Extension after extension was granted to the owner of a failing wastewater treatment plant suspected of discharging contaminated effluent into renowned Queenstown rivers.
When issues first emerged at the Shotover Wastewater Treatment Plant (Shotover WWTP) in 2021, the wastewater being discharged from its inadequate disposal field was understood to be treated and was not considered a significant environmental risk.
However, Otago Regional Council principal compliance officer Shelley Reed’s detailed account of site visits to the plant since 2021 show that more than a year ago she became concerned the discharges, which at times flowed freely beyond the plant’s boundary, were ‘‘under-treated’’.
Ms Reed’s account is included in a swathe of documents released ahead of Environment Court proceedings against the Queenstown Lakes District Council over the operation of the plant.
Historically, the plant used an oxidation pond system and was consented to discharge wastewater directly into the Shotover River until 2014, Ms Reed said.
But in 2013, the QLDC initiated an upgrade at the plant and moved to a system that discharged treated wastewater on to land by means of a disposal field.
‘‘Unfortunately, since February 2021, the Shotover WWTP disposal field has faced compliance issues due to sludge binding, believed to be carryover from the treatment process.
‘‘This has hindered infiltration, causing surface ponding of wastewater (which includes undertreated wastewater) and the discharge of treated or undertreated effluent outside the consented disposal field area.’’
The first of two abatement notices was issued by the ORC in May 2021 due to the plant’s disposal-field ponding issues.
When Ms Reed inspected the site on December 27, 2023, odour issues had also emerged.
Wastewater was discharging through the fence around the disposal field.
‘‘The wastewater was flowing like a small river away from the disposal field and ponding on the Shotover Delta,’’ Ms Reed said.
‘‘I believe the wastewater was not properly treated because it was discoloured, silt laden and smelt of sewage.’’
The following day Ms Reed returned and saw the flow of wastewater had extended another 20m.
Wastewater was discharging under a gate to the southeast of the disposal field where it seemed to disappear, and another large ponded area of what was believed to be wastewater was discharging overland directly into the Kawarau River.
Testing found the wastewater ponding outside the disposal field had ‘‘extremely high’’ levels of Escherichia coli and total suspended solids.
The testing of the new ponded area that was discharging into the Kawarau River showed E. coli levels higher than the resource consent limits, she said.
Further, downstream samples from the river showed higher levels of E. coli and other contaminants than upstream samples.
After an investigation lasting more than a year, the ORC applied last month to the Environment Court for an enforcement order against the QLDC over its operation of the treatment plant.
The documents released this week by Environment Court Judge John Hassan, which included Ms Reed’s sworn statement, showed that after the May 2021 abatement notice was issued, the QLDC was granted eight extensions as issues persisted at the site.
The first abatement notice, issued on May 27, 2021, and supposed to be dealt with by August 25, 2021, was due to ponding of fully treated wastewater ‘‘and was, therefore, not considered to be a significant environmental risk by the ORC at that time’’.
However, the issues behind it proved ‘‘quite complex’’ and investigations identified ‘‘significant unplanned investment’’ would be required to address the issues, Ms Reed said.
Correspondence between the two councils showed often months-long extensions were requested just days before the deadline for compliance.
The latest extension granted by the ORC was until November 30 last year.
On December 3, the QLDC asked for another three-month extension until February 28 this year.
On January 22, the ORC lodged its application with the Environment Court seeking an enforcement order.
Ms Reed’s evidence said the treatment plant serviced the communities of Queenstown, Arthurs Point, Frankton, Kelvin Heights, Quail Rise, Shotover Country, Lake Hayes Estate, Lake Hayes and Arrowtown.
Upgrades under way at the site would allow it to receive additional wastewater flows from Jacks Point Village, Hanley’s Farm, Ladies Mile and an extension of the Quail Rise residential area, she said.
Ms Reed’s evidence included one visit in January last year when she saw wastewater discharging from the disposal field, creating a pond about 100m long and 3m wide near the Twin Rivers Trail cycle path.
E. coli and total suspended solids were again ‘‘significantly higher’’ than the resource consent limits and several weeks later ‘‘an extensive sludge ‘crust’ ’’ was visible in the area of the discharge, she said.
At this point, ‘‘earth bunds’’ had been built in and around the disposal field.
Ms Reed said the disposal field looked like an oxidation pond and was estimated to be 1m deep.
She described how the newly constructed bund ‘‘suddenly failed completely’’ on the eastern side of the disposal field, releasing a substantial flow of wastewater into publicly accessible land.
Ms Reed visited the site the following day and, although the flow had stopped, wastewater remained in a pond outside the disposal field.
This incident prompted the second abatement notice to be issued on March 18 last year.
On November 9 last year, the QLDC plant operator, Veolia, reported about 1.30pm that the treatment plant’s disposal field was discharging beyond the perimeter fencing.
Then, about 3.30pm that day, two ‘‘out-of-hours’’ ORC officers saw wastewater discharging through a large pipe directed to the boundary fence of the disposal field — a violation of the resource consent.
Again wastewater was creating a large flooded area on land that was publicly accessible.
Nine follow-up visits between November 19 and December 16 last year confirmed the discharge was ongoing, she said.
Ms Reed said the pipe appeared to have been installed as a way to prevent the disposal-field bund walls from collapsing when the disposal field became overwhelmed. The main flow was spreading out across the river delta, she said.
‘‘The effluent was about halfway up my gumboots in some places. ‘‘I was surprised at how bad the discharge had got.
‘‘There had been no notification from QLDC/Veolia that it was this bad. ‘‘I saw small red invertebrates swimming in the discharge. ‘‘There was also a lot of green algae and other floating debris that looked like sludge.’’
She followed the discharge for some time and due to the duration and extent of it she said she suspected that it could by that stage be reaching the Kawarau River.
She returned the following day, accessing the site through public land ‘‘and without signing into the site’’.
Along with another ORC staff member she saw the wastewater flowing ‘‘like a small river’’ and creating a large pond in the delta.
‘‘The ponding was the worst I had seen at the site,’’ she said.
In parts, the river of wastewater appeared to be deeper than her gumboots, she said.
Mott MacDonald senior engineering geologist Tobias Zaege said the plant’s disposal field was failing due to its ‘‘hydrogeological setting and its design choice’’.
‘‘A deviation from resource consent conditions should be sought, as returning [the disposal field] operation under the conditions is not considered feasible,’’ he said.
‘‘Focus should be given to preventing overflow discharge into the environment.’’
The ponding at the disposal field was largely due to a ‘‘shallow, highly fluctuating groundwater table’’.
Mr Zaege said the environmental impact of the resource consent breaches should be monitored through regular groundwater and river-water sampling.
He called for limiting the flow of discharge into the disposal field until a solution was in place, but said consideration should be given to altering the resource consent ‘‘by permitting surface ponding’’.
To get the disposal field to meet its consent conditions, backfilling was required, but this was ‘‘not recommended due to the inherent hydrogeological conditions’’.
Mott MacDonald technical director David Hume visited in September after the March abatement notice.
In his evidence, he described ‘‘clear changes needed’’ to the plant’s treatment system.
Mr Hume noted ‘‘two key issues’’ at the plant — the deterioration of the functioning of the disposal field and the deterioration in the quality of the effluent concentrations.
He said monthly sampling started in 2018 and the plant had been compliant until December 2023, but efforts to resolve the issues were returning the treated effluent to normal levels.
Elevated concentrations in the effluent in December 2023 and again in July last year resulted in elevated levels within ‘‘many of the groundwater bores surrounding the disposal field’’.
However, he said the plant upgrade now under way would provide further treatment capacity out to 2048 and was due to be completed this year.
Mr Hume said, as long as the upgrade worked, ‘‘the issue of high solids loading to the disposal field will only exist until late 2025’’.
Further, he said Mott MacDonald’s recommendations in many cases involved installing infrastructure at the plant that would take time and work already under way would ‘‘overtake these proposed changes’’.
