A new multi-million wastewater project could start in Mahurangi next year as Watercare is about to lodge a consent for a massive sewage upgrade.
Watercare’s preferred option is to decommission the Warkworth wastewater treatment plant and pipe sewerage to a new hi-tech plant in Snells Beach, where sewage will be treated and pumped to the existing outflow at Martins Bay.
This will cater for predicted population growth, as the area serviced by the Warkworth and Snells Beach treatment plants is expected to grow from 8400 to 35,000 by 2040.
Watercare environment and consents manager Mark Bourne says the new plant will be vastly superior to the existing Snells Beach plant and will be much better for the environment (see opposite page).
The treatment plant will be built in stages over 35 years as the population grows. The total project is expected to cost $135 million.
The consents for the new treatment plant and wastewater discharge will be lodged in the next month. The document will include extensive detail of how Watercare has developed its preferred option, including technical studies and a summary of public consultation.
Mr Bourne says Watercare expects the consents to be granted early next year and construction on the first phase would start soon after that and be completed over about five years.
Watercare did extensive investigation into whether a land-based discharge would better serve the area, rather than discharging to the ocean, but the geology of the area made it unviable, he says.
“That was a very real option up until the final stages of our investigation,” Mr Bourne says. “At Omaha, we have a land-based disposal treatment, but the difference is that the area within 10km of Snells Beach and Warkworth is significantly steeper and the clay soils are far less absorbent, so there would be a higher level of runoff and more land would be required. But we may still look into using a land-based discharge in the future.”
Mr Bourne says people don’t need to be concerned about pumping treated wastewater into the ocean.
“I firmly believe that the proposed ocean outfall will have very minor environmental effects. The concentration of nitrogen will be significantly less than what currently exists.”
The goal is to have the new system up and running by 2022, when up to 290-hectares of land will be live-zoned for development in Warkworth.
About 25 people attended an open day on the proposal in Snells Beach on June 14. Consultation will continue as Watercare refines its proposal.
Watercare is currently replacing a section of the outfall pipeline near Snells Beach as it has become past its useful life.
“A property development is underway and it makes sense to do work before the development takes place, rather than once houses are in the area. We had to upgrade the pipeline in any case, regardless of what future wastewater system is put in place.”