The District Plan's outer perimeter or boundary of the Onerahi airport ringfencing (the outer control boundary) allows for up to 55 decibels of average combined day and night noise to be produced per 24 hours (Ldn).
The 24-hour period is averaged over three-months. A second key inner zone within that and closer to the airport runway and operational area (airport noise boundary), allows for more noise production - up to 65dba of Ldn.
The difference in noise production between these District Plan allowable noise zones and WDC's newly-produced additional predicted extra helicopter noise production is visually displayed on the draft map. Mapping noise production and the differences between zones results in a topographic-like noise contour map which will be central to the meeting.
Kula said that while emergency services were exempt from District Plan airport noise production contours, their impact in relation to the new helicopter noise production zones would still be part of the meeting's consideration.
He said it was important to note that the map was in draft form. Further noise management work would be done and include council noise impact mitigation considerations.
The new WDC mapping was calculated on the new emergency service's helicopter base being located at the airport, just east of the main Handforth St airport terminal and including the former air control tower and adjacent blue hangar.
Kula said the meeting's purpose was to look into the draft noise mapping to assist the airport noise committee moving forward, including around its recommendations to a full council meeting about how to proceed further.
The mapping shows the amount of noise produced by the Northland Emergency Services Trust (Nest) helicopters' presence would technically exceed the District Plan's 55dba Ldn outer control boundary limits in several geographic points around the airport including parts of Church St, Cockburn St, Handforth St, Pah Rd, Whimp Ave and Weir Cres.
It also shows a new additional area of much louder 65dba Ldn noise production in a northern extension to the inner zone (airport noise boundary), near the proposed new helicopter base site. The extension skirts the airport terminal building, where thousands of people visit annually. It then runs east towards Church St. Houses between roughly 105 and 115 Church St in particular would be much closer to this louder noise production.
Doherty said the World Health Organisation's community noise guidelines recommended an Ldn of 45dba for the protection of health, amenity and to reduce the likelihood of sleep disturbance.
He said a new 50dba Ldn noise contour line was also included on the new map. This showed swathes of Onerahi peninsula properties affected in a new area between it and the District Plan's existing 55dba Ldn noise production allowance contour line limit, including large numbers of houses around several parts of Beach Rd, Cockburn St, Handforth St, Pah Rd and Weir Crest.
Doherty said the new helicopter noise production mapping was being presented as based on the three busiest months of the year, but it had used the quieter winter period from May, June and July 2021 for its figures.
"Nest data from 2020 shows its summer period – November, December and January – with 371 flights to be 58 per cent busier than winter - May, June and July – with 235 flights," Doherty said.
"The summer figures would show even more serious breaches of the contours," Doherty said.
He said that on top of that, there had been no allowance for Nest's addition 15 per cent predicted annual growth.
A tracked-changes updated Airport Noise Management Plan is also being presented. This guides day-to-day management and long-term strategic planning decisions around procedures, obligations and best practicable options relating to noise emissions.
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