Permanent chlorination of the Malvern Hills Hartleys Road water supply

This  process started at 1pm on Thursday 4 October 2018.

Chlorination is one of the methods we use to ensure we are providing our communities with safe drinking water. Initial assessment of the Malvern Hills Hartleys Road water supply identified it as having a high level of risk. It is a non-secure groundwater supply, serving a significant population, and has been subject to a number of E. coli issues in the past (most recently in March  2018).

Chlorination of this supply was signalled during consultation on our Long-Term Plan 2018-2028. After hearing and considering submissions on this matter, the Council confirmed the decision to permanently chlorinate this supply.  The decision is recorded in the Long-Term Plan as follows:

“Current projects to chlorinate the community supplies at Malvern Hills and Sheffield-Waddington, on a risk-based approach, were also endorsed by the Council.” (page 11) and,

“The proposal to chlorinate the community supplies at Malvern Hills and Sheffield-Waddington will proceed in the first quarter of the 2018/19 year.” (page 84)

The addition of chlorination to this supply was also supported by the Canterbury District Health Board in its submission to the Long-Term Plan, on the basis that the system’s extensive reticulation networks and on-site storage make it more susceptible to contamination from pipe breaks, backflow, or compromised on-site storage tanks.

Chlorination is widely and reliably used in water supplies throughout New Zealand to protect community health, and several water schemes in the Selwyn district are already chlorinated including Acheron, Castle Hill, Dalethorpe, Hororata, Sheffield/Waddington and Springfield.

Chlorine treatment will be in the form of sodium hypochlorite solution which is added to the water supply at the treatment plant. Water users are likely to notice a gradual increase of chlorine levels as new treated water moves through the scheme and mixes with unchlorinated water in the Council’s reservoirs and in private on-site storage tanks. We will aim to keep chlorine levels at a minimum while providing the required level of residue disinfectant at the extremities of the scheme.

Selwyn District Council has comprehensive information on how we treat our water, as well information on our rationale behind chlorinating our water.