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Managing Wastewater in Rural Canterbury: A Guide for Property Owners

By Anna Bensemann, Senior Planner, Baseline Group Ph 0800123257 E: info@ blg.nz | Apr 17, 2024
Managing Wastewater in Rural Canterbury

Onsite wastewater systems in Rural Canterbury are reasonably common and are also known as septic tank systems. Appropriately dealing with sewage from rural property is important to ensure waste is not entering streams, groundwater or pooling in the backyard your children play in. It is essentially a public health matter, and the installation of on-site wastewater treatment systems is controlled by the Regional Council, Environment Canterbury (ECan).

The design of these systems has advanced significantly since the original “septic tank overflowing to a soak pit” days. Modern engineering designed systems include methods to treat waste and discharge into soils at a rate the soils can cope with.

ECan’s concern with rural wastewater treatment is the cumulative effect of many discharges, which may have the potential to impact on groundwater quality by increasing nitrates in the soils. Canterbury groundwater is known to be high in nitrates, which is attributed to the use of fertilisers in farming systems.

ECan has adopted an approach to manage the number of systems across the Plains by requiring resource consents for discharges on properties less than 4 ha in size. This enables the systems to be spread out and reduces the amount of nitrate loss to groundwater. The 4 ha size property was the minimum allotment size under the Inner Plains zone, under the Selwyn planning framework over the last few decades.

When applying for a building consent on rural land, Local Council’s check to ensure any sewer discharge can be appropriately provided for and if your property is less than 4 ha a resource consent for discharge to ground from Ecan is required. The engineering design for the treatment system itself is submitted along with an assessment of effects on the receiving environment (including groundwater). ECan will consider how many other systems are in the immediate area along with how many wells are in the area. They will consider if the effects from that designed system will, along with neighbouring discharges, affect groundwater quality. This can be a rigorous test given there are underlying concerns with nitrate levels in groundwater in Canterbury. However, subject to meeting all other conditions, if your rural site is over 4 ha (with no other sewer connection available) resource consent for disposal of wastewater may not be required.

We also encounter the need for resource consents for systems when subdividing around an existing house leaving it on a title of less than 4 ha, requiring consent where it was previously a permitted activity. As systems need to meet modern-day standards, landowners may find themselves having to upgrade old systems when they subdivide. This can be a hefty cost if not budgeted for as part of the subdivision and can hold up the subdivision process.

For all new dwellings in rural areas, or for subdivisions around existing dwellings to less than 4 ha, providing for appropriate wastewater disposal is a must. Without an appropriate disposal solution identified at the outset subdivision may be delayed or out of reach. To ensure you are fully informed for rural subdivision requirements and or building on rural land we recommend getting specialist planning input to identify the costs, and requirements of this process.

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