trigger as defined in the Incident Management Plan,at their discretion, or on the advice of any independent advisor.WasteA Waste Management Plan will be required prior to commencement of the proposed worksas part of the CEMP and must be followed by all contactors. This Plan should specifyalternative recycling and/or disposal methods for any material, including dredge spoil, whichcannot be reused.Any waste that is generated that cannot be reused, such as the geotextile bags (if theycontain unsuitable chemical residue), should be transported off site as soon as practicable toa suitable waste management or recycling facility. This will also aid in maintaining visualamenity (Section 5.9).To apply the treated dredge spoil to land, a Resource Recovery Exemption (LandApplication) must be submitted to and approved by DECCW. An application for thisExemption is being prepared in a parallel process. To be suitable for reuse the treated2 July 2010 Cardno (NSW/ACT) Pty Ltd 113H:\Doc\2010\Reports.2010\Rep2580v4.doc
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Manly Lagoon Dredging Project - Manly Council - NSW Government

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