People might notice the Manuherekia River has turned a fluorescent colour just south of Omakau over the next 24 hours, but it’s for a good reason. 

As part of the Omakau wastewater treatment plant consent, the Central Otago District Council is undertaking an ecological assessment of the river.

This includes releasing a florescent dye into the river to evaluate the treatment plant discharge mixing zone. The dye is non-toxic, biodegradable and safe for the environment.

The last time council carried out dye testing was in March 2023, and district wide in March 2020.

In July 2023, urgent repairs were carried out at the Omakau site after extensive rainfall and flooding of the river caused damage to the oxidation ponds, causing untreated wastewater to enter the river.

But, in November 2023, the council was provided with recommendations for moving forward with two new infrastructure projects designed to provide safe, reliable and resilient wastewater services.

The Omakau wastewater indicative business case recommends constructing a new wastewater treatment site at Omakau in a more resilient location, near the Omakau Golf Course.

This includes moving the discharge of the treated wastewater away from the Manuherekia River to discharge to land.

Once the investigation and preliminary designs were done, council will be provided with updated business cases with refined costs and a delivery strategy for approval.

Funding for the investigation and preliminary design work will be included in the draft 2024 long term plan (LTP).

The Alexandra wastewater indicative business case also recommends constructing a new wastewater treatment site on council land near the Alexandra Airport. 

This includes moving the discharge of the treated wastewater away from the Clutha Mata-au River to discharge to land. 

Council requested further investigation also be undertaken to determine if the existing Alexandra treatment site at Graveyard Gully has the capability to be expanded to meet long term requirements.

Both the Alexandra and Omakau resource consents are due for renewal in the next five years.

A solution, which provides treatment and discharge to meet current environmental requirements, is expected to be in the region of $30 million to $60 million.