Plan Change 14 is currently being developed to include updated policies and rules for managing the safe treatment and disposal of onsite wastewater. The plan change covers septic tanks, greywater, composting toilets, pit latrines and aerated wastewater systems. All of these systems are a form of onsite effluent treatment (OSET).

The new provisions will eventually replace the existing On-Site Effluent Treatment Regional Plan (OSET Plan) and will be incorporated into the Regional Natural Resources Plan. The OSET Plan will be withdrawn when Plan Change 14 is operative.

Under Plan Change 14, Mamaku is proposed as a Maintenance Zone. It was included as a Maintenance Zone in the current plan’s maps and schedules but was removed from the rule in hearings. That means the requirement to pump out and inspect septic tanks hasn’t been enforced.

At a community meeting in late 2018 to discuss the Draft plan change requirements for Mamaku, a wastewater investigation programme was proposed to the community. Investigations were undertaken to inform the best long term solution for Mamaku and better understand whether onsite wastewater treatment systems (OSETs) are suitable in the Mamaku environment. This includes how they’re operating at the moment, and the risks around using them – both for the environment and for human health.

These reports made clear that Mamaku has an issue with wastewater. It backs up what we’ve been hearing from the community and these two reports show there are real issues.

You can read the reports here:

The reports highlighted the key challenge Mamaku is the hard ignimbrite rock layer across much of Mamaku, which doesn’t allow wastewater to discharge properly to ground. Therefore this presents a significant environmental constraint to effective and sustainable OSET discharges in the village.

During winter shallow groundwater perches on the rock layer and rises towards the ground surface. Above the rock are shallow soils which don’t drain well, meaning the wastewater might not be fully treated before merging with groundwater.

Historically Regional Council has had a relatively high number of complaints reported relating to OSETs and water monitoring of surface water drains has shown some presence of E.coli which has been linked to septic tanks, presenting a risk to people’s health.

Using systems that are old, inadequate or need replacing pose a risk to the health of both the community and the environment. We need to put rules in place now to protect both our people and our waterways.

Plan Change 14 – proposed rules

Regional Council is proposing Maintenance Zone rules for Mamaku.* This would:

  • Require tanks to be pumped out and inspected to relieve the impacts of discharges on the environment and ‘reset’ systems
  • Remove the automatic requirement to meet minimum septic tank sizes
  • Instead link actions required (if any) with outcomes of septic tank inspections
  • Provide the ability for more lenient rules as an Interim Maintenance Zone where reticulation is planned and committed to by a territorial authority (this means it’s included in Years 1 to 3 in the Long Term Plan). These rules mean there’s no requirement for an outlet filter to be installed and based on the septic tank inspection, they provide a greater threshold before action must be taken to address an OSET issue.
  • Provide for the situation that reticulation may not eventuate and at that point require people upgrade their wastewater systems to an AWTS+NR (Aerated wastewater treatment system with nutrient reduction) to address the risk from OSETs in Mamaku. Noting this is not ideal for Mamaku as many lot sizes and slopes aren’t suitable for these systems.

    * These Maintenance Zone Rules will not commence until completion of the plan change, which is expected to be a couple of years away.

Other considerations

Our reports show that even with rules in place, the environment isn’t well suited for OSETs in Mamaku and there will be problems with their effectiveness.

If Mamaku is not reticulated, the community will eventually need to upgrade to a high quality on site system. These are referred to an AWTS+NR system (Aerated Wastewater Treatment System).
Subsidies aren’t available for upgraded OSET systems as they aren’t a community solution.

Next steps

A meeting is planned for 28 June in Mamaku. This is an opportunity to find out more, understand the investigations that have happened to date and potentially the future rules. At the meeting we will also be able to explain the pathways to potential long term solutions for Mamaku’s wastewater.

The community will have the opportunity to make formal submissions on the Proposed Plan Change when it is notified later this year.

If you want to tell us your thoughts on the reports, or what you think wastewater in Mamaku should look like, please email mamaku.pc14@boprc.govt.nz.

The community will have the opportunity to make formal submissions on the Proposed Plan Change when it is notified later this year.

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15 May 2020

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