International Review Backs New Wastewater Systems

An international peer review has backed Christchurch City Council’s decision to replace the gravity wastewater system in Parklands with a new pressure wastewater system. The Council is introducing new wastewater technology as part of the rebuild of earthquake-damaged infrastructure to build stronger systems, better able to withstand any future earthquakes.

City Water and Waste Manager Mark Christison says the old gravity wastewater system failed in parts of the city where the earthquakes caused land movement. Many thousands of residents were left without functioning toilets for several months because of significant damage to the system.

“The Council could not in good conscience replace the damaged system with the same technology which failed so badly.

“We went through a thorough process to determine the best system for different areas of the city. In some areas, we concluded that the gravity system was not damaged enough to require replacement; in others we are introducing new pressure or vacuum sewers to make the system stronger. The MWH report has confirmed this was the right process in the Parklands East area which we asked them to review.

“We understand that this is a new way of doing things and residents will have a lot of questions. The Stronger Christchurch Infrastructure Rebuild Team (SCIRT) is installing these systems on behalf of the Council and is working closely with residents to explain how the new system works and what it means for them.

“There is a process for people to formally object to public infrastructure being placed on private property and we are working through that. We have also recently responded to specific requests from a group of Parklands residents about the process,” he says.

An international peer review of the Council’s decision to install the new system in Parklands East has just been completed by international consultants MWH. The review notes the resilience of pressure sewer systems in areas subject to ground movement. The reviewers comment on the steps and logic in the selection process for this solution and, from their wide experience of pressure sewer systems in Australia, are able to comment on the suitability of a pressure sewer system in this situation.

The Council is also involved with two applications that have been lodged with the High Court for review of the introduction of the new systems. In both cases, additional applications by the residents for interim relief (to stop work on the roll-out of the new systems) have been withdrawn after the Council agreed to halt work in the immediate area where the applicants live. The first application for review will be considered by the High Court in coming weeks.