Manly Lagoon Dredging Project - Manly Council - NSW Government

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Manly Lagoon Dredging Project – Review of Environmental FactorsPrepared for Manly and Warringah Councilsthe lagoon, and the occupants will be temporarily affected by noise from dredgingoperations.The DECC (2009c) Interim Construction Noise Guideline contains guidelines to minimise theimpacts of construction-related noise. The DEFRA (2005) Update on Noise Database forPrediction of Noise on Construction and Open Sites, referenced in DECC (2009c), containstypical A-weighted sound pressure levels, L Aeq , (where A-weighted means an adjustment hasbeen made to the sound level measurement to approximate the response of the human ear)at a 10m distance from the plant. Typical L Aeq values for construction equipment at 10mdistance, as set out in DEFRA (2005), that may be used during the proposed works include:Excavator 52-89 dB(A);Dump Truck 74-92 dB(A); andDiesel Generator 56-74 dB(A).No value is specifically reported for a cutter suction dredger, but it can be assumed therange would be similar to that of an excavator.The closest receptors to the highest noise impacts during dredging works are considered tobe properties located along Riverview Parade, directly adjacent to dredging works withinManly Lagoon. The closest properties are approximately 10m distance from the lagoonbanks. Hence, the received noise levels at these properties could be up to 89 dB(A) (L Aeq ) asa result of dredging operations within the lagoon.This is above the ‘highly noise affected’ L Aeq noise management level of 75 dB(A), as statedby the Interim Construction Noise Guideline (DECC, 2009c), for construction noise receivedat residences. The guideline states that there may be strong community reaction to noiseabove 75 dB(A).However, due to the progressive nature of the works (i.e. once dredging works are completein one location, the dredge will proceed downstream to the next location), no one residenceshould be highly noise affected for an extended period of time. However, this is dependenton the ultimate progression of dredging works. Mitigation measures should be used tofurther minimise the impacts.The increase in local heavy vehicle movements associated with removal of treated dredgespoil from the site will have noise and vibration impacts on the wider residential area.However these impacts are considered negligible when compared to existing road trafficnoise levels associated with Pittwater Road and Condamine Street.VibrationGuidelines for vibration are set out in Assessing Vibration: A Technical Guideline –Environmental Noise Management (DEC, 2006). When dealing with construction vibration,the effects on buildings can be divided into three broad categories:Those in which the occupants or users of the building are inconvenienced;Those in which the integrity of the building or the structure itself may be prejudiced;and2 July 2010 Cardno (NSW/ACT) Pty Ltd 102H:\Doc\2010\Reports.2010\Rep2580v4.doc
Manly Lagoon Dredging Project – Review of Environmental FactorsPrepared for Manly and Warringah CouncilsThose where the building contents may be affected.Individuals can detect building vibration values that are well below those that can cause anyrisk of damage to the building or its contents, i.e. the level of vibration that affects amenity islower than that associated with building damage (DEC, 2006).Vibration may be continuous (with magnitudes either remaining constant or varying overtime), impulsive (in shocks) or intermittent (with the magnitude of each event being eitherconstant or varying over time) (DEC, 2006). Examples of typical types of vibration and theirsources are shown in Table 5.13.Table 5.13: Examples of Types of Vibration (After: DEC, 2006)Continuous Vibration Impulsive Vibration Intermittent VibrationMachinery, steady roadtraffic, continuousconstruction activity(such as tunnel boringmachinery).2 July 2010 Cardno (NSW/ACT) Pty Ltd 103H:\Doc\2010\Reports.2010\Rep2580v4.docInfrequent activities that create upto 3 distinct vibration events in anassessment period, e.g.occasional dropping of heavyequipment, occasional loadingand unloading.Trains, nearby intermittentconstruction activity, passing heavyvehicles, forging machines, impactpile driving, jackhammers (more thanthree vibration events within anassessment period).Vibrations due to dredging operations at the proposed site and heavy vehicle movementsduring relocation of treated dredge spoil are considered to be intermittent. The relevantvibration criteria provided in DEC (2006) are listed in Table 5.14.Table 5.14: Acceptable Vibration Dose Values for Intermittent Vibration during the Daytime (7am-10pm)(After: DEC, 2006)LocationVibration Dose Values (m/s 1.75 )Preferred ValueMaximum ValueResidences 0.20 0.40Offices, schools, educational institutions and places ofworship0.40 0.80Due to the nature of the works occurring (dredging operations within the lagoon water body),it is not anticipated that operations would generate substantial vibration levels. At a distanceof 10m from the lagoon banks, the closest residences are not expected to experiencediscomfort due to vibrations during dredging operations.Mitigation MeasuresDuring dredging and sediment relocation operations measures to minimise impacts ofconstruction related noise as set out in the Interim Construction Noise Guideline (DECC,2009c) and other guiding documents (such as the RTA Environmental Noise ManagementManual, RTA, 2001) should be adhered to.It is recommended that a Noise and Vibration Management Plan be developed by thecontractor (as part of the CEMP) prior to commencement of the proposed works to addressissues associated with emitted noise and vibration. Mitigation measures within the planshould include:
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Manly Lagoon Dredging Project - Manly Council - NSW Government

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