Participate Palmy

Option 3: Treated wastewater applied to land, with discharge to the Manawatū River in exceptional circumstances

Treated wastewater would be applied to land approximately 97% of the time. The remaining 3% of time, treated wastewater would be discharged into the Manawatū River from the existing discharge point at Tōtara Road. This would occur when the river is least sensitive to the discharge – when the river is full and in high flow, likely to be in winter.

Photo shows illustration of treated wastewater applied to land, with discharge to the river in exceptional circumstances.

This option would require either leasing or buying large areas of land, about 2,500 to 3,500 ha depending on drainage and topography of the site. This could affect a large number of landowners given the large area required and relatively small landholdings on the Manawatū plains.

What we'd need to install or build

  • pipes to move the treated wastewater from the treatment plant to the land application site
  • storage basin and rapid infiltration basin to buffer flows to the land application area
  • irrigation infrastructure
  • a wetland or land passage facility for the river discharge
  • upgrades to the treatment plant at Tōtara Road

The plant upgrades could vary from minor capacity upgrades to a new treatment process, depending on the nature of the soils at the land application site. We would need to purchase or lease this land. If a site with better quality soils is selected, then the treatment plant will require less upgrading. However, costs saved may be offset by higher land acquisition or lease costs.

We’d need to ensure we can acquire enough land with the right soils for absorbing treated wastewater, but we don’t believe this is a significant concern.

Cost

  • Lifetime cost: $416-765 million
  • Potential rate increase per year: $480-920
  • Total wastewater charge per ratable unit per year: $730-1,200