Water Quality & Standards

Built in 2024, The Lake Dunstan Water Supply services the townships of Clyde and Alexandra. This is a membrane treatment plant with chlorination which provides treatment barriers for bacteria and protozoa.

The source water is from bores adjacent to Lake Dunstan. These draw on lake water, which is considered to be a surface water source.

The Naseby treatment plant consists of flocculation, sand filtration, UV and chlorination which provide treatment barriers for bacteria and protozoa under normal operating conditions.

The source water for Naseby is from the Hawkdun Irrigation Race, which is a surface water source. This source is vulnerable to turbidity following rain. When this occurs, the plant is shut down, treated water is supplied from reservoirs and a conserve water notice is put in place.

If the reservoir level drops to a point where partially untreated water is needed to refill it, then a boil water notice must be put in place until the source water clears. This typically occurs when reservoirs have about six hours storage available. Note that extra bacteria samples are taken during these events.

The population in Naseby varies considerably between normal population and peak population. The Naseby plant has to run continuously to produce enough treated water during peak periods. This does not provide sufficient capacity to accommodate typical maintenance outages during peak periods, or changes in the source water quality.

Investigation is underway to identify the options for increasing capacity and providing resilience to weather events that affect the source water quality.

The Omakau Water Supply services the townships of Omakau and Ophir. The treatment plant consists of coagulation, flocculation, sand filtration and chlorination. This provides treatment for bacteria, and a barrier for protozoa.

The source water for Omakau is from an infiltration gallery in the Manuherekia Riverbed. This is a surface water source and is vulnerable to turbidity following rain. When this occurs, the plant is shut down and a boil water notice is required. It is also vulnerable to low river flow during summer when water restrictions may be required.

Council is investigating options to provide a resilient and compliant water supply for Omakau. This has involved considering other source water options. A business case has been developed and Council will consider the options within the next two months. Significant investment, in the range of $20-25 million, will be required to build the new plant.

The Patearoa water supply feeds a small urban area and multiple rural properties. The Patearoa treatment plant consists of UV Treatment, now in place to treat protozoa. Cartridge filtration is in place to get water quality to a level where UV can treat.

The source water for Patearoa is from the Sowburn River. This is a surface water source and is vulnerable to turbidity following rain. When this occurs, the plant is shut down, treated water is supplied from reservoirs, and a conserve water notice is put in place.

If the reservoir level drops to a point where untreated water is needed to refill it, then a boil water notice must be put in place until the source water clears.

The Ranfurly treatment plant consists of coarse filter and cartridge filter, chlorination and a protozoa barrier. This provides treatment for bacteria and protozoa.

The source water for Ranfurly is from two locations on the East Eweburn River. This is a surface water source and is vulnerable to turbidity following rain. When this occurs, the plant is shut down, treated water is supplied from reservoirs. and a conserve water notice is put in place.

At normal water demand, Ranfurly has several days storage in the reservoir.

The Roxburgh Water Supply services the townships of Roxburgh and Lake Roxburgh Village, and some properties between Roxburgh and Lake Roxburgh Village.

The Roxburgh treatment plant consists of cartridge filtration, UV and chlorination, which provides treatment barriers for bacteria and protozoa.

The source water for Roxburgh is from bores adjacent to Clutha Mata-au which draw on river water. This is considered a surface water source. There is sediment drawn through the bore which has required a larger micron filter to be used. While providing protection, the filter does not fully meet the requirements for compliance with the New Zealand Drinking Water Quality Assurance Rules. The UV still provides a barrier to protozoa.

Council is currently reviewing alternative bore locations to address the sediment issue.