The Council is applying to Environment Canterbury for a new consent for wastewater overflows to waterways. This will allow the discharge of untreated wastewater to waterways during large storms, when the capacity of the wastewater network is exceeded.
The main purpose of a wastewater network is to protect public health, and to prevent people from coming into contact with raw wastewater. Constructed wastewater overflows to waterways act as safety valves on the wastewater network, so that when the network is overwhelmed in a large storm, wastewater does not overflow onto people’s properties or on the street.
Since 2010, Environment Canterbury (ECan) granted the Council consent for occasional overflows of wastewater to the environment during large storms. Due to earthquake damage and the likelihood there would be overflows more often than allowed, a non-enforcement agreement with ECan is in place. However, the Council needs to comply with its consent by September 2017, or apply for a new consent. The earthquake damage means that more stormwater and groundwater gets into the pipes than before. It seems unlikely that Council will be able to comply with its existing consent, so the process of applying for a new consent is underway.
The new consent will need to cover Christchurch (as at present) and Lyttelton and Akaroa harbours. Christchurch overflows are located on the Avon River, Heathcote River and the Avon/Heathcote Estuary. On Banks Peninsula, there are overflows at Lyttelton, Diamond Harbour, Governors Bay and Akaroa.
The previous consent focussed on reducing the frequency of overflows to waterways. However, there is only a limited link between the frequency of overflows and the effects on the waterways.
For this consent the Council plans to take more of an effects-based approach. We will focus on the values of the waterways, the effects of the overflows on those values, and therefore how we are best to reduce those effects.
The consent process will involve extensive consultation with key stakeholders, including the rūnanga and the wider community. Presentations to key stakeholders and the community have been given:
Future meetings will cover the following topics:
The Council will submit its consent application by 17 September 2017. People can make submissions once the consent is notified by ECan and give evidence at the hearing, if they wish.
The consent will consider the six values for waterways and the effects that wastewater overflows have on each of these values. The six values are:
The Council has developed a catchment vision and values for the Avon River and is developing a catchment vision and values for the Heathcote River.
We all want to improve the quality of our waterways and we need to work out the best way to do that. It might be that we will get better outcomes by reducing contaminants in stormwater, rather than spending a lot of money reducing wastewater overflows. For example, to eliminate wastewater overflows altogether would require converting most of the city to a pressure sewer system, and would cost more than $3 billion to build. However, it would not necessarily result in an improvement in water quality.
The Council carries out extensive monitoring of the water quality in our waterways and in the past year has collected and analysed over 7,000 water quality samples.
The key contaminants were:
Most water quality monitoring sites show no change since 2007 and following the removal of large amounts of sediment, the waterways have been returned to prequake environments. The Council has prepared a water quality monitoring report for 2016 and previous years.
The Council plans to spend more than $212 million over the next 10 years on projects to improve water quality:
The Council has already done a lot to reduce wastewater overflows:
These measures, combined with low groundwater levels due to dry winters, mean that there has only been three wet weather overflow in the past two years in Christchurch city. This is already better than most cities in New Zealand and around the world. The Council maintains a list of recent wastewater overflows.
Improving the quality of our waterways can’t be done by the Council alone – it needs to be done by the whole community. There are several things that you can do: