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9. Mitigation and Management
9.1 Training
All staff will participate in an induction training session when they commence work on the main works. The induction will include a briefing on this CNV DWP, with attention given to the following matters:
Roles and responsibilities for management of noise and vibration Construction noise and vibration limits Information about noise and vibration sources on-site Noise and vibration mitigation and management procedures The sensitivity of receivers to noise and vibration (including MediaWorks), and any operational requirements and constraints identified through communication and consultation Complaints management procedures
Awareness of current noise and vibration matters on, or near active worksites, will be addressed during site meetings and/or ‘toolbox’ training sessions.
9.2 Construction Hours
9.2.1. General Timing of Works
Table 9-1 shows the general construction hours, and any special conditions related to timing.
Table 9-1 Construction hours and conditions that require specific timing
Activity
General hours
MediaWorks Sensitive Times (3 Flower St)
Days
Monday to Saturday:
Sundays & Public Holidays All other times (night) Monday to Friday
Saturday
Sunday
Times
0700 –1900 hrs 1900 –2200 hrs 0700 –2200 hrs
2200 –0700 hrs 0600 –0915 hrs 1600 –1700 hrs 1730 –1915 hrs 2020 –2330 hrs 0900 –1230 hrs 1700 –1915 hrs 1700 –1915 hrs
Condition: Comment
31: Prioritise. 31: Minimise where practicable. 31: Minimise where practicable.
31: Avoid where practicable. 35.2: Amended by MediaWorks SSCNVMP in Appendix C1.
Piling and road cutting
Concrete/rock breaking Monday to Saturday
Monday to Saturday
Blasting Monday to Saturday 0700 –1900 hrs
Avoid Sensitive Times
1032 and 1432 hrs as agreed with MediaWorks 36.3 (b): Restricted period.
35.2A: Within 100m of the MediaWorks building unless monitoring verifies compliance with the limits in Condition 35.2.
32.6 and 35.10: Avoid MediaWorks Sensitive Times (above) during daylight hours.
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9.2.2. Night-time, Sunday and Public Holiday Works
Normal hours of works are 7am to 7pm Monday to Saturday, extending to 10pm if required. After 10pm, the approach to night works will be as follows:
Avoid where practicable Where required, review the construction methodology to identify high noise activities that can be prioritised before 10pm, preferably before 7pm Minimise the duration of high noise activities Minimise the number of periods (e.g. complete high noise activity in one extended period rather than two shorter periods with the same overall duration)
Note that people tend to be less disturbed by low frequency, continuous engine noise, than intermittent noise or activities with special audible character (e.g. reversing beepers, whistling or shouting).
9.3 Equipment Selection
Some activities have the potential to exceed the limits for construction noise and vibration at close nearby receiver distances. It is essential that appropriate mitigation and management measures are identified and employed in advance of the works to avoid exceedances. When selecting construction equipment:
Equipment will be suitably sized for the proposed task Equipment will be well maintained Exhaust silencers will be fitted Fit or upgrade engine covers in consultation with equipment manufacturer where appropriate Substitute diesel engines with electric motors where practicable
9.4 General Mitigation Measures
Best Practical Option (BPO) mitigation will be implemented throughout the construction programme to avoid exceedances. This will include, but not be limited to the following:
Page 31 Keep the construction time near noise sensitive areas to a minimum Avoid unnecessary noise, such as shouting, the use of horns, loud site radios, rough handling of material and equipment, and banging or shaking excavator buckets Avoid metal on metal contact where practicable by minimising drop height of materials, such as during loading and unloading of trucks Tonal reversing alarms shall be prohibited on site. Suitable alternatives may include flashing lights, broadband audible alarms or reversing cameras inside vehicles. Staff acting as spotters are mandatory for reversing equipment Mitigate track squeal from tracked equipment, such as excavators and piling rigs. This may include tensioning and watering or lubricating the tracks regularly Avoid high engine revs where practicable through appropriate equipment selection and turn engines off when idle / parked Avoid steep internal haul routes and keep the road surface smooth and well maintained Maximise the distance between the noise source and the nearest sensitive receiver by positioning fixed plant away from sensitive receivers, or orienting machinery to maximise
Mt Eden Main Works CNV DWP
the distance between the engine exhaust and the nearest sensitive building façade where practicable (e.g. bored piling rig, excavators and mobile cranes) Crane and secure loads using straps in preference to chains where safe and practicable Utilise power from the national grid in preference to generators where practicable Utilise noise barriers and enclosures where effective (Section 9.5) Implement further measures identified through communication and consultation with sensitive receivers (Section 10) Undertake noise and vibration monitoring to confirm compliance or identify high noise and/or vibration machinery (Section 11)
9.5 Noise Barriers and Enclosures
Site boundary fences will be constructed, or existing fences upgraded as required, to provide effective noise mitigation during construction. Temporary noise barriers will be used where a construction noise limit is predicted to be exceeded and the barriers would noticeably reduce the construction noise level. Noise barriers will be installed prior to works commencing and be maintained throughout the works. Effective noise barriers typically reduce the received noise level by 10 decibels. The following guidelines will be incorporated in the design and utilisation of noise barriers:
The panels will be constructed from materials with a minimum surface mass of 6.5 kg/m 2 , including the following proprietary ‘noise curtains’: Duraflex ‘Noise Control Barrier - Premium Series’ (www.duraflex.co.nz) Soundex ‘Acoustic Curtain - Performance Series' (www.ultimate-solutions.co.nz) Flexshield ‘Sonic Curtain with 4 kg/m2 mass loaded vinyl backing’ (www.flexshield.co.nz) Alternatives will be approved by a suitably qualified acoustic specialist because some proprietary noise curtains have insufficient surface mass for general use The panels will be a minimum height of 2m, and higher if practicable to block line-of-sight The panels will be abutted or overlapped to provide a continuous screen without gaps at the bottom or sides of the panels The panels will be positioned as close as practicable to the noisy construction activity to block line-of-sight between the activity and noise sensitive receivers Where positioned on the site boundary, additional local barriers will be considered near the activity to ensure effective mitigation for sensitive receivers on upper floor levels
Noise enclosures surround the sound source with noise barriers on more than one side and include a ‘roof’. The effectiveness of noise enclosures depends on the extent that the source can be enclosed without constraining the operation of the equipment and resulting in an unacceptable occupational health and safety environment (e.g. noise exposure, heat, dust, poor lighting etc). Enclosures can also result in traffic management issues and increase construction duration for short term or transient activities.
Enclosures will be used for stationary plant where a noise barrier is not sufficient to achieve compliance with the noise limits and it is practicable to do so (e.g. fixed paver cutting stations, pumps, spoil handling conveying equipment etc).
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The enclosure can be erected using the noise curtains listed above, or alternatively, the following proprietary cutting station ‘noise enclosures’ can be used:
Soundex ‘E6/2 Quick-Tech Cutting Enclosure' (www.ultimate-solutions.co.nz)
Hushtec ‘Acoustic Tent’ (www.duraflex.co.nz) Alternatively, a suitably qualified and experienced acoustic specialist (such as MASNZ) will be involved in the custom design of the enclosure (an example is included as Figure B.3 in NZS 6803:1999).
9.6 Concrete and Paver Cutting
Use noise enclosures where practicable, otherwise barriers (Section 9.5) Minimise the concrete cutting period, and, the number of cutting periods (e.g. complete all cutting in one extended period rather than two shorter periods with the same overall duration) Select blades that are sharp, maximise the number of teeth, minimise the blade width, minimise gullet depth, and have built in vibration damping slots Use a unit fitted with a blade shroud and operate with a water supply
9.7 Concrete and Rock Breaking
Avoid MediaWorks broadcast ‘Sensitive Times’ for breaking within 100m of the MediaWorks studios (at 3 Flower St and 71 Boston Road), unless monitoring verifies compliance with the limits in designation Condition 35.2. Refer their SSCNVMPs in Appendices C1 and C24. Other general measures include the following: • Use local noise barriers to screen the breaker tip where practicable • For concrete breaking near buildings, an initial perimeter saw cut will be made at the perimeter to reduce vibration transfer • For rock breaking, initial breaking will be undertaken at the perimeter of the rock face closest to neighbouring buildings where practicable. This will enable monitoring of the highest vibration levels received at nearby buildings for compliance purposes. It will also mitigate the vibration transfer from subsequent breaking by creating a ‘trench’ of fractured rock between the breaker and nearby buildings • Minimise the volume of breaking (e.g. use a crushing shear or pulveriser attachment in place of a breaker, or use a cut and lift approach to enable breaking in the centre of site) • Minimise the duration of breaking, and the number of breaking periods (e.g. complete all breaking in one extended period rather than two shorter periods with the same overall duration) • Match the size of breaker to the scale of the works (i.e. large enough to undertake the works efficiently, but avoiding oversized units) • Match the chisel/tip type to the material and use a dampened bit to avoid ringing; and • Avoid ‘blank’ firing by engaging the material before commencing and stopping before it fires through the material.
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9.8 Piling
Prioritise piling methods that minimise noise and vibration where practicable (e.g. augured, screw or press-in piles over impact driven or vibratory piling methods) Minimise alternating rotation of the bored piling auger to loosen spoil into the muck bin. Shaking the ‘kelly bit’ connection creates very loud banging that can result in noise complaints. It is understood this action can be avoided for general auger use but is necessary specifically when a coring barrel is used to drill through obstructions (due to Health and Safety issues related to alternative ways of loosening material from the bit).
9.9 Blasting
The blasting contractor will keep the Blasting Management Plan (BMP) updated. The following general mitigation should be used:
A shroud will enclose the cutting head of the blast hole drilling rig where practicable Comprehensive vibration and air overpressure level predictions will be performed prior to every blast event Signature hole analysis (small trial blasts) will be undertaken to determine site specific vibration attenuation characteristics, air overpressure levels and maximum instantaneous charge weight (MIC) thresholds. Outcomes will be documented in a Trial Blast Report. This Trial Blasting Report shall be used for subsequent design of production blasting Where predicted vibration levels exceed the cosmetic building damage limits (Section 4.2.1), investigate modifications to the blasting technique (e.g. charge weight, charge layout, firing order, hole depths etc). Where blasting is the BPO and is still predicted to exceed the cosmetic building damage limits, a SSCNVMP will be prepared Where practicable and appropriate, the production blasting will commence at the closest position to sensitive receivers. Fracturing the basalt layer can reduce vibration transmission to receivers from subsequent blasts further away Blasting times will be agreed with MediaWorks and avoid Sensitive Times (Appendix C1) Startle caused by blasting will be mitigated through communicating exactly when blasts will occur (e.g. 10:32am and 2:32pm) and having an audible countdown sequence
9.10 Vibro-Rolling
Avoid evening and night-time periods and Sundays/public holidays where practicable Match the size of roller to the scale of the works (i.e. large enough to undertake the works efficiently, but avoiding oversized units) Prioritise the use of static rollers over vibratory rollers
For vibratory rollers using the vibro mode:
Only use outside the predicted safe setback distances from buildings (Section 7.1) unless a suitable SSCNVMP is in place Timing will be agreed with MediaWorks and avoid Sensitive Times (Appendix C1) Match the vibration output to the scale of the works (i.e. combination of minimising the amplitude of the drum vibration and/or maximising the vibration frequency of operation) Ramp up/down (i.e. start/stop vibro mode) away from buildings (refer safe distances Section 7.1) and progress closer to buildings as required once vibro mode is constant/stable
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Minimise the duration (e.g. use vibro mode to settle and align aggregate, then turn vibro mode off away from buildings for subsequent static rolling compaction) Minimise the number of periods (e.g. complete all vibratory rolling in one extended period rather than two shorter periods with the same overall duration)
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