Protecting the Waitao Stream: three new wastewater systems for a kaumātua papakāinga in Welcome Bay
At a marae papakāinga in Welcome Bay, Tauranga, the wastewater systems serving six kaumātua (elders') flats were failing and leaking toward the Waitao Stream. WaterFlow designed a replacement, worked alongside Bay of Plenty Regional Council on a new resource consent, and supplied three EconoTreat secondary treatment systems, installed by local drainlayers Tasman Plumbing Contractors.
The challenge: failing systems beside the estuary
The papakāinga sits on a 6.8-hectare whenua block off Welcome Bay Road, next to the marae, on land that slopes gently down to the Waitao Stream and the Tauranga Harbour estuary. Six two-bedroom kaumātua flats were served by three older treatment tanks, all discharging to a dripline field near the stream.
Over the years, those systems had struggled:
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Overloaded tanks. The three existing units had been through repeated periods of organic and hydraulic overloading, and needed extensive maintenance throughout their consent.
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A damaged disposal field. Vehicles had driven over the dripline field and broken it, causing leaks.
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Effluent reaching the creek. The leaks meant wastewater was making its way into the Waitao Stream, which flows straight into Tauranga Harbour.
Any fix also meant replacing the old resource consent, which needed Bay of Plenty Regional Council's sign-off before anything could change.
Our approach: start with the ground, then the consent
WaterFlow's Senior Design Engineer, Matt Riddell, carried out the site assessment. Matt has more than 25 years' experience across design, consulting and project management, and is a Bay of Plenty Regional Council approved OSET system designer. Bore holes to 1.2 metres found a thin layer of dark topsoil over free-draining Ngākuru sandy loam, with no sign of groundwater. The chosen disposal area was flat, around 6.5 metres above the Waitao Stream and roughly 100 metres away from it.
Our designers then sized the new system around how the flats are actually lived in:
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Three separate treatment plants. Each EconoTreat aerated system serves two flats, so a problem at one never affects all six homes.
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Plenty of headroom. Each plant handles up to 2,200 litres a day, against a design flow of 1,160 litres per system (3,480 litres across the site).
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One new disposal field, well away from the stream. Treated water from all three plants is pumped to a single 70 m² soakage bed near the road boundary, replacing the old vehicle-damaged dripline field.
Because the discharge is over 2,000 litres a day, it needed a full resource consent under the Bay of Plenty On-Site Effluent Treatment Regional Plan. WaterFlow prepared the application and design report, working closely with Bay of Plenty Regional Council's consents team from the first conversation, and applied for a 15-year consent to replace the old one.
The tricky bit: replacing everything while kaumātua live on site
This wasn't an empty section. Six households of elders were living in the flats, so the new systems had to go in with as little disruption as possible:
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Built around the homes. Each treatment plant sits beside its pair of flats, at least 3 metres from the buildings, and connects into the existing drains.
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One shared rising main. A 32 mm pumped line links all three plants and carries treated water up to the new soakage bed by the road, keeping the disposal area clear of the stream and the bush line.
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A team effort. WaterFlow handled the design, consent and supply, local drainlayers Tasman Plumbing Contractors carried out the installation, and the trust's representative kept the whānau informed throughout.
The result
The three new systems were powered up and certified by a licensed electrician on 29 August 2025, with the old tanks disconnected the same day. The papakāinga now has three modern secondary treatment systems and a new, purpose-built disposal field.
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No more leaks to the stream. The old tanks and the damaged dripline field have been replaced, and treated water now goes to a soakage bed well away from the Waitao Stream.
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Resilience built in. With three independent plants, a fault at one system affects two flats at most, and each plant has emergency storage and a high-water alarm.
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Consented for the long term. The new design was submitted under a fresh resource consent with Bay of Plenty Regional Council.
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Easy to look after. WaterFlow provides regular servicing for all three plants, with the soakage bed protected from stock and vehicles so the same problem can't happen again.
Project details
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Location |
Welcome Bay, Tauranga, Bay of Plenty |
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Property type |
Marae papakāinga, six 2-bedroom kaumātua flats, rainwater supply |
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Problem |
Three failing treatment tanks and a vehicle-damaged disposal field leaking toward the Waitao Stream |
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Design flow |
3,480 litres per day (24 people) |
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Treatment systems |
3 x EconoTreat VBB-C-2200, secondary treatment, pumped discharge |
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Disposal field |
70 m² soakage bed, plus reserve area |
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Soil |
Ngākuru sandy loam, free draining, no groundwater found to 1.2 m |
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Consent |
Resource consent application to Bay of Plenty Regional Council (On-Site Effluent Treatment Regional Plan), replacing the previous consent |
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Timeline |
Site assessment February 2024, design March 2025, systems live August 2025 |
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WaterFlow team |
Matt Riddell, Senior Design Engineer (site assessment, consent and design review), Sandra Sabath (design), Caleb Pirini (sales) |
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Installed by |
Tasman Plumbing Contractors, with ongoing servicing by WaterFlow |
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