Infrastructure Strategy The Council will implement a proactive, planned renewals programme and invest more The likely effects of climate change will be taken into consideration when Council in condition assessment technology, field data collection and data management to applies to renew the treatment plant resource consents. The next resource consents address the renewal challenges, which are described in more detail below. New will include conditions to prevent environmental deterioration. installation and pipe rehabilitation techniques are becoming more commonplace, reducing the costs and disruption of renewal upgrades. Cultural values Earthquakes Iwi have a strong cultural relationship with the environment, and the disposal of human waste into the aquatic environment is of concern to them. The Council is working with The Blenheim and Havelock treatment plants are built on coastal plains. The areas are Iwi on an Iwi engagement plan, and will continue to work with Iwi on mutually flat and low-lying and vulnerable to tsunami inundation. The land is also prone to acceptable solutions to wastewater management. A pipeline has been installed liquefaction and ground deformation which could have important consequences, as the alongside the Picton Trunk Main upgrade. It will facilitate the recycling of treated flows through the plant rely on gravity flows along a shallow gradient. effluent for irrigation at a later date. Further improved practices can be expected over time. Earthenware pipes are particularly vulnerable to ground movement. Asbestos cement and the older concrete pipes also perform less well. PVC plastic mains perform better. Infiltration & Inflow Polyethylene mains perform best of all, but these pipes do attract grease and fat which The capacity of the wastewater system can be put under strain from the additional flow sticks to them, so they need to be cleaned more regularly. due to the ingress of stormwater through inflow or infiltration. Leaky joints in pipes and Climate change manholes, and accidental connections between stormwater and wastewater pipes, all contribute to the problem. Stormwater infiltration into the wastewater network becomes a more significant problem during storms and when groundwater levels are high. Climate change is likely Finding the source of ingress can be time consuming and expensive. Progress is often to make this problem worse as storms are predicted to become more intense and frustrated as fixing one leak is quickly replaced by inflow from another leak. It can also frequent. be difficult to identify if the leak is on the public pipework or within private property. Pipe renewal can be a more sustained solution than repairing individual leaks. Hotter drier summers will have an impact on the bacteria and algae used in the wastewater treatment process, because they require dissolved oxygen in the New technologies wastewater to effectively process the waste into treated effluent. Dissolved oxygen Similar to water supply assets, the adoption of new ‘smart’ technologies by residents decreases as the temperature of the ponds increases. Additional aeration plant may be will give them more choices about how they use water, and this is likely to smooth the required to increase the oxygen in the treatment ponds. peaks and troughs of sewage flows, allowing for more economic designs. Grey water The Seddon treatment plant discharges to the Starborough Creek which can have very recycling and water-efficient appliances will counterbalance the increase in growth low natural flows. The impact of the discharge may be affected by a change in the New treatment processes are being developed and high quality treated effluent volume and temperature of the receiving water. discharges are becoming easier to achieve consistently. Many new treatment The Blenheim wastewater treatment plant includes a facility to recycle a portion of the technologies are becoming ‘scalable’. It may become efficient for small businesses, treated effluent to irrigate land. This is only permitted when the soil requires additional and even domestic properties, to treat their wastewater. This will reduce both the moisture and when the groundwater levels are low enough to prevent surface ponding. strength and the volume discharged to sewer and enable recycling of a portion of the Longer, drier summers may prolong the irrigation season but rising sea levels may ‘grey water’ for use as irrigation or other low quality uses. raise the groundwater levels, preventing irrigation. 2018-2028 Long Term Plan Page 196