The Otago Regional Council publicly notified the Dunedin City Council application for the ‘‘continued operation, expansion, closure, and aftercare’’ of the landfill at the weekend.
Regional council senior consents planner Shay McDonald said adverse odour effects could be more than minor and there was uncertainty about the extent to which leachate might impact the groundwater and surface water in the area.
Ms McDonald’s notification recommendation report said the Green Island landfill was expected to reach full capacity about April 2027 and to account for the landfill’s closure the city’s next landfill would be developed at Smooth Hill, near Brighton.
However, before waste could be accepted there, the city council needed to complete 36 months of baseline monitoring, finish a detailed landfill design, prepare management plans, and complete initial works, including roading upgrades at that site.
The earliest Smooth Hill could be ready to accept waste would be 2027, ‘‘but there is risk of further delays’’, she said.
To account for this, the city council proposed increasing the height of the Green Island landfill at its western end, allowing it to remain within its overall ‘‘footprint’’ at the present site while also allowing for its expansion.
That expansion would allow the landfill to take waste until the end of 2029, or March 2031, depending on the amount of waste coming into the site.
Once the new landfill was operational at Smooth Hill, Green Island would close and its operation would shift to ‘‘aftercare’’.
In her summary of the city council’s application, Ms McDonald said in total 145 complaints about odour at Green Island were received from July 2017 to August 2022 — most complaints were due to normal operations, but up to six complaints a year were due to deliveries from wastewater treatment plants.
When the source of those complaints was known most (91 of 112) came from the southeast of the site, Clariton Ave alone accounted for 54 of those complaints.
The complaint history indicated odour was affecting those nearby, she said.
However, an analysis of ‘‘frequency, intensity, duration, effectiveness, and location’’ factors had resulted in a range of proposals for how to better manage the problem.
Minimising truck waiting times and employing an odour neutralising cannon during light winds would assist, so too would expanding the landfill at its western edge, away from those residences most affected.
The city council said with the proposed management and mitigation measures, and proposed changes to the site, odour issues were expected to reduce in terms of both intensity, frequency, and duration, Ms McDonald said.
The city council application said while odours might still be ‘‘detectable on occasions’’, as long as the proposed mitigation measures were rigorously implemented, the likelihood of off-site odours being considered offensive was low ‘‘and unlikely to cause a more than minor adverse effect’’, she said.
However, she noted Jacobs New Zealand Ltd principal air quality specialist Tracy Freeman, in her technical audit, disagreed.
‘‘Whilst the proposed measures should result in a reduction in odour emissions, the applicant has not established that off-site odour impacts will reduce to the extent that there is no offensive or objectionable odour effect due to landfill activities,’’ Ms Freeman said.
Ms McDonald also noted a technical audit of the city council’s application suggested uncertainty around the effectiveness of the leachate collection trench, noted significant collection of leachate within the landfill, and said there was insufficient data to support some of the city council’s claims as to water quality effects.
Submissions close on December 13.
