The 450 or so affected households either had to connect to reticulated sewerage or seek consent to upgrade their wastewater systems – although consent was unlikely to be granted if reticulation was possible.

Connection to the grid scheme was expected to cost households about $50,000 eachbut the costs are not finalized.

Construction was almost complete but had been interrupted by protests by mana whenua concerned about the pipeline route.

The district council recently placed posters in public toilets around the lake with the ‘facts’ about the scheme.

“Water quality in Lake Tarawera is declining,” the posters read. “Every day over 200,000 liters of sewage from septic tanks seeps into the ground and into Lake Tarawera.”

The council previously said the figure was 300,000 liters and between 200,000 liters and 300,000 litres.

Thomas said he saw the figures as “misleading”, “propaganda” and “physically impossible”.

“How do you arrive at the numbers, a guess? The only gross sewage I ever saw flowing into the lake was from the council’s own toilets at Stoney Pt and The Landing.”

He understood that most of the lake’s nutrient load came from other sources, such as farm runoff, forestry and geothermal systems.

“Everyone agrees that the sewerage re-linking scheme needs to be completed, but to blame the ‘lake water enrichment’ on residents’ septic tanks is outrageous.”

He also said that the posters are bad for tourism.

“People will say, ‘I don’t let my kids swim in that lake.’

The lake’s water quality is rated ‘excellent’ on Land, Air Water Aotearoa’s swimming website.

Tarawera resident Tracey McLeod said she believed the council had “hugely exaggerated” the figures and used false information that septic tanks had been “banned” since 2017.

Its website, which has since been changed, said they were banned under the regional council’s Change 14 Plan – a plan that never got past the draft stage.

Sewer-lake figure based on estimates

Infrastructure and environment group manager Stavros Michael said the council took down posters that had not already been taken down by others.

Michael said information about “banned” septic tanks has been removed from his website.

“We recognize that this is inaccurate and apologize for any confusion that was created – it was certainly not the intention.”

The use of the word “leaks” was wrong and should have been “leches”.

He said the leaching estimate is based on average estimates of water use and how septic tanks work.

As domestic sewage entered a tank, the same amount of liquid flowed from an outfall pipe into a ground absorption system and down to the water table.

He said the estimate is based on 450 households consuming an industry estimate of 700 liters of water per day. The number of households was reduced by 20% to allow outdoor water use and “some properties to be permanently unoccupied”.

This resulted in an estimated average of 252,000 liters per day.

Reporting on local democracy called for further explanation and clarity on the difference between the council’s estimate of 80% permanent occupancy and the 2015 and 2017 reports which estimated 25% of Tarawera’s 390 homes were permanently occupied.

Michael said the number of homes connecting to the scheme came from the ratings database and the 20% was an estimate as he “doesn’t have data on how many homes are occupied full-time, part-time or rented as holiday accommodation. “.

He said the other reports aren’t from the district council, so he can’t talk about those numbers.

The 2017 report was prepared for the Bay of Plenty Regional Council and the 2015 report was the regional council’s Tarawera Lakes Restoration Plan.

Ray White real estate licensee and Tarawera resident Norman Donald said permanent occupancy had increased over the years and 35 per cent would be a safe estimate.

Michael said the posters were intended to provide visitors to the lake with key information about the scheme in light of concerns about the pipeline’s route.

Michael said that the reticulation and maintenance of sewerage and stormwater infrastructure was the council’s key contribution to the lake’s water quality.

There was no response to a request for an explanation of how the scheme was justified against costs and benefits.

The district council’s manager of land and water compliance, Matthew Harrex, said his view was the district council had oversimplified its rules and should have specified the resource agreement for new or upgraded septic tank systems was a bit likely to be granted where reticulation was available.

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The council’s plans and policies supported reticulation, but the discretionary rule allowed for situations where a connection was not technically feasible.

Michael said in response that when the community “asked the council to initiate a reticulation system” for Tarawera, people were aware that only septic tanks would be non-compliant, consent to improve compliance was unlikely to be approved where reticulation is nearby and nearly 40% of properties were found unsuitable for upgrading due to steep slopes or other features.

Helen Creagh, Rotorua regional council’s catchment manager, said all 10 actions in her Lake Tarawera restoration plan were or were being implemented, including reticulation and the development of environmental management plans for all farms in the catchment .

Laura Smith is a Local Democracy Reporting journalist based at the Rotorua Daily Post. She previously reported general news for the Otago Daily Times and Southland Express and has been a journalist since 2019.

– LDR is the journalism of a local body, co-funded by RNZ and NZ On Air.

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