PROPOSED CHILDCARE 11 CRYERS ROAD, HIGHBROOK ASSESSMENT OF NOISE

Transcription

1 1/355 Manukau Road Epsom, Auckland 1023 PO Box Epsom, Auckland 1344 T: E: PROPOSED CHILDCARE 11 CRYERS ROAD, HIGHBROOK ASSESSMENT OF NOISE Report No Prepared for: Kaipara Limited PO Box 8 Beachlands Prepared by:. Rhys Hegley November 2016

2 2 CONTENTS 1. Introduction Assessment Criteria Road Traffic Noise Calculation Method Proposed Mitigation Road Traffic Noise Levels Assessment of Noise Levels Conclusions... 9

3 3 1. INTRODUCTION The site at 11 Cryers Road in Highbrook is at present, partially developed with a single large commercial building to the north. Kaipara Ltd, the owner of the site, proposes to develop the remainder of the site as shown on Figure 1 below. A commercial building (A, Figure 1) is currently under construction with the intention of developing a second commercial building (B, Figure 1) in the near future. To complete the site s development, Kaipara also propose a childcare centre near to the middle of the site (C, Figure 1). It is understood that Auckland Council has requested an assessment of the effects of road traffic noise on the childcare, which is the subject of this assessment. Figure 2 Figure 1. Plan of the Development and the Surrounding Area

4 4 2. ASSESSMENT CRITERIA There are no statutory criteria for childcare centres, as the Auckland Unitary Plan ( AUP ) is silent on the matter. The Ministry of Education s document Licensing Criteria for Centre-based ECE Services (the MoE Criteria ) adopts the recommendations of the World Health Organisation ( WHO ), which it summarises in PF12 as: Table 1. MoE Criteria SETTING HEALTH EFFECT L eq (dba) L max (dba) Sleep rooms Sleep disturbance Indoors Speech interference 35 - Outdoor Annoyance (from external source) 55 - The MoE criteria are considered to offer an excellent level of protection. By way of comparison, AS/NZS2107: 2000 Acoustics - Recommended Design Sound Levels and Reverberation Times for Building Interiors gives internal levels of 35 45dBA L eq for teaching areas, albeit in primary schools, and 30 40dBA L eq for bedrooms in houses near busy roads. In both cases, the MoE criteria are at the lower end of the range recommended by AS/ NZS The L max level from traffic on a road generally has a large variation, as it is dependent upon each specific vehicle and would vary for different vehicle horns, loads and driving styles. For that reason, it is not practicable to confirm that a building will achieve a specified L max internally. The following design has been undertaken on the basis that by achieving a high level of acoustic amenity internally via the L eq criterion, the rooms will be suitable for sleeping and teaching. 3. ROAD TRAFFIC NOISE 3.1. Calculation Method Typically, the existing levels of road traffic noise that the proposal would be exposed to would be measured on site as part of the assessment. However, in this instance the noise from the installation of the Building A piles would adversely affect the measurements. For this reason, noise levels have been calculated.

5 5 The default method of calculating noise from road traffic in New Zealand is the United Kingdom Department of Transport and Welsh Office Calculation of Road Traffic Noise (CoRTN). This method is identified as being suitable by the New Zealand traffic noise Standard 1. The adjustments contained within the Land Transport New Zealand research report 326 have been incorporated into the calculations. Calculations require traffic data for the surrounding road network. With reference to Figure 1, traffic data was available on the Auckland Transport website for Highbrook Road, Cryers Road and Allens Road. As there is no data for Crooks Road to the south, analysis proceeded based on the same traffic movements as Allens Road, further to the south. Based on a visit to site this is considered to be a conservative assumption, as Allens Road appeared to be considerably busier than Crooks Road. Road traffic noise is typically calculated as an average noise level over an entire 24 hour period (L Aeq(24hr) ) for the assessment of residential properties. However, as the childcare will only be used during the day time, the reported noise levels are for the busiest peak hour during the day time. The screening of road traffic that is offered by the existing buildings is included in the analysis. As Building A (Figure 1) is under construction and will be complete prior to the opening of the childcare centre, it too is included in the analysis. While it is intended that the Building will be open shortly after the childcare centre opens, the levels reported below are for the initial period in its absence with further calculations showing that it will provide between 1 and 2dB reduction to the childcare centre, depending upon the exact location considered Proposed Mitigation Analysis has been based on the outdoor play area and the northern facade being screened from the adjacent road network by a 2.0m high wall as shown on Figure 2. 1 NZS6806: 2010 Acoustics Road-traffic noise New and altered roads

6 6 Proposed 2m wall 1 Outdoor Play Area 2 3 Childcare Building 4 1 Assessment location Figure 2. Extent of Proposed Noise Wall To be effective, the noise wall must be constructed from a material with a surface density of nominally 10kg/m 2 or greater with materials such as 20mm pine or construction grade plywood, or 6mm fibre cement sheet being suitable options. The wall must be a minimum of 2.0m high and seal to both the existing building at its northern extremity and the purposed childcare centre to the south. There must be no gap at its base for noise to pass through meaning that the fence must seal to the ground. Figure 3 shows a suitable fence detail.

7 7 Batten Palings Barrier to be fixed to the ground Figure 3. Noise Barrier Construction Option 3.3. Road Traffic Noise Levels The resulting noise levels about the proposed childcare centre are summarised below. Table 2. Road Traffic Noise Levels to the Proposed Childcare Site (Figure 2) Location Noise Level (dba L eq(1 hour) 1 Outdoor play area 53 2 Northern façade 50 3 Western façade 60 4 South eastern façade 57

8 8 4. ASSESSMENT OF NOISE LEVELS The predicted external level in the outdoor play area of 53dBA L eq(1 hr) achieves the 55dBA MoE criterion. Given that the predicted noise level is considered to be conservative (due to the traffic flows assumed for Crooks Road likely being higher than exists on the road) and that the MoE criterion (which repeat those of the WHO) offer an excellent level of protection, it is considered that the resulting noise levels in the outdoor play area are appropriate for a childcare centre. While Table 2 provides external levels only, the remaining MoE criteria are internal within the childcare building meaning that the façade will be required to provide the following reductions to the most exposed facade: = 30dBA to sleep rooms; and = 25dBA to teaching areas. While the actual construction materials of the childcare are yet to be determined, preliminary calculations and experience with other, similar buildings, shows that the required reductions would be achieved through a number of different construction types. Generic examples of suitable construction types for the most exposed facade include: Double glazing with a layer of 8mm glass, a 12mm cavity and a layer of 6.38mm laminated glass; Framed construction with a Gib Board lining and an external cladding of profiled metal on RAB Board, weather boards or fibre cement sheet; Concrete panels, either bare or strapped and lined. Lesser constructions would be suitable for the les exposed facades

9 9 The reductions would require closed windows to all sleep rooms and to teaching areas with glazing to the west or south east. Teaching rooms to the north could have open top hung windows for ventilation but larger openings, such as ranch sliders would have to be closed to achieve the required reductions. The closed windows would necessitate alternative ventilation which in practice would mean mechanical plant. To maintain the required internal noise levels, the cumulative level from the traffic noise and the mechanical plant would have to comply with the MoE internal criteria. Given the numerous methods of controlling the noise from mechanical plant, such as the selection of suitable plant, silences and enclosures, it is considered practicable to design the plant so that the cumulative level with traffic noise will remain compliant with the MoE criterion. It is understood that the MoE has a further requirement that the children should have unrestricted access to the outdoor play area which would initially seem at odds with the requirement for closed windows and doors. One option to address this issue would be the introduction of a lobby system so that rather than exiting to the outdoor play area the children would have to pass through a lobby. A simple form of this would be classrooms off of a corridor. It is an important point that this would not prohibit the childcare centre opening directly to the outdoor play area if required by the teachers, as the MoE criterion only requires that the building be capable of meeting the internal noise criteria. 5. CONCLUSIONS Analysis has shown that it will be practicable to achieve the noise criteria of the MoE for external play areas and internal teaching and sleeping areas based on the noise resulting from traffic on the surrounding road network. Mitigation measures include a 2.0m high wall to screen the outdoor play area and northern façade and a specifically designed building envelope to the teaching and sleep rooms. By achieving the MoE criteria, it has been concluded that the road traffic noise levels within the childcare centre will be appropriate and that any adverse effects will therefore be less than minor.