Ponds upgrade on track

The modifications to the oxidation ponds at the Christchurch Wastewater Treatment Plant are almost complete, ahead of schedule.

All that remains is the construction of new discharge pipes from the final pond into the estuary.

The upgrades, which began in November 2002, have changed how the flow moves through the pond system to provide significant improvements to the wastewater quality before it is discharged into the estuary. The wastewater used to pass through three ponds in series before being discharged. It now passes through seven ponds.

The upgrades are expected to produce an effluent quality that is some 10 times better than what was previously discharged into the estuary.

Christchurch City Council operations and maintenance manager Mike Bourke says that extra monitoring of the pond water is being carried out to identify the improvements in water quality, before consent applications are lodged for the Ocean Outfall in December.

The whole project of pond deepening and reshaping and new interconnecting pipes has cost $4 million and is an essential part of the overall treatment plant upgrade. As well as effluent quality improvements the work has also provided an additional safe habitat for birdlife.

• The upgrades to the oxidation ponds are linked to other upgrades around the city to improve the quality of treated wastewater, better protect the environment and ensure the entire wastewater system will cope with expected city growth, including:

• Treatment plant improvements

• The major sewer upgrade — a $36 million, 10-year project which involves the laying of more than 30km of new pipe

• The Ocean Outfall pipeline.

• An online information site at www.ccc.govt.nz/WasteWater outlines the works planned for the city’s sewerage system.