21 May 2021

A 12-month project to reduce the risk of flooding and wastewater overflow during storm events has officially been closed out by Christchurch City Council.

The project involved the installation of a new 900-metre wastewater main beneath the southern end of Colombo Street, from Cashmere Road to Fisher Avenue. A special syphon system was engineered to run beneath the intersection with the Heathcote River.

At the same time, the Council also upgraded a 200-metre-long wastewater cross-connection beneath nearby Beckenham Street.

“Merging the two projects meant we made the most efficient use of time and money in getting them done while minimising any interruptions for local residents,” says Council Head of Three Waters and Waste Helen Beaumont.

“The new Colombo Street main allows for much greater resilience in the local wastewater network, because it functions as a backup to the existing main when we need it during storm events or for maintenance purposes. It also increases the network’s capacity to allow for future growth in the surrounding suburbs.”

During heavy rainfall, excess surface water from footpaths and roads can flow into manholes and flood the wastewater network.

“There is now a much lower risk of flooding in the area from storm events, including any overflow of wastewater into the Heathcote River. This is a successful outcome for the local community and also for protecting the health of the river,” says Ms Beaumont.