Ponds get final clean-up before $24m upgrade

Wanganui wastewater treatment plant Photo/File

There is just a thin layer of sludge still to be removed from Wanganui's wastewater treatment ponds before that part of the plant's upgrade is signed off.

The de-sludging of the beleaguered treatment plant is part of a clean-out as a prelude to starting a $24 million upgrade at Airport Rd.

The sludge had built up since the plan was commissioned in 2007 and has been blamed for creating the stink that came from the ponds in the summer of 2012-13. The stench prompted investigations into the plant's performance before the council decided a multi-million dollar overhaul was required to get it back on track.

Mark Hughes, the council's infrastructure manager, told this week's operations and reporting committee, that there was only the half-metre deep layer to be removed along with a final clean of the sides of the main pond. The smaller pond was the first to have the sludge removed.

Mr Hughes said the membrane lining the pond would be retained and it was matter of cleaning it without damaging it.

He said the next stage would be the council awarding the main contract, and he expected there would be another six weeks of lead-in time with the contractor to make sure all the issues were covered.

"Then the contractor would be on site and starting work, which should take 11-12 months to complete. So if council signs it off in July, then we would be looking at a completion date of July-August, 2015."

The council is currently using emergency consents from Horizons Regional Council to bypass the treatment plant and pump partially treated waste through its South Beach outfall into the sea.