The Queenstown Lakes District Council undertook urgent clean-up work last week, after an overlooked pipeline, thought inactive, was discovered to have been discharging waste water to the Shotover River bank, QLDC water services manager Garry McGraw said.

On Tuesday 3 March Fulton Hogan reported to the Otago Regional Council (ORC) that there was a flow discharge at the rear of its gravel storage yard which is located between pond 2 of the Shotover Treatment Plant and the riverbank of the Shotover River.

The ORC contacted QLDC contractor United Water, which attended the site to investigate the source of the flow.

“Investigations showed that an emergency outlet pipe situated at a high level on pond two was discharging directly to the Shotover River bank deep in the overgrowth behind the Fulton Hogan yard,” Mr McGraw said.

What happens is that sewage enters the treatment ponds and then moves to a settling or polishing pond. Due to this error, partly treated sewage has been bypassing the final part of the process.

“The levels have not been high historically in pond two but in recent months the levels have been high,” Mr McGraw said.

Pond two discharged to pond three and at the time of the installation of pond three, the high level discharge on pond two should have been closed off. Whilst the top layer of waste water in pond two would not meet the Council’s discharge consents, it was not raw, untreated sewage.

“Unfortunately this redundant pipe was overlooked. Once this was identified the Council acted as quickly as possible to remedy the situation. In fact the discharge had been completely shut off within half an hour, with a major clean-up of the area being undertaken last week,” Mr McGraw said.

It was difficult to say how much waste water had been discharged and over what period of time.

“What we know is that on the basis of the size of the pipe the amount would have been rapidly diluted in the river and we have been able to remove the contaminated soil,” Mr McGraw said.

Soil samples of the area have now been taken to ensure the area has been satisfactorily sanitised.

“Once the results from the soils testing is returned this will determine if any additional action will need to be taken in regards to the cleanup,” Mr McGraw said.

The situation was not acceptable but the Council had been advised by its engineers that the level of contamination was not likely to have posed any health risks.

“We were fortunate that the outlet was in an isolated and inaccessible position and that the river has a vast quantity of water moving through it to dilute the waste water,” Mr McGraw said.

Nevertheless, QLDC chief executive Duncan Field had requested an independent investigation into the matter.

“This is an operation error, I need to understand how that occurred and more importantly, that it will not occur again in the future,’ Mr Field said.

The new waste water disposal to land project, Project Shotover, was expected to be operational by 2013 and would introduce new standards that would eliminate any similar potential risk in the future.

ENDS

For further information please contact Duncan Field or Garry McGraw 03 441 0499.

By: Kiri